WorldWideScience

Sample records for ocean bottom topography

  1. 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.

  2. Shallow flows with bottom topography

    NARCIS (Netherlands)

    Heijst, van G.J.F.; Kamp, L.P.J.; Theunissen, R.; Rodi, W.; Uhlmann, M.

    2012-01-01

    This paper discusses laboratory experiments and numerical simulations of dipolar vortex flows in a shallow fluid layer with bottom topography. Two cases are considered: a step topography and a linearly sloping bottom. It is found that viscous effects – i.e., no-slip conditions at the non-horizontal

  3. 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.

  4. Ocean-Bottom Topography: The Divide between the Sohm and Hatteras Abyssal Plains.

    Science.gov (United States)

    Pratt, R M

    1965-06-18

    A compilation of precision echo soundings has delineated the complex topography between the Sohm and Hatteras abyssal plains off the Atlantic coast of the United States. At present the divide between the two plains is a broad, flat area about 4950 meters deep; however, the configuration of channels and depressions suggests spillage of turbidity currents from the Sohm Plain into the Hatteras Plain and a shifting of the divide toward the northeast. Hudson Canyon terminates in the divide area and has probably fed sediment into both plains.

  5. Ocean Bottom Seismic Scattering

    Science.gov (United States)

    1989-11-01

    EPR, the Clipperton and Orozco fracture zones , and along the coast of Mexico, were recorded for a two month period using ocean bottom seismometers...67. Tuthill, J.D., Lewis, B.R., and Garmany, J.D., 1981, Stonely waves, Lopez Island noise, and deep sea noise from I to 5 hz, Marine Geophysical...Patrol Pell Marine Science Library d/o Coast Guard R & D Center University of Rhode Island Avery Point Narragansett Bay Campus Groton, CT 06340

  6. Ocean bottom seismometer technology

    Science.gov (United States)

    Prothero, William A., Jr.

    Seismometers have been placed on the ocean bottom for about 45 years, beginning with the work of Ewing and Vine [1938], and their current use to measure signals from earthquakes and explosions constitutes an important research method for seismological studies. Approximately 20 research groups are active in the United Kingdom, France, West Germany, Japan, Canada, and the United States. A review of ocean bottom seismometer (OBS) instrument characteristics and OBS scientific studies may be found in Whitmarsh and Lilwall [1984]. OBS instrumentation is also important for land seismology. The recording systems that have been developed have been generally more sophisticated than those available for land use, and several modern land seismic recording systems are based on OBS recording system designs.The instrumentation developed for OBS work was the topic of a meeting held at the University of California, Santa Barbara, in July 1982. This article will discuss the state of the art of OBS Technology, some of the problems remaining to be solved, and some of the solutions proposed and implemented by OBS scientists and engineers. It is not intended as a comprehensive review of existing instrumentation.

  7. Mean Dynamic Topography of the Arctic Ocean

    Science.gov (United States)

    Farrell, Sinead Louise; Mcadoo, David C.; Laxon, Seymour W.; Zwally, H. Jay; Yi, Donghui; Ridout, Andy; Giles, Katherine

    2012-01-01

    ICESat and Envisat altimetry data provide measurements of the instantaneous sea surface height (SSH) across the Arctic Ocean, using lead and open water elevation within the sea ice pack. First, these data were used to derive two independent mean sea surface (MSS) models by stacking and averaging along-track SSH profiles gathered between 2003 and 2009. The ICESat and Envisat MSS data were combined to construct the high-resolution ICEn MSS. Second, we estimate the 5.5-year mean dynamic topography (MDT) of the Arctic Ocean by differencing the ICEn MSS with the new GOCO02S geoid model, derived from GRACE and GOCE gravity. Using these satellite-only data we map the major features of Arctic Ocean dynamical height that are consistent with in situ observations, including the topographical highs and lows of the Beaufort and Greenland Gyres, respectively. Smaller-scale MDT structures remain largely unresolved due to uncertainties in the geoid at short wavelengths.

  8. Exact Riemann solutions of the Ripa model for flat and non-flat bottom topographies

    Science.gov (United States)

    Rehman, Asad; Ali, Ishtiaq; Qamar, Shamsul

    2018-03-01

    This article is concerned with the derivation of exact Riemann solutions for Ripa model considering flat and non-flat bottom topographies. The Ripa model is a system of shallow water equations accounting for horizontal temperature gradients. In the case of non-flat bottom topography, the mass, momentum and energy conservation principles are utilized to relate the left and right states across the step-type bottom topography. The resulting system of algebraic equations is solved iteratively. Different numerical case studies of physical interest are considered. The solutions obtained from developed exact Riemann solvers are compared with the approximate solutions of central upwind scheme.

  9. Ekman effects in a rotating flow over bottom topography

    NARCIS (Netherlands)

    Zavala Sansón, L.; Heijst, van G.J.F.

    2002-01-01

    This paper presents a general two-dimensional model for rotating barotropic flows over topography. The model incorporates in a vorticity–stream function formulation both inviscid topography effects, associated with stretching and squeezing of fluid columns enforced by their motion over variable

  10. Cascadia Initiative Ocean Bottom Seismograph Performance

    Science.gov (United States)

    Evers, B.; Aderhold, K.

    2017-12-01

    The Ocean Bottom Seismograph Instrument Pool (OBSIP) provided instrumentation and operations support for the Cascadia Initiative community experiment. This experiment investigated geophysical processes across the Cascadia subduction zone through a combination of onshore and offshore seismic data. The recovery of Year 4 instruments in September 2015 marked the conclusion of a multi-year experiment that utilized 60 ocean-bottom seismographs (OBSs) specifically designed for the subduction zone boundary, including shallow/deep water deployments and active fisheries. The new instruments featured trawl-resistant enclosures designed by Lamont-Doherty Earth Observatory (LDEO) and Scripps Institution of Oceanography (SIO) for shallow deployment [water depth ≤ 500 m], as well as new deep-water instruments designed by Woods Hole Oceanographic Institute (WHOI). Existing OBSIP instruments were also deployed along the Blanco Transform Fault and on the Gorda Plate through complementary experiments. Station instrumentation included weak and strong motion seismometers, differential pressure gauges (DPG) and absolute pressure gauges (APG). All data collected from the Cascadia, Blanco, and Gorda deployments is available through the Incorporated Research Institutions for Seismology (IRIS) Data Management Center (DMC). The Cascadia Initiative is the largest amphibious seismic experiment undertaken to date, encompassing a diverse technical implementation and demonstrating an effective structure for community experiments. Thus, the results from Cascadia serve as both a technical and operational resource for the development of future community experiments, such as might be contemplated as part of the SZ4D Initiative. To guide future efforts, we investigate and summarize the quality of the Cascadia OBS data using basic metrics such as instrument recovery and more advanced metrics such as noise characteristics through power spectral density analysis. We also use this broad and diverse

  11. Propagation of bottom-trapped waves over variable topography

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.

    Fig. 5. Variation in the magnitude of bottom-intensification of the incident and reflected waves (a and if) with meridional wavenumber (B, in dimensionless units). The values of parameters used in the computations are defined in the caption to Fig. 4... 1 I I I 0'0 1.0 (X) =~ Fig. 8. p~°)(x, y, z, 0) on the planes (a) z = 1, and (b) y = 0. The spatial coordinates are in dimensionless units. The values of the parameters used to compute the solution are defined in the caption to Fig. 4. The zonal...

  12. Thorium content in bottom sediments of Pacific and Indian oceans

    International Nuclear Information System (INIS)

    Gurvich, E.G.; Lisitsyn, A.P.

    1980-01-01

    Presented are the results of 232 Th distribution study in different substance-genetic types of bottom sediments of Pacific and Indian oceans. Th content determination has been carried out by the method of instrumental neutron activation analysis. Th distribution maps in the surface layer of bottom sediments of Pacific and Indian oceans are drawn. It is noted that Indian ocean sediments are much richer with Th moreover Th distribution in different types of sediments is very non-uniform. Non-uniformity of Th distribution in different types of Pacific ocean sediments is considerably less than that of Indian ocean and exceeds it only in red oozes

  13. 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.

  14. 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.

  15. 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.

  16. The Proposed Surface Water and Ocean Topography (SWOT) Mission

    Science.gov (United States)

    Fu, Lee-Lueng; Alsdorf, Douglas; Rodriguez, Ernesto; Morrow, Rosemary; Mognard, Nelly; Vaze, Parag; Lafon, Thierry

    2012-01-01

    A new space mission concept called Surface Water and Ocean Topography (SWOT) is being developed jointly by a collaborative effort of the international oceanographic and hydrological communities for making high-resolution measurement of the water elevation of both the ocean and land surface water to answer the questions about the oceanic submesoscale processes and the storage and discharge of land surface water. The key instrument payload would be a Ka-band radar interferometer capable of making high-resolution wide-swath altimetry measurement. This paper describes the proposed science objectives and requirements as well as the measurement approach of SWOT, which is baselined to be launched in 2019. SWOT would demonstrate this new approach to advancing both oceanography and land hydrology and set a standard for future altimetry missions.

  17. A Record-High Ocean Bottom Pressure in the South Pacific Observed by GRACE

    Science.gov (United States)

    Boening, Carmen; Lee, Tong; Zlotnicki, Victor

    2011-01-01

    In late 2009 to early 2010, the Gravity Recovery and Climate Experiment (GRACE) satellite pair observed a record increase in ocean bottom pressure (OBP) over a large mid-latitude region of the South East Pacific. Its magnitude is substantially larger than other oceanic events in the Southern Hemisphere found in the entire GRACE data records (2003-2010) on multi-month time scales. The OBP data help to understand the nature of a similar signal in sea surface height (SSH) anomaly observed by altimetry: the SSH increase is mainly due to mass convergence. Analysis of the barotropic vorticity equation using scatterometer data, atmospheric reanalysis product, and GRACE and altimeter an atmospheric reanalysis product observations suggests that the observed OBP/SSH signal was primarily caused by wind stress curl associated with a strong and persistent anticyclone in late 2009 in combination with effects of planetary vorticity gradient, bottom topography, and friction

  18. Far-field tsunami magnitude determined from ocean-bottom pressure gauge data around Japan

    Science.gov (United States)

    Baba, T.; Hirata, K.; Kaneda, Y.

    2003-12-01

    \\hspace*{3mm}Tsunami magnitude is the most fundamental parameter to scale tsunamigenic earthquakes. According to Abe (1979), the tsunami magnitude, Mt, is empirically related to the crest to trough amplitude, H, of the far-field tsunami wave in meters (Mt = logH + 9.1). Here we investigate the far-field tsunami magnitude using ocean-bottom pressure gauge data. The recent ocean-bottom pressure measurements provide more precise tsunami data with a high signal-to-noise ratio. \\hspace*{3mm}Japan Marine Science and Technology Center is monitoring ocean bottom pressure fluctuations using two submarine cables of depths of 1500 - 2400 m. These geophysical observatory systems are located off Cape Muroto, Southwest Japan, and off Hokkaido, Northern Japan. The ocean-bottom pressure data recorded with the Muroto and Hokkaido systems have been collected continuously since March, 1997 and October, 1999, respectively. \\hspace*{3mm}Over the period from March 1997 to June 2003, we have observed four far-field tsunami signals, generated by earthquakes, on ocean-bottom pressure records. These far-field tsunamis were generated by the 1998 Papua New Guinea eq. (Mw 7.0), 1999 Vanuatu eq. (Mw 7.2), 2001 Peru eq. (Mw 8.4) and 2002 Papua New Guinea eq. (Mw 7.6). Maximum amplitude of about 30 mm was recorded by the tsunami from the 2001 Peru earthquake. \\hspace*{3mm}Direct application of the Abe's empirical relation to ocean-bottom pressure gauge data underestimates tsunami magnitudes by about an order of magnitude. This is because the Abe's empirical relation was derived only from tsunami amplitudes with coastal tide gauges where tsunami is amplified by the shoaling of topography and the reflection at the coastline. However, these effects do not work for offshore tsunami in deep oceans. In general, amplification due to shoaling near the coastline is governed by the Green's Law, in which the tsunami amplitude is proportional to h-1/4, where h is the water depth. Wave amplitude also is

  19. Spreading of Antarctic Bottom Water in the Atlantic Ocean

    OpenAIRE

    Morozov, E.; Tarakanov, R. Y.; Zenk, Walter

    2012-01-01

    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 Bra...

  20. Ocean Dynamic Topography from GPS - Galathea-3 First results

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Olesen, Arne Vestergaard; Forsberg, René

    2010-01-01

    From August 14, 2006–April 24, 2007 the Danish expedition called Galathea-3 circumnavigated the globe. The Danish Technical University, DTU space, participated in the expedition with two experiments on-board. From Perth in Australia to Copenhagen Denmark measurements of the exact position and mov...... to permanent currents in the ocean. Comparison with the DNSC08 mean dynamic topography derived from satellite altimetry across the Gulf Stream yields agreement on the 20 cm level, which is a very satisfactory preliminary result calling for further refinement of the technique....

  1. 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...

  2. 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.

  3. SWOT, The Surface Water and Ocean Topography Satellite Mission (Invited)

    Science.gov (United States)

    Alsdorf, D.; Andreadis, K.; Bates, P. D.; Biancamaria, S.; Clark, E.; Durand, M. T.; Fu, L.; Lee, H.; Lettenmaier, D. P.; Mognard, N. M.; Moller, D.; Morrow, R. A.; Rodriguez, E.; Shum, C.

    2009-12-01

    Surface fresh water is essential for life, yet we have surprisingly poor knowledge of its variability in space and time. Similarly, ocean circulation fundamentally drives global climate variability, yet the ocean current and eddy field that affects ocean circulation and heat transport at the sub-mesoscale resolution and particularly near coastal and estuary regions, is poorly known. About 50% of the vertical exchange of water properties (nutrients, dissovled CO2, heat, etc) in the upper ocean is taking place at the sub-mesoscale. Measurements from the Surface Water and Ocean Topography satellite mission (SWOT) will make strides in understanding these processes and improving global ocean models for studying climate change. SWOT is a swath-based interferometric-altimeter designed to acquire elevations of ocean and terrestrial water surfaces at unprecedented spatial and temporal resolutions. The mission will provide measurements of storage changes in lakes, reservoirs, and wetlands as well as estimates of discharge in rivers. These measurements are important for global water and energy budgets, constraining hydrodynamic models of floods, carbon evasion through wetlands, and water management, especially in developing nations. Perhaps most importantly, SWOT measurements will provide a fundamental understanding of the spatial and temporal variations in global surface waters, which for many countries are the primary source of water. An on-going effort, the “virtual mission” (VM) is designed to help constrain the required height and slope accuracies, the spatial sampling (both pixels and orbital coverage), and the trade-offs in various temporal revisits. Example results include the following: (1) Ensemble Kalman filtering of VM simulations recover water depth and discharge, reducing the discharge RMSE from 23.2% to 10.0% over an 84-day simulation period, relative to a simulation without assimilation. (2) Ensemble-based data assimilation of SWOT like measurements yields

  4. Precise Comparisons of Bottom-Pressure and Altimetric Ocean Tides

    Science.gov (United States)

    Ray, Richard D.

    2013-01-01

    A new set of pelagic tide determinations is constructed from seafloor pressure measurements obtained at 151 sites in the deep ocean. To maximize precision of estimated tides, only stations with long time series are used; median time series length is 567 days. Geographical coverage is considerably improved by use of the international tsunami network, but coverage in the Indian Ocean and South Pacific is still weak. As a tool for assessing global ocean tide models, the data set is considerably more reliable than older data sets : the root-mean-square difference with a recent altimetric tide model is approximately 5 mm for the M2 constituent. Precision is sufficiently high to allow secondary effects in altimetric and bottom-pressure tide differences to be studied. The atmospheric tide in bottom pressure is clearly detected at the S1, S2, and T2 frequencies. The altimetric tide model is improved if satellite altimetry is corrected for crustal loading by the atmospheric tide. Models of the solid body tide can also be constrained. The free corenutation effect in the K1 Love number is easily detected, but the overall estimates are not as accurate as a recent determination with very long baseline interferometry.

  5. Precise comparisons of bottom-pressure and altimetric ocean tides

    Science.gov (United States)

    Ray, R. D.

    2013-09-01

    A new set of pelagic tide determinations is constructed from seafloor pressure measurements obtained at 151 sites in the deep ocean. To maximize precision of estimated tides, only stations with long time series are used; median time series length is 567 days. Geographical coverage is considerably improved by use of the international tsunami network, but coverage in the Indian Ocean and South Pacific is still weak. As a tool for assessing global ocean tide models, the data set is considerably more reliable than older data sets: the root-mean-square difference with a recent altimetric tide model is approximately 5 mm for the M2 constituent. Precision is sufficiently high to allow secondary effects in altimetric and bottom-pressure tide differences to be studied. The atmospheric tide in bottom pressure is clearly detected at the S1, S2, and T2 frequencies. The altimetric tide model is improved if satellite altimetry is corrected for crustal loading by the atmospheric tide. Models of the solid body tide can also be constrained. The free core-nutation effect in the K1 Love number is easily detected, but the overall estimates are not as accurate as a recent determination with very long baseline interferometry.

  6. 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.

  7. Optical image modulation above the submarine bottom topography: a case study on the Taiwan Banks, China

    Science.gov (United States)

    Li, Yan; Hu, Jianyu; Li, Jing; Fu, Bin; Ma, Liming

    2003-05-01

    A possible mechanism to explain the correlation between submarine topography and the direct sunlight specially reflected from the sea surface with variable roughness caused by the bottom-current effect was suggested fifteen years ago by Henning et al. in International Journal of Remote Sensing, 9, 45-67, after comparing radar satellite image and Skylab satellite photograph of the North American east coast (Nantucket Shoals) with submarine relief features. A case study is carried out in the famous sand waves field located at the Taiwan banks of Taiwan Strait in August 1998. The TM images, either visible bands (TM1, TM2, TM3) or near infrared bands (TM4, TM5, TM7), shows submarine relief features for sand waves, with wavelength of 300 to 2000 meters, riding on the lager scale sand ridges and channel system. Sea truth data including 660 nm beam attenuation coefficient profiles were conducted in the same period. We compare signals of TM images, attenuation coefficient profiles, and sounding maps of the Taiwan Bands. The subsurface upwelling signals with contributions of the water column and the bottom, either estimated by single or quasi-single-scattering theory or revealed by the TM images after removing the contribution of direct sunlight reflected signals from sea surface, were too weak to distinguish the ridges and troughs of bedforms especially for red and near infrared bands. However, the direct sunlight specially reflected signals from the sea surface, approximately at same level in water-leaving reflectance not only for visible bands (TM1, TM2, TM3) but also for near infrared bands (TM4, TM5, TM7), was the major submarine bottom topography signals especially for those pixels towards the direction of the sun azimuth. Following a physical description for the lee waves appeared on free surface when the current flows round an underwater obstacle, the direct sunlight reflected signals related wave face slope, is dominated by the height and depth of sand waves and

  8. Inversion of Solid Earth's Varying Shape 2: Using Self-Consistency to Infer Static Ocean Topography

    Science.gov (United States)

    Blewitt, G.; Clarke, P. J.

    2002-12-01

    We have developed a spectral approach to invert for the redistribution of mass on the Earth's surface given precise global geodetic measurements of the solid Earth's geometrical shape. We used the elastic load Love number formalism to characterize the redistributed mass as a spherical harmonic expansion, truncated at some degree and order n. [Clarke and Blewitt, this meeting]. Here we incorporate the additional physical constraint that the sea surface in hydrostatic equilibrium corresponds to an equipotential surface, to infer the non-steric component of static ocean topography. Our model rigorously accounts for self-gravitation of the ocean, continental surface mass, and the deformed solid Earth, such that the sea surface adopts a new equipotential surface consistent with ocean-land mass exchange, deformation of the geoid, deformation of the sea floor, and the geographical configuration of the oceans and continents. We develop a self-consistent spectral inversion method to solve for the distribution of continental surface mass that would generate geographic variations in relative mean sea level such that the total (ocean plus continental) mass distribution agrees with the original geodetic estimates to degree and order n. We apply this theory to study the contribution of seasonal inter-hemispheric (degree-1) mass transfer to seasonal variation in static ocean topography, using a published empirical seasonal model for degree-1 surface loading derived using GPS coordinate time series from the global IGS network [Blewitt et al., Science 294, 2,342-2,345, 2001]. The resulting predictions of seasonal variations of relative sea level strongly depend on location, with peak variations ranging from 3 mm to 19 mm. The largest peak variations are predicted in mid-August around Antarctica and the southern hemisphere in general; the lowest variations are predicted in the northern hemisphere. Corresponding maximum continental loading occurs in Canada and Siberia at the water

  9. The Ocean Surface Topography Sentinel-6/Jason-CS Mission

    Science.gov (United States)

    Giulicchi, L.; Cullen, R.; Donlon, C.; Vuilleumier@esa int, P.

    2016-12-01

    The Sentinel-6/Jason-CS mission consists of two identical satellites flying in sequence and designed to provide operational measurements of sea surface height significant wave high and wind speed to support operational oceanography and climate monitoring. The mission will be the latest in a series of ocean surface topography missions that will span nearly three decades. They follow the altimeters on- board TOPEX/Poseidon through to Jason-3 (launched in January 2016). Jason-CS will continue to fulfil objectives of the reference series whilst introducing a major enhancement in capability providing the operational and science oceanographic community with the state of the art in terms of spacecraft, measurement instrumentation design thus securing optimal operational and science data return. As a secondary objective the mission will also include Radio Occultation user services. Each satellite will be launched sequentially into the Jason orbit (up to 66 latitude) respectively in 2020 and 2025. The principle payload instrument is a high precision Ku/C band radar altimeter with retrieval of geophysical parameters (surface elevation, wind speed and SWH) from the altimeter data require supporting measurements: a DORIS receiver for Precise Orbit Determination; The Climate Quality Advanced Microwave Radiometer (AMR-C) for high stability path delay correction. Orbit tracking data are also provided by GPS & LRA. An additional GPS receiver will be dedicated to radio-occultation measurements. The programme is a part of the European Community Copernicus initiative, whose objective is to support Europe's goals regarding sustainable development and global governance of the environment by providing timely and quality data, information, services and knowledge. The Sentinel-6/Jason-CS in particular is a cooperative mission with contributions from NASA, NOAA, EUMETSAT, ESA, CNES and the European Union.

  10. 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.

  11. 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

  12. On the assimilation of absolute geodetic dynamic topography in a global ocean model: impact on the deep ocean state

    Science.gov (United States)

    Androsov, Alexey; Nerger, Lars; Schnur, Reiner; Schröter, Jens; Albertella, Alberta; Rummel, Reiner; Savcenko, Roman; Bosch, Wolfgang; Skachko, Sergey; Danilov, Sergey

    2018-05-01

    General ocean circulation models are not perfect. Forced with observed atmospheric fluxes they gradually drift away from measured distributions of temperature and salinity. We suggest data assimilation of absolute dynamical ocean topography (DOT) observed from space geodetic missions as an option to reduce these differences. Sea surface information of DOT is transferred into the deep ocean by defining the analysed ocean state as a weighted average of an ensemble of fully consistent model solutions using an error-subspace ensemble Kalman filter technique. Success of the technique is demonstrated by assimilation into a global configuration of the ocean circulation model FESOM over 1 year. The dynamic ocean topography data are obtained from a combination of multi-satellite altimetry and geoid measurements. The assimilation result is assessed using independent temperature and salinity analysis derived from profiling buoys of the AGRO float data set. The largest impact of the assimilation occurs at the first few analysis steps where both the model ocean topography and the steric height (i.e. temperature and salinity) are improved. The continued data assimilation over 1 year further improves the model state gradually. Deep ocean fields quickly adjust in a sustained manner: A model forecast initialized from the model state estimated by the data assimilation after only 1 month shows that improvements induced by the data assimilation remain in the model state for a long time. Even after 11 months, the modelled ocean topography and temperature fields show smaller errors than the model forecast without any data assimilation.

  13. 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

  14. The Ocean Surface Topography SENTINEL-6/JASON-CS Mission

    Science.gov (United States)

    Cullen, R.

    2015-12-01

    The Sentinel-6/Jason-CS mission will consist of 2 spacecraft and will be the latest in a series of ocean surface topography missions that will span nearly three decades. They follow the altimeters on- board TOPEX/Poseidon through to Jason-3 (expected March 2015). Jason-CS will continue to fulfil objectives of the reference series whilst introducing a major enhancement in capability providing the operational and science oceanographic community with the state of the art in terms of platform, measurement instrumentation design thus securing optimal operational and science data return. The programme is a part of the EC Copernicus initiative, whose objective is to support Europe's goals regarding sustainable development and global governance of the environment by providing timely and quality data, information, services and knowledge. The programme brings together: ESA for development, procurement & early orbit activities; EUMETSAT for mission management, ground segment, flight ops, contributing funding of the 1st satellite and participation in funding for the 2nd satellite; NASA for the US payload and launcher procurement in addition to funding US science opportunities; EC for funding the operations and participation in funding (with EUMETSAT) for the 2nd satellite; NOAA are expected to provide US ground stations & operations services; CNES for mission expertise and provision of the POD service. The consortium plan to procure 2 satellites with the 1st planned for launch readiness in the 1st half of 2020 with the 2nd satellite 5 years later. The first major commitment to funding was given by the ESA member states that approved the programme in June 2014 and in addition the European Commission funding is also fully secure. The design is based on a platform derived from CryoSat-2 adjusted to the specific requirements of the higher orbit. The principle payload instrument is a high precision Ku/C band radar altimeter with retrieval of geophysical parameters (surface

  15. The Ocean Surface Topography JASON-CS/SENTINEL-6 Mission

    Science.gov (United States)

    Cullen, R.; Francis, R.

    2014-12-01

    The Jason-CS/Sentinel-6 programme will consist of 2 spacecraft and will be the latest in a series of ocean surface topography missions that will span nearly three decades. They follow the altimeters on-board TOPEX/Poseidon through to Jason-3 (expected March 2015). Jason-CS will continue to fulfil objectives of the reference series whilst introducing a major enhancement in capability providing the operational and science oceanographic community with the state of the art in terms of platform, measurement instrumentation design thus securing optimal operational and science data return. The programme is a part of the EC Copernicus initiative, whose objective is to support Europe's goals regarding sustainable development and global governance of the environment by providing timely and quality data, information, services and knowledge. The programme brings together: ESA for development, procurement & early orbit activities; EUMETSAT for mission management, ground segment, flight ops, contributing funding of the 1st satellite and participation in funding for the 2nd satellite; NOAA for US payload instruments, launcher, ground stations & operations; NASA for developing the US payload, launcher procurement and funding US science; EU for funding the operations and participation in funding (with EUMETSAT) for the 2nd satellite; CNES for mission expertise and provision of POD. The consortium plan to procure 2 satellites with the 1st planned for launch readiness in the 1st half of 2020 with the 2nd satellite 5 years later. The first major commitment to funding was given by the ESA member states that approved the programme in June 2014 and in addition the European Union funding is also secure. The design will be based on a platform derived from CryoSat-2 but adjusted to the specific requirements of the higher orbit. The principle payload instrument is a high precision Ku/C band radar altimeter with retrieval of geophysical parameters (surface elevation, wind speed and SWH) from

  16. Ocean Bottom Seismograph Performance during the Cascadia Initiative

    Science.gov (United States)

    Aderhold, K.; Evers, B.

    2015-12-01

    The Ocean Bottom Seismograph Instrument Pool (OBSIP) provides instrumentation and operations support for the Cascadia Initiative community experiment. This experiment investigates geophysical processes across the Cascadia subduction zone through a combination of onshore and offshore seismic data. The recovery of Year 4 instruments in September 2015 marks the conclusion of a multi-year experiment that utilized 60 ocean-bottom seismographs (OBSs) specifically designed for the subduction zone boundary, including shallow/deep water deployments and active fisheries. The new instruments feature trawl-resistant enclosures designed by Lamont-Doherty Earth Observatory (LDEO) and Scripps Institution of Oceanography (SIO) for shallow deployment [water depth ≤ 500 m], as well as new deep-water instruments designed by Woods Hole Oceanographic Institute (WHOI). Existing OBSIP instruments were also deployed along the Blanco Transform Fault and on the Gorda Plate through complementary experiments. Stations include differential pressure gauges (DPG) and absolute pressure gauges (APG). All data collected from the Cascadia, Blanco, and Gorda deployments will be freely available through the Incorporated Research Institutions for Seismology (IRIS) Data Management Center (DMC). The Cascadia Initiative is the largest amphibious seismic experiment undertaken to date and demonstrates an effective structure for community experiments through collaborative efforts from the Cascadia Initiative Expedition Team (CIET), OBSIP (institutional instrument contributors [LDEO, SIO, WHOI] and Management Office [IRIS]), and the IRIS DMC. The successes and lessons from Cascadia are a vital resource for the development of a Subduction Zone Observatory (SZO). To guide future efforts, we investigate the quality of the Cascadia OBS data using basic metrics such as instrument recovery and more advanced metrics such as noise characteristics through power spectral density analysis. We also use this broad and

  17. 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

  18. 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

  19. 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.

  20. Ocean and laboratory observations on waves over topography

    NARCIS (Netherlands)

    Lam, F.P. A.

    2007-01-01

    This thesis addresses the observation, analysis and dynamics of waves as being trapped, generated and focused by sloping topography. ---Shelf waves with diurnal tidal frequency off Greenland--- Tidal analysis has been carried out on current measurements at a “cross-shelf” transect off Greenland at

  1. Southern Ocean Predicted Seafloor Topography Poster - MGG9

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This 36 by 48 inch full color poster is MGG Report 9. In many areas of the global ocean, the depth of the seafloor is not well known because survey lines by ships...

  2. 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

  3. Enhanced Mean Dynamic Topography And Ocean Circulation Estimation Using Goce Preliminary Mode

    DEFF Research Database (Denmark)

    Knudsen, Per; Bingham, Rory; Andersen, Ole Baltazar

    2011-01-01

    have been combined with the recent DNSC08MSS mean sea surface model to construct a global GOCE satellite-only mean dynamic topography model. At a first glance, the GOCE MDT display the well known features related to the major ocean current systems. A closer look, however, reveals that the improved...

  4. Evolution of ocean wave statistics in shallow water : Refraction and diffraction over seafloor topography

    NARCIS (Netherlands)

    Janssen, T.T.; Herbers, T.H.C.; Battjes, J.A.

    2008-01-01

    We present a stochastic model for the evolution of random ocean surface waves in coastal waters with complex seafloor topography. First, we derive a deterministic coupled-mode model based on a forward scattering approximation of the nonlinear mild slope equation; this model describes the evolution

  5. Improving NOAA's NWLON Through Enhanced Data Inputs from NASA's Ocean Surface Topography

    Science.gov (United States)

    Guest, DeNeice C.

    2010-01-01

    This report assesses the benefit of incorporating NASA's OSTM (Ocean Surface Topography Mission) altimeter data (C- and Ku-band) into NOAA's (National Oceanic and Atmospheric Administration) NWLON (National Water Level Observation Network) DSS (Decision Support System). This data will enhance the NWLON DSS by providing additional inforrnation because not all stations collect all meteorological parameters (sea-surface height, ocean tides, wave height, and wind speed over waves). OSTM will also provide data where NWLON stations are not present. OSTM will provide data on seasurface heights for determining sea-level rise and ocean circulation. Researchers and operational users currently use satellite altimeter data products with the GSFCOO NASA data model to obtain sea-surface height and ocean circulation inforrnation. Accurate and tirnely inforrnation concerning sea-level height, tide, and ocean currents is needed to irnprove coastal tidal predictions, tsunarni and storm surge warnings, and wetland restoration.

  6. Mapping of sea bottom topography over western offshore, India using TOPEX/ERS-1 altimeter data

    Digital Repository Service at National Institute of Oceanography (India)

    Mohanty, K.K.; Majumdar, T.J.; Kunte, P.D.; Srivastava, A.K.

    topography in SSH. Cross-over corrections are applied to account for the orbital error in the altimetric observation. The corrected SSH has been used as an approximation to the marine geoid. The bathymetry is related with the geoid through a convolution model...

  7. Sequential assimilation of multi-mission dynamical topography into a global finite-element ocean model

    Directory of Open Access Journals (Sweden)

    S. Skachko

    2008-12-01

    Full Text Available This study focuses on an accurate estimation of ocean circulation via assimilation of satellite measurements of ocean dynamical topography into the global finite-element ocean model (FEOM. The dynamical topography data are derived from a complex analysis of multi-mission altimetry data combined with a referenced earth geoid. The assimilation is split into two parts. First, the mean dynamic topography is adjusted. To this end an adiabatic pressure correction method is used which reduces model divergence from the real evolution. Second, a sequential assimilation technique is applied to improve the representation of thermodynamical processes by assimilating the time varying dynamic topography. A method is used according to which the temperature and salinity are updated following the vertical structure of the first baroclinic mode. It is shown that the method leads to a partially successful assimilation approach reducing the rms difference between the model and data from 16 cm to 2 cm. This improvement of the mean state is accompanied by significant improvement of temporal variability in our analysis. However, it remains suboptimal, showing a tendency in the forecast phase of returning toward a free run without data assimilation. Both the mean difference and standard deviation of the difference between the forecast and observation data are reduced as the result of assimilation.

  8. Near-inertial motions over a mid-Ocean Ridge; Effects of topography and hydrothermal plumes

    Science.gov (United States)

    Thomson, Richard E.; Roth, Sharon E.; Dymond, Jack

    1990-05-01

    We investigate the spatial structure of near-inertial motions in the vicinity of the Endeavour segment of Juan de Fuca Ridge (approximately 48°N, 129°W) in the northeast Pacific Ocean. On the basis of time series current and water property data collected from September 1984 to September 1987, near-inertial motions are ubiquitous features of the 2200-m water column, with root-mean-square (rms) current speeds comparable to those of the dominant M2 tidal currents. Within the lower 1000 m of the water column where most of the observations were obtained, near-inertial oscillations have rms current speeds of O(1 cm/s) and vertical isotherm displacements of O(10 m). The fluctuations are confined to the frequency band 0.966-1.079 f(f is the local Coriolis parameter) and have characteristic event durations of 1 week. Although the spectra of subsurface motions are dominated by the "blue-shifted" superinertial band, significant spectral peaks are found also in the subinertial and inertial frequency bands. Marked alteration of the near-inertial current amplitudes occurs over two well-defined depth zones within the study region. Within the 200-m zone immediately above the 2100-m ridge crest, current amplitudes are amplified by a factor of 1.2-1.7 because of bottom reflection and/or scattering of the downward propagating energy. Evidence that the amplification may be linked to bottom reflection rather than to scattering is provided by flattening and cross-slope rotation of the near-inertial current ellipses with increased proximity to the top of the ridge. Reflection would occur at grazing angles of less than 1° and would be associated with surface-generated waves originating at distances of over 100 km from the observational site. In contrast to the enhanced amplitudes immediately above the top of the ridge, near-inertial currents within the 1600- to 1800-m depth range undergo pronounced attenuation and frequency alteration. Amplitude attenuation is especially pronounced for

  9. Tsunami Simulation Method Assimilating Ocean Bottom Pressure Data Near a Tsunami Source Region

    Science.gov (United States)

    Tanioka, Yuichiro

    2018-02-01

    A new method was developed to reproduce the tsunami height distribution in and around the source area, at a certain time, from a large number of ocean bottom pressure sensors, without information on an earthquake source. A dense cabled observation network called S-NET, which consists of 150 ocean bottom pressure sensors, was installed recently along a wide portion of the seafloor off Kanto, Tohoku, and Hokkaido in Japan. However, in the source area, the ocean bottom pressure sensors cannot observe directly an initial ocean surface displacement. Therefore, we developed the new method. The method was tested and functioned well for a synthetic tsunami from a simple rectangular fault with an ocean bottom pressure sensor network using 10 arc-min, or 20 km, intervals. For a test case that is more realistic, ocean bottom pressure sensors with 15 arc-min intervals along the north-south direction and sensors with 30 arc-min intervals along the east-west direction were used. In the test case, the method also functioned well enough to reproduce the tsunami height field in general. These results indicated that the method could be used for tsunami early warning by estimating the tsunami height field just after a great earthquake without the need for earthquake source information.

  10. SWOT: The Surface Water and Ocean Topography Mission. Wide- Swath Altimetric Elevation on Earth

    Science.gov (United States)

    Fu, Lee-Lueng (Editor); Alsdorf, Douglas (Editor); Morrow, Rosemary; Rodriguez, Ernesto; Mognard, Nelly

    2012-01-01

    The elevation of the surface of the ocean and freshwater bodies on land holds key information on many important processes of the Earth System. The elevation of the ocean surface, called ocean surface topography, has been measured by conventional nadirlooking radar altimeter for the past two decades. The data collected have been used for the study of large-scale circulation and sea level change. However, the spatial resolution of the observations has limited the study to scales larger than about 200 km, leaving the smaller scales containing substantial kinetic energy of ocean circulation that is responsible for the flux of heat, dissolved gas and nutrients between the upper and the deep ocean. This flux is important to the understanding of the ocean's role in regulatingfuture climate change.The elevation of the water bodies on land is a key parameter required for the computation of storage and discharge of freshwater in rivers, lakes, and wetlands. Globally, the spatial and temporal variability of water storage and discharge is poorly known due to the lack of well-sampled observations. In situ networks measuring river flows are declining worldwide due to economic and political reasons. Conventional altimeter observations suffers from the complexity of multiple peaks caused by the reflections from water, vegetation canopy and rough topography, resulting in much less valid data over land than over the ocean. Another major limitation is the large inter track distance preventing good coverage of rivers and other water bodies.This document provides descriptions of a new measurement technique using radar interferometry to obtain wide-swath measurement of water elevation at high resolution over both the ocean and land. Making this type of measurement, which addresses the shortcomings of conventional altimetry in both oceanographic and hydrologic applications, is the objective of a mission concept called Surface Water and Ocean Topography (SWOT), which was recommended by

  11. A global, high-resolution data set of ice sheet topography, cavity geometry, and ocean bathymetry

    Science.gov (United States)

    Schaffer, Janin; Timmermann, Ralph; Arndt, Jan Erik; Savstrup Kristensen, Steen; Mayer, Christoph; Morlighem, Mathieu; Steinhage, Daniel

    2016-10-01

    The ocean plays an important role in modulating the mass balance of the polar ice sheets by interacting with the ice shelves in Antarctica and with the marine-terminating outlet glaciers in Greenland. Given that the flux of warm water onto the continental shelf and into the sub-ice cavities is steered by complex bathymetry, a detailed topography data set is an essential ingredient for models that address ice-ocean interaction. We followed the spirit of the global RTopo-1 data set and compiled consistent maps of global ocean bathymetry, upper and lower ice surface topographies, and global surface height on a spherical grid with now 30 arcsec grid spacing. For this new data set, called RTopo-2, we used the General Bathymetric Chart of the Oceans (GEBCO_2014) as the backbone and added the International Bathymetric Chart of the Arctic Ocean version 3 (IBCAOv3) and the International Bathymetric Chart of the Southern Ocean (IBCSO) version 1. While RTopo-1 primarily aimed at a good and consistent representation of the Antarctic ice sheet, ice shelves, and sub-ice cavities, RTopo-2 now also contains ice topographies of the Greenland ice sheet and outlet glaciers. In particular, we aimed at a good representation of the fjord and shelf bathymetry surrounding the Greenland continent. We modified data from earlier gridded products in the areas of Petermann Glacier, Hagen Bræ, and Sermilik Fjord, assuming that sub-ice and fjord bathymetries roughly follow plausible Last Glacial Maximum ice flow patterns. For the continental shelf off Northeast Greenland and the floating ice tongue of Nioghalvfjerdsfjorden Glacier at about 79° N, we incorporated a high-resolution digital bathymetry model considering original multibeam survey data for the region. Radar data for surface topographies of the floating ice tongues of Nioghalvfjerdsfjorden Glacier and Zachariæ Isstrøm have been obtained from the data centres of Technical University of Denmark (DTU), Operation Icebridge (NASA

  12. 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.

  13. A global high-resolution data set of ice sheet topography, cavity geometry and ocean bathymetry

    DEFF Research Database (Denmark)

    Schaffer, Janin; Timmermann, Ralph; Arndt, Jan Erik

    2016-01-01

    of the Southern Ocean (IBCSO) version 1. While RTopo-1 primarily aimed at a good and consistent representation of the Antarctic ice sheet, ice shelves, and sub-ice cavities, RTopo-2now also contains ice topographies of the Greenland ice sheet and outlet glaciers. In particular, we aimed at agood representation....... For the continental shelf off Northeast Greenland and the floating ice tongue of Nioghalvfjerdsfjorden Glacier at about79 N, we incorporated a high-resolution digital bathymetry model considering original multibeam survey datafor the region. Radar data for surface topographies of the floating ice tongues...... for the geometry of Getz, Abbot, andFimbul ice shelf cavities. The data set is available in full and in regional subsets in NetCDF format from thePANGAEA database at doi:10.1594/PANGAEA.856844....

  14. Investigating the Potential Impact of the Surface Water and Ocean Topography (SWOT) Altimeter on Ocean Mesoscale Prediction

    Science.gov (United States)

    Carrier, M.; Ngodock, H.; Smith, S. R.; Souopgui, I.

    2016-02-01

    NASA's Surface Water and Ocean Topography (SWOT) satellite, scheduled for launch in 2020, will provide sea surface height anomaly (SSHA) observations with a wider swath width and higher spatial resolution than current satellite altimeters. It is expected that this will help to further constrain ocean models in terms of the mesoscale circulation. In this work, this expectation is investigated by way of twin data assimilation experiments using the Navy Coastal Ocean Model Four Dimensional Variational (NCOM-4DVAR) data assimilation system using a weak constraint formulation. Here, a nature run is created from which SWOT observations are sampled, as well as along-track SSHA observations from simulated Jason-2 tracks. The simulated SWOT data has appropriate spatial coverage, resolution, and noise characteristics based on an observation-simulator program provided by the SWOT science team. The experiment is run for a three-month period during which the analysis is updated every 24 hours and each analysis is used to initialize a 96 hour forecast. The forecasts in each experiment are compared to the available nature run to determine the impact of the assimilated data. It is demonstrated here that the SWOT observations help to constrain the model mesoscale in a more consistent manner than traditional altimeter observations. The findings of this study suggest that data from SWOT may have a substantial impact on improving the ocean model analysis and forecast of mesoscale features and surface ocean transport.

  15. KARIN: The Ka-Band Radar Interferometer for the Proposed Surface Water and Ocean Topography (SWOT) Mission

    Science.gov (United States)

    Esteban-Fernandez, Daniel; Peral, Eva; McWatters, Dalia; Pollard, Brian; Rodriguez, Ernesto; Hughes, Richard

    2013-01-01

    Over the last two decades, several nadir profiling radar altimeters have provided our first global look at the ocean basin-scale circulation and the ocean mesoscale at wavelengths longer than 100 km. Due to sampling limitations, nadir altimetry is unable to resolve the small wavelength ocean mesoscale and sub-mesoscale that are responsible for the vertical mixing of ocean heat and gases and the dissipation of kinetic energy from large to small scales. The proposed Surface Water and Ocean Topography (SWOT) mission would be a partnership between NASA, CNES (Centre National d'Etudes Spaciales) and the Canadian Space Agency, and would have as one of its main goals the measurement of ocean topography with kilometer-scale spatial resolution and centimeter scale accuracy. In this paper, we provide an overview of all ocean error sources that would contribute to the SWOT mission.

  16. 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.

  17. Engaging the Applications Community of the future Surface Water and Ocean Topography (SWOT) Mission

    Science.gov (United States)

    Srinivasan, M.; Andral, A.; Dejus, M.; Hossain, F.; Peterson, C.; Beighley, E.; Pavelsky, T.; Chao, Y.; Doorn, B.; Bronner, E.; Houpert, L.

    2015-04-01

    NASA and the French space agency, CNES, with contributions from the Canadian Space Agency (CSA) and United Kingdom Space Agency (UKSA) are developing new wide swath altimetry technology that will cover most of the world's ocean and surface freshwater bodies. The proposed Surface Water and Ocean Topography (SWOT) mission will have the capability to make observations of surface water (lakes, rivers, wetland) heights and measurements of ocean surface topography with unprecedented spatial coverage, temporal sampling, and spatial resolution compared to existing technologies. These data will be useful for monitoring the hydrologic cycle, flooding, and characterizing human impacts on a changing environment. The applied science community is a key element in the success of the SWOT mission, demonstrating the high value of the science and data products in addressing societal issues and needs. The SWOT applications framework includes a working group made up of applications specialists, SWOT science team members, academics and SWOT Project members to promote applications research and engage a broad community of potential SWOT data users. A defined plan and a guide describing a program to engage early adopters in using proxies for SWOT data, including sophisticated ocean and hydrology simulators, an airborne analogue for SWOT (AirSWOT), and existing satellite datasets, are cornerstones for the program. A user survey is in development and the first user workshop was held in 2015, with annual workshops planned. The anticipated science and engineering advances that SWOT will provide can be transformed into valuable services to decision makers and civic organizations focused on addressing global disaster risk reduction initiatives and potential science-based mitigation activities for water resources challenges of the future. With the surface water measurements anticipated from SWOT, a broad range of applications can inform inland and coastal managers and marine operators of

  18. 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

  19. 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.

  20. Topography Grid

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NGDC builds and distributes high-resolution, coastal digital elevation models (DEMs) that integrate ocean bathymetry and land topography to support NOAA's mission to...

  1. 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

  2. A Novel Low-cost, Ka-band, High Altitude, Multi-Baseline Unmanned Aerial Vehicle Sensor for Surface Water Ocean Topography, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The NRC Decadal Survey recommended the Surface Water Ocean Topography (SWOT) satellite mission to address terrestrial fresh water hydrology and physical oceanography...

  3. Measuring Zonal Transport Variability of the Antarctic Circumpolar Current Using GRACE Ocean Bottom Pressure

    Science.gov (United States)

    Makowski, J.; Chambers, D. P.; Bonin, J. A.

    2012-12-01

    Previous studies have suggested that ocean bottom pressure (OBP) can be used to measure the transport variability of the Antarctic Circumpolar Current (ACC). Using OBP data from the JPL ECCO model and the Gravity Recovery and Climate Experiment (GRACE), we examine the zonal transport variability of the ACC integrated between the major fronts between 2003-2010. The JPL ECCO data are used to determine average front positions for the time period studies, as well as where transport is mainly zonal. Statistical analysis will be conducted to determine the uncertainty of the GRACE observations using a simulated data set. We will also begin looking at low frequency changes and how coherent transport variability is from region to region of the ACC. Correlations with bottom pressure south of the ACC and the average basin transports will also be calculated to determine the probability of using bottom pressure south of the ACC as a means for describing the ACC dynamics and transport.

  4. 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.

  5. Flight dynamics facility operational orbit determination support for the ocean topography experiment

    Science.gov (United States)

    Bolvin, D. T.; Schanzle, A. F.; Samii, M. V.; Doll, C. E.

    1991-01-01

    The Ocean Topography Experiment (TOPEX/POSEIDON) mission is designed to determine the topography of the Earth's sea surface across a 3 yr period, beginning with launch in June 1992. The Goddard Space Flight Center Dynamics Facility has the capability to operationally receive and process Tracking and Data Relay Satellite System (TDRSS) tracking data. Because these data will be used to support orbit determination (OD) aspects of the TOPEX mission, the Dynamics Facility was designated to perform TOPEX operational OD. The scientific data require stringent OD accuracy in navigating the TOPEX spacecraft. The OD accuracy requirements fall into two categories: (1) on orbit free flight; and (2) maneuver. The maneuver OD accuracy requirements are of two types; premaneuver planning and postmaneuver evaluation. Analysis using the Orbit Determination Error Analysis System (ODEAS) covariance software has shown that, during the first postlaunch mission phase of the TOPEX mission, some postmaneuver evaluation OD accuracy requirements cannot be met. ODEAS results also show that the most difficult requirements to meet are those that determine the change in the components of velocity for postmaneuver evaluation.

  6. 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.

  7. GNSS reflectometry aboard the International Space Station: phase-altimetry simulation to detect ocean topography anomalies

    Science.gov (United States)

    Semmling, Maximilian; Leister, Vera; Saynisch, Jan; Zus, Florian; Wickert, Jens

    2016-04-01

    An ocean altimetry experiment using Earth reflected GNSS signals has been proposed to the European Space Agency (ESA). It is part of the GNSS Reflectometry Radio Occultation Scatterometry (GEROS) mission that is planned aboard the International Space Station (ISS). Altimetric simulations are presented that examine the detection of ocean topography anomalies assuming GNSS phase delay observations. Such delay measurements are well established for positioning and are possible due to a sufficient synchronization of GNSS receiver and transmitter. For altimetric purpose delays of Earth reflected GNSS signals can be observed similar to radar altimeter signals. The advantage of GNSS is the synchronized separation of transmitter and receiver that allow a significantly increased number of observation per receiver due to more than 70 GNSS transmitters currently in orbit. The altimetric concept has already been applied successfully to flight data recorded over the Mediterranean Sea. The presented altimetric simulation considers anomalies in the Agulhas current region which are obtained from the Region Ocean Model System (ROMS). Suitable reflection events in an elevation range between 3° and 30° last about 10min with ground track's length >3000km. Typical along-track footprints (1s signal integration time) have a length of about 5km. The reflection's Fresnel zone limits the footprint of coherent observations to a major axis extention between 1 to 6km dependent on the elevation. The altimetric performance depends on the signal-to-noise ratio (SNR) of the reflection. Simulation results show that precision is better than 10cm for SNR of 30dB. Whereas, it is worse than 0.5m if SNR goes down to 10dB. Precision, in general, improves towards higher elevation angles. Critical biases are introduced by atmospheric and ionospheric refraction. Corresponding correction strategies are still under investigation.

  8. 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.

  9. Near 7-day response of ocean bottom pressure to atmospheric surface pressure and winds in the northern South China Sea

    Science.gov (United States)

    Zhang, Kun; Zhu, Xiao-Hua; Zhao, Ruixiang

    2018-02-01

    Ocean bottom pressures, observed by five pressure-recording inverted echo sounders (PIESs) from October 2012 to July 2014, exhibit strong near 7-day variability in the northern South China Sea (SCS) where long-term in situ bottom pressure observations are quite sparse. This variability was strongest in October 2013 during the near two years observation period. By joint analysis with European Center for Medium-Range Weather Forecasts (ECMWF) data, it is shown that the near 7-day ocean bottom pressure variability is closely related to the local atmospheric surface pressure and winds. Within a period band near 7 days, there are high coherences, exceeding 95% significance level, of observed ocean bottom pressure with local atmospheric surface pressure and with both zonal and meridional components of the wind. Ekman pumping/suction caused by the meridional component of the wind in particular, is suggested as one driving mechanism. A Kelvin wave response to the near 7-day oscillation would propagate down along the continental slope, observed at the Qui Nhon in the Vietnam. By multiple and partial coherence analyses, we find that local atmospheric surface pressure and Ekman pumping/suction show nearly equal influence on ocean bottom pressure variability at near 7-day periods. A schematic diagram representing an idealized model gives us a possible mechanism to explain the relationship between ocean bottom pressure and local atmospheric forcing at near 7-day periods in the northern SCS.

  10. How well will the Surface Water and Ocean Topography (SWOT) mission observe global reservoirs?

    Science.gov (United States)

    Solander, Kurt C.; Reager, John T.; Famiglietti, James S.

    2016-03-01

    Accurate observations of global reservoir storage are critical to understand the availability of managed water resources. By enabling estimates of surface water area and height for reservoir sizes exceeding 250 m2 at a maximum repeat orbit of up to 21 days, the NASA Surface Water and Ocean Topography (SWOT) satellite mission (anticipated launch date 2020) is expected to greatly improve upon existing reservoir monitoring capabilities. It is thus essential that spatial and temporal measurement uncertainty for water bodies is known a priori to maximize the utility of SWOT observations as the data are acquired. In this study, we evaluate SWOT reservoir observations using a three-pronged approach that assesses temporal aliasing, errors due to specific reservoir spatial properties, and SWOT performance over actual reservoirs using a combination of in situ and simulated reservoir observations from the SWOTsim instrument simulator. Results indicate temporal errors to be less than 5% for the smallest reservoir sizes (100 km2). Surface area and height errors were found to be minimal (area SWOT, this study will be have important implications for future applications of SWOT reservoir measurements in global monitoring systems and models.

  11. 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

  12. The Sentinel-3 Surface Topography Mission (S-3 STM): Level 2 SAR Ocean Retracker

    Science.gov (United States)

    Dinardo, S.; Lucas, B.; Benveniste, J.

    2015-12-01

    The SRAL Radar Altimeter, on board of the ESA Mission Sentinel-3 (S-3), has the capacity to operate either in the Pulse-Limited Mode (also known as LRM) or in the novel Synthetic Aperture Radar (SAR) mode. Thanks to the initial results from SAR Altimetry obtained exploiting CryoSat-2 data, lately the interest by the scientific community in this new technology has significantly increased and consequently the definition of accurate processing methodologies (along with validation strategies) has now assumed a capital importance. In this paper, we present the algorithm proposed to retrieve from S-3 STM SAR return waveforms the standard ocean geophysical parameters (ocean topography, wave height and sigma nought) and the validation results that have been so far achieved exploiting the CryoSat-2 data as well as the simulated data. The inversion method (retracking) to extract from the return waveform the geophysical information is a curve best-fitting scheme based on the bounded Levenberg-Marquardt Least-Squares Estimation Method (LEVMAR-LSE). The S-3 STM SAR Ocean retracking algorithm adopts, as return waveform’s model, the “SAMOSA” model [Ray et al, 2014], named after the R&D project SAMOSA (led by Satoc and funded by ESA), in which it has been initially developed. The SAMOSA model is a physically-based model that offers a complete description of a SAR Altimeter return waveform from ocean surface, expressed in the form of maps of reflected power in Delay-Doppler space (also known as stack) or expressed as multilooked echoes. SAMOSA is able to account for an elliptical antenna pattern, mispointing errors in roll and yaw, surface scattering pattern, non-linear ocean wave statistics and spherical Earth surface effects. In spite of its truly comprehensive character, the SAMOSA model comes with a compact analytical formulation expressed in term of Modified Bessel functions. The specifications of the retracking algorithm have been gathered in a technical document (DPM

  13. Flow- topography Interactions in the Vicinity of a Deep Ocean Island and a Ridge

    Science.gov (United States)

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Flow- topography Interactions in the Vicinity of a Deep...flow around abrupt topography in operational Navy models. RELATED PROJECTS NRL FY17 6.2 New Start proposal (pending proposal), titled...Predictability of Flow Interacting with Abrupt Topography (FIAT)”; lead PI: Ana Rice, NRL-SSC. The objective of FIAT is to use observations to develop Navy

  14. Ocean bottom pressure observations near the source of the 2011 Tohoku earthquake

    Science.gov (United States)

    Inazu, D.; Hino, R.; Suzuki, S.; Osada, Y.; Ohta, Y.; Iinuma, T.; Tsushima, H.; Ito, Y.; Kido, M.; Fujimoto, H.

    2011-12-01

    A Mw9.0 earthquake occurred off Miyagi, northeast Japan, on 11 March 2011 (hereafter mainshock). An earthquake of M7.3, considered to be the largest foreshock of the mainshock, occurred on 9 March 2011 near the mainshock hypocenter. A suite of seismic and geodetic variations related to these earthquakes was observed by autonomous, ocean bottom pressure (OBP) gauges at multiple sites (4 sites at present) near the sources within a distance of about 100 km. This paper presents the OBP records with a focus on the earthquakes. Thanks to correcting tides, instrumental drifts, and non-tidal oceanic variations, we can detect OBP signals of tsunamis and vertical seafloor deformation of the order of centimeters with timescales of less than months. In the following we review the detected signals and how to correct the OBP data. The coseismic seafloor displacement and the tsunami accompanied by the mainshock were of the order of meters and large enough to be distinctly identified (Ito et al., 2011, GRL). Co- and post-seismic seafloor displacement and tsunami accompanied by the foreshock were of the order of centimeters which is difficult to be identified from the raw OBP records. The first evident pulses of these tsunamis in the deep sea have durations (periods) of ~20 minutes and ~10 minutes, for the mainshock and the foreshock, respectively. Amounts of seafloor vertical displacement due to post-mainshock deformation reached a few tens of centimeters in two months. It is worth noting that elevation and depression of seafloor were detected at rates of a couple of centimeters in a day after the largest foreshock. The seafloor displacement of centimeters between the largest foreshock and the mainshock can be reasonably identified after correcting non-tidal oceanic variations. The oceanic variations are simulated by a barotropic ocean model driven by atmospheric disturbances (Inazu et al., 2011, Ann. Rep. Earth Simulator Center 2011). The model enables residual OBP time series of

  15. Dynamic ocean topography from CryoSat-2: examining recent changes in ice-ocean stress and advancing a theory for Beaufort Gyre stabilization

    Science.gov (United States)

    Dewey, S.; Morison, J.; Kwok, R.; Dickinson, S.; Morison, D.; Andersen, R.

    2017-12-01

    Model and sparse observational evidence has shown the ocean current speed in the Beaufort Gyre to have increased and recently stabilized. However, full-basin altimetric observations of dynamic ocean topography (DOT) and ocean surface currents have yet to be applied to the dynamics of gyre stabilization. DOT fields from retracked CryoSat-2 retrievals in Arctic Ocean leads have enabled us to calculate 2-month average ocean geostrophic currents. These currents are crucial to accurately computing ice-ocean stress, especially because they have accelerated so that their speed rivals that of the overlying sea ice. Given these observations, we can shift our view of the Beaufort Gyre as a system in which the wind drives the ice and the ice drives a passive ocean to a system with the following feedback: After initial input of energy by wind, ice velocity decreases due to water drag and internal ice stress and the ocean drives the ice, reversing Ekman pumping and decelerating the gyre. This reversal changes the system from a persistently convergent regime to one in which freshwater is released from the gyre and doming of the gyre decreases, without any change in long-term average wind stress curl. Through these processes, the ice-ocean stress provides a key feedback in Beaufort Gyre stabilization.

  16. Automated River Reach Definition Strategies: Applications for the Surface Water and Ocean Topography Mission

    Science.gov (United States)

    Frasson, Renato Prata de Moraes; Wei, Rui; Durand, Michael; Minear, J. Toby; Domeneghetti, Alessio; Schumann, Guy; Williams, Brent A.; Rodriguez, Ernesto; Picamilh, Christophe; Lion, Christine; Pavelsky, Tamlin; Garambois, Pierre-André

    2017-10-01

    The upcoming Surface Water and Ocean Topography (SWOT) mission will measure water surface heights and widths for rivers wider than 100 m. At its native resolution, SWOT height errors are expected to be on the order of meters, which prevent the calculation of water surface slopes and the use of slope-dependent discharge equations. To mitigate height and width errors, the high-resolution measurements will be grouped into reaches (˜5 to 15 km), where slope and discharge are estimated. We describe three automated river segmentation strategies for defining optimum reaches for discharge estimation: (1) arbitrary lengths, (2) identification of hydraulic controls, and (3) sinuosity. We test our methodologies on 9 and 14 simulated SWOT overpasses over the Sacramento and the Po Rivers, respectively, which we compare against hydraulic models of each river. Our results show that generally, height, width, and slope errors decrease with increasing reach length. However, the hydraulic controls and the sinuosity methods led to better slopes and often height errors that were either smaller or comparable to those of arbitrary reaches of compatible sizes. Estimated discharge errors caused by the propagation of height, width, and slope errors through the discharge equation were often smaller for sinuosity (on average 8.5% for the Sacramento and 6.9% for the Po) and hydraulic control (Sacramento: 7.3% and Po: 5.9%) reaches than for arbitrary reaches of comparable lengths (Sacramento: 8.6% and Po: 7.8%). This analysis suggests that reach definition methods that preserve the hydraulic properties of the river network may lead to better discharge estimates.

  17. Diagnostic model of 3-D circulation in the Arabian Sea and western equatorial Indian Ocean: Results of monthly mean sea surface topography

    Digital Repository Service at National Institute of Oceanography (India)

    Bahulayan, N.; Shaji, C.

    A three-dimensional diagnostic model has been developed to compute the monthly mean circulation and sea surface topography in the Western Tropical Indian Ocean north of 20 degrees S and west of 80 degrees E. The diagnostic model equations...

  18. A Novel Low-cost, Ka-band, High Altitude, Multi-Baseline Unmanned Aerial Vehicle Sensor for Surface Water Ocean Topography, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal presents the Ka-band SWOT Phenomenology Airborne Radar (KaSPAR) to support the surface water ocean topography (SWOT) mission for science and algorithm...

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. Noise Reduction of Ocean-Bottom Pressure Data Toward Real-Time Tsunami Forecasting

    Science.gov (United States)

    Tsushima, H.; Hino, R.

    2008-12-01

    We discuss a method of noise reduction of ocean-bottom pressure data to be fed into the near-field tsunami forecasting scheme proposed by Tsushima et al. [2008a]. In their scheme, the pressure data is processed in real time as follows: (1) removing ocean tide components by subtracting the sea-level variation computed from a theoretical tide model, (2) applying low-pass digital filter to remove high-frequency fluctuation due to seismic waves, and (3) removing DC-offset and linear-trend component to determine a baseline of relative sea level. However, it turns out this simple method is not always successful in extracting tsunami waveforms from the data, when the observed amplitude is ~1cm. For disaster mitigation, accurate forecasting of small tsunamis is important as well as large tsunamis. Since small tsunami events occur frequently, successful tsunami forecasting of those events are critical to obtain public reliance upon tsunami warnings. As a test case, we applied the data-processing described above to the bottom pressure records containing tsunami with amplitude less than 1 cm which was generated by the 2003 Off-Fukushima earthquake occurring in the Japan Trench subduction zone. The observed pressure variation due to the ocean tide is well explained by the calculated tide signals from NAO99Jb model [Matsumoto et al., 2000]. However, the tide components estimated by BAYTAP-G [Tamura et al., 1991] from the pressure data is more appropriate for predicting and removing the ocean tide signals. In the pressure data after removing the tide variations, there remain pressure fluctuations with frequencies ranging from about 0.1 to 1 mHz and with amplitudes around ~10 cm. These fluctuations distort the estimation of zero-level and linear trend to define relative sea-level variation, which is treated as tsunami waveform in the subsequent analysis. Since the linear trend is estimated from the data prior to the origin time of the earthquake, an artificial linear trend is

  4. Ocean Surface Topography Mission (OSTM) /Jason-3: Orbital Information, 2015- (NODC Accession 0122598)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Jason-3 is the fourth mission in U.S.-European series of satellite missions that measure the height of the ocean surface. Scheduled to launch in 2015, the mission...

  5. Ocean Surface Topography Mission (OSTM) /Jason-2: Level-2 Geophysical Data Records (GDR) (NODC Accession 0043269)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — OSTM/JASON-2 is a follow-on mission continuing the TOPEX/Poseidon and Jason-1, and is designed to ensure continuity of high quality measurements for ocean science...

  6. Ocean Surface Topography Mission (OSTM) /Jason-3: Telemetry, 2015- (NODC Accession 0122599)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Jason-3 is the fourth mission in U.S.-European series of satellite missions that measure the height of the ocean surface. Scheduled to launch in 2015, the mission...

  7. Ocean Surface Topography Mission (OSTM) /Jason-2 Data Collection, 2008-present (NODC Accession 0118277)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — OSTM/JASON-2 is a follow-on mission continuing the TOPEX/Poseidon and Jason-1, and is designed to ensure continuity of high quality measurements for ocean science...

  8. Ocean Surface Topography Mission (OSTM) /Jason-3: Auxiliary Files, 2015- (NODC Accession 0122597)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Jason-3 is the fourth mission in U.S.-European series of satellite missions that measure the height of the ocean surface. Scheduled to launch in 2015, the mission...

  9. Ocean Surface Topography Mission (OSTM) /Jason-3: Ancillary Files, 2015- (NCEI Accession 0122596)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Jason-3 is the fourth mission in U.S.-European series of satellite missions that measure the height of the ocean surface. Scheduled to launch in 2015, the mission...

  10. Solutions Network Formulation Report: Improving NOAA's PORTS(R) Through Enhanced Data Inputs from NASA's Ocean Surface Topography Mission

    Science.gov (United States)

    Guest, DeNeice

    2007-01-01

    The Nation uses water-level data for a variety of practical purposes, including nautical charting, maritime navigation, hydrography, coastal engineering, and tsunami and storm surge warnings. Long-term applications include marine boundary determinations, tidal predictions, sea-level trend monitoring, oceanographic research, and climate research. Accurate and timely information concerning sea-level height, tide, and ocean current is needed to understand their impact on coastal management, disaster management, and public health. Satellite altimeter data products are currently used by hundreds of researchers and operational users to monitor ocean circulation and to improve scientists understanding of the role of the oceans in climate and weather. The NOAA (National Oceanic and Atmospheric Administration) National Ocean Service has been monitoring sea-level variations for many years. NOAA s PORTS (Physical Oceanographic Real-Time System) DST (decision support tool), managed by the Center for Operational Oceanographic Products and Services, supports safe and cost-efficient navigation by providing ship masters and pilots with accurate real-time information required to avoid groundings and collisions. This report assesses the capacity of NASA s satellite altimeter data to meet societal decision support needs through incorporation into NOAA s PORTS. NASA has a long heritage of collecting data for ocean research, including its current Terra and Aqua missions. Numerous other missions provide additional important information for coastal management issues, and data collection will continue in the coming decade with such missions as the OSTM (Ocean Surface Topography Mission). OSTM will provide data on sea-surface heights for determining ocean circulation, climate change, and sea-level rise. We suggest that NASA incorporate OSTM altimeter data (C- and Ku-band) into NOAA s PORTS DST in support of NASA s Coastal Management National Application with secondary support to the

  11. 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

  12. A global mean ocean circulation estimation using goce gravity models - the DTU12MDT mean dynamic topography model

    DEFF Research Database (Denmark)

    Knudsen, Per; Andersen, Ole Baltazar

    2012-01-01

    The Gravity and Ocean Circulation Experiment - GOCE satellite mission measure the Earth gravity field with unprecedented accuracy leading to substantial improvements in the modelling of the ocean circulation and transport. In this study of the performance of GOCE, a newer gravity model have been...... combined with the DTU10MSS mean sea surface model to construct a global mean dynamic topography model named DTU10MDT. The results of preliminary analyses using preliminary GOCE gravity models clearly demonstrated the potential of GOCE mission. Both the resolution and the estimation of the surface currents...... have been improved significantly compared to results obtained using pre-GOCE gravity field models. The results of this study show that geostrophic surface currents associated with the mean circulation have been further improved and that currents having speeds down to 5 cm/s have been recovered....

  13. The DTU12MDT global mean dynamic topography and ocean circulation model

    DEFF Research Database (Denmark)

    Knudsen, Per; Andersen, Ole B.

    2013-01-01

    combined with the DTU10MSS mean sea surface model to construct a global mean dynamic topography model named DTU10MDT. The results of analyses clearly demonstrated the value of the GOCE mission. Both the resolution and the estimation of the surface currents have been improved significantly compared...

  14. 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

  15. Ocean Surface Topography Mission (OSTM) /Jason-3 Data Collection, 2015- (NCEI Accession 0118278)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — OSTM/JASON-3 is a follow-on mission continuing the TOPEX/Poseidon and Jason-1/2, and is designed to ensure continuity of high quality measurements for ocean science...

  16. 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

  17. BedMachine v3: Complete Bed Topography and Ocean Bathymetry Mapping of Greenland From Multibeam Echo Sounding Combined With Mass Conservation

    DEFF Research Database (Denmark)

    Morlighem, M.; Williams, C. N.; Rignot, E.

    2017-01-01

    Greenland's bed topography is a primary control on ice flow, grounding line migration, calving dynamics, and subglacial drainage. Moreover, fjord bathymetry regulates the penetration of warm Atlantic water (AW) that rapidly melts and undercuts Greenland's marine‐terminating glaciers. Here we...... present a new compilation of Greenland bed topography that assimilates seafloor bathymetry and ice thickness data through a mass conservation approach. A new 150 m horizontal resolution bed topography/bathymetric map of Greenland is constructed with seamless transitions at the ice/ocean interface...

  18. 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

  19. Ocean Surface Topography Mission (OSTM) /Jason-2: Ancillary Files (NODC Accession 0044982)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This accession contains the data descriptions for the OSTM/Jason-2 Ancillary data files, which is served through the NOAA/NESDIS Comprehensive Large Array-data...

  20. Ocean Surface Topography Mission (OSTM) /Jason-2: Orbital Information (NODC Accession 0044985)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This accession contains the descriptions for the OSTM/Jason-2 orbital information, which is served through the NOAA/NESDIS Comprehensive Large Array-data Stewardship...

  1. Ocean Surface Topography Mission (OSTM) /Jason-2: Telemetry (NODC Accession 0044986)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This accession contains the data descriptions for the OSTM/Jason-2 Telemetry data, which is served through the NOAA/NESDIS Comprehensive Large Array-data Stewardship...

  2. Ocean Surface Topography Mission (OSTM) /Jason-2: Auxiliary Files (NODC Accession 0044983)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This accession contains the data descriptions for the OSTM/Jason-2 Auxiliary data files, which is served through the NOAA/NESDIS Comprehensive Large Array-data...

  3. Ocean Surface Topography Mission (OSTM) - Jason-2 and Jason-3: Data Documentation Records (NCEI Accession 0118276)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — OSTM/JASON-2 and Jason-3 (scheduled for launch in 2015) are follow-on missions continuing the TOPEX/Poseidon and Jason-1 missions, and are designed to ensure...

  4. 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

  5. Expected Performance of the Upcoming Surface Water and Ocean Topography Mission Measurements of River Height, Width, and Slope

    Science.gov (United States)

    Wei, R.; Frasson, R. P. M.; Williams, B. A.; Rodriguez, E.; Pavelsky, T.; Altenau, E. H.; Durand, M. T.

    2017-12-01

    The upcoming Surface Water and Ocean Topography (SWOT) mission will measure river widths and water surface elevations of rivers wider than 100 m. In preparation for the SWOT mission, the Jet Propulsion Laboratory built the SWOT hydrology simulator with the intent of generating synthetic SWOT overpasses over rivers with realistic error characteristics. These synthetic overpasses can be used to guide the design of processing methods and data products, as well as develop data assimilation techniques that will incorporate the future SWOT data into hydraulic and hydrologic models as soon as the satellite becomes operational. SWOT simulator uses as inputs water depth, river bathymetry, and the surrounding terrain digital elevation model to create simulated interferograms of the study area. Next, the simulator emulates the anticipated processing of SWOT data by attempting to geolocate and classify the radar returns. The resulting cloud of points include information on water surface elevation, pixel area, and surface classification (land vs water). Finally, we process the pixel clouds by grouping pixels into equally spaced nodes located at the river centerline. This study applies the SWOT simulator to six different rivers: Sacramento River, Tanana River, Saint Lawrence River, Platte River, Po River, and Amazon River. This collection of rivers covers a range of size, slope, and planform complexity with the intent of evaluating the impact of river width, slope, planform complexity, and surrounding topography on the anticipated SWOT height, width, and slope error characteristics.

  6. Bottom-pressure observations of deep-sea internal hydrostatic and non-hydrostatic motions

    NARCIS (Netherlands)

    van Haren, H.

    2013-01-01

    In the ocean, sloping bottom topography is important for the generation and dissipation of internal waves. Here, the transition of such waves to turbulence is demonstrated using an accurate bottom-pressure sensor that was moored with an acoustic Doppler current profiler and high-resolution

  7. Diffusive boundary layers over varying topography

    KAUST Repository

    Dell, R. W.

    2015-03-25

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

  8. A global mean dynamic topography and ocean circulation estimation using a preliminary GOCE gravity model

    DEFF Research Database (Denmark)

    Knudsen, Per; Bingham, R.; Andersen, Ole Baltazar

    2011-01-01

    The Gravity and steady-state Ocean Circulation Explorer (GOCE) satellite mission measures Earth’s gravity field with an unprecedented accuracy at short spatial scales. In doing so, it promises to significantly advance our ability to determine the ocean’s general circulation. In this study, an ini...

  9. Seabed topography and distribution of manganese nodules in the Central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.; Kodagali, V.N.

    in number in all the topographic environments. Mn/Fe ratio was least (2.2) for nodules from hill taps whereas it was maximum for those from the plains (4.4). Cu+Ni+Co compositioin varied antipathetically with nodule abundance in the Central Indian Ocean....

  10. 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

  11. 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

  12. 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

  13. 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

  14. Extracting Hydrologic Understanding from the Unique Space-time Sampling of the Surface Water and Ocean Topography (SWOT) Mission

    Science.gov (United States)

    Nickles, C.; Zhao, Y.; Beighley, E.; Durand, M. T.; David, C. H.; Lee, H.

    2017-12-01

    The Surface Water and Ocean Topography (SWOT) satellite mission is jointly developed by NASA, the French space agency (CNES), with participation from the Canadian and UK space agencies to serve both the hydrology and oceanography communities. The SWOT mission will sample global surface water extents and elevations (lakes/reservoirs, rivers, estuaries, oceans, sea and land ice) at a finer spatial resolution than is currently possible enabling hydrologic discovery, model advancements and new applications that are not currently possible or likely even conceivable. Although the mission will provide global cover, analysis and interpolation of the data generated from the irregular space/time sampling represents a significant challenge. In this study, we explore the applicability of the unique space/time sampling for understanding river discharge dynamics throughout the Ohio River Basin. River network topology, SWOT sampling (i.e., orbit and identified SWOT river reaches) and spatial interpolation concepts are used to quantify the fraction of effective sampling of river reaches each day of the three-year mission. Streamflow statistics for SWOT generated river discharge time series are compared to continuous daily river discharge series. Relationships are presented to transform SWOT generated streamflow statistics to equivalent continuous daily discharge time series statistics intended to support hydrologic applications using low-flow and annual flow duration statistics.

  15. 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

  16. 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

  17. Lithospheric structure of southern Indian shield and adjoining oceans: integrated modelling of topography, gravity, geoid and heat flow data

    Science.gov (United States)

    Kumar, Niraj; Zeyen, H.; Singh, A. P.; Singh, B.

    2013-07-01

    For the present 2-D lithospheric density modelling, we selected three geotransects of more than 1000 km in length each crossing the southern Indian shield, south of 16°N, in N-S and E-W directions. The model is based on the assumption of local isostatic equilibrium and is constrained by the topography, gravity and geoid anomalies, by geothermal data, and where available by seismic data. Our integrated modelling approach reveals a crustal configuration with the Moho depth varying from ˜40 km beneath the Dharwar Craton, and ˜39 km beneath the Southern Granulite Terrane to about 15-20 km beneath the adjoining oceans. The lithospheric thickness varies significantly along the three profiles from ˜70-100 km under the adjoining oceans to ˜130-135 km under the southern block of Southern Granulite Terrane including Sri Lanka and increasing gradually to ˜165-180 km beneath the northern block of Southern Granulite Terrane and the Dharwar Craton. This step-like lithosphere-asthenosphere boundary (LAB) structure indicates a normal lithospheric thickness beneath the adjoining oceans, the northern block of Southern Granulite Terrane and the Dharwar Craton. The thin lithosphere below the southern block of Southern Granulite Terrane including Sri Lanka is, however, atypical considering its age. Our results suggest that the southern Indian shield as a whole cannot be supported isostatically only by thickened crust; a thin and hot lithosphere beneath the southern block of Southern Granulite Terrane including Sri Lanka is required to explain the high topography, gravity, geoid and crustal temperatures. The widespread thermal perturbation during Pan-African (550 Ma) metamorphism and the breakup of Gondwana during late Cretaceous are proposed as twin cause mechanism for the stretching and/or convective removal of the lower part of lithospheric mantle and its replacement by hotter and lighter asthenosphere in the southern block of Southern Granulite Terrane including Sri Lanka

  18. CALCULATION AND ANALYSIS OF THE EXPECTED IMPACT OF THE HYDROTECHNICAL CONSTRUCTION ON THE ENVIRONMENTAL CONDITION IN THE WATER AREA AND BOTTOM TOPOGRAPHY IN CASE OF THE CONSTRUCTION OF THE APPROACH CHANNEL TO THE SABETTA PORT

    Directory of Open Access Journals (Sweden)

    Vvedensky Alexei Rostislavovich

    2017-05-01

    Full Text Available The estimation of changes in the ecological situation and bottom topography in the Ob Bay, which may be caused by the construction of the approach channel to the port of Sabetta, was carried out with the help of the developed complex of numerical models. Particular attention was paid to the study of the displacement of the boundaries of the saline water expansion and the sediment accumulation in the channel area. It is established that the possible influence of the approach channel on the hydrologic-hydrochemical characteristics is less than their natural interannual and seasonal variability in the investigated water area. The change in the bottom topography after the construction of the approach channel does not entail a significant change in the regime of hydrologic-hydrochemical parameters of the Ob Bay and, consequently, should not affect the biocenosis. The calculated changes in the bottom topography in the approach channel area will not exceed 2 % of the depth per year and will not become a significant obstacle to the reliable and uninterrupted operation of the Sabetta port.

  19. Ocean-bottom pressure changes above a fault area for tsunami excitation and propagation observed by a submarine dense network

    Science.gov (United States)

    Yomogida, K.; Saito, T.

    2017-12-01

    Conventional tsunami excitation and propagation have been formulated by incompressible fluid with velocity components. This approach is valid in most cases because we usually analyze tunamis as "long gravity waves" excited by submarine earthquakes. Newly developed ocean-bottom tsunami networks such as S-net and DONET have dramatically changed the above situation for the following two reasons: (1) tsunami propagations are now directly observed in a 2-D array manner without being suffered by complex "site effects" of sea shore, and (2) initial tsunami features can be directly detected just above a fault area. Removing the incompressibility assumption of sea water, we have formulated a new representation of tsunami excitation based on not velocity but displacement components. As a result, not only dynamics but static term (i.e., the component of zero frequency) can be naturally introduced, which is important for the pressure observed on the ocean floor, which ocean-bottom tsunami stations are going to record. The acceleration on the ocean floor should be combined with the conventional tsunami height (that is, the deformation of the sea level above a given station) in the measurement of ocean-bottom pressure although the acceleration exists only during fault motions in time. The M7.2 Off Fukushima earthquake on 22 November 2016 was the first event that excited large tsunamis within the territory of S-net stations. The propagation of tsunamis is found to be highly non-uniform, because of the strong velocity (i.e., sea depth) gradient perpendicular to the axis of Japan Trench. The earthquake was located in a shallow sea close to the coast, so that all the tsunami energy is reflected by the trench region of high velocity. Tsunami records (pressure gauges) within its fault area recorded clear slow motions of tsunamis (i.e., sea level changes) but also large high-frequency signals, as predicted by our theoretical result. That is, it may be difficult to extract tsunami

  20. Inferring cetacean population densities from the absolute dynamic topography of the ocean in a hierarchical Bayesian framework.

    Directory of Open Access Journals (Sweden)

    Mario A Pardo

    Full Text Available We inferred the population densities of blue whales (Balaenoptera musculus and short-beaked common dolphins (Delphinus delphis in the Northeast Pacific Ocean as functions of the water-column's physical structure by implementing hierarchical models in a Bayesian framework. This approach allowed us to propagate the uncertainty of the field observations into the inference of species-habitat relationships and to generate spatially explicit population density predictions with reduced effects of sampling heterogeneity. Our hypothesis was that the large-scale spatial distributions of these two cetacean species respond primarily to ecological processes resulting from shoaling and outcropping of the pycnocline in regions of wind-forced upwelling and eddy-like circulation. Physically, these processes affect the thermodynamic balance of the water column, decreasing its volume and thus the height of the absolute dynamic topography (ADT. Biologically, they lead to elevated primary productivity and persistent aggregation of low-trophic-level prey. Unlike other remotely sensed variables, ADT provides information about the structure of the entire water column and it is also routinely measured at high spatial-temporal resolution by satellite altimeters with uniform global coverage. Our models provide spatially explicit population density predictions for both species, even in areas where the pycnocline shoals but does not outcrop (e.g. the Costa Rica Dome and the North Equatorial Countercurrent thermocline ridge. Interannual variations in distribution during El Niño anomalies suggest that the population density of both species decreases dramatically in the Equatorial Cold Tongue and the Costa Rica Dome, and that their distributions retract to particular areas that remain productive, such as the more oceanic waters in the central California Current System, the northern Gulf of California, the North Equatorial Countercurrent thermocline ridge, and the more

  1. BedMachine v3: Complete Bed Topography and Ocean Bathymetry Mapping of Greenland From Multibeam Echo Sounding Combined With Mass Conservation

    DEFF Research Database (Denmark)

    Morlighem, M.; Williams, C. N.; Rignot, E.

    2017-01-01

    Greenland's bed topography is a primary control on ice flow, grounding line migration, calving dynamics, and subglacial drainage. Moreover, fjord bathymetry regulates the penetration of warm Atlantic water (AW) that rapidly melts and undercuts Greenland's marine‐terminating glaciers. Here we...... present a new compilation of Greenland bed topography that assimilates seafloor bathymetry and ice thickness data through a mass conservation approach. A new 150 m horizontal resolution bed topography/bathymetric map of Greenland is constructed with seamless transitions at the ice/ocean interface......, yielding major improvements over previous data sets, particularly in the marine‐terminating sectors of northwest and southeast Greenland. Our map reveals that the total sea level potential of the Greenland ice sheet is 7.42 ± 0.05 m, which is 7 cm greater than previous estimates. Furthermore, it explains...

  2. BedMachine v3: Complete Bed Topography and Ocean Bathymetry Mapping of Greenland From Multibeam Echo Sounding Combined With Mass Conservation

    DEFF Research Database (Denmark)

    Morlighem, M.; Williams, C. N.; Rignot, E.

    2017-01-01

    Greenland's bed topography is a primary control on ice flow, grounding line migration, calving dynamics, and subglacial drainage. Moreover, fjord bathymetry regulates the penetration of warm Atlantic water (AW) that rapidly melts and undercuts Greenland's marine‐terminating glaciers. Here we...... recent calving front response of numerous outlet glaciers and reveals new pathways by which AW can access glaciers with marine‐based basins, thereby highlighting sectors of Greenland that are most vulnerable to future oceanic forcing....

  3. 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.)

  4. 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.)

  5. Trends in Arctic Ocean bottom pressure, sea surface height and freshwater content using GRACE and the ice-ocean model PIOMAS from 2008-2012

    Science.gov (United States)

    Peralta-Ferriz, Cecilia; Morison, James; Zhang, Jinlun; Bonin, Jennifer

    2014-05-01

    The variability of ocean bottom pressure (OBP) in the Arctic is dominated by the variations in sea surface height (SSH) from daily to monthly timescales. Conversely, OBP variability is dominated by the changes in the steric pressure (StP) at inter-annual timescales, particularly off the continental shelves. The combination of GRACE-derived ocean bottom pressure and ICESat altimetry-derived sea surface height variations in the Arctic Ocean have provided new means of identifying inter-annual trends in StP (StP = OBP-SSH) and associated freshwater content (FWC) of the Arctic region (Morison et al., 2012). Morison et al. (2012) showed that from 2004 to 2008, the FWC increased in the Beaufort Gyre and decreased in the Siberian and Central Arctic, resulting in a relatively small net basin-averaged FWC change. In this work, we investigate the inter-annual trends from 2008 to 2012 in OBP from GRACE, SSH from the state-of-the-art pan-Arctic ocean model PIOMAS -validated with tide and pressure gauges in the Arctic-, and compute the trends in StP and FWC from 2008-2012. We compare these results with the previous trends from 2005-2008 described in Morison et al. (2012). Our initial findings suggest increased salinity in the entire Arctic basin (relative to the climatological seasonal variation) from 2008-2012, compared to the preceding four years (2005-2008). We also find that the trends in OBP, SSH and StP from 2008-2012 present a different behavior during the spring-summer and fall-winter, unlike 2005-2008, in which the trends were generally consistent through all months of the year. It seems since 2009, when the Beaufort Gyre relaxed and the export of freshwater from the Canada Basin into the Canadian Archipelago and Fram Strait, via the Lincoln Sea, was anomalously large (de Steur et al., 2013), the Arctic Ocean has entered a new circulation regime. The causes of such changes in the inter-annual trends of OBP, SSH and StP -hence FWC-, associated with the changes in the

  6. The Surface Water and Ocean Topography Satellite Mission - An Assessment of Swath Altimetry Measurements of River Hydrodynamics

    Science.gov (United States)

    Wilson, Matthew D.; Durand, Michael; Alsdorf, Douglas; Chul-Jung, Hahn; Andreadis, Konstantinos M.; Lee, Hyongki

    2012-01-01

    The Surface Water and Ocean Topography (SWOT) satellite mission, scheduled for launch in 2020 with development commencing in 2015, will provide a step-change improvement in the measurement of terrestrial surface water storage and dynamics. In particular, it will provide the first, routine two-dimensional measurements of water surface elevations, which will allow for the estimation of river and floodplain flows via the water surface slope. In this paper, we characterize the measurements which may be obtained from SWOT and illustrate how they may be used to derive estimates of river discharge. In particular, we show (i) the spatia-temporal sampling scheme of SWOT, (ii) the errors which maybe expected in swath altimetry measurements of the terrestrial surface water, and (iii) the impacts such errors may have on estimates of water surface slope and river discharge, We illustrate this through a "virtual mission" study for a approximately 300 km reach of the central Amazon river, using a hydraulic model to provide water surface elevations according to the SWOT spatia-temporal sampling scheme (orbit with 78 degree inclination, 22 day repeat and 140 km swath width) to which errors were added based on a two-dimension height error spectrum derived from the SWOT design requirements. Water surface elevation measurements for the Amazon mainstem as may be observed by SWOT were thereby obtained. Using these measurements, estimates of river slope and discharge were derived and compared to those which may be obtained without error, and those obtained directly from the hydraulic model. It was found that discharge can be reproduced highly accurately from the water height, without knowledge of the detailed channel bathymetry using a modified Manning's equation, if friction, depth, width and slope are known. Increasing reach length was found to be an effective method to reduce systematic height error in SWOT measurements.

  7. Hydrodynamic modeling in the Peace-Athabasca Delta for the upcoming Surface Water and Ocean Topography (SWOT) mission

    Science.gov (United States)

    Bergeron, J.; Carter, T.; Langlois, S.; Leconte, R.; Peters, D.; Pietroniro, A.; Russell, M.; Saint-Jean, R.; Siles, G. L.; Trudel, M.

    2017-12-01

    The upcoming Surface Water and Ocean Topography (SWOT) mission aims to retrieve water levels elevations via satellite remote sensing. In anticipation of the launch, scheduled for 2021, multiple regions are selected for calibration/validation purposes. The Peace-Athabasca Delta (PAD), a fresh water wetland complex located in the northeastern part of Alberta, Canada, is one of those regions. The PAD comprises numerous lakes and rivers, including Lake Mamawi and the Athabasca River presented in this study. Since it is a region of interest for many projects, including this one, the region has been monitored via multiple types of observations over time, including airborne LiDAR, water level, discharge, bathymetric surveys retrieved from traditional point-measurements tied to Global Positioning System and from an acoustic Doppler current profiler, and more recently, the airborne support instrument AirSWOT. Using a SWOT imagery simulator and a 2D hydrodynamic model (H2D2), we model the hydrologic steady-state conditions of Lake Mamawi and the Athabasca River, as well as the simulated SWOT imagery resulting from a virtual overpass. A digital terrain model derived from airborne LiDAR and bathymetric surveys, as well as water level and discharge measurements collected during the summers of 2016 and 2017, are used to provide a calibrated H2D2 model, from which simulated SWOT images are generated. The objectives of the research are to explore the capabilities of the simulated SWOT data to 1) calibrate and validate the H2D2 model over the PAD, and 2) to improve the water balance of the PAD in a synthetic context.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Using ocean bottom pressure from the gravity recovery and climate experiment (GRACE) to estimate transport variability in the southern Indian Ocean

    Science.gov (United States)

    Makowski, Jessica K.; Chambers, Don P.; Bonin, Jennifer A.

    2015-06-01

    Previous studies have suggested that ocean bottom pressure (OBP) from the Gravity Recovery and Climate Experiment (GRACE) can be used to measure the depth-averaged, or barotropic, transport variability of the Antarctic Circumpolar Current (ACC). Here, we use GRACE OBP observations to calculate transport variability in a region of the southern Indian Ocean encompassing the major fronts of the ACC. We use a statistical analysis of a simulated GRACE-like data set to determine the uncertainty of the estimated transport for the 2003.0-2013.0 time period. We find that when the transport is averaged over 60° of longitude, the uncertainty (one standard error) is close to 1 Sv (1 Sv = 106 m3 s-1) for low-pass filtered transport, which is significantly smaller than the signal and lower than previous studies have found. The interannual variability is correlated with the Southern Annual mode (SAM) (0.61), but more highly correlated with circumpolar zonally averaged winds between 45°S and 65°S (0.88). GRACE transport reflects significant changes in transport between 2007 and 2009 that is observed in the zonal wind variations but not in the SAM index. We also find a statistically significant trend in transport (-1.0 ± 0.4 Sv yr-1, 90% confidence) that is correlated with a local deceleration in zonal winds related to an asymmetry in the SAM on multidecadal periods.

  15. 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.

  16. 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.

  17. 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

  18. 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

  19. 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

    Science.gov (United States)

    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.

  20. 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

  1. 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

  2. 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

  3. Ocean Surface Topography Mission (OSTM) /Jason-2: Near Real-Time Altimetry Validation System (NRTAVS) QA Reports (NODC Accession 0044984)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This accession contains the descriptions for the OSTM/Jason-2 Near Real-Time Altimetry Validation System Quality Reports, which are served through the NOAA/NESDIS...

  4. Toward Improved Estimation of the Dynamic Topography and Ocean Circulation in the High Latitude and Arctic Ocean: The Importance of GOCE

    DEFF Research Database (Denmark)

    Johannessen, J. A.; Raj, R. P.; Nilsen, J. E. Ø.

    2014-01-01

    The Arctic plays a fundamental role in the climate system and shows significant sensitivity to anthropogenic climate forcing and the ongoing climate change. Accelerated changes in the Arctic are already observed, including elevated air and ocean temperatures, declines of the summer sea ice extent...... quantify this. Moreover, changes in the temperature and salinity of surface waters in the Arctic Ocean and Nordic Seas may also influence the flow of dense water through the Denmark Strait, which are found to be a precursor for changes in the Atlantic meridional overturning circulation with a lead time...... circulation and transport variability in the high latitude and Arctic Ocean. In this respect, this study combines in situ hydrographical data, surface drifter data and direct current meter measurements, with coupled sea ice–ocean models, radar altimeter data and the latest GOCE-based geoid in order...

  5. 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

  6. 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

  7. 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,...

  8. 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...

  9. 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....

  10. 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...

  11. Tsunami simulation method initiated from waveforms observed by ocean bottom pressure sensors for real-time tsunami forecast; Applied for 2011 Tohoku Tsunami

    Science.gov (United States)

    Tanioka, Yuichiro

    2017-04-01

    After tsunami disaster due to the 2011 Tohoku-oki great earthquake, improvement of the tsunami forecast has been an urgent issue in Japan. National Institute of Disaster Prevention is installing a cable network system of earthquake and tsunami observation (S-NET) at the ocean bottom along the Japan and Kurile trench. This cable system includes 125 pressure sensors (tsunami meters) which are separated by 30 km. Along the Nankai trough, JAMSTEC already installed and operated the cable network system of seismometers and pressure sensors (DONET and DONET2). Those systems are the most dense observation network systems on top of source areas of great underthrust earthquakes in the world. Real-time tsunami forecast has depended on estimation of earthquake parameters, such as epicenter, depth, and magnitude of earthquakes. Recently, tsunami forecast method has been developed using the estimation of tsunami source from tsunami waveforms observed at the ocean bottom pressure sensors. However, when we have many pressure sensors separated by 30km on top of the source area, we do not need to estimate the tsunami source or earthquake source to compute tsunami. Instead, we can initiate a tsunami simulation from those dense tsunami observed data. Observed tsunami height differences with a time interval at the ocean bottom pressure sensors separated by 30 km were used to estimate tsunami height distribution at a particular time. In our new method, tsunami numerical simulation was initiated from those estimated tsunami height distribution. In this paper, the above method is improved and applied for the tsunami generated by the 2011 Tohoku-oki great earthquake. Tsunami source model of the 2011 Tohoku-oki great earthquake estimated using observed tsunami waveforms, coseimic deformation observed by GPS and ocean bottom sensors by Gusman et al. (2012) is used in this study. The ocean surface deformation is computed from the source model and used as an initial condition of tsunami

  12. EFFECTS OF MEDU AND COASTAL TOPOGRAPHY ON THE DAMAGE PATTERN DURING THE RECENT INDIAN OCEAN TSUNAMI ALONG THE COAST OF TAMILNADU

    Directory of Open Access Journals (Sweden)

    J.P. Narayan

    2005-01-01

    Full Text Available Effects of Medu (naturally elevated landmass very close to the seashore and elongated parallel to the coast and coastal topography on the damage pattern during the deadliest Indian Ocean tsunami of December 26, 2004 is reported. The tsunami caused severe damage and claimed many victims in the coastal areas of eleven countries bordering the Indian Ocean. The damage survey revealed large variation in damage along the coastal region of Tamilnadu (India.The most severe damage was observed in the Nagapattinam district on the east coast and the west coast of Kanyakumari district. Decrease of damage from Nagapattinam to Kanchipuram district was observed. Intense damage again appeared to the north of Adyar River (from Srinivaspuri to Anna Samadhi Park. Almost, no damage was observed along the coast of Thanjavur, Puddukkotai and Ramnathpuram districts in Palk Strait, situated in the shadow zone of Sri Lanka.It was concluded that the width of continental shelf has played a major role in the pattern of tsunami damage. It was inferred that the width of the continental shelf and the interference of reflected waves from Sri Lanka and Maldives Islands with direct waves and receding waves was responsible for intense damage in Nagapattinam and Kanyakumari districts, respectively. During the damage survey authors also noted that there was almost no damage or much lesser damage to houses situated on or behind the Medu. Many people observed the first arrival. The largest tsunami amplitude occurred as the first arrival on the eastern coast and in the second arrival on the western coast.

  13. 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.

  14. 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)

  15. 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.

  16. 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.

  17. 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

  18. 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

  19. Ocean Surface Topography Mission (OSTM) /Jason-3: Near Real-Time Altimetry Validation System (NRTAVS) QA Reports, 2015 - (NCEI Accession 0122600)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Jason-3 is the fourth mission in U.S.-European series of satellite missions that measure the height of the ocean surface. Scheduled to launch in 2015, the mission...

  20. 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.

  1. 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.

  2. Multiscale Study of Currents Affected by Topography

    Science.gov (United States)

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Multiscale Study of Currents Affected by Topography ...the effects of topography on the ocean general and regional circulation with a focus on the wide range of scales of interactions. The small-scale...details of the topography and the waves, eddies, drag, and turbulence it generates (at spatial scales ranging from meters to mesoscale) interact in the

  3. 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.

  4. Seismic velocity structure and spatial distribution of reflection intensity off the Boso Peninsula, Central Japan, revealed by an ocean bottom seismographic experiment

    Science.gov (United States)

    Kono, Akihiro; Sato, Toshinori; Shinohara, Masanao; Mochizuki, Kimihiro; Yamada, Tomoaki; Uehira, Kenji; Shinbo, Takashi; Machida, Yuuya; Hino, Ryota; Azuma, Ryosuke

    2016-04-01

    Off the Boso Peninsula, central Japan, where the Sagami Trough is in the south and the Japan Trench is in the east, there is a triple junction where the Pacific plate (PAC), the Philippine Sea plate (PHS) and the Honshu island arc (HIA) meet each other. In this region, the PAC subducts beneath the PHS and the HIA, and the PHS subducts beneath the HIA. Due to the subduction of 2 oceanic plates, numerous seismic events took place in the past. In order to understand these events, it is important to image structure of these plates. Hence, many researchers attempted to reveal the substructure from natural earthquakes and seismic experiments. Because most of the seismometers are placed inland area and the regular seismicity off Boso is inactive, it is difficult to reveal the precise substructure off Boso area using only natural earthquakes. Although several marine seismic experiments using active sources were conducted, vast area remains unclear off Boso Peninsula. In order to improve the situation, a marine seismic experiment, using airgun as an active source, was conducted from 30th July to 4th of August, 2009. The survey line has 216 km length and 20 Ocean Bottom Seismometers (OBSs) were placed on it. We estimated 2-D P-wave velocity structure from the airgun data using the PMDM (Progressive Model Development Method; Sato and Kenett, 2000) and the FAST (First Arrival Seismic Tomography ; Zelt and Barton, 1998). Furthermore, we identified the probable reflection phases from the data and estimated the location of reflectors using Travel time mapping method (Fujie et al. 2006). We found some reflection phases from the data, and the reflectors are located near the region where P-wave velocity is 5.0 km/s. We interpret that the reflectors indicate the plate boundary between the PHS and the HIA. The variation of the intensity of reflection along the upper surface of PHS seems to be consistent with the result from previous reflection seismic experiment conducted by Kimura et

  5. 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

  6. Flow Around Steep Topography

    Science.gov (United States)

    2015-09-30

    Flow around steep topography T. M. Shaun Johnston Scripps Institution of Oceanography University of California, San Diego 9500 Gilman Drive, M...tall, steep, submarine topography and islands. During the Flow Encountering Abrupt Topography (FLEAT) DRI, investigators will determine: • Whether...estimates from making accurate statistical/deterministic predictions at ᝺ km resolution around submarine topography and islands? How can we

  7. Relative contributions of local wind and topography to the coastal upwelling intensity in the northern South China Sea

    Science.gov (United States)

    Wang, Dongxiao; Shu, Yeqiang; Xue, Huijie; Hu, Jianyu; Chen, Ju; Zhuang, Wei; Zu, TingTing; Xu, Jindian

    2014-04-01

    Topographically induced upwelling caused by the interaction between large-scale currents and topography was observed during four cruises in the northern South China Sea (NSCS) when the upwelling favorable wind retreated. Using a high-resolution version of the Princeton Ocean Model, we investigate relative contributions of local wind and topography to the upwelling intensity in the NSCS. The results show that the topographically induced upwelling is sensitive to alongshore large-scale currents, which have an important contribution to the upwelling intensity. The topographically induced upwelling is comparable with the wind-driven upwelling at surface and has a stronger contribution to the upwelling intensity than the local wind does at bottom in the near-shore shelf region. The widened shelf to the southwest of Shanwei and west of the Taiwan Banks intensifies the bottom friction, especially off Shantou, which is a key factor for topographically induced upwelling in terms of bottom Ekman transport and Ekman pumping. The local upwelling favorable wind enhances the bottom friction as well as net onshore transport along the 50 m isobath, whereas it has less influence along the 30 m isobath. This implies the local wind is more important in upwelling intensity in the offshore region than in the nearshore region. The contribution of local upwelling favorable wind on upwelling intensity is comparable with that of topography along the 50 m isobath. The effects of local upwelling favorable wind on upwelling intensity are twofold: on one hand, the wind transports surface warm water offshore, and as a compensation of mass the bottom current transports cold water onshore; on the other hand, the wind enhances the coastal current, and the bottom friction in turn increases the topographically induced upwelling intensity.

  8. Diffusive boundary layers over varying topography

    KAUST Repository

    Dell, R.  W.; Pratt, L.  J.

    2015-01-01

    Diffusive bottom boundary layers can produce upslope flows in a stratified fluid. Accumulating observations suggest that these boundary layers may drive upwelling and mixing in mid-ocean ridge flank canyons. However, most studies of diffusive bottom

  9. Elucidating Dynamical Processes Relevant to Flow Encountering Abrupt Topography (FLEAT)

    Science.gov (United States)

    2015-09-30

    Encountering Abrupt Topography (FLEAT) Bo Qiu Dept of Oceanography, University of Hawaii at Manoa 1000 Pope Rd. Honolulu, HI 96822 phone: (808) 956...c) to explore relevant dynamics by using both simplified models and OGCM output with realistic topography and surface boundary conditions...scale abyssal circulation, we propose to use the Hallberg Isopycnal Model (HIM). The HIM allows sloping isopycnals to interact with bottom topography

  10. Gravity Terrain Effect of the Seafloor Topography in Taiwan

    Directory of Open Access Journals (Sweden)

    Lun-Tao Tong Tai-Rong Guo

    2007-01-01

    Full Text Available Gravity terrain correction is used to compensate for the gravitational effects of the topography residual to the Bouguer plate. The seafloor topography off the eastern offshore of Taiwan is extremely rugged, and the depth of the sea bottom could be greater than 5000 m. In order to evaluate the terrain effect caused by the seafloor topography, a modern computer algorithm is used to calculate the terrain correction based on the digital elevation model (DEM.

  11. Experiments on topographies lacking tidal conversion

    Science.gov (United States)

    Maas, Leo; Paci, Alexandre; Yuan, Bing

    2015-11-01

    In a stratified sea, internal tides are supposedly generated when the tide passes over irregular topography. It has been shown that for any given frequency in the internal wave band there are an infinite number of exceptions to this rule of thumb. This ``stealth-like'' property of the topography is due to a subtle annihilation of the internal waves generated during the surface tide's passage over the irregular bottom. We here demonstrate this in a lab-experiment. However, for any such topography, subsequently changing the surface tide's frequency does lead to tidal conversion. The upshot of this is that a tidal wave passing over an irregular bottom is for a substantial part trapped to this irregularity, and only partly converted into freely propagating internal tides. Financially supported by the European Community's 7th Framework Programme HYDRALAB IV.

  12. On effects of topography in rotating flows

    Science.gov (United States)

    Burmann, Fabian; Noir, Jerome; Jackson, Andrew

    2017-11-01

    Both, seismological studies and geodynamic arguments suggest that there is significant topography at the core mantle boundary (CMB). This leads to the question whether the topography of the CMB could influence the flow in the Earth's outer core. As a preliminary experiment, we investigate the effects of bottom topography in the so-called Spin-Up, where motion of a contained fluid is created by a sudden increase of rotation rate. Experiments are performed in a cylindrical container mounted on a rotating table and quantitative results are obtained with particle image velocimetry. Several horizontal length scales of topography (λ) are investigated, ranging from cases where λ is much smaller then the lateral extend of the experiment (R) to cases where λ is a fraction of R. We find that there is an optimal λ that creates maximum dissipation of kinetic energy. Depending on the length scale of the topography, kinetic energy is either dissipated in the boundary layer or in the bulk of the fluid. Two different phases of fluid motion are present: a starting flow in the from of solid rotation (phase I), which is later replaced by meso scale vortices on the length scale of bottom topography (phase II).

  13. 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...

  14. 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.

  15. 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.

  16. 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)

  17. Deep ocean current profiles, water temperatures, and echo amplitudes from bottom-moored ADCP during 2011-2013 of the Aloha Cabled Observatory (NCEI Accession 0123608)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The ALOHA Cabled Observatory (ACO) is a system of hardware and software that extends electric power and the Internet offshore, supporting sustained real-time...

  18. 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...

  19. ocean_city_md.grd

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NGDC builds and distributes high-resolution, coastal digital elevation models (DEMs) that integrate ocean bathymetry and land topography to support NOAA's mission to...

  20. Bottom Production

    CERN Document Server

    Nason, P.; Schneider, O.; Tartarelli, G.F.; Vikas, P.; Baines, J.; Baranov, S.P.; Bartalini, P.; Bay, A.; Bouhova, E.; Cacciari, M.; Caner, A.; Coadou, Y.; Corti, G.; Damet, J.; Dell'Orso, R.; De Mello Neto, J.R.T.; Domenech, J.L.; Drollinger, V.; Eerola, P.; Ellis, N.; Epp, B.; Frixione, S.; Gadomski, S.; Gavrilenko, I.; Gennai, S.; George, S.; Ghete, V.M.; Guy, L.; Hasegawa, Y.; Iengo, P.; Jacholkowska, A.; Jones, R.; Kharchilava, A.; Kneringer, E.; Koppenburg, P.; Korsmo, H.; Kramer, M.; Labanca, N.; Lehto, M.; Maltoni, F.; Mangano, Michelangelo L.; Mele, S.; Nairz, A.M.; Nakada, T.; Nikitin, N.; Nisati, A.; Norrbin, E.; Palla, F.; Rizatdinova, F.; Robins, S.; Rousseau, D.; Sanchis-Lozano, M.A.; Shapiro, M.; Sherwood, P.; Smirnova, L.; Smizanska, M.; Starodumov, A.; Stepanov, N.; Vogt, R.

    2000-01-01

    We review the prospects for bottom production physics at the LHC. Members of the working group who has contributed to this document are: J. Baines, S.P. Baranov, P. Bartalini, A. Bay, E. Bouhova, M. Cacciari, A. Caner, Y. Coadou, G. Corti, J. Damet, R. Dell'Orso, J.R.T. De Mello Neto, J.L. Domenech, V. Drollinger, P. Eerola, N. Ellis, B. Epp, S. Frixione, S. Gadomski, I. Gavrilenko, S. Gennai, S. George, V.M. Ghete, L. Guy, Y. Hasegawa, P. Iengo, A. Jacholkowska, R. Jones, A. Kharchilava, E. Kneringer, P. Koppenburg, H. Korsmo, M. Kraemer, N. Labanca, M. Lehto, F. Maltoni, M.L. Mangano, S. Mele, A.M. Nairz, T. Nakada, N. Nikitin, A. Nisati, E. Norrbin, F. Palla, F. Rizatdinova, S. Robins, D. Rousseau, M.A. Sanchis-Lozano, M. Shapiro, P. Sherwood, L. Smirnova, M. Smizanska, A. Starodumov, N. Stepanov, R. Vogt

  1. Bottom up

    International Nuclear Information System (INIS)

    Ockenden, James

    1999-01-01

    This article presents an overview of the electric supply industries in Eastern Europe. The development of more competitive and efficient plant in Poland and work on emissions control ahead of EU membership; the Czech's complicated tariff system; Hungary's promised 8% return on investment in their electricity supply industry and its tariff problems; Bulgaria and Ukraine's desperate need for investment to build alternative plants to their aging nuclear plants; and demand outstripping supply in Romania are among the topics considered.. The viscous circle of poor service and low utility income is considered, and the top-down approach for breaking the cycle by improving plant efficiency, and the bottom up approach of improving plant income as practiced by Moldavia are explained. (UK)

  2. Bottom production

    International Nuclear Information System (INIS)

    Baines, J.; Baranov, S.P.; Bartalini, P.; Bay, A.; Bouhova, E.; Cacciari, M.; Caner, A.; Coadou, Y.; Corti, G.; Damet, J.; Dell-Orso, R.; De Mello Neto, J.R.T.; Domenech, J.L.; Drollinger, V.; Eerola, P.; Ellis, N.; Epp, B.; Frixione, S.; Gadomski, S.; Gavrilenko, I.; Gennai, S.; George, S.; Ghete, V.M.; Guy, L.; Hasegawa, Y.; Iengo, P.; Jacholkowska, A.; Jones, R.; Kharchilava, A.; Kneringer, E.; Koppenburg, P.; Korsmo, H.; Kramer, M.; Labanca, N.; Lehto, M.; Maltoni, F.; Mangano, M.L.; Mele, S.; Nairz, A.M.; Nakada, T.; Nikitin, N.; Nisati, A.; Norrbin, E.; Palla, F.; Rizatdinova, F.; Robins, S.; Rousseau, D.; Sanchis-Lozano, M.A.; Shapiro, M.; Sherwood, P.; Smirnova, L.; Smizanska, M.; Starodumov, A.; Stepanov, N.; Vogt, R.

    2000-01-01

    In the context of the LHC experiments, the physics of bottom flavoured hadrons enters in different contexts. It can be used for QCD tests, it affects the possibilities of B decays studies, and it is an important source of background for several processes of interest. The physics of b production at hadron colliders has a rather long story, dating back to its first observation in the UA1 experiment. Subsequently, b production has been studied at the Tevatron. Besides the transverse momentum spectrum of a single b, it has also become possible, in recent time, to study correlations in the production characteristics of the b and the b. At the LHC new opportunities will be offered by the high statistics and the high energy reach. One expects to be able to study the transverse momentum spectrum at higher transverse momenta, and also to exploit the large statistics to perform more accurate studies of correlations

  3. Bottom production

    Energy Technology Data Exchange (ETDEWEB)

    Baines, J.; Baranov, S.P.; Bartalini, P.; Bay, A.; Bouhova, E.; Cacciari, M.; Caner, A.; Coadou, Y.; Corti, G.; Damet, J.; Dell-Orso, R.; De Mello Neto, J.R.T.; Domenech, J.L.; Drollinger, V.; Eerola, P.; Ellis, N.; Epp, B.; Frixione, S.; Gadomski, S.; Gavrilenko, I.; Gennai, S.; George, S.; Ghete, V.M.; Guy, L.; Hasegawa, Y.; Iengo, P.; Jacholkowska, A.; Jones, R.; Kharchilava, A.; Kneringer, E.; Koppenburg, P.; Korsmo, H.; Kramer, M.; Labanca, N.; Lehto, M.; Maltoni, F.; Mangano, M.L.; Mele, S.; Nairz, A.M.; Nakada, T.; Nikitin, N.; Nisati, A.; Norrbin, E.; Palla, F.; Rizatdinova, F.; Robins, S.; Rousseau, D.; Sanchis-Lozano, M.A.; Shapiro, M.; Sherwood, P.; Smirnova, L.; Smizanska, M.; Starodumov, A.; Stepanov, N.; Vogt, R.

    2000-03-15

    In the context of the LHC experiments, the physics of bottom flavoured hadrons enters in different contexts. It can be used for QCD tests, it affects the possibilities of B decays studies, and it is an important source of background for several processes of interest. The physics of b production at hadron colliders has a rather long story, dating back to its first observation in the UA1 experiment. Subsequently, b production has been studied at the Tevatron. Besides the transverse momentum spectrum of a single b, it has also become possible, in recent time, to study correlations in the production characteristics of the b and the b. At the LHC new opportunities will be offered by the high statistics and the high energy reach. One expects to be able to study the transverse momentum spectrum at higher transverse momenta, and also to exploit the large statistics to perform more accurate studies of correlations.

  4. Constraints in using Cerium-animaly of bulk sediments as an indicator of paleo bottom water redox environment: A case study from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.; Pearce, N.J.G.; Mislankar, P.G.

    for paleo-oceanic redox conditions. Geochem. Cosmo- chim. Acta 5, 1361–1371. Lyle, M., Dymond, J., Heath, G.R., 1977. Copper–nickel enriched ferromanganese nodules and associated crusts from the Baur Basin, northwest Nazca plate. Earth Planet. Sci. Lett. 35.... Cosmo- chim. Acta 61, 2375–2388. Nozaki, Y., Horible, Y., Tsubota, H., 1981. The water column distribution of thorium isotopes in the western North Pacific. Earth Planet. Sci. Lett. 66, 73–90. Pattan, J.N., Banakar, V.K., 1997. Diagenetic remobilization...

  5. Inner core boundary topography explored with reflected and diffracted P waves

    Science.gov (United States)

    deSilva, Susini; Cormier, Vernon F.; Zheng, Yingcai

    2018-03-01

    The existence of topography of the inner core boundary (ICB) can affect the amplitude, phase, and coda of body waves incident on the inner core. By applying pseudospectral and boundary element methods to synthesize compressional waves interacting with the ICB, these effects are predicted and compared with waveform observations in pre-critical, critical, post-critical, and diffraction ranges of the PKiKP wave reflected from the ICB. These data sample overlapping regions of the inner core beneath the circum-Pacific belt and the Eurasian, North American, and Australian continents, but exclude large areas beneath the Pacific and Indian Oceans and the poles. In the pre-critical range, PKiKP waveforms require an upper bound of 2 km at 1-20 km wavelength for any ICB topography. Higher topography sharply reduces PKiKP amplitude and produces time-extended coda not observed in PKiKP waveforms. The existence of topography of this scale smooths over minima and zeros in the pre-critical ICB reflection coefficient predicted from standard earth models. In the range surrounding critical incidence (108-130 °), this upper bound of topography does not strongly affect the amplitude and waveform behavior of PKIKP + PKiKP at 1.5 Hz, which is relatively insensitive to 10-20 km wavelength topography height approaching 5 km. These data, however, have a strong overlap in the regions of the ICB sampled by pre-critical PKiKP that require a 2 km upper bound to topography height. In the diffracted range (>152°), topography as high as 5 km attenuates the peak amplitudes of PKIKP and PKPCdiff by similar amounts, leaving the PKPCdiff/PKIKP amplitude ratio unchanged from that predicted by a smooth ICB. The observed decay of PKPCdiff into the inner core shadow and the PKIKP-PKPCdiff differential travel time are consistent with a flattening of the outer core P velocity gradient near the ICB and iron enrichment at the bottom of the outer core.

  6. 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

  7. Integrated Monitoring of the Soya Warm Current Using HF Ocean Radars, Satellite Altimeters, Coastal Tide Gauges, and a Bottom-Mounted ADCP

    Science.gov (United States)

    Ebuchi, N.; Fukamachi, Y.; Ohshima, K. I.; Wakatsuchi, M.

    2007-12-01

    The Soya Warm Current (SWC) is a coastal boundary current, which flows along the coast of Hokkaido in the Sea of Okhotsk. The SWC flows into the Sea of Okhotsk from the Sea of Japan through the Soya/La Perouse Strait, which is located between Hokkaido, Japan, and Sakhalin, Russia. It supplies warm, saline water in the Sea of Japan to the Sea of Okhotsk and largely affects the ocean circulation and water mass formation in the Sea of Okhotsk, and local climate, environment and fishery in the region. However, the SWC has never been continuously monitored due to the difficulties involved in field observations related to, for example, severe weather conditions in the winter, political issues at the border strait, and conflicts with fishing activities in the strait. Detailed features of the SWC and its variations have not yet been clarified. In order to monitor variations in the SWC, three HF ocean radar stations were installed around the strait. The radar covers a range of approximately 70 km from the coast. It is shown that the HF radars clearly capture seasonal and subinertial variations of the SWC. The velocity of the SWC reaches its maximum, approximately 1 m/s, in summer, and weakens in winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately 50 km. The surface transport by the Soya Warm Current shows a significant correlation with the sea level difference along the strait, as derived from coastal tide gauge records. The cross-current sea level difference, which is estimated from the sea level anomalies observed by the Jason-1 altimeter and a coastal tide gauge, also exhibits variation in concert with the surface transport and along-current sea level difference.

  8. Rewetting during bottom flooding

    International Nuclear Information System (INIS)

    Pearson, K.G.

    1984-11-01

    A qualitative description of the rewetting process during bottom reflooding of a PWR is presented. Rewetting is seen as the end product of a path taken over a heat transfer surface which defines how the surface heat flux varies with surface temperature and with distance from the rewetting front. The main components are liquid contact, vapour convection and thermal radiation. In this paper the general topography of the heat transfer surface is deduced from consideration of the ways in which the conditions of the vapour and liquid phases in the flow are expected to vary with distance from the rewetting front. The deduced surface has a heat transfer ridge which decreases in height, and whose steep face moves to lower temperatures, with increasing distance from the rewetting front, and a valley which becomes negative with increasing distance. There is a different surface for each position along a subchannel, strongly influenced by the proximity of spacer grids, and by whether these grids are wet or dry. The form of this family of heat transfer surfaces is used to explain the phenomena of reflooding of clusters of heated rods. (U.K.)

  9. 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.

  10. 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.)

  11. Dynamic Topography Revisited

    Science.gov (United States)

    Moresi, Louis

    2015-04-01

    Dynamic Topography Revisited Dynamic topography is usually considered to be one of the trinity of contributing causes to the Earth's non-hydrostatic topography along with the long-term elastic strength of the lithosphere and isostatic responses to density anomalies within the lithosphere. Dynamic topography, thought of this way, is what is left over when other sources of support have been eliminated. An alternate and explicit definition of dynamic topography is that deflection of the surface which is attributable to creeping viscous flow. The problem with the first definition of dynamic topography is 1) that the lithosphere is almost certainly a visco-elastic / brittle layer with no absolute boundary between flowing and static regions, and 2) the lithosphere is, a thermal / compositional boundary layer in which some buoyancy is attributable to immutable, intrinsic density variations and some is due to thermal anomalies which are coupled to the flow. In each case, it is difficult to draw a sharp line between each contribution to the overall topography. The second definition of dynamic topography does seem cleaner / more precise but it suffers from the problem that it is not measurable in practice. On the other hand, this approach has resulted in a rich literature concerning the analysis of large scale geoid and topography and the relation to buoyancy and mechanical properties of the Earth [e.g. refs 1,2,3] In convection models with viscous, elastic, brittle rheology and compositional buoyancy, however, it is possible to examine how the surface topography (and geoid) are supported and how different ways of interpreting the "observable" fields introduce different biases. This is what we will do. References (a.k.a. homework) [1] Hager, B. H., R. W. Clayton, M. A. Richards, R. P. Comer, and A. M. Dziewonski (1985), Lower mantle heterogeneity, dynamic topography and the geoid, Nature, 313(6003), 541-545, doi:10.1038/313541a0. [2] Parsons, B., and S. Daly (1983), The

  12. DNSC08 mean sea surface and mean dynamic topography models

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Knudsen, Per

    2009-01-01

    -2004. It is the first global MSS without a polar gap including all of the Arctic Ocean by including laser altimetry from the ICESat mission. The mean dynamic topography (MDT) is the quantity that bridges the geoid and the mean sea surface constraining large-scale ocean circulation. Here we present a new high...

  13. Anomalous sea surface structures as an object of statistical topography

    Science.gov (United States)

    Klyatskin, V. I.; Koshel, K. V.

    2015-06-01

    By exploiting ideas of statistical topography, we analyze the stochastic boundary problem of emergence of anomalous high structures on the sea surface. The kinematic boundary condition on the sea surface is assumed to be a closed stochastic quasilinear equation. Applying the stochastic Liouville equation, and presuming the stochastic nature of a given hydrodynamic velocity field within the diffusion approximation, we derive an equation for a spatially single-point, simultaneous joint probability density of the surface elevation field and its gradient. An important feature of the model is that it accounts for stochastic bottom irregularities as one, but not a single, perturbation. Hence, we address the assumption of the infinitely deep ocean to obtain statistic features of the surface elevation field and the squared elevation gradient field. According to the calculations, we show that clustering in the absolute surface elevation gradient field happens with the unit probability. It results in the emergence of rare events such as anomalous high structures and deep gaps on the sea surface almost in every realization of a stochastic velocity field.

  14. Current meter data from moored current meter casts in the Northeast Pacific Ocean as part of the Flow Over Abrupt Topography project from 1990-01-06 to 1991-12-03 (NODC Accession 9500077)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Northeast Pacific Ocean from January 6, 1990 to December 3, 1991. Data were submitted by...

  15. Topography. Ch. 10

    International Nuclear Information System (INIS)

    Chikawa, Jun-Ichi; Kuriyama, Masao

    1991-01-01

    The uniqueness of synchrotron X-ray topography does not lie in new theoretical or experimental notions about the topographic method, but in the characteristics of this new source as a critical optical element. At most synchrotron facilities, the spectrum ranging from 5 keV (2.5A) to 30 keV (0.4A0 can be made available for topography. A synchrotron-radiation source gives tunability (choice of wavelengths) and pulsed time structure with highly collimated an intense photon beams. The continuous spectrum and excellent collimation have made white-beam X-ray topography a practical reality. The high intensity of the synchrotron X-ray source, even after beam monochromatization and further collimation, permits time-dependent observation of kinetics. By selecting the mono-chromatized wavelength close to an absorption edge of an element in the sample crystal, the topographic data selectively emphasize or de-emphasize structures related to that element. For full use of such properties of synchrotron radiation, however, development of new optical systems and imaging detectors is required, and is in progress at most synchrotron facilities. This chapter covers a brief review of X-ray topography, its basic principles, and the necessary X-ray optical and imaging systems. The capability of synchrotron-radiation topography is demonstrated with some recent results. (author). 118 refs.; 22 figs

  16. The geostrophic velocity field in shallow water over topography

    Science.gov (United States)

    Charnock, Henry; Killworth, Peter D.

    1998-01-01

    A recent note (Hopkins, T.S., 1996. A note on the geostrophic velocity field referenced to a point. Continental Shelf Research 16, 1621-1630) suggests a method for evaluating absolute pressure gradients in stratified water over topography. We demonstrate that this method requires no along-slope bottom velocity, in contradiction to what is usually observed, and that mass is not conserved.

  17. Large band gaps of water waves through two-dimensional periodic topography

    International Nuclear Information System (INIS)

    Yang Shaohua; Wu Fugen; Zhong Huilin; Zhong Lanhua

    2006-01-01

    In this Letter, the band structures and band gaps of liquid surface waves propagating over two-dimensional periodic topography was investigated by plane-waves expansion method. The periodic topography drilled by square hollows with square lattice was considered. And the effects of the filling fraction and the orientation of bottom-hollows on the band gaps are investigated in detail

  18. Lopez Island Ocean Bottom Seismometer Intercomparison Experiment.

    Science.gov (United States)

    1980-10-01

    al. ,1980.) Intuitively one would expect a squat , low-profile instrument design to be preferable; this intuitive argument may extend even to the...of the mass-- spc ing-damper analog. A sinusoidal volt a c is ap1iedto geophonc A, canusing the m,,oving mass to oscillate and tnap)vi4a sinusoidal

  19. Eddy dynamics in the Southern Ocean: How does the interaction of the Antarctic Circumpolar Current with sea-bed topography influence the surface mixed layer and hence the carbon-climate feedback processes?

    CSIR Research Space (South Africa)

    Kobo, N

    2012-10-01

    Full Text Available The Southern Ocean is an important sink for heat and CO2 and is one of the world’s most productive regions. The unique absence of blocking continents allows the Antarctic Circumpolar Current (ACC) to connect all ocean basins (Atlantic, Pacific...

  20. 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

  1. 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...

  2. The Dawn Topography Investigation

    Science.gov (United States)

    Raymond, C. A.; Jaumann, R.; Nathues, A.; Sierks, H.; Roatsch, T.; Preusker, E; Scholten, F.; Gaskell, R. W.; Jorda, L.; Keller, H.-U.; hide

    2011-01-01

    The objective of the Dawn topography investigation is to derive the detailed shapes of 4 Vesta and 1 Ceres in order to create orthorectified image mosaics for geologic interpretation, as well as to study the asteroids' landforms, interior structure, and the processes that have modified their surfaces over geologic time. In this paper we describe our approaches for producing shape models, plans for acquiring the needed image data for Vesta, and the results of a numerical simulation of the Vesta mapping campaign that quantify the expected accuracy of our results. Multi-angle images obtained by Dawn's framing camera will be used to create topographic models with 100 m/pixel horizontal resolution and 10 m height accuracy at Vesta, and 200 m/pixel horizontal resolution and 20 m height accuracy at Ceres. Two different techniques, stereophotogrammetry and stereophotoclinometry, are employed to model the shape; these models will be merged with the asteroidal gravity fields obtained by Dawn to produce geodetically controlled topographic models for each body. The resulting digital topography models, together with the gravity data, will reveal the tectonic, volcanic and impact history of Vesta, and enable co-registration of data sets to determine Vesta's geologic history. At Ceres, the topography will likely reveal much about processes of surface modification as well as the internal structure and evolution of this dwarf planet.

  3. Temperature, salinity, and water chemistry data from quarterly bottom transects of the Comprehensive Environmental Monitoring Program at the Ocean Thermal Energy Conversion plant in Keahole, Island of Hawaii 1993-2007 (NCEI Accession 0156980)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NATURAL ENERGY LABORATORY OF HAWAII AUTHORITY (NELHA) is a state agency that operates a unique and innovative ocean science and technology park in Kailua-Kona on...

  4. 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...

  5. 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....

  6. 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....

  7. 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....

  8. 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....

  9. 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....

  10. 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....

  11. 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....

  12. 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....

  13. 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....

  14. 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...

  15. 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...

  16. 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....

  17. 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....

  18. 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....

  19. 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....

  20. 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....

  1. 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....

  2. 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....

  3. 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....

  4. 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....

  5. 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....

  6. 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....

  7. 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....

  8. 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....

  9. 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....

  10. 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....

  11. 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....

  12. 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....

  13. 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....

  14. 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....

  15. 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....

  16. 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....

  17. 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....

  18. 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....

  19. 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....

  20. 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....

  1. 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....

  2. 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

  3. The East Greenland Caledonides from the viewpoint of Receiver Functions, gravity and topography data

    DEFF Research Database (Denmark)

    Schiffer, Christian; Balling, N.; Jacobsen, B. H.

    The topography and crustal structure of the Caledonides were shaped by various events, including the Caledonian orogeny, lithospheric extensional collapse, continental breakup and erosional processes. Before the closure of the Iapetus Ocean (480 Ma), convergence of Laurentia, Baltica and Avalonia...

  4. OW Smith and Sandwell v8.2 - 1/30 Degree Bathymetry & Topography

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Global bathymetry and topography information at 1/30 degree resolution. Data collected by means of in-situ and satellite measurements.

  5. 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...

  6. Mixing Over Rough Topography

    Science.gov (United States)

    2017-10-25

    www.apl.washington.edu/ people /profile.php?last_name=Gregg&first_name=Mike LONG-TERM GOALS To understand quantify diapycnal mixing in the ocean...ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) Office of Naval Research ONR 875 North Randolph Street Arlington, VA 22203-1995 11

  7. Topography and distribution of central graben in Okinawa Trough Miyoko Section

    Science.gov (United States)

    Luan, X.; Qin, Y.

    2006-05-01

    Based on geophysical data obtained by R/V "Science 1¡± of Institute of Oceanology, Chinese Academy of Sciences (IOCAS) and R/V "Xiangyanghong 9¡± of State Oceanic Administration (SOA) in a 200 km long area of Okinawa Trough Miyoko Section recent years, we show the topography and distribution of central graben in great detail for the first time. Central graben within Miyoko Section is separated into 9 discontinuous segments by strike slip faults, from north to south namely Laoshan, Huangdao, Jiaonan, Jiaozhou, Pingdu, Jimo, Laixi, Chengyang and Licang Segment respectively, and shows a dextral echelon pattern in general. By cross shapes, three types of central graben can be distinguished, namely U type, V type and half graben. U type is the most common central graben among those found in our study area. The depth of central graben is from 40 m to 250 m, wide from 6 km to 14 km, length from 17 km to 33 km. The largest water depth of Miyoko Section is 2244.4 m, found at the east side of north end bottom of Chengyang Segment (125°19.3'E, 25°49.8'N). Within the dextral echelon pattern, Huangdao, Chengyang, Licang Segment moves to the west relatively to Laoshan, Laixi and Chengyang Segment respectively, showing a local sinistral echelon pattern. The striking direction of central graben is N60°E roughly, that is 15° more to the east comparing to the striking of the Okinawa Trough. There is 6 km long overlap distance between Laixi Segment and Chengyang Segments, simile with an overlap spreading center in the Mid-Ocean Ridge. Two volcanic chains, the central axis volcanic chain which located within the central graben and the island arc volcanic chain which located at the west side of Ryukyu Island Arc are clearly found in this section. The island volcanic chain has a good continuity, but the axis volcanic chain is sporadic comparatively. From seismic profile, we understand that the development of central axis volcanic chain is after the development of central graben

  8. Rita Bottoms: Polyartist Librarian

    OpenAIRE

    Bottoms, Rita; Reti, Irene; Regional History Project, UCSC Library

    2005-01-01

    Project Director Irene Reti conducted fourteen hours of interviews with Rita Bottoms, Head of Special Collections at the University Library, UC Santa Cruz, shortly before her retirement in March 2003. This oral history provides a vivid and intimate look at thirty-seven years behind the scenes in the library's Special Collections. For thirty-seven years Bottoms dedicated herself to collecting work by some of the most eminent writers and photographers of the twentieth century, includin...

  9. Benthic data for corals, macroalgae, invertebrates, and non-living bottom types from Fagatele Bay National Marine Sanctuary, South Pacific Ocean, 2007-04-02 to 2008-12-31 (NODC Accession 0068364)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Benthic transects were repeated at 12 sites around Tutuila at various depths on the reef slopes and flats. Benthic coverage categories include coral species,...

  10. Metabolic topography of Parkinsonism

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae Seung [Asan Medical Center, University of Ulsan College of Medicine, Seoul (Korea, Republic of)

    2007-04-15

    Parkinson's disease is one of the most frequent neurodegenerative diseases, which mainly affects the elderly. Parkinson's disease is often difficult to differentiate from atypical parkinson disorder such as progressive supranuclear palsy, multiple system atrophy, dementia with Lewy body, and corticobasal ganglionic degeneration, based on the clinical findings because of the similarity of phenotypes and lack of diagnostic markers. The accurate diagnosis of Parkinson's disease and atypical Parkinson disorders is not only important for deciding on treatment regimens and providing prognosis, but also it is critical for studies designed to investigate etiology and pathogenesis of parkinsonism and to develop new therapeutic strategies. Although degeneration of the nigrostriatal dopamine system results in marked loss of striatal dopamine content in most of the diseases causing parkinsonism, pathologic studies revealed different topographies of the neuronal cell loss in Parkinsonism. Since the regional cerebral glucose metabolism is a marker of integrated local synaptic activity and as such is sensitive to both direct neuronal/synaptic damage and secondary functional disruption at synapses distant from the primary site of pathology, and assessment of the regional cerebral glucose metabolism with F-18 FDG PET is useful in the differential diagnosis of parkinsonism and evaluating the pathophysiology of Parkinsonism.

  11. Metabolic topography of Parkinsonism

    International Nuclear Information System (INIS)

    Kim, Jae Seung

    2007-01-01

    Parkinson's disease is one of the most frequent neurodegenerative diseases, which mainly affects the elderly. Parkinson's disease is often difficult to differentiate from atypical parkinson disorder such as progressive supranuclear palsy, multiple system atrophy, dementia with Lewy body, and corticobasal ganglionic degeneration, based on the clinical findings because of the similarity of phenotypes and lack of diagnostic markers. The accurate diagnosis of Parkinson's disease and atypical Parkinson disorders is not only important for deciding on treatment regimens and providing prognosis, but also it is critical for studies designed to investigate etiology and pathogenesis of parkinsonism and to develop new therapeutic strategies. Although degeneration of the nigrostriatal dopamine system results in marked loss of striatal dopamine content in most of the diseases causing parkinsonism, pathologic studies revealed different topographies of the neuronal cell loss in Parkinsonism. Since the regional cerebral glucose metabolism is a marker of integrated local synaptic activity and as such is sensitive to both direct neuronal/synaptic damage and secondary functional disruption at synapses distant from the primary site of pathology, and assessment of the regional cerebral glucose metabolism with F-18 FDG PET is useful in the differential diagnosis of parkinsonism and evaluating the pathophysiology of Parkinsonism

  12. Formulation of an ocean model for global climate simulations

    Directory of Open Access Journals (Sweden)

    S. M. Griffies

    2005-01-01

    Full Text Available This paper summarizes the formulation of the ocean component to the Geophysical Fluid Dynamics Laboratory's (GFDL climate model used for the 4th IPCC Assessment (AR4 of global climate change. In particular, it reviews the numerical schemes and physical parameterizations that make up an ocean climate model and how these schemes are pieced together for use in a state-of-the-art climate model. Features of the model described here include the following: (1 tripolar grid to resolve the Arctic Ocean without polar filtering, (2 partial bottom step representation of topography to better represent topographically influenced advective and wave processes, (3 more accurate equation of state, (4 three-dimensional flux limited tracer advection to reduce overshoots and undershoots, (5 incorporation of regional climatological variability in shortwave penetration, (6 neutral physics parameterization for representation of the pathways of tracer transport, (7 staggered time stepping for tracer conservation and numerical efficiency, (8 anisotropic horizontal viscosities for representation of equatorial currents, (9 parameterization of exchange with marginal seas, (10 incorporation of a free surface that accomodates a dynamic ice model and wave propagation, (11 transport of water across the ocean free surface to eliminate unphysical ``virtual tracer flux' methods, (12 parameterization of tidal mixing on continental shelves. We also present preliminary analyses of two particularly important sensitivities isolated during the development process, namely the details of how parameterized subgridscale eddies transport momentum and tracers.

  13. Bottom water oxygenation changes in the northern Okinawa Trough since the last 88ka: Controlled by local hydrology and climate

    Science.gov (United States)

    Zou, Jianjun; Shi, Xuefa; Zhu, Aimei; Bai, Yazhi; Selvaraj, Kandasamy

    2014-05-01

    Dissolved oxygen content in oceanic bottom water is closely related to the surface organic carbon export and subsurface water stratification, regulating the biogeochemical cycles of some key nutrients and trace elements in intermediate and deep water columns. Further, the rate of organic carbon flux to sediments and bottom water oxygen concentration together determine the intensity of reducing conditions in sediments. In this study, we obtain high-resolution geochemical elements (TOC, TN, TS, CaCO3, Cd, U, Mn and Mo) in a radiocarbon (14C) and δ18O dated, sediment core CSH1 collected from the northern Okinawa Trough to reconstruct the history of bottom water redox conditions over 88 ka. Our data revealed the presence of hypoxic bottom water in the northern Okinawa Trough during late MIS5a-early MIS4, Last Glacial Maximum, and the early Last Deglacial intervals. During the Holocene and the early MIS5a, the dissolved oxygen content in bottom water has increased with decreasing water stratification, which was probably caused by the increased upwelling from the bottom in tandem with the climbing of Kuroshio Current and subdued freshwater effect in the northern Okinawa Trough. The reasons that caused the change of dissolved oxygen content in bottom water in the northern Okinawa Trough varied during different periods. The main factors are related to sea level, strengths of East Asian monsoon and the Kuroshio Current, and the shift of Westerly Jet Axis. The semi-closed topography in the northern Okinawa Trough provides a space framework for the presence of anoxia, while the sea level together with the Kuroshio Current, the East Asian monsoon and the Westerly Jet Axis seems to affect the strength of water stratification and the nutrient supply; thereby, regulating the dissolved oxygen exchange between surface and bottom waters. This work was supported by the National Natural Science Foundation of China(Grant No.:40906035,40710069004) and by basic scientific fund for

  14. 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...

  15. Bottom Topographic Changes of Poyang Lake During Past Decade Using Multi-temporal Satellite Images

    Science.gov (United States)

    Zhang, S.

    2015-12-01

    Poyang Lake, as a well-known international wetland in the Ramsar Convention List, is the largest freshwater lake in China. It plays crucial ecological role in flood storage and biological diversity. Poyang Lake is facing increasingly serious water crises, including seasonal dry-up, decreased wetland area, and water resource shortage, all of which are closely related to progressive bottom topographic changes over recent years. Time-series of bottom topography would contribute to our understanding of the lake's evolution during the past several decades. However, commonly used methods for mapping bottom topography fail to frequently update quality bathymetric data for Poyang Lake restricted by weather and accessibility. These deficiencies have limited our ability to characterize the bottom topographic changes and understanding lake erosion or deposition trend. To fill the gap, we construct a decadal bottom topography of Poyang Lake with a total of 146 time series medium resolution satellite images based on the Waterline Method. It was found that Poyang Lake has eroded with a rate of -14.4 cm/ yr from 2000 to 2010. The erosion trend was attributed to the impacts of human activities, especially the operation of the Three Gorge Dams, sand excavation, and the implementation of water conservancy project. A decadal quantitative understanding bottom topography of Poyang Lake might provide a foundation to model the lake evolutionary processes and assist both researchers and local policymakers in ecological management, wetland protection and lake navigation safety.

  16. A coarse resolution North Atlantic ocean circulation model: an intercomparison study with a paleoceanographic example

    Directory of Open Access Journals (Sweden)

    Dan Seidov

    Full Text Available Paleoreconstructions suggest that during the Last Glacial Maximum (LGM the North Atlantic circulation was noticeably different from its present state. However, the glacial salt conveyor belt is believed to be similar to the present-day's conveyor, albeit weaker and shallower because of an increased freshwater flux in high-latitudes. We present here the investigation of the conveyor operation based on ocean circulation modelling using two numerical models in parallel. The GFDL primitive equation model and a planetary geostrophic model are employed to address the problem of the paleocirculation modelling in cases of uncertain and sparse data comprising the glacial surface boundary conditions. The role of different simplifications that may be used in the ocean climate studies, including the role of grid resolution, bottom topography, coast-line, etc., versus glacial-interglacial changes of the ocean surface climatology is considered. The LGM reverse conveyor gyre appeared to be the most noticeable feature of the glacial-to-interglacial alteration of the ocean circulation. The reversed upper-ocean conveyor, weaker and subducting 'normal' conveyor in the intermediate depths, and the change of the deep-ocean return flow route are robust signatures of the glacial North Atlantic climate. The results are found to be 'model-independent' and fairly insensitive to all factors other than the onset of the glacial surface conditions.

  17. A coarse resolution North Atlantic ocean circulation model: an intercomparison study with a paleoceanographic example

    Directory of Open Access Journals (Sweden)

    D. Seidov

    1996-02-01

    Full Text Available Paleoreconstructions suggest that during the Last Glacial Maximum (LGM the North Atlantic circulation was noticeably different from its present state. However, the glacial salt conveyor belt is believed to be similar to the present-day's conveyor, albeit weaker and shallower because of an increased freshwater flux in high-latitudes. We present here the investigation of the conveyor operation based on ocean circulation modelling using two numerical models in parallel. The GFDL primitive equation model and a planetary geostrophic model are employed to address the problem of the paleocirculation modelling in cases of uncertain and sparse data comprising the glacial surface boundary conditions. The role of different simplifications that may be used in the ocean climate studies, including the role of grid resolution, bottom topography, coast-line, etc., versus glacial-interglacial changes of the ocean surface climatology is considered. The LGM reverse conveyor gyre appeared to be the most noticeable feature of the glacial-to-interglacial alteration of the ocean circulation. The reversed upper-ocean conveyor, weaker and subducting 'normal' conveyor in the intermediate depths, and the change of the deep-ocean return flow route are robust signatures of the glacial North Atlantic climate. The results are found to be 'model-independent' and fairly insensitive to all factors other than the onset of the glacial surface conditions.

  18. The viscous lee wave problem and its implications for ocean modelling

    Science.gov (United States)

    Shakespeare, Callum J.; Hogg, Andrew McC.

    2017-05-01

    Ocean circulation models employ 'turbulent' viscosity and diffusivity to represent unresolved sub-gridscale processes such as breaking internal waves. Computational power has now advanced sufficiently to permit regional ocean circulation models to be run at sufficiently high (100 m-1 km) horizontal resolution to resolve a significant part of the internal wave spectrum. Here we develop theory for boundary generated internal waves in such models, and in particular, where the waves dissipate their energy. We focus specifically on the steady lee wave problem where stationary waves are generated by a large-scale flow acting across ocean bottom topography. We generalise the energy flux expressions of [Bell, T., 1975. Topographically generated internal waves in the open ocean. J. Geophys. Res. 80, 320-327] to include the effect of arbitrary viscosity and diffusivity. Applying these results for realistic parameter choices we show that in the present generation of models with O(1) m2s-1 horizontal viscosity/diffusivity boundary-generated waves will inevitably dissipate the majority of their energy within a few hundred metres of the boundary. This dissipation is a direct consequence of the artificially high viscosity/diffusivity, which is not always physically justified in numerical models. Hence, caution is necessary in comparing model results to ocean observations. Our theory further predicts that O(10-2) m2s-1 horizontal and O(10-4) m2s-1 vertical viscosity/diffusivity is required to achieve a qualitatively inviscid representation of internal wave dynamics in ocean models.

  19. The role of Southern Ocean mixing and upwelling in glacial-interglacial atmospheric CO2 change

    International Nuclear Information System (INIS)

    Watson, Andrew J.; Naveira Garabato, Alberto C.

    2006-01-01

    Decreased ventilation of the Southern Ocean in glacial time is implicated in most explanations of lower glacial atmospheric CO 2 . Today, the deep (>2000 m) ocean south of the Polar Front is rapidly ventilated from below, with the interaction of deep currents with topography driving high mixing rates well up into the water column. We show from a buoyancy budget that mixing rates are high in all the deep waters of the Southern Ocean. Between the surface and 2000 m depth, water is upwelled by a residual meridional overturning that is directly linked to buoyancy fluxes through the ocean surface. Combined with the rapid deep mixing, this upwelling serves to return deep water to the surface on a short time scale. We propose two new mechanisms by which, in glacial time, the deep Southern Ocean may have been more isolated from the surface. Firstly, the deep ocean appears to have been more stratified because of denser bottom water resulting from intense sea ice formation near Antarctica. The greater stratification would have slowed the deep mixing. Secondly, subzero atmospheric temperatures may have meant that the present-day buoyancy flux from the atmosphere to the ocean surface was reduced or reversed. This in turn would have reduced or eliminated the upwelling (contrary to a common assumption, upwelling is not solely a function of the wind stress but is coupled to the air/sea buoyancy flux too). The observed very close link between Antarctic temperatures and atmospheric CO 2 could then be explained as a natural consequence of the connection between the air/sea buoyancy flux and upwelling in the Southern Ocean, if slower ventilation of the Southern Ocean led to lower atmospheric CO 2 . Here we use a box model, similar to those of previous authors, to show that weaker mixing and reduced upwelling in the Southern Ocean can explain the low glacial atmospheric CO 2 in such a formulation

  20. 77 FR 20590 - Ocean Dumping; Designation of Ocean Dredged Material Disposal Sites Offshore of Yaquina Bay, OR

    Science.gov (United States)

    2012-04-05

    ... sediment, short-term disruption in avian foraging behavior, modification of bottom topography, loss of... species or result in the destruction or adverse modification of any critical habitat. The EPA prepared a...

  1. Bottom and top physics

    International Nuclear Information System (INIS)

    Foley, K.J.; Fridman, A.; Gilman, F.J.; Herten, G.; Hinchliffe, I.; Jawahery, A.; Sanda, A.; Schmidt, M.P.; Schubert, K.R.

    1987-09-01

    The production of bottom quarks at the SSC and the formalism and phenomenology of observing CP violation in B meson decays is discussed. The production of a heavy t quark which decays into a real W boson, and what we might learn from its decays is examined

  2. Determining Coastal Mean Dynamic Topography by Geodetic Methods

    Science.gov (United States)

    Huang, Jianliang

    2017-11-01

    In geodesy, coastal mean dynamic topography (MDT) was traditionally determined by spirit leveling technique. Advances in navigation satellite positioning (e.g., GPS) and geoid determination enable space-based leveling with an accuracy of about 3 cm at tide gauges. Recent CryoSat-2, a satellite altimetry mission with synthetic aperture radar (SAR) and SAR interferometric measurements, extends the space-based leveling to the coastal ocean with the same accuracy. However, barriers remain in applying the two space-based geodetic methods for MDT determination over the coastal ocean because current geoid modeling focuses primarily on land as a substitute to spirit leveling to realize the vertical datum.

  3. Preferential states of rotating turbulent flows in a square container with a step topography

    NARCIS (Netherlands)

    Tenreiro, M.; Trieling, R.R.; Zavala Sansón, L.; Heijst, van G.J.F.

    2013-01-01

    The self-organization of confined, quasi-two-dimensional turbulent flows in a rotating square container with a step-like topography is investigated by means of laboratory experiments and numerical simulations based on a rigid lid, shallow-water formulation. The domain is divided by a bottom

  4. Examinations for quantifying the difference in radiation doses at the least favorable locations between facility sites in highly structured topographies (valleys) and in plane terrain (licensing procedures)

    International Nuclear Information System (INIS)

    Raskob, W.

    1995-01-01

    The MCF wind field model and the LASAT Lagrange particle model served to study topography effects on the spreading of radionuclides. Concentrations in bottom layers of the atmosphere at maximum-dose positions in hilly country topography are up to a factor 6 higher than in plain country. For concentrations in the soil the results have a similar relation. (orig.)

  5. 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.

  6. Shearwater foraging in the Southern Ocean: the roles of prey availability and winds.

    Directory of Open Access Journals (Sweden)

    Ben Raymond

    Full Text Available BACKGROUND: Sooty (Puffinus griseus and short-tailed (P. tenuirostris shearwaters are abundant seabirds that range widely across global oceans. Understanding the foraging ecology of these species in the Southern Ocean is important for monitoring and ecosystem conservation and management. METHODOLOGY/PRINCIPAL FINDINGS: Tracking data from sooty and short-tailed shearwaters from three regions of New Zealand and Australia were combined with at-sea observations of shearwaters in the Southern Ocean, physical oceanography, near-surface copepod distributions, pelagic trawl data, and synoptic near-surface winds. Shearwaters from all three regions foraged in the Polar Front zone, and showed particular overlap in the region around 140 degrees E. Short-tailed shearwaters from South Australia also foraged in Antarctic waters south of the Polar Front. The spatial distribution of shearwater foraging effort in the Polar Front zone was matched by patterns in large-scale upwelling, primary production, and abundances of copepods and myctophid fish. Oceanic winds were found to be broad determinants of foraging distribution, and of the flight paths taken by the birds on long foraging trips to Antarctic waters. CONCLUSIONS/SIGNIFICANCE: The shearwaters displayed foraging site fidelity and overlap of foraging habitat between species and populations that may enhance their utility as indicators of Southern Ocean ecosystems. The results highlight the importance of upwellings due to interactions of the Antarctic Circumpolar Current with large-scale bottom topography, and the corresponding localised increases in the productivity of the Polar Front ecosystem.

  7. 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...

  8. 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...

  9. 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.

  10. 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

  11. Surface Micro Topography Replication in Injection Moulding

    DEFF Research Database (Denmark)

    Arlø, Uffe Rolf; Hansen, Hans Nørgaard; Kjær, Erik Michael

    2005-01-01

    The surface micro topography of injection moulded plastic parts can be important for aesthetical and technical reasons. The quality of replication of mould surface topography onto the plastic surface depends among other factors on the process conditions. A study of this relationship has been...... carried out with rough EDM (electrical discharge machining) mould surfaces, a PS grade, and by applying established three-dimensional topography parameters. Significant quantitative relationships between process parameters and topography parameters were established. It further appeared that replication...

  12. Bottom and top physics

    International Nuclear Information System (INIS)

    Foley, K.J.; Gilman, F.J.; Herten, G.; Hinchliffe, I.; Jawahery, A.; Sanda, A.; Schmidt, M.P.; Schubert, K.R.; Fridman, A.

    1988-01-01

    The production of heavy quark flavors occurs primarily by the strong interactions and offers another arena in which to test QCD and to probe gluon distributions at very small values of x. Such quarks can also be produced as decay products of possible new, yet undiscovered particles, e.g., Higgs bosons, and therefore are a necessary key to reconstructing such particles. The decay products of heavy quarks, especially from their semileptonic decays, can themselves form a background to other new physics processes. The production of bottom quarks at the SSC and the formalism and phenomenology of observing CP violation in B meson decays is discussed. The production of a heavy t quark which decays into a real W boson, and what might be learned from its decays is examined

  13. 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...

  14. 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....

  15. An ocean gazetteer for education and research

    Science.gov (United States)

    Delaney, R.; Staudigel, D.; Staudigel, H.

    2003-04-01

    Global travel, economy, and news coverage often challenge the student's and teacher's knowledge of the geography of the seas. The International Hydrographic Organization (IHO) has published a description of all the major seas making up earth's oceans, but there is currently no electronic tool that identifies them on a digital map. During an internship at Scripps Institution of Oceanography, we transferred the printed visual description of the seas from IHO publication 23 into a digital format. This digital map was turned into a (Flash) web application that allows a user to identify any of the IHO seas on a world map, simply by moving the computer cursor over it. In our presentation, we will describe the path taken to produce this web application and the learning process involved in this path during our internship at Scripps. The main steps in this process included the digitization of the official IHO maps, the transfer of this information onto a modern digital map by Smith and Sandwell. Adjustments were necessary due to the fact that many of the landmasses were placed incorrectly on a lat/long grid, off by as much as 100km. Boundaries between seas were often misrepresented by the IHO as straight lines on a Mercator projection. Once the digitization of the seas was completed we used the 2d animation environment Flash and we produced an interactive map environment that allows any teacher or student of ocean geography to identify an ocean by name and location. Aside from learning about the geography of the oceans, we were introduced to the use of digitizers, we learned to make maps using Generic Mapping Tools (GMT) and digital global bathymetry data sets, and we learned about map projections. We studied Flash to produce an interactive map of the oceans that displays bathymetry and topography, highlighting any particular sea the cursor moves across. The name of the selected sea in our Flash application appears in a textbox on the bottom of the map. The result of this

  16. 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

  17. 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

  18. A 4.5 km resolution Arctic Ocean simulation with the global multi-resolution model FESOM 1.4

    Science.gov (United States)

    Wang, Qiang; Wekerle, Claudia; Danilov, Sergey; Wang, Xuezhu; Jung, Thomas

    2018-04-01

    In the framework of developing a global modeling system which can facilitate modeling studies on Arctic Ocean and high- to midlatitude linkage, we evaluate the Arctic Ocean simulated by the multi-resolution Finite Element Sea ice-Ocean Model (FESOM). To explore the value of using high horizontal resolution for Arctic Ocean modeling, we use two global meshes differing in the horizontal resolution only in the Arctic Ocean (24 km vs. 4.5 km). The high resolution significantly improves the model's representation of the Arctic Ocean. The most pronounced improvement is in the Arctic intermediate layer, in terms of both Atlantic Water (AW) mean state and variability. The deepening and thickening bias of the AW layer, a common issue found in coarse-resolution simulations, is significantly alleviated by using higher resolution. The topographic steering of the AW is stronger and the seasonal and interannual temperature variability along the ocean bottom topography is enhanced in the high-resolution simulation. The high resolution also improves the ocean surface circulation, mainly through a better representation of the narrow straits in the Canadian Arctic Archipelago (CAA). The representation of CAA throughflow not only influences the release of water masses through the other gateways but also the circulation pathways inside the Arctic Ocean. However, the mean state and variability of Arctic freshwater content and the variability of freshwater transport through the Arctic gateways appear not to be very sensitive to the increase in resolution employed here. By highlighting the issues that are independent of model resolution, we address that other efforts including the improvement of parameterizations are still required.

  19. 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

  20. 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.

  1. Corneal topography with an aberrometry-topography system.

    Science.gov (United States)

    Mülhaupt, Michael; Dietzko, Sven; Wolffsohn, James; Bandlitz, Stefan

    2018-05-07

    To investigate the agreement between the central corneal radii and corneal eccentricity measurements generated by the new Wave Analyzer 700 Medica (WAV) compared to the Keratograph 4 (KER) and to test the repeatability of the instruments. 20 subjects (10 male, mean age 29.1 years, range 21-50 years) were recruited from the students and staff of the Cologne School of Optometry. Central corneal radii for the flat (r c/fl ) and steep (r c/st ) meridian as well as corneal eccentricity for the nasal (e nas ), temporal (e temp ), inferior (e inf ) and superior (e sup ) directions were measured using WAV and KER by one examiner in a randomized order. Central radii of the flat (r c/fl ) and steep (r c/st ) meridian measured with both instruments were statically significantly correlated (r = 0.945 and r = 0.951; p  0.05). Limits of agreement (LoA) indicate a better repeatability for the KER compared to WAV. Corneal topography measurements captured with the WAV were strongly correlated with the KER. However, due to the differences in measured corneal radii and eccentricities, the devices cannot be used interchangeably. For corneal topography the KER demonstrated better repeatability. Copyright © 2018 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  2. A consistent data set of Antarctic ice sheet topography, cavity geometry, and global bathymetry

    Directory of Open Access Journals (Sweden)

    R. Timmermann

    2010-12-01

    Full Text Available Sub-ice shelf circulation and freezing/melting rates in ocean general circulation models depend critically on an accurate and consistent representation of cavity geometry. Existing global or pan-Antarctic topography data sets have turned out to contain various inconsistencies and inaccuracies. The goal of this work is to compile independent regional surveys and maps into a global data set. We use the S-2004 global 1-min bathymetry as the backbone and add an improved version of the BEDMAP topography (ALBMAP bedrock topography for an area that roughly coincides with the Antarctic continental shelf. The position of the merging line is individually chosen in different sectors in order to capture the best of both data sets. High-resolution gridded data for ice shelf topography and cavity geometry of the Amery, Fimbul, Filchner-Ronne, Larsen C and George VI Ice Shelves, and for Pine Island Glacier are carefully merged into the ambient ice and ocean topographies. Multibeam survey data for bathymetry in the former Larsen B cavity and the southeastern Bellingshausen Sea have been obtained from the data centers of Alfred Wegener Institute (AWI, British Antarctic Survey (BAS and Lamont-Doherty Earth Observatory (LDEO, gridded, and blended into the existing bathymetry map. The resulting global 1-min Refined Topography data set (RTopo-1 contains self-consistent maps for upper and lower ice surface heights, bedrock topography, and surface type (open ocean, grounded ice, floating ice, bare land surface. The data set is available in NetCDF format from the PANGAEA database at doi:10.1594/pangaea.741917.

  3. 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.

  4. Photogrammetric portrayal of Mars topography.

    Science.gov (United States)

    Wu, S.S.C.

    1979-01-01

    Special photogrammetric techniques have been developed to portray Mars topography, using Mariner and Viking imaging and nonimaging topographic information and earth-based radar data. Topography is represented by the compilation of maps at three scales: global, intermediate, and very large scale. The global map is a synthesis of topographic information obtained from Mariner 9 and earth-based radar, compiled at a scale of 1:25,000,000 with a contour interval of 1 km; it gives a broad quantitative view of the planet. At intermediate scales, Viking Orbiter photographs of various resolutions are used to compile detailed contour maps of a broad spectrum of prominent geologic features; a contour interval as small as 20 m has been obtained from very high resolution orbital photography. Imagery from the Viking lander facsimile cameras permits construction of detailed, very large scale (1:10) topographic maps of the terrain surrounding the two landers; these maps have a contour interval of 1 cm. This paper presents several new detailed topographic maps of Mars.-Author

  5. MAPPING OF THE RUSSIAN NORTHERN SEAS BOTTOM RELIEF USING DIGITAL ELEVATION MODELS

    Directory of Open Access Journals (Sweden)

    S. M. Koshel

    2014-01-01

    Full Text Available The task of the project is the design of the digital elevation models (DEM of the bottoms of Barents Sea, Pechora Sea, and the White Sea. Accuracy (resolution of DEMs allows for adequate delineation of morphological structures and peculiarities of the sea bottoms and the design of bathymetrical and derivative maps. DEMs of the sea bottom were compiled using data from navigation charts of different scales, where additional isobaths were drawn manually taking into account the classification features of the bottom topography forms. Next procedures were carried out: scanning of these charts, processing of scanned images, isobaths vectorization and creation of attribute tables, vector layers transformation to geographical coordinates as well editing, merging and joining of the map sheets, correction of geometry and attributes. For generation of digital model of bottom topography it is important to choose algorithm which allows for representation all of the sea bottom features expressed by isobaths in most details. The original algorithm based on fast calculation of distances to the two different nearest isobaths was used. Interpretation of isolines as vector linear objects is the main peculiarity of this algorithm. The resulted DEMs were used to design bathymetrical maps of Barents Sea of 1:2 500 000 scale, Pechora Sea of 1:1 000 000 scale, and White Sea of 1:750 000 scale. Different derivative maps were compiled based on DEM of the White Sea.

  6. Dynamic topography and the Cenozoic carbonate compensation depth

    Science.gov (United States)

    Campbell, S. M.; Moucha, R.; Raymo, M. E.; Derry, L. A.

    2015-12-01

    The carbonate compensation depth (CCD), the ocean depth at which the calcium carbonate accumulation rate goes to zero, can provide valuable insight into climatic and weathering conditions over the Cenozoic. The paleoposition of the CCD can be inferred from sediment core data. As the carbonate accumulation rate decreases linearly with depth between the lysocline and CCD, the CCD can be calculated using a linear regression on multiple sediment cores with known carbonate accumulation rates and paleodepths. It is therefore vital to have well-constrained estimates of paleodepths. Paleodepths are typically calculated using models of thermal subsidence and sediment loading and compaction. However, viscous convection-related stresses in the mantle can warp the ocean floor by hundreds of meters over broad regions and can also vary significantly over millions of years. This contribution to paleobathymetry, termed dynamic topography, can be calculated by modeling mantle flow backwards in time. Herein, we demonstrate the effect dynamic topography has on the inference of the late Cenozoic CCD with an example from the equatorial Pacific, considering sites from IODP Expeditions 320/321. The equatorial Pacific, given its large size and high productivity, is closely tied to the global carbon cycle. Accordingly, long-term changes in the equatorial Pacific CCD can be considered to reflect global changes in weathering fluxes and the carbon cycle, in addition to more regional changes in productivity and thermohaline circulation. We find that, when the dynamic topography contribution to bathymetry is accounted for, the equatorial Pacific CCD is calculated to be appreciably shallower at 30 Ma than previous estimates would suggest, implying a greater deepening of the Pacific CCD over the late Cenozoic.

  7. 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

  8. Ocean surface waves in Hurricane Ike (2008) and Superstorm Sandy (2012): Coupled model predictions and observations

    Science.gov (United States)

    Chen, Shuyi S.; Curcic, Milan

    2016-07-01

    Forecasting hurricane impacts of extreme winds and flooding requires accurate prediction of hurricane structure and storm-induced ocean surface waves days in advance. The waves are complex, especially near landfall when the hurricane winds and water depth varies significantly and the surface waves refract, shoal and dissipate. In this study, we examine the spatial structure, magnitude, and directional spectrum of hurricane-induced ocean waves using a high resolution, fully coupled atmosphere-wave-ocean model and observations. The coupled model predictions of ocean surface waves in Hurricane Ike (2008) over the Gulf of Mexico and Superstorm Sandy (2012) in the northeastern Atlantic and coastal region are evaluated with the NDBC buoy and satellite altimeter observations. Although there are characteristics that are general to ocean waves in both hurricanes as documented in previous studies, wave fields in Ike and Sandy possess unique properties due mostly to the distinct wind fields and coastal bathymetry in the two storms. Several processes are found to significantly modulate hurricane surface waves near landfall. First, the phase speed and group velocities decrease as the waves become shorter and steeper in shallow water, effectively increasing surface roughness and wind stress. Second, the bottom-induced refraction acts to turn the waves toward the coast, increasing the misalignment between the wind and waves. Third, as the hurricane translates over land, the left side of the storm center is characterized by offshore winds over very short fetch, which opposes incoming swell. Landfalling hurricanes produce broader wave spectra overall than that of the open ocean. The front-left quadrant is most complex, where the combination of windsea, swell propagating against the wind, increasing wind-wave stress, and interaction with the coastal topography requires a fully coupled model to meet these challenges in hurricane wave and surge prediction.

  9. 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

  10. Surface micro topography replication in injection moulding

    DEFF Research Database (Denmark)

    Arlø, Uffe Rolf

    Thermoplastic injection moulding is a widely used industrial process that involves surface generation by replication. The surface topography of injection moulded plastic parts can be important for aesthetical or technical reasons. With the emergence of microengineering and nanotechnology additional...... importance of surface topography follows. In general the replication is not perfect and the topography of the plastic part differs from the inverse topography of the mould cavity. It is desirable to be able to control the degree of replication perfection or replication quality. This requires an understanding...... of the physical mechanisms of replication. Such understanding can lead to improved process design and facilitate in-line process quality control with respect to surface properties. The purpose of the project is to identify critical factors that affect topography replication quality and to obtain an understanding...

  11. GOCE Data for Ocean Modelling

    DEFF Research Database (Denmark)

    Herceg, Matija

    and order. The method makes use of all available GOCE gradient data in addition to the global models and aims at improving the determination of Earth’s gravitational field in regional areas. Subsequently, the calculated equipotential surface, known as the geoid, is used together with measurements of sea...... surface height in a calculation of the Mean Dynamic Topography (MDT). This reflects the geostrophic ocean currents and leads to a better understanding of ocean mass and heat transfer. In regional geoid recovery from GOCE gradients, two methods are used, one of them being Least-Squares Collocation (LSC...

  12. 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.)

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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...

  7. 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...

  8. 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...

  9. 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

  10. 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...

  11. 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...

  12. 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...

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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,...

  2. 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...

  3. An ocean circulation model in σS- z- σB hybrid coordinate and its validation

    Science.gov (United States)

    Zhuang, Zhanpeng; Yuan, Yeli; Yang, Guangbing

    2018-02-01

    A 3D, two-time-level, σS- z- σB hybrid-coordinate Marine Science and Numerical Modeling numerical ocean circulation model (HyMOM) is developed in this paper. In HyMOM, the σ coordinate is employed in the surface and bottom regions, and the z coordinate is used in the intermediate layers. This method can overcome problems with vanishing surface cells and minimize the unwanted deviation in representing bottom topography. The connection between the σ and z layers vertically includes an expanded "ghost" method and the linear interpolation. The governing equations in the σS- z- σB hybrid coordinate based on the complete Reynolds-averaged Navier-Stokes equations are derived in detail. The two-level time staggered and Eulerian forward and backward schemes, which are of second-order of accuracy, are adopted for the temporal difference in internal and external mode, respectively. The computation of the baroclinic gradient force is tested in an analytic test problem; the errors for two methods in HyMOM, which are relatively large only in the bottom layers, are obviously smaller than those in the pure σ and z models in almost all of the vertical layers. A quasi-global climatologic numerical experiment is constructed to test the simulation performance of HyMOM. With the monthly mean Levitus climatology data as reference, the HyMOM can improve the simulating accuracy compared with its pure z or σ coordinate implementation.

  4. Tidal Friction in the Earth and Ocean

    Science.gov (United States)

    Ray, R. D.

    2006-12-01

    "Tidal Friction" is a classic subject in geophysics, with ties to some of the great scientists of the Victorian era. The subject has been reinvigorated over the past decade by space geodesy, and particularly by the Topex/Poseidon satellite altimeter mission. In fact, the topic has now taken on some significance in oceanography, with potential implications for problems of mixing, thermocline maintenance, and the thermohaline circulation. Likewise, tidal measurements have become sufficiently precise to reveal new information about the solid earth. In this respect, the tidal force is an invaluable "probe" of the earth, at frequencies well outside the seismic band. This talk will "follow the energy" of tides while noting some important geophysical implications at each stage. In the present earth-moon-sun configuration, energy for tides is extracted from the earth's rotation. Ancient eclipses bear witness to this, and the discrepancy between Babylonian (and other) observations and tidal predictions yields unique information about the mantle and the overlying fluid envelope. Complementary information comes from tidal anelasticity estimates, which are now available at frequencies ranging from semidiurnal to fortnightly, monthly, and 18.6 years. These data, when combined with various kinds of gravity measurements, are relevant to the present-day sea-level problem. Solid-earth tidal dissipation represents less than 5% of the system total. As has long been realized, the largest energy sink is the ocean. About 70% of the oceanic dissipation occurs in shallow seas (the traditional sink) and 30% in the deep ocean, generally near rugged bottom topography. The latter represents a substantial amount of power, roughly 1 gigawatt, available for generation of internal tides and other baroclinic motions. Experiments like HOME are helping unravel the links between barotropic tides, internal tides, turbulence, and mixing. The latter opens possible linkages to climate, and recent work

  5. Internal wave mode resonant triads in an arbitrarly stratified finite-depth ocean with background rotation

    Science.gov (United States)

    Varma, Dheeraj; Mathur, Manikandan

    2017-11-01

    Internal tides generated by barotropic tides on bottom topography or the spatially compact near-inertial mixed layer currents excited by surface winds can be conveniently represented in the linear regime as a superposition of vertical modes at a given frequency in an arbitrarily stratified ocean of finite depth. Considering modes (m , n) at a frequency ω in the primary wave field, we derive the weakly nonlinear solution, which contains a secondary wave at 2 ω that diverges when it forms a resonant triad with the primary waves. In nonuniform stratifications, resonant triads are shown to occur when the horizontal component of the classical RTI criterion k->1 +k->2 +k->3 = 0 is satisfied along with a non-orthogonality criterion. In nonuniform stratifications with a pycnocline, infinitely more pairs of primary wave modes (m , n) result in RTI when compared to a uniform stratification. Further, two nearby high modes at around the near-inertial frequency often form a resonant triad with a low mode at 2 ω , reminiscent of the features of PSI near the critical latitude. The theoretical framework is then adapted to investigate RTI in two different scenarios: low-mode internal tide scattering over topography, and internal wave beams incident on a pycnocline. The authors thank the Ministry of Earth Sciences, Government of India for financial support under the Monsoon Mission Grant MM/2014/IND-002.

  6. SECTION 6.2 SURFACE TOPOGRAPHY ANALYSIS

    DEFF Research Database (Denmark)

    Seah, M. P.; De Chiffre, Leonardo

    2005-01-01

    Surface physical analysis, i.e. topography characterisation, encompasses measurement, visualisation, and quantification. This is critical for both component form and for surface finish at macro-, micro- and nano-scales. The principal methods of surface topography measurement are stylus profilometry......, optical scanning techniques, and scanning probe microscopy (SPM). These methods, based on acquisition of topography data from point by point scans, give quantitative information of heights with respect to position. Based on a different approach, the so-called integral methods produce parameters...

  7. Earth's structure and evolution inferred from topography, gravity, and seismicity.

    Science.gov (United States)

    Watkinson, A. J.; Menard, J.; Patton, R. L.

    2016-12-01

    Earth's wavelength-dependent response to loading, reflected in observed topography, gravity, and seismicity, can be interpreted in terms of a stack of layers under the assumption of transverse isotropy. The theory of plate tectonics holds that the outermost layers of this stack are mobile, produced at oceanic ridges, and consumed at subduction zones. Their toroidal motions are generally consistent with those of several rigid bodies, except in the world's active mountain belts where strains are partitioned and preserved in tectonite fabrics. Even portions of the oceanic lithosphere exhibit non-rigid behavior. Earth's gravity-topography cross-spectrum exhibits notable variations in signal amplitude and character at spherical harmonic degrees l=13, 116, 416, and 1389. Corresponding Cartesian wavelengths are approximately equal to the respective thicknesses of Earth's mantle, continental mantle lithosphere, oceanic thermal lithosphere, and continental crust, all known from seismology. Regional variations in seismic moment release with depth, derived from the global Centroid Moment Tensor catalog, are also evident in the crust and mantle lithosphere. Combined, these observations provide powerful constraints for the structure and evolution of the crust, mantle lithosphere, and mantle as a whole. All that is required is a dynamically consistent mechanism relating wavelength to layer thickness and shear-strain localization. A statistically-invariant 'diharmonic' relation exhibiting these properties appears as the leading order approximation to toroidal motions on a self-gravitating body of differential grade-2 material. We use this relation, specifically its predictions of weakness and rigidity, and of folding and shear banding response as a function of wavelength-to-thickness ratio, to interpret Earth's gravity, topography, and seismicity in four-dimensions. We find the mantle lithosphere to be about 255-km thick beneath the Himalaya and the Andes, and the long

  8. Ocean Acidification | Smithsonian Ocean Portal

    Science.gov (United States)

    Natural History Blog For Educators At The Museum Media Archive Ocean Life & Ecosystems Mammals Sharks Mangroves Poles Census of Marine Life Planet Ocean Tides & Currents Waves & Storms The Seafloor ocean is affected. Such a relatively quick change in ocean chemistry doesn't give marine life, which

  9. 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

  10. Mapping Bedrock Topography using Electromagnetic Profiling ...

    African Journals Online (AJOL)

    Mapping Bedrock Topography using Electromagnetic Profiling. ... will be constructed The area under study is within the Abakaliki Shales Geologic Formation. ... micaceous sandstone; micaceous siltstone, sandy shales and shelly limestone.

  11. 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))

  12. Culture from the Bottom Up

    Science.gov (United States)

    Atkinson, Dwight; Sohn, Jija

    2013-01-01

    The culture concept has been severely criticized for its top-down nature in TESOL, leading arguably to its falling out of favor in the field. But what of the fact that people do "live culturally" (Ingold, 1994)? This article describes a case study of culture from the bottom up--culture as understood and enacted by its individual users.…

  13. Decay of the Bottom mesons

    International Nuclear Information System (INIS)

    Duong Van Phi; Duong Anh Duc

    1992-12-01

    The channels of the decay of Bottom mesons are deduced from a selection rule and the Lagrangians which are formed on the LxO(4) invariance and the principle of minimal structure. The estimation of the corresponding decay probabilities are considered. (author). 21 refs

  14. Bottom reflector for power reactors

    International Nuclear Information System (INIS)

    Elter, C.; Kissel, K.F.; Schoening, J.; Schwiers, H.G.

    1982-01-01

    In pebble bed reactors erosion and damage due fuel elements movement on the surface of the bottom reflector should be minimized. This can be achieved by chamfering and/or rounding the cover edges of the graphite blocks and the edges between the drilled holes and the surface of the graphite block. (orig.) [de

  15. A bottom-driven mechanism for distributed faulting: Insights from the Gulf of California Rift

    Science.gov (United States)

    Persaud, P.; Tan, E.; Choi, E.; Contreras, J.; Lavier, L. L.

    2017-12-01

    The Gulf of California is a young oblique rift that displays a variation in rifting style along strike. Despite the rapid localization of strain in the Gulf at 6 Ma, the northern rift segment has the characteristics of a wide rift, with broadly distributed extensional strain and small gradients in topography and crustal thinning. Observations of active faulting in the continent-ocean transition of the Northern Gulf show multiple oblique-slip faults distributed in a 200 x 70 km2area developed some time after a westward relocation of the plate boundary at 2 Ma. In contrast, north and south of this broad pull-apart structure, major transform faults accommodate Pacific-North America plate motion. Here we propose that the mechanism for distributed brittle deformation results from the boundary conditions present in the Northern Gulf, where basal shear is distributed between the Cerro Prieto strike-slip fault (southernmost fault of the San Andreas fault system) and the Ballenas Transform fault. We hypothesize that in oblique-extensional settings whether deformation is partitioned in a few dip-slip and strike-slip faults, or in numerous oblique-slip faults may depend on (1) bottom-driven, distributed extension and shear deformation of the lower crust or upper mantle, and (2) the rift obliquity. To test this idea, we explore the effects of bottom-driven shear on the deformation of a brittle elastic-plastic layer with pseudo-three dimensional numerical models that include side forces. Strain localization results when the basal shear is a step-function while oblique-slip on numerous faults dominates when basal shear is distributed. We further investigate how the style of faulting varies with obliquity and demonstrate that the style of faulting observed in the Northern Gulf of California is reproduced in models with an obliquity of 0.7 and distributed basal shear boundary conditions, consistent with the interpreted obliquity and boundary conditions of the study area. Our

  16. Surface Topography Hinders Bacterial Surface Motility.

    Science.gov (United States)

    Chang, Yow-Ren; Weeks, Eric R; Ducker, William A

    2018-03-21

    We demonstrate that the surface motility of the bacterium, Pseudomonas aeruginosa, is hindered by a crystalline hemispherical topography with wavelength in the range of 2-8 μm. The motility was determined by the analysis of time-lapse microscopy images of cells in a flowing growth medium maintained at 37 °C. The net displacement of bacteria over 5 min is much lower on surfaces containing 2-8 μm hemispheres than on flat topography, but displacement on the 1 μm hemispheres is not lower. That is, there is a threshold between 1 and 2 μm for response to the topography. Cells on the 4 μm hemispheres were more likely to travel parallel to the local crystal axis than in other directions. Cells on the 8 μm topography were less likely to travel across the crowns of the hemispheres and were also more likely to make 30°-50° turns than on flat surfaces. These results show that surface topography can act as a significant barrier to surface motility and may therefore hinder surface exploration by bacteria. Because surface exploration can be a part of the process whereby bacteria form colonies and seek nutrients, these results help to elucidate the mechanism by which surface topography hinders biofilm formation.

  17. Impact of lithospheric rheology on surface topography

    Science.gov (United States)

    Liao, K.; Becker, T. W.

    2017-12-01

    The expression of mantle flow such as due to a buoyant plume as surface topography is a classical problem, yet the role of rheological complexities could benefit from further exploration. Here, we investigate the topographic expressions of mantle flow by means of numerical and analytical approaches. In numerical modeling, both conventional, free-slip and more realistic, stress-free boundary conditions are applied. For purely viscous rheology, a high viscosity lithosphere will lead to slight overestimates of topography for certain settings, which can be understood by effectively modified boundary conditions. Under stress-free conditions, numerical and analytical results show that the magnitude of dynamic topography decreases with increasing lithosphere thickness (L) and viscosity (ηL), as L-1 and ηL-3. The wavelength of dynamic topography increases linearly with L and (ηL/ ηM) 1/3. We also explore the time-dependent interactions of a rising plume with the lithosphere. For a layered lithosphere with a decoupling weak lower crust embedded between stronger upper crust and lithospheric mantle, dynamic topography increases with a thinner and weaker lower crust. The dynamic topography saturates when the decoupling viscosity is 3-4 orders lower than the viscosity of upper crust and lithospheric mantle. We further explore the role of visco-elastic and visco-elasto-plastic rheologies.

  18. Measuring topographies from conventional SEM acquisitions.

    Science.gov (United States)

    Shi, Qiwei; Roux, Stéphane; Latourte, Félix; Hild, François; Loisnard, Dominique; Brynaert, Nicolas

    2018-04-27

    The present study extends the stereoscopic imaging principle for estimating the surface topography to two orientations, namely, normal to the electron beam axis and inclined at 70° as suited for EBSD analyses. In spite of the large angle difference, it is shown that the topography can be accurately determined using regularized global Digital Image Correlation. The surface topography is compared to another estimate issued from a 3D FIB-SEM procedure where the sample surface is first covered by a Pt layer, and its initial topography is progressively revealed from successive FIB-milling. These two methods are successfully compared on a 6% strained steel specimen in an in situ mechanical test. This analysis is supplemented by a third approach estimating the change of topography from crystal rotations as measured from successive EBSD images. This last technique ignores plastic deformation, and thus only holds in an elastic regime. For the studied example, despite the large plastic flow, it is shown that crystal rotation already accounts for a significant part of the deformation-induced topography. Copyright © 2018 Elsevier B.V. All rights reserved.

  19. Corneal topography measurements for biometric applications

    Science.gov (United States)

    Lewis, Nathan D.

    The term biometrics is used to describe the process of analyzing biological and behavioral traits that are unique to an individual in order to confirm or determine his or her identity. Many biometric modalities are currently being researched and implemented including, fingerprints, hand and facial geometry, iris recognition, vein structure recognition, gait, voice recognition, etc... This project explores the possibility of using corneal topography measurements as a trait for biometric identification. Two new corneal topographers were developed for this study. The first was designed to function as an operator-free device that will allow a user to approach the device and have his or her corneal topography measured. Human subject topography data were collected with this device and compared to measurements made with the commercially available Keratron Piccolo topographer (Optikon, Rome, Italy). A third topographer that departs from the standard Placido disk technology allows for arbitrary pattern illumination through the use of LCD monitors. This topographer was built and tested to be used in future research studies. Topography data was collected from 59 subjects and modeled using Zernike polynomials, which provide for a simple method of compressing topography data and comparing one topographical measurement with a database for biometric identification. The data were analyzed to determine the biometric error rates associated with corneal topography measurements. Reasonably accurate results, between three to eight percent simultaneous false match and false non-match rates, were achieved.

  20. The study of the ocean from space

    Energy Technology Data Exchange (ETDEWEB)

    Novogrudskii, B V; Skliarov, V E; Fedorov, K N; Shifrin, K S

    1978-01-01

    The application of earth satellites and manned spacecraft to the study of the world's oceans is reviewed. Attention is given to the atmospheric transfer function in the visible, near-IR, middle-IR and microwave regions and the use of satellites in ocean data acquisition and transmission systems. The measurement of sea level and the topography of the ocean surface by means of orbital radar altimeters is discussed, together with IR and microwave measurements of ocean surface temperature and the study of surface roughness, surface evidence of internal waves, oil pollution and ice fields. Consideration is also given to the determination of ocean chlorophyll content and color distribution, coastal region characteristics, ocean salinity and other biological parameters from space.

  1. The interior structure of Ceres as revealed by surface topography

    Science.gov (United States)

    Fu, Roger R.; Ermakov, Anton; Marchi, Simone; Castillo-Rogez, Julie C.; Raymond, Carol A.; Hager, Bradford; Zuber, Maria; King, Scott D.; Bland, Michael T.; De Sanctis, Maria Cristina; Preusker, Frank; Park, Ryan S.; Russell, Christopher T.

    2017-01-01

    Ceres, the largest body in the asteroid belt (940 km diameter), provides a unique opportunity to study the interior structure of a volatile-rich dwarf planet. Variations in a planetary body's subsurface rheology and density affect the rate of topographic relaxation. Preferential attenuation of long wavelength topography (≥150 km) on Ceres suggests that the viscosity of its crust decreases with increasing depth. We present finite element (FE) geodynamical simulations of Ceres to identify the internal structures and compositions that best reproduce its topography as observed by the NASA Dawn mission. We infer that Ceres has a mechanically strong crust with maximum effective viscosity ∼1025 Pa s. Combined with density constraints, this rheology suggests a crustal composition of carbonates or phyllosilicates, water ice, and at least 30 volume percent (vol.%) low-density, high-strength phases most consistent with salt and/or clathrate hydrates. The inference of these crustal materials supports the past existence of a global ocean, consistent with the observed surface composition. Meanwhile, we infer that the uppermost ≥60 km of the silicate-rich mantle is mechanically weak with viscosity <1021 Pa s, suggesting the presence of liquid pore fluids in this region and a low temperature history that avoided igneous differentiation due to late accretion or efficient heat loss through hydrothermal processes.

  2. 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.

  3. Ocean tides

    Science.gov (United States)

    Hendershott, M. C.

    1975-01-01

    A review of recent developments in the study of ocean tides and related phenomena is presented. Topics briefly discussed include: the mechanism by which tidal dissipation occurs; continental shelf, marginal sea, and baroclinic tides; estimation of the amount of energy stored in the tide; the distribution of energy over the ocean; the resonant frequencies and Q factors of oceanic normal modes; the relationship of earth tides and ocean tides; and numerical global tidal models.

  4. GOCE++ Dynamical Coastal Topography and tide gauge unification using altimetry and GOCE

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Knudsen, Per; Nielsen, Karina

    Mean Dynamic Topography (MDT) of the ocean along a coastline which contributes/requires reconciling altimetry, tide gauge and vertical land motion. The fundamental use of the MDT computed using altimetry, ocean models or through the use of tide gauges has values of between -2 and +1 meters at different...... processes and physics responsible for sea level changes on various temporal/spatial scales. The study runs from October 2015 to march 2017 and involves elements like: Develop an approach to estimate a consistent DT at tide gauges, coastal areas, and open ocean; Validate the approach in well-surveyed areas......ESA has recently released a study on the potential of ocean levelling as a novel approach to the study of height system unification taking the recent development in geoid accuracy trough GOCE data into account. The suggested investigation involves the use of measurements and modelling to estimate...

  5. 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.

  6. 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...

  7. 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

  8. 77 FR 55144 - Ocean Dumping; Designation of Ocean Dredged Material Disposal Sites Offshore of Yaquina Bay, Oregon

    Science.gov (United States)

    2012-09-07

    ... in avian foraging behavior, modification of bottom topography, loss of benthic prey species from... or adverse modification of any critical habitat. The EPA prepared a Biological Assessment (BA) to... modification of designated critical habitat for southern DPS North American green sturgeon. The NMFS also...

  9. Electronic Cigarette Topography in the Natural Environment.

    Science.gov (United States)

    Robinson, R J; Hensel, E C; Morabito, P N; Roundtree, K A

    2015-01-01

    This paper presents the results of a clinical, observational, descriptive study to quantify the use patterns of electronic cigarette users in their natural environment. Previously published work regarding puff topography has been widely indirect in nature, and qualitative rather than quantitative, with the exception of three studies conducted in a laboratory environment for limited amounts of time. The current study quantifies the variation in puffing behaviors among users as well as the variation for a given user throughout the course of a day. Puff topography characteristics computed for each puffing session by each subject include the number of subject puffs per puffing session, the mean puff duration per session, the mean puff flow rate per session, the mean puff volume per session, and the cumulative puff volume per session. The same puff topography characteristics are computed across all puffing sessions by each single subject and across all subjects in the study cohort. Results indicate significant inter-subject variability with regard to puffing topography, suggesting that a range of representative puffing topography patterns should be used to drive machine-puffed electronic cigarette aerosol evaluation systems.

  10. Sensitivity experiments with an adaptation model of circulation of western tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Bahulayan, N.; Shaji, C.; Rao, A.D.; Dube, S.K.

    circulation at 10 m depth is controlled by both wind stress and sea surface topography. Circulation at 50 m depth is mainly controlled by thermohaline forcing and sea surface topography. The current speed in the western tropical Indian Ocean is of the order...

  11. Examinations for quantifying the difference in radiation doses at the least favorable locations between facility sites in highly structured topographies (valleys) and in plane terrain (licensing procedures); Untersuchungen zur Quantifizierung des Unterschieds in der Dosisbelastung am unguenstigsten Aufpunkt zwischen Standorten in topographisch stark strukturiertem Gelaende (Tal-Lagen) und in ebenem Terrain (Genehmigungsverfahren)

    Energy Technology Data Exchange (ETDEWEB)

    Raskob, W. [Dr. Trippe Ingenieurgesellschaft mbH, Karlsruhe (Germany)

    1995-08-01

    The MCF wind field model and the LASAT Lagrange particle model served to study topography effects on the spreading of radionuclides. Concentrations in bottom layers of the atmosphere at maximum-dose positions in hilly country topography are up to a factor 6 higher than in plain country. For concentrations in the soil the results have a similar relation. (orig.)

  12. Spatio-temporal variability of internal waves in the northern Gulf of Mexico studied with the Navy Coastal Ocean Model, NCOM

    Science.gov (United States)

    Cambazoglu, M. K.; Jacobs, G. A.; Howden, S. D.; Book, J. W.; Arnone, R.; Soto Ramos, I. M.; Vandermeulen, R. A.; Greer, A. T.; Miles, T. N.

    2016-02-01

    Internal waves enhance mixing in the upper ocean, transport nutrients and plankton over the water column and across the shelf from deeper waters to shallower coastal areas, and could also transport pollutants such as hydrocarbons onshore during an oil spill event. This study aims to characterize internal waves in the northern Gulf of Mexico (nGoM) and investigate the possible generation and dissipation mechanisms using a high-resolution (1-km) application of the Navy Coastal Ocean Model (NCOM). Three dimensional model products are used to detect the propagation patterns of internal waves. The vertical structure of internal waves is studied and the role of stratification is analyzed by looking at the temperature, salinity and velocity variations along the water column. The model predictions suggest the generation of internal waves on the continental shelf, therefore the role of ocean bottom topography interacting with tides and general circulation features such as the Loop Current Eddy front, on the internal wave generation will be discussed. The time periods of internal wave occurrences are identified from model predictions and compared to satellite ocean color imagery. Further data analysis, e.g. Fourier analysis, is implemented to determine internal wavelengths and frequencies and to determine if the response of internal waves are at tidal periods or at different frequencies. The atmospheric forcing provided to NCOM and meteorological data records are analyzed to define the interaction between wind forcing and internal wave generation. Wavelet analysis characterizes the ocean response to atmospheric events with periodic frequencies. Ocean color satellite imagery was used to visualize the location of the Mississippi river plume (and other oceanic features) and compared to the model predictions because the enhanced stratification from freshwater plumes which propagate across the Mississippi Bight can provide favorable conditions in coastal waters for internal wave

  13. High-speed X-ray topography

    International Nuclear Information System (INIS)

    Eckers, W.; Oppolzer, H.

    1977-01-01

    The investigation of lattice defects in semiconductor crystals by conventional X-ray diffraction topography is very time-consuming. Exposure times can be reduced by using high-intensity X-rays and X-ray image intensifiers. The described system comprises a high-power rotating-anode X-ray tube, a remote-controlled X-ray topography camera, and a television system operating with an X-ray sensing VIDICON. System performance is demonstrated with reference to exploratory examples. The exposure time for photographic plates is reduced to 1/20 and for the X-ray TV system (resolution of the order of 30 μm) to 1/100 relative to that required when using a conventional topography system. (orig.) [de

  14. Assimilation of satellite altimeter data into an open ocean model

    Science.gov (United States)

    Vogeler, Armin; SchröTer, Jens

    1995-08-01

    Geosat sea surface height data are assimilated into an eddy-resolving quasi-geostrophic open ocean model using the adjoint technique. The method adjusts the initial conditions for all layers and is successful on the timescale of a few weeks. Time-varying values for the open boundaries are prescribed by a much larger quasi-geostrophic model of the Antarctic Circumpolar Current (ACC). Both models have the same resolution of approximately 20×20 km (1/3°×1/6°), have three layers, and include realistic bottom topography and coastlines. The open model box is embedded in the African sector of the ACC. For continuous assimilation of satellite data into the larger model the nudging technique is applied. These results are used for the adjoint optimization procedure as boundary conditions and as a first guess for the initial condition. For the open model box the difference between model and satellite sea surface height that remains after the nudging experiment amounts to a 19-cm root-mean-square error (rmse). By assimilation into the regional model this value can be reduced to a 6-cm rmse for an assimilation period of 20 days. Several experiments which attempt to improve the convergence of the iterative optimization method are reported. Scaling and regularization by smoothing have to be applied carefully. Especially during the first 10 iterations, the convergence can be improved considerably by low-pass filtering of the cost function gradient. The result of a perturbation experiment shows that for longer assimilation periods the influence of the boundary values becomes dominant and they should be determined inversely by data assimilation into the open ocean model.

  15. 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...

  16. Reconciling Long-Wavelength Dynamic Topography, Geoid Anomalies and Mass Distribution on Earth

    Science.gov (United States)

    Hoggard, M.; Richards, F. D.; Ghelichkhan, S.; Austermann, J.; White, N.

    2017-12-01

    Since the first satellite observations in the late 1950s, we have known that that the Earth's non-hydrostatic geoid is dominated by spherical harmonic degree 2 (wavelengths of 16,000 km). Peak amplitudes are approximately ± 100 m, with highs centred on the Pacific Ocean and Africa, encircled by lows in the vicinity of the Pacific Ring of Fire and at the poles. Initial seismic tomography models revealed that the shear-wave velocity, and therefore presumably the density structure, of the lower mantle is also dominated by degree 2. Anti-correlation of slow, probably low density regions beneath geoid highs indicates that the mantle is affected by large-scale flow. Thus, buoyant features are rising and exert viscous normal stresses that act to deflect the surface and core-mantle boundary (CMB). Pioneering studies in the 1980s showed that a viscosity jump between the upper and lower mantle is required to reconcile these geoid and tomographically inferred density anomalies. These studies also predict 1-2 km of dynamic topography at the surface, dominated by degree 2. In contrast to this prediction, a global observational database of oceanic residual depth measurements indicates that degree 2 dynamic topography has peak amplitudes of only 500 m. Here, we attempt to reconcile observations of dynamic topography, geoid, gravity anomalies and CMB topography using instantaneous flow kernels. We exploit a density structure constructed from blended seismic tomography models, combining deep mantle imaging with higher resolution upper mantle features. Radial viscosity structure is discretised, and we invert for the best-fitting viscosity profile using a conjugate gradient search algorithm, subject to damping. Our results suggest that, due to strong sensitivity to radial viscosity structure, the Earth's geoid seems to be compatible with only ± 500 m of degree 2 dynamic topography.

  17. Oceanic archipelagos

    DEFF Research Database (Denmark)

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

    2016-01-01

    Since the contributions of Charles Darwin and Alfred Russel Wallace, oceanic archipelagos have played a central role in the development of biogeography. However, despite the critical influence of oceanic islands on ecological and evolutionary theory, our focus has remained limited to either the i...... of the archipelagic geological dynamics that can affect diversity at both the island and the archipelagic level. We also reaffirm that oceanic archipelagos are appropriate spatiotemporal units to frame analyses in order to understand large scale patterns of biodiversity....

  18. 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

  19. 3D modelling of interaction of strongly nonlinear internal seiches with a concave lake topography and a phenomenon of the "lake monsters".

    Science.gov (United States)

    Terletska, Kateryna; Maderich, Vladimir; Brovchenko, Igor; Jung, Kyung Tae

    2013-04-01

    critical values after which jet sink to maximal depth, then stop and rapidly rising up to surface interacting with thermocline where vortex pair is formed, 4) the just formed vortex pair continue moving in thermocline with a critical speed causing wave wake. This wake is also can be visible on the surface of the lake, 5) the final stage of interaction is the formation of solitons and the second internal mode. The appearance of surface wake in such idealized elongated elliptic-shape lake was the motivation for carrying further modeling of internal seiches in the real lake. This phenomenon can be the explanation of the fact that number of eyewitness around the world claimed to see "lake monsters" moved rapidly and then submerged leaving a wake. Its usually occur in elongated lakes in moderate latitude with a well defined seasonal termocline. Numerical modeling of the interaction of internal seiche with a North end of the Loch Ness confirms possibility of the supercritical internal jet generation and subsequent internal and surface disturbances. We hypotheses that some of eyewitness and legends on the "lake monsters" can be explained by such observations of suddently occurred surface wake behind disturbance generated by focusing flows by bottom topography. [1] Horn DA, Imberger J, Ivey GN.: The degeneration of large-scale interfacial gravity waves in lakes. J. Fluid Mech 434: 181-207, 2001. [2] Maderich V., Brovchenko I., Terletska K., Hutter K.: Numerical simulations of the nonhydrostatic transformation of basin-scale internal gravity waves and wave-enhanced meromixis in lakes. Ch. 4 in Hutter K. (Ed.) Nonlinear internal waves in lakes. Springer. Series: Advances in Geophysical and Environmental Mechanics p. 193-276, 2012. [3] Kanarska Y, Maderich V.: A non-hydrostatic numerical model for calculating free-surface stratified flows. Ocean Dynamics 53: 176-185, 2003.

  20. Ocean transportation

    National Research Council Canada - National Science Library

    Frankel, Ernst G; Marcus, Henry S

    1973-01-01

    .... This analysis starts with a review of ocean transportation demand and supply including projections of ship capacity demand and world shipbuilding capacity under various economic and political assumptions...

  1. Topography of the Betics: crustal thickening, dynamic topography and relief inheritance

    Science.gov (United States)

    Janowski, Marianne; Loget, Nicolas; Bellahsen, Nicolas; Husson, Laurent; Le Pourhiet, Laetitia; Meyer, Bertrand

    2017-04-01

    The main mechanism that explains high orogenic topographies is the isostatic adjustment due to crustal thickening. However in the Betic Cordillera (South Spain), the present-day elevation and crustal thickness are not correlated. That is at odds with the general premise of isostasy and requires reappraising the question of the driving mechanisms leading to the current topography. The Betics are located at the western edge of the alpine Mediterranean belt. Its Cenozoic orogenic building was disrupted by a major crustal thinning event induced by a slab rollback in the internal zones (Alboran domain) during Neogene. Topography was largely levelled and flooded by the sea during Neogene extension, and then has been folded since the Late Tortonian inversion. The present-day topography shows flat summits still preserved from fluvial regression in the internal zones (central and eastern Betics). These low-relief surfaces may be inherited from the Neogene planation toward sea-level as rocks cooling histories inferred from low-temperature thermochronology seem to point it out. Post-Tortonian shortening estimated thanks to a crustal-scale N-S cross-section in the eastern Betics (at the Sierra Nevada longitude) does not exceed few kilometers which is much lower than the shortening required by isostatic equilibrium, and is thus insufficient to explain the post-Tortonian topography building. We tested the hypothesis that mantle dynamics could in fact be an important mechanism that explains the topography of the Betics. We first computed the residual topography (i.e. the non-isostatic component of the elevation) using the most recent published Moho mapping of the area. In the western Betics, our results show important negative residual topography (down to -3 km) possibly associated with the west-Alboran slab suction. In the eastern Betics however, positive residual topography is important (up to +3 km) and can be explained by the dynamic mantle support of the topography, possibly

  2. X-ray topography and multiple diffraction

    International Nuclear Information System (INIS)

    Chang, S.-L.

    1983-01-01

    A short summary on X-ray topography, which is based on the dynamical theory of X-ray diffraction, is made. The applications and properties related to the use of the multiple diffraction technique are analized and discussed. (L.C.) [pt

  3. 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

  4. 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

  5. TWO- AND THREE-DIMENSIONAL SIMULATIONS OF ASTEROID OCEAN IMPACTS

    Directory of Open Access Journals (Sweden)

    Michael Gittings

    2003-01-01

    Full Text Available We have performed a series of two-dimensional and three-dimensional simulations of asteroid impacts into an ocean using the SAGE code from Los Alamos National Laboratory and Science Applications International Corporation. The SAGE code is a compressible Eulerian hydrodynamics code using continuous adaptive mesh refinement for following discontinuities with a fine grid while treating the bulk of the simulation more coarsely. We have used realistic equations of state for the atmosphere, sea water, the oceanic crust, and the mantle. In two dimensions, we simulated asteroid impactors moving at 20 km/s vertically through an exponential atmosphere into a 5 km deep ocean. The impactors were composed of mantle material (3.32 g/cc or iron (7.8 g/cc with diameters from 250m to 10 km. In our three-dimensional runs we simulated asteroids of 1 km diameter composed of iron moving at 20 km/s at angles of 45 and 60 degrees from the vertical. All impacts, including the oblique ones, produce a large underwater cavities with nearly vertical walls followed by a collapse starting from the bottom and subsequent vertical jetting. Substantial amounts of water are vaporized and lofted high into the atmosphere. In the larger impacts, significant amounts of crustal and even mantle material are lofted as well. Tsunamis up to a kilometer in initial height are generated by the collapse of the vertical jet. These waves are initially complex in form, and interact strongly with shocks propagating through the water and the crust. The tsunami waves are followed out to 100 km from the point of impact. Their periods and wavelengths show them to be intermediate type waves, and not (in general shallow-water waves. At great distances, the waves decay as the inverse of the distance from the impact point, ignoring sea-floor topography. For all impactors smaller than about 2 km diameter, the impacting body is highly fragmented and its remains lofted into the stratosphere with the water

  6. Geothermal heat flux in the Amundsen Sea sector of West Antarctica: New insights from temperature measurements, depth to the bottom of the magnetic source estimation, and thermal modeling

    Science.gov (United States)

    Dziadek, R.; Gohl, K.; Diehl, A.; Kaul, N.

    2017-07-01

    Focused research on the Pine Island and Thwaites glaciers, which drain the West Antarctic Ice Shelf (WAIS) into the Amundsen Sea Embayment (ASE), revealed strong signs of instability in recent decades that result from variety of reasons, such as inflow of warmer ocean currents and reverse bedrock topography, and has been established as the Marine Ice Sheet Instability hypothesis. Geothermal heat flux (GHF) is a poorly constrained parameter in Antarctica and suspected to affect basal conditions of ice sheets, i.e., basal melting and subglacial hydrology. Thermomechanical models demonstrate the influential boundary condition of geothermal heat flux for (paleo) ice sheet stability. Due to a complex tectonic and magmatic history of West Antarctica, the region is suspected to exhibit strong heterogeneous geothermal heat flux variations. We present an approach to investigate ranges of realistic heat fluxes in the ASE by different methods, discuss direct observations, and 3-D numerical models that incorporate boundary conditions derived from various geophysical studies, including our new Depth to the Bottom of the Magnetic Source (DBMS) estimates. Our in situ temperature measurements at 26 sites in the ASE more than triples the number of direct GHF observations in West Antarctica. We demonstrate by our numerical 3-D models that GHF spatially varies from 68 up to 110 mW m-2.

  7. High-frequency internal waves and thick bottom mixed layers observed by gliders in the Gulf Stream

    Science.gov (United States)

    Todd, Robert E.

    2017-06-01

    Autonomous underwater gliders are conducting high-resolution surveys within the Gulf Stream along the U.S. East Coast. Glider surveys reveal two mechanisms by which energy is extracted from the Gulf Stream as it flows over the Blake Plateau, a portion of the outer continental shelf between Florida and North Carolina where bottom depths are less than 1000 m. Internal waves with vertical velocities exceeding 0.1 m s-1 and frequencies just below the local buoyancy frequency are routinely found over the Blake Plateau, particularly near the Charleston Bump, a prominent topographic feature. These waves are likely internal lee waves generated by the subinertial Gulf Stream flow over the irregular bathymetry of the outer continental shelf. Bottom mixed layers with O(100) m thickness are also frequently encountered; these thick bottom mixed layers likely form in the lee of topography due to enhanced turbulence generated by O(1) m s-1 near-bottom flows.

  8. Spiraling pathways of global deep waters to the surface of the Southern Ocean

    OpenAIRE

    Tamsitt, Veronica; Drake, Henri F.; Morrison, Adele K.; Talley, Lynne D.; Dufour, Carolina O.; Gray, Alison R.; Griffies, Stephen M.; Mazloff, Matthew R.; Sarmiento, Jorge L.; Wang, Jinbo; Weijer, Wilbert

    2017-01-01

    Upwelling of global deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. However, the exact pathways and role of topography in Southern Ocean upwelling remain largely unknown. Here we show detailed upwelling pathways in three dimensions, using hydrographic observations and particle trac...

  9. Ocean technology

    Digital Repository Service at National Institute of Oceanography (India)

    Peshwe, V.B.

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

  10. Ocean acidification

    National Research Council Canada - National Science Library

    Gattuso, J.P; Hansson, L

    2011-01-01

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

  11. Brief communication: A nonlinear self-similar solution to barotropic flow over varying topography

    Science.gov (United States)

    Ibanez, Ruy; Kuehl, Joseph; Shrestha, Kalyan; Anderson, William

    2018-03-01

    Beginning from the shallow water equations (SWEs), a nonlinear self-similar analytic solution is derived for barotropic flow over varying topography. We study conditions relevant to the ocean slope where the flow is dominated by Earth's rotation and topography. The solution is found to extend the topographic β-plume solution of Kuehl (2014) in two ways. (1) The solution is valid for intensifying jets. (2) The influence of nonlinear advection is included. The SWEs are scaled to the case of a topographically controlled jet, and then solved by introducing a similarity variable, η = cxnxyny. The nonlinear solution, valid for topographies h = h0 - αxy3, takes the form of the Lambert W-function for pseudo velocity. The linear solution, valid for topographies h = h0 - αxy-γ, takes the form of the error function for transport. Kuehl's results considered the case -1 ≤ γ < 1 which admits expanding jets, while the new result considers the case γ < -1 which admits intensifying jets and a nonlinear case with γ = -3.

  12. 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.

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. 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...

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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.

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. 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...

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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

  7. Fish species, Fish biomass, Fishery survey, invertebrate species, and other variables collected from midwater net tows, and bottom trawl observations using net, trawl, and other instruments from the Arctic Ocean, and Beaufort Sea from August 6, 2008 to August 21, 2008 (NODC Accession 0112823)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Alaska Fisheries Science Center's Status of Stocks and Multispecies Assessment (SSMA) Programs Fishery Interaction Team (FIT) conducted a fish survey in the...

  8. Historical development of synchrotron x-ray diffraction topography

    International Nuclear Information System (INIS)

    Kawado, Seiji

    2011-01-01

    After a short history of X-ray diffraction topography, from the early stage of laboratory X-ray topography to recent synchrotron-radiation applications, is described, the development of science and technology for the synchrotron X-ray topography and its industrial applications are reviewed in more detail. In addition, the recent trend to synchrotron topography research is clarified on the basis of several data obtained from 256 papers which have been published since 2000. (author)

  9. Measured and Estimated Seafloor Topography - Poster

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This 34 by 53 inch full-color poster is report WDC for MGG RP-1. In many areas of the global ocean, the depth of the seafloor is not well known because survey lines...

  10. Geophysical, petrological and mineral physics constraints on Earth's surface topography

    Science.gov (United States)

    Guerri, Mattia; Cammarano, Fabio; Tackley, Paul J.

    2015-04-01

    Earth's surface topography is controlled by isostatically compensated density variations within the lithosphere, but dynamic topography - i.e. the topography due to adjustment of surface to mantle convection - is an important component, specially at a global scale. In order to separate these two components it is fundamental to estimate crustal and mantle density structure and rheological properties. Usually, crustal density is constrained from interpretation of available seismic data (mostly VP profiles) based on empirical relationships such those in Brocher [2005]. Mantle density structure is inferred from seismic tomography models. Constant coefficients are used to interpret seismic velocity anomalies in density anomalies. These simplified methods are unable to model the effects that pressure and temperature variations have on mineralogical assemblage and physical properties. Our approach is based on a multidisciplinary method that involves geophysical observables, mineral physics constraints, and petrological data. Mantle density is based on the thermal interpretation of global seismic tomography models assuming various compositional structures, as in Cammarano et al. [2011]. We further constrain the top 150 km by including heat-flow data and considering the thermal evolution of the oceanic lithosphere. Crustal density is calculated as in Guerri and Cammarano [2015] performing thermodynamic modeling of various average chemical compositions proposed for the crust. The modeling, performed with the code PerpleX [Connolly, 2005], relies on the thermodynamic dataset from Holland and Powell [1998]. Compressional waves velocity and crustal layers thickness from the model CRUST 1.0 [Laske et al., 2013] offer additional constrains. The resulting lithospheric density models are tested against gravity (GOCE) data. Various crustal and mantle density models have been tested in order to ascertain the effects that uncertainties in the estimate of those features have on the

  11. Ocean energy

    International Nuclear Information System (INIS)

    2006-01-01

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

  12. Description of two-process surface topography

    International Nuclear Information System (INIS)

    Grabon, W; Pawlus, P

    2014-01-01

    After two machining processes, a large number of surface topography measurements were made using Talyscan 150 stylus measuring equipment. The measured samples were divided into two groups. The first group contained two-process surfaces of random nature, while the second group used random-deterministic textures of random plateau parts and portions of deterministic valleys. For comparison, one-process surfaces were also analysed. Correlation and regression analysis was used to study the dependencies among surface texture parameters in 2D and 3D systems. As the result of this study, sets of parameters describing multi-process surface topography were obtained for two-process surfaces of random and of random-deterministic types. (papers)

  13. Topography and malaria transmission heterogeneity in western Kenya highlands: prospects for focal vector control

    Directory of Open Access Journals (Sweden)

    Ndenga Bryson A

    2006-11-01

    Full Text Available Abstract Background Recent resurgence of malaria in the highlands of Western Kenya has called for a more comprehensive understanding of the previously neglected complex highland vector ecology. Besides other drivers of malaria epidemiology, topography is likely to have a major effect on spatial vector and parasite distribution. The aim of this study was to determine the effects of topography on malaria spatial vector distribution and parasite prevalence. Methodology Indoor resting adult malaria vectors and blood parasites were collected in three villages along a 4 km transect originating from the valley bottom and ending at the hilltop for 13 months. Members of the Anopheles gambiae complex were identified by PCR. Blood parasites were collected from children 6–13 years old and densities categorized by site of home location and age of the children. Results Ninety eight percent (98% of An. gambiae s.s. and (99% Anopheles funestus were collected in houses located at the edge of the valley bottom, whereas 1% of An. gambiae s.s. were collected at mid hill and at the hilltop respectively. No An. funestus were collected at the hilltop. Malaria prevalence was 68% at the valley bottom, 40.2% at mid hill and 26.7% at the hilltop. Children aged six years and living at the edge of the valley bottom had an annual geometric mean number of 66.1 trophozoites for every 200 white blood cells, while those living at mid-hill had a mean of 84.8, and those living at hilltop had 199.5 trophozoites. Conclusion Malaria transmission in this area is mainly confined to the valley bottom. Effective vector control could be targeted at the foci. However, the few vectors observed at mid-hill maintained a relatively high prevalence rate. The higher variability in blood parasite densities and their low correlation with age in children living at the hilltop suggests a lower stability of transmission than at the mid-hill and valley bottom.

  14. Spike voltage topography in temporal lobe epilepsy.

    Science.gov (United States)

    Asadi-Pooya, Ali A; Asadollahi, Marjan; Shimamoto, Shoichi; Lorenzo, Matthew; Sperling, Michael R

    2016-07-15

    We investigated the voltage topography of interictal spikes in patients with temporal lobe epilepsy (TLE) to see whether topography was related to etiology for TLE. Adults with TLE, who had epilepsy surgery for drug-resistant seizures from 2011 until 2014 at Jefferson Comprehensive Epilepsy Center were selected. Two groups of patients were studied: patients with mesial temporal sclerosis (MTS) on MRI and those with other MRI findings. The voltage topography maps of the interictal spikes at the peak were created using BESA software. We classified the interictal spikes as polar, basal, lateral, or others. Thirty-four patients were studied, from which the characteristics of 340 spikes were investigated. The most common type of spike orientation was others (186 spikes; 54.7%), followed by lateral (146; 42.9%), polar (5; 1.5%), and basal (3; 0.9%). Characteristics of the voltage topography maps of the spikes between the two groups of patients were somewhat different. Five spikes in patients with MTS had polar orientation, but none of the spikes in patients with other MRI findings had polar orientation (odds ratio=6.98, 95% confidence interval=0.38 to 127.38; p=0.07). Scalp topographic mapping of interictal spikes has the potential to offer different information than visual inspection alone. The present results do not allow an immediate clinical application of our findings; however, detecting a polar spike in a patient with TLE may increase the possibility of mesial temporal sclerosis as the underlying etiology. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. ATM Coastal Topography-Mississippi, 2001

    Science.gov (United States)

    Nayegandhi, Amar; Yates, Xan; Brock, John C.; Sallenger, A.H.; Klipp, Emily S.; Wright, C. Wayne

    2009-01-01

    These remotely sensed, geographically referenced elevation measurements of lidar-derived first-surface (FS) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the Mississippi coastline, from Lakeshore to Petit Bois Island, acquired September 9-10, 2001. The datasets are made available for use as a management tool to research scientists and natural-resource managers. An innovative scanning lidar instrument originally developed by NASA, and known as the Airborne Topographic Mapper (ATM), was used during data acquisition. The ATM system is a scanning lidar system that measures high-resolution topography of the land surface and incorporates a green-wavelength laser operating at pulse rates of 2 to 10 kilohertz. Measurements from the laser-ranging device are coupled with data acquired from inertial navigation system (INS) attitude sensors and differentially corrected global positioning system (GPS) receivers to measure topography of the surface at accuracies of +/-15 centimeters. The nominal ATM platform is a Twin Otter or P-3 Orion aircraft, but the instrument may be deployed on a range of light aircraft. Elevation measurements were collected over the survey area using the ATM system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of lidar data in an interactive or batch mode. Modules for presurvey flight-line definition, flight-path plotting, lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS

  16. ATM Coastal Topography-Alabama 2001

    Science.gov (United States)

    Nayegandhi, Amar; Yates, Xan; Brock, John C.; Sallenger, A.H.; Bonisteel, Jamie M.; Klipp, Emily S.; Wright, C. Wayne

    2009-01-01

    These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the Alabama coastline, acquired October 3-4, 2001. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative scanning Lidar instrument originally developed by NASA, and known as the Airborne Topographic Mapper (ATM), was used during data acquisition. The ATM system is a scanning Lidar system that measures high-resolution topography of the land surface, and incorporates a green-wavelength laser operating at pulse rates of 2 to 10 kilohertz. Measurements from the laser ranging device are coupled with data acquired from inertial navigation system (INS) attitude sensors and differentially corrected global positioning system (GPS) receivers to measure topography of the surface at accuracies of +/-15 centimeters. The nominal ATM platform is a Twin Otter or P-3 Orion aircraft, but the instrument may be deployed on a range of light aircraft. Elevation measurements were collected over the survey area using the ATM system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for pre-survey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is routinely used to create maps that

  17. 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.)

  18. Refining the ischemic penumbra with topography.

    Science.gov (United States)

    Thirugnanachandran, Tharani; Ma, Henry; Singhal, Shaloo; Slater, Lee-Anne; Davis, Stephen M; Donnan, Geoffrey A; Phan, Thanh

    2018-04-01

    It has been 40 years since the ischemic penumbra was first conceptualized through work on animal models. The topography of penumbra has been portrayed as an infarcted core surrounded by penumbral tissue and an extreme rim of oligemic tissue. This picture has been used in many review articles and textbooks before the advent of modern imaging. In this paper, we review our understanding of the topography of the ischemic penumbra from the initial experimental animal models to current developments with neuroimaging which have helped to further define the temporal and spatial evolution of the penumbra and refine our knowledge. The concept of the penumbra has been successfully applied in clinical trials of endovascular therapies with a time window as long as 24 h from onset. Further, there are reports of "good" outcome even in patients with a large ischemic core. This latter observation of good outcome despite having a large core requires an understanding of the topography of the penumbra and the function of the infarcted regions. It is proposed that future research in this area takes departure from a time-dependent approach to a more individualized tissue and location-based approach.

  19. Airborne laser altimeter measurements of landscape topography

    International Nuclear Information System (INIS)

    Ritchie, J.C.

    1995-01-01

    Measurements of topography can provide a wealth of information on landscape properties for managing hydrologic and geologic systems and conserving natural and agricultural resources. This article discusses the application of an airborne laser altimeter to measure topography and other landscape surface properties. The airborne laser altimeter makes 4000 measurements per second with a vertical recording resolution of 5 cm. Data are collected digitally with a personal computer. A video camera, borehole sighted with the laser, records an image for locating flight lines. GPS data are used to locate flight line positions on the landscape. Laser data were used to measure vegetation canopy topography, height, cover, and distribution and to measure microtopography of the land surface and gullies with depths of 15–20 cm. Macrotopography of landscape profiles for segments up to 4 km were in agreement with available topographic maps but provided more detail. Larger gullies with and without vegetation, and stream channel cross sections and their associated floodplains have also been measured and reported in other publications. Landscape segments for any length could be measured for either micro- or macrotopography. Airborne laser altimeter measurements of landscape profiles can provide detailed information on landscape properties or specific needs that will allow better decisions on the design and location of structures (i.e., roads, pipe, and power lines) and for improving the management and conservation of natural and agricultural landscapes. (author)

  20. Coarsely resolved topography along protein folding pathways

    Science.gov (United States)

    Fernández, Ariel; Kostov, Konstantin S.; Berry, R. Stephen

    2000-03-01

    The kinetic data from the coarse representation of polypeptide torsional dynamics described in the preceding paper [Fernandez and Berry, J. Chem. Phys. 112, 5212 (2000), preceding paper] is inverted by using detailed balance to obtain a topographic description of the potential-energy surface (PES) along the dominant folding pathway of the bovine pancreatic trypsin inhibitor (BPTI). The topography is represented as a sequence of minima and effective saddle points. The dominant folding pathway displays an overall monotonic decrease in energy with a large number of staircaselike steps, a clear signature of a good structure-seeker. The diversity and availability of alternative folding pathways is analyzed in terms of the Shannon entropy σ(t) associated with the time-dependent probability distribution over the kinetic ensemble of contact patterns. Several stages in the folding process are evident. Initially misfolded states form and dismantle revealing no definite pattern in the topography and exhibiting high Shannon entropy. Passage down a sequence of staircase steps then leads to the formation of a nativelike intermediate, for which σ(t) is much lower and fairly constant. Finally, the structure of the intermediate is refined to produce the native state of BPTI. We also examine how different levels of tolerance to mismatches of side chain contacts influence the folding kinetics, the topography of the dominant folding pathway, and the Shannon entropy. This analysis yields upper and lower bounds of the frustration tolerance required for the expeditious and robust folding of BPTI.

  1. Ocean Acidification

    Science.gov (United States)

    Ocean and coastal acidification is an emerging issue caused by increasing amounts of carbon dioxide being absorbed by seawater. Changing seawater chemistry impacts marine life, ecosystem services, and humans. Learn what EPA is doing and what you can do.

  2. Ocean transportation

    National Research Council Canada - National Science Library

    Frankel, Ernst G; Marcus, Henry S

    1973-01-01

    .... The discussion of technology considers the ocean transportation system as a whole, and the composite subsystems such as hull, outfit, propulsion, cargo handling, automation, and control and interface technology...

  3. Ocean transportation

    National Research Council Canada - National Science Library

    Frankel, Ernst G; Marcus, Henry S

    1973-01-01

    .... In ocean transportation economics we present investment and operating costs as well as the results of a study of financing of shipping. Similarly, a discussion of government aid to shipping is presented.

  4. Ocean Color

    Data.gov (United States)

    National Aeronautics and Space Administration — Satellite-derived Ocean Color Data sets from historical and currently operational NASA and International Satellite missions including the NASA Coastal Zone Color...

  5. Ocean Quality

    OpenAIRE

    Brevik, Roy Schjølberg; Jordheim, Nikolai; Martinsen, John Christian; Labori, Aleksander; Torjul, Aleksander Lelis

    2017-01-01

    Bacheloroppgave i Internasjonal Markedsføring fra ESADE i Spania, 2017 In this thesis we were going to answer the problem definition “which segments in the Spanish market should Ocean Quality target”. By doing so we started to collect data from secondary sources in order to find information about the industry Ocean Quality are operating in. After conducting the secondary research, we still lacked essential information about the existing competition in the aquaculture industry o...

  6. Topography-modified refraction: adjustment of treated cylinder amount and axis to the topography versus standard clinical refraction in myopic topography-guided LASIK

    OpenAIRE

    Alpins, Noel

    2017-01-01

    Noel Alpins1,2 1NewVision Clinics, Melbourne, VIC, Australia; 2Department Ophthalmology, Melbourne University, Melbourne, VIC, Australia It is encouraging to see the results in the article by Kanellopoulos “Topography-modified refraction (TMR): adjustment of treated cylinder amount and axis to the topography versus standard clinical refraction in myopic topography-guided LASIK”,1 where the combination of refractive and corneal data in the treatment parameters pro...

  7. Adaptation of a general circulation model to ocean dynamics

    Science.gov (United States)

    Turner, R. E.; Rees, T. H.; Woodbury, G. E.

    1976-01-01

    A primitive-variable general circulation model of the ocean was formulated in which fast external gravity waves are suppressed with rigid-lid surface constraint pressires which also provide a means for simulating the effects of large-scale free-surface topography. The surface pressure method is simpler to apply than the conventional stream function models, and the resulting model can be applied to both global ocean and limited region situations. Strengths and weaknesses of the model are also presented.

  8. OpenTopography: Enabling Online Access to High-Resolution Lidar Topography Data and Processing Tools

    Science.gov (United States)

    Crosby, Christopher; Nandigam, Viswanath; Baru, Chaitan; Arrowsmith, J. Ramon

    2013-04-01

    High-resolution topography data acquired with lidar (light detection and ranging) technology are revolutionizing the way we study the Earth's surface and overlying vegetation. These data, collected from airborne, tripod, or mobile-mounted scanners have emerged as a fundamental tool for research on topics ranging from earthquake hazards to hillslope processes. Lidar data provide a digital representation of the earth's surface at a resolution sufficient to appropriately capture the processes that contribute to landscape evolution. The U.S. National Science Foundation-funded OpenTopography Facility (http://www.opentopography.org) is a web-based system designed to democratize access to earth science-oriented lidar topography data. OpenTopography provides free, online access to lidar data in a number of forms, including the raw point cloud and associated geospatial-processing tools for customized analysis. The point cloud data are co-located with on-demand processing tools to generate digital elevation models, and derived products and visualizations which allow users to quickly access data in a format appropriate for their scientific application. The OpenTopography system is built using a service-oriented architecture (SOA) that leverages cyberinfrastructure resources at the San Diego Supercomputer Center at the University of California San Diego to allow users, regardless of expertise level, to access these massive lidar datasets and derived products for use in research and teaching. OpenTopography hosts over 500 billion lidar returns covering 85,000 km2. These data are all in the public domain and are provided by a variety of partners under joint agreements and memoranda of understanding with OpenTopography. Partners include national facilities such as the NSF-funded National Center for Airborne Lidar Mapping (NCALM), as well as non-governmental organizations and local, state, and federal agencies. OpenTopography has become a hub for high-resolution topography

  9. Perceptual learning: top to bottom.

    Science.gov (United States)

    Amitay, Sygal; Zhang, Yu-Xuan; Jones, Pete R; Moore, David R

    2014-06-01

    Perceptual learning has traditionally been portrayed as a bottom-up phenomenon that improves encoding or decoding of the trained stimulus. Cognitive skills such as attention and memory are thought to drive, guide and modulate learning but are, with notable exceptions, not generally considered to undergo changes themselves as a result of training with simple perceptual tasks. Moreover, shifts in threshold are interpreted as shifts in perceptual sensitivity, with no consideration for non-sensory factors (such as response bias) that may contribute to these changes. Accumulating evidence from our own research and others shows that perceptual learning is a conglomeration of effects, with training-induced changes ranging from the lowest (noise reduction in the phase locking of auditory signals) to the highest (working memory capacity) level of processing, and includes contributions from non-sensory factors that affect decision making even on a "simple" auditory task such as frequency discrimination. We discuss our emerging view of learning as a process that increases the signal-to-noise ratio associated with perceptual tasks by tackling noise sources and inefficiencies that cause performance bottlenecks, and present some implications for training populations other than young, smart, attentive and highly-motivated college students. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

  10. Augmented Lagrangian for shallow viscoplastic flow with topography

    Science.gov (United States)

    Ionescu, Ioan R.

    2013-06-01

    In this paper we have developed a robust numerical algorithm for the visco-plastic Saint-Venant model with topography. For the time discretization an implicit (backward) Euler scheme was used. To solve the resulting nonlinear equations, a four steps iterative algorithm was proposed. To handle the non-differentiability of the plastic terms an iterative decomposition-coordination formulation coupled with the augmented Lagrangian method was adopted. The proposed algorithm is consistent, i.e. if the convergence is achieved then the iterative solution satisfies the nonlinear system at each time iteration. The equations for the velocity field are discretized using the finite element method, while a discontinuous Galerkin method, with an upwind choice of the flux, is adopted for solving the hyperbolic equations that describe the evolution of the thickness. The algorithm permits to solve alternatively, at each iteration, the equations for the velocity field and for the thickness. The iterative decomposition coordination formulation coupled with the augmented Lagrangian method works very well and no instabilities are present. The proposed algorithm has a very good convergence rate, with the exception of large Reynolds numbers (Re≫1000), not involved in the applications concerned by the shallow viscoplastic model. The discontinuous Galerkin technique assure the mass conservation of the shallow system. The model has the exact C-property for a plane bottom and an asymptotic C-property for a general topography. Some boundary value problems were selected to analyze the robustness of the numerical algorithm and the predictive capabilities of the mechanical model. The comparison with an exact rigid flow solution illustrates the accuracy of the numerical scheme in handling the non-differentiability of the plastic terms. The influence of the mesh and of the time step are investigated for the flow of a Bingham fluid in a talweg. The role of the material cohesion in stopping a

  11. The Southern Ocean's role in ocean circulation and climate transients

    Science.gov (United States)

    Thompson, A. F.; Stewart, A.; Hines, S.; Adkins, J. F.

    2017-12-01

    The ventilation of deep and intermediate density classes at the surface of the Southern Ocean impacts water mass modification and the air-sea exchange of heat and trace gases, which in turn influences the global overturning circulation and Earth's climate. Zonal variability occurs along the Antarctic Circumpolar Current and the Antarctic margins related to flow-topography interactions, variations in surface boundary conditions, and exchange with northern basins. Information about these zonal variations, and their impact on mass and tracer transport, are suppressed when the overturning is depicted as a two-dimensional (depth-latitude) streamfunction. Here we present an idealized, multi-basin, time-dependent circulation model that applies residual circulation theory in the Southern Ocean and allows for zonal water mass transfer between different ocean basins. This model efficiently determines the temporal evolution of the ocean's stratification, ventilation and overturning strength in response to perturbations in the external forcing. With this model we explore the dynamics that lead to transitions in the circulation structure between multiple, isolated cells and a three-dimensional, "figure-of-eight," circulation in which traditional upper and lower cells are interleaved. The transient model is also used to support a mechanistic explanation of the hemispheric asymmetry and phase lag associated with Dansgaard-Oeschger (DO) events during the last glacial period. In particular, the 200 year lag in southern hemisphere temperatures, following a perturbation in North Atlantic deep water formation, depends critically on the migration of Southern Ocean isopycnal outcropping in response to low-latitude stratification changes. Our results provide a self-consistent dynamical framework to explain various ocean overturning transitions that have occurred over the Earth's last 100,000 years, and motivate an exploration of these mechanisms in more sophisticated climate models.

  12. The rôle of the complete Coriolis force in cross-equatorial flow of abyssal ocean currents

    Science.gov (United States)

    Stewart, A. L.; Dellar, P. J.

    Ocean currents flowing close to or across the equator are strongly constrained by the change in sign of f, the locally vertical component of the Earth's rotation vector, across the equator. We investigate these currents using a shallow water model that includes both the locally vertical and locally horizontal components of the Earth's rotation vector, thus accounting for the complete Coriolis force. We therefore avoid making the so-called "traditional approximation" that retains only the part of the Coriolis force associated with the locally vertical component of the rotation vector. Including the complete Coriolis force contributes an additional term to the fluid's potential vorticity, which may partially balance the change in sign of f as fluid crosses the equator over suitably shaped bathymetry. We focus on the Antarctic Bottom Water, which crosses the equator northwards in the western Atlantic ocean where the local bathymetry forms an almost-zonal channel. We show that this bathymetry facilitates the current's equatorial crossing via the action of the "non-traditional" component of the Coriolis force. We illustrate this process using both analytical and numerical solutions for flow of an abyssal current over idealised equatorial topography. We also consider the one-dimensional geostrophic adjustment of a body of fluid across the equator, and show that the "non-traditional" contribution to the fluid's angular momentum permits a larger cross-equatorial transport. These results underline the importance of including the complete Coriolis force in studies of the equatorial ocean, particularly in the weakly-stratified abyssal ocean where the non-traditional component is most pronounced.

  13. Turbulence and finestructure in a deep ocean channel with sill overflow on the mid-Atlantic ridge

    Science.gov (United States)

    Tippenhauer, Sandra; Dengler, Marcus; Fischer, Tim; Kanzow, Torsten

    2015-05-01

    Diapycnal mixing in the deep ocean is known to be much stronger in the vicinity of rough topography of mid-ocean ridges than above abyssal plains. In this study a horizontally profiling microstructure probe attached to an autonomous underwater vehicle (AUV) is used to infer the spatial distribution of the dissipation rate of turbulent kinetic energy (ε) in the central valley of the Mid-Atlantic Ridge. To the authors' knowledge, this is the first successful realization of a horizontal, deep-ocean microstructure survey. More than 22 h of horizontal, near-bottom microstructure data from the Lucky Strike segment (37°N) are presented. The study focuses on a channel with unidirectional sill overflow. Density was found to decrease along the channel following the mean northward flow of 3 to 8 cm/s. The magnitude of the rate of turbulent kinetic energy dissipation was distributed asymmetrically relative to the position of the sill. Elevated dissipation rates were present in a segment 1-4 km downstream (north) of the sill with peak values of 1 ×10-7 W/kg. Large flow speeds and elevated density finestructure were observed within this segment. Lowered hydrographic measurements indicated unstable stratification in the same region. The data indicate that hydraulic control was established at least temporarily. Inside the channel at wavelengths between 1 m and 250 m the slopes of AUV-inferred horizontal temperature gradient spectra were found to be consistent with turbulence in the inertial-convective subrange. Integrated temperature gradient variance in this wavelength interval was consistent with an ε2/3 dependence. The results illustrate that deep-reaching AUVs are a useful tool to study deep ocean turbulence over complex terrain where free-falling and lowered turbulence measurements are inefficient and time-consuming.

  14. Wet physical separation of MSWI bottom ash

    NARCIS (Netherlands)

    Muchova, L.

    2010-01-01

    Bottom ash (BA) from municipal solid waste incineration (MSWI) has high potential for the recovery of valuable secondary materials. For example, the MSWI bottom ash produced by the incinerator at Amsterdam contains materials such as non-ferrous metals (2.3%), ferrous metals (8-13%), gold (0.4 ppm),

  15. CryoSat Data Quality, Product Evolutions and Activities in Support to the Sentinel-3 Topography Mission

    Science.gov (United States)

    Bouffard, J.; Femenias, P.; Parrinello, T.; Bojkov, B.; Dinardo, S.; Fornari, M.; Benveniste, J.

    2015-12-01

    It is well known that conventional nadir altimetry acquisitions are not always suitable to monitor oceanic small-scale dynamics, coastal processes as well as ice sheet areas of rough topography. CryoSat (CS) is the first SAR(in) altimeter concept to be flown on Earth and therefore represents a unique opportunity to process SAR data for which we still have poor knowledge. After briefly presenting the CS data quality and recent evolutions, this paper provide a high level overview of CS activities specifically aiming at supporting the Copernicus Sentinel-3 Topography mission (S-3) within the framework of: - The ground segment processing development and evolution - The data validation and quality control - The potential synergies for future scientific and operational exploitation over ice and ocean.

  16. 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.

  17. 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.

  18. Learning topography with Tangible Landscape games

    Science.gov (United States)

    Petrasova, A.; Tabrizian, P.; Harmon, B. A.; Petras, V.; Millar, G.; Mitasova, H.; Meentemeyer, R. K.

    2017-12-01

    Understanding topography and its representations is crucial for correct interpretation and modeling of surface processes. However, novice earth science and landscape architecture students often find reading topographic maps challenging. As a result, many students struggle to comprehend more complex spatial concepts and processes such as flow accumulation or sediment transport.We developed and tested a new method for teaching hydrology, geomorphology, and grading using Tangible Landscape—a tangible interface for geospatial modeling. Tangible Landscape couples a physical and digital model of a landscape through a real-time cycle of hands-on modeling, 3D scanning, geospatial computation, and projection. With Tangible Landscape students can sculpt a projection-augmented topographic model of a landscape with their hands and use a variety of tangible objects to immediately see how they are changing geospatial analytics such as contours, profiles, water flow, or landform types. By feeling and manipulating the shape of the topography, while seeing projected geospatial analytics, students can intuitively learn about 3D topographic form, its representations, and how topography controls physical processes. Tangible Landscape is powered by GRASS GIS, an open source geospatial platform with extensive libraries for geospatial modeling and analysis. As such, Tangible Landscape can be used to design a wide range of learning experiences across a large number of geoscience disciplines.As part of a graduate level course that teaches grading, 16 students participated in a series of workshops, which were developed as serious games to encourage learning through structured play. These serious games included 1) diverting rain water to a specified location with minimal changes to landscape, 2) building different combinations of landforms, and 3) reconstructing landscapes based on projected contour information with feedback.In this poster, we will introduce Tangible Landscape, and

  19. Modelling wetting and drying effects over complex topography

    Science.gov (United States)

    Tchamen, G. W.; Kahawita, R. A.

    1998-06-01

    The numerical simulation of free surface flows that alternately flood and dry out over complex topography is a formidable task. The model equation set generally used for this purpose is the two-dimensional (2D) shallow water wave model (SWWM). Simplified forms of this system such as the zero inertia model (ZIM) can accommodate specific situations like slowly evolving floods over gentle slopes. Classical numerical techniques, such as finite differences (FD) and finite elements (FE), have been used for their integration over the last 20-30 years. Most of these schemes experience some kind of instability and usually fail when some particular domain under specific flow conditions is treated. The numerical instability generally manifests itself in the form of an unphysical negative depth that subsequently causes a run-time error at the computation of the celerity and/or the friction slope. The origins of this behaviour are diverse and may be generally attributed to:1. The use of a scheme that is inappropriate for such complex flow conditions (mixed regimes).2. Improper treatment of a friction source term or a large local curvature in topography.3. Mishandling of a cell that is partially wet/dry.In this paper, a tentative attempt has been made to gain a better understanding of the genesis of the instabilities, their implications and the limits to the proposed solutions. Frequently, the enforcement of robustness is made at the expense of accuracy. The need for a positive scheme, that is, a scheme that always predicts positive depths when run within the constraints of some practical stability limits, is fundamental. It is shown here how a carefully chosen scheme (in this case, an adaptation of the solver to the SWWM) can preserve positive values of water depth under both explicit and implicit time integration, high velocities and complex topography that may include dry areas. However, the treatment of the source terms: friction, Coriolis and particularly the bathymetry

  20. 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.)

  1. Synchrotron-radiation plane-wave topography

    International Nuclear Information System (INIS)

    Riglet, P.; Sauvage, M.; Petroff, J.F.; Epelboin, Y.

    1980-01-01

    A computer program based on the Takagi-Taupin differential equations for X-ray propagation in distorted crystals has been developed in order to simulate dislocation images in the Bragg case. The program is valid both for thin and thick crystals. Simulated images of misfit dislocations formed either in a thin epilayer or in a thick substrate are compared with experimental images obtained by synchrotron-radiation plane-wave topography. The influence of the various strain components on the image features is discussed. (author)

  2. Welcome to Surface Topography: Metrology and Properties

    Science.gov (United States)

    Leach, Richard

    2013-11-01

    I am delighted to welcome readers to this inaugural issue of Surface Topography: Metrology and Properties (STMP). In these days of citation indexes and academic reviews, it is a tough, and maybe a brave, job to start a new journal. But the subject area has never been more active and we are seeing genuine breakthroughs in the use of surfaces to control functional performance. Most manufactured parts rely on some form of control of their surface characteristics. The surface is usually defined as that feature on a component or device, which interacts with either the environment in which it is housed (or in which the device operates), or with another surface. The surface topography and material characteristics of a part can affect how fluids interact with it, how the part looks and feels and how two bearing parts will slide together. The need to control, and hence measure, surface features is becoming increasingly important as we move into a miniaturized world. Surface features can become the dominant functional features of a part and may become large in comparison to the overall size of an object. Research into surface texture measurement and characterization has been carried out for over a century and is now more active than ever, especially as new areal surface texture specification standards begin to be introduced. The range of disciplines for which the function of a surface relates to its topography is very diverse; from metal sheet manufacturing to art restoration, from plastic electronics to forensics. Until now, there has been no obvious publishing venue to bring together all these applications with the underlying research and theory, or to unite those working in academia with engineering and industry. Hence the creation of Surface Topography: Metrology and Properties . STMP will publish the best work being done across this broad discipline in one journal, helping researchers to share common themes and highlighting and promoting the extraordinary benefits this

  3. Oceans Past

    DEFF Research Database (Denmark)

    Based on research for the History of Marine Animal Populations project, Oceans Past examines the complex relationship our forebears had with the sea and the animals that inhabit it. It presents eleven studies ranging from fisheries and invasive species to offshore technology and the study of marine...... environmental history, bringing together the perspectives of historians and marine scientists to enhance understanding of ocean management of the past, present and future. In doing so, it also highlights the influence that changes in marine ecosystems have upon the politics, welfare and culture of human...

  4. 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.)

  5. CHARACTERISTICS OF SLUDGE BOTTOM MESH

    Directory of Open Access Journals (Sweden)

    Kamil Szydłowski

    2016-05-01

    Full Text Available The main aim of the study was to assess the selected heavy metals pollution of bottom sediments of small water bodies of different catchment management. Two ponds located in Mostkowo village were chosen for investigation. The first small water reservoir is surrounded by the cereal fields, cultivated without the use of organic and mineral fertilizers (NPK. The second reservoir is located in a park near rural buildings. Sediment samples were collected by the usage of KC Denmark sediments core probe. Samples were taken from 4 layers of sediment, from depth: 0–5, 5–10, 10–20 and 20–30 cm. Sampling was made once during the winter period (2014 year when ice occurred on the surface of small water bodies, from three points. The material was prepared for further analysis according to procedures used in soil science. The content of heavy metals (Cd, Cr, Cu, Ni, Pb and Zn were determined by atomic absorption spectrometry by usage of ASA ICE 3000 Thermo Scientific after prior digestion in the mixture (5: 1 of concentrated acids (HNO3 and HClO4. Higher pH values ​​were characteristic for sediments of pond located in a park than in pond located within the agricultural fields. In both small water bodies the highest heavy metal concentrations occurred in the deepest points of the research. In the sediments of the pond located within crop fields the highest concentration of cadmium, copper, lead and zinc were observed in a layer of 0–5 cm, wherein the nickel and chromium in a layer of 20–30 cm. In the sediments of the pond, located in the park the highest values ​​occurred at the deepest sampling point in the layer taken form 10–20 cm. Sediments from second reservoir were characterized by the largest average concentrations of heavy metals, except the lead content in sediment form the layer of 10–20 cm. According to the geochemical evaluation of sediments proposed by Bojakowska and Sokołowska [1998], the majority of samples belongs to Ist

  6. Persistent and energetic bottom-trapped topographic Rossby waves observed in the southern South China Sea

    Science.gov (United States)

    Shu, Yeqiang; Xue, Huijie; Wang, Dongxiao; Chai, Fei; Xie, Qiang; Cai, Shuqun; Chen, Rongyu; Chen, Ju; Li, Jian; He, Yunkai

    2016-01-01

    Energetic fluctuations with periods of 9–14 days below a depth of 1400 m were observed in the southern South China Sea (SCS) from 5 years of direct measurements. We interpreted such fluctuations as topographic Rossby waves (TRWs) because they obey the dispersion relation. The TRWs persisted from May 24, 2009 to August 23, 2013, and their bottom current speed with a maximum of ~10 cm/s was one order of magnitude greater than the mean current and comparable to the tidal currents near the bottom. The bottom-trapped TRWs had an approximate trapping depth of 325 m and reference wavelength of ~82 km, which were likely excited by eddies above. Upper layer current speed that peaked approximately every 2 months could offer the energy sources for the persistent TRWs in the southern SCS. Energetic bottom-trapped TRWs may have a comparable role in deep circulation to tides in areas with complex topography. PMID:27075644

  7. The Impact of Ocean Observations in Seasonal Climate Prediction

    Science.gov (United States)

    Rienecker, Michele; Keppenne, Christian; Kovach, Robin; Marshak, Jelena

    2010-01-01

    The ocean provides the most significant memory for the climate system. Hence, a critical element in climate forecasting with coupled models is the initialization of the ocean with states from an ocean data assimilation system. Remotely-sensed ocean surface fields (e.g., sea surface topography, SST, winds) are now available for extensive periods and have been used to constrain ocean models to provide a record of climate variations. Since the ocean is virtually opaque to electromagnetic radiation, the assimilation of these satellite data is essential to extracting the maximum information content. More recently, the Argo drifters have provided unprecedented sampling of the subsurface temperature and salinity. Although the duration of this observation set has been too short to provide solid statistical evidence of its impact, there are indications that Argo improves the forecast skill of coupled systems. This presentation will address the impact these different observations have had on seasonal climate predictions with the GMAO's coupled model.

  8. Brain function measurement using optical topography

    International Nuclear Information System (INIS)

    Koizumi, Hideaki; Maki, Atsushi; Yamamoto, Tsuyoshi; Kawaguchi, Hideo

    2003-01-01

    Optical topography is a completely non-invasive method to image the high brain function with the near infrared spectroscopy, does not need the restriction of human behavior for imaging and thereby is applicable even for infants. The principle is based on irradiation of the near infrared laser beam with the optical-fiber onto the head surface and detection with the fiber of the reflection, of which spectroscopy for blood-borne hemoglobin gives the local cerebral homodynamics related with the nerve activity. The infrared laser beam of 1-10 mW is found safe on direct irradiation to the human body. The topography is applicable in the fields of clinical medicine like internal neurology (an actual image of the activated Broca's and Welnicke's areas at writing is presented), neurosurgery, psychiatry and pedriatric neurology, of developmental cognitive neuroscience, of educational science and of communication. ''MIT Technology Reviews'' mentions that this technique is one of 4 recent promising innovative techniques in the world. (N.I.)

  9. Altered Global Signal Topography in Schizophrenia.

    Science.gov (United States)

    Yang, Genevieve J; Murray, John D; Glasser, Matthew; Pearlson, Godfrey D; Krystal, John H; Schleifer, Charlie; Repovs, Grega; Anticevic, Alan

    2017-11-01

    Schizophrenia (SCZ) is a disabling neuropsychiatric disease associated with disruptions across distributed neural systems. Resting-state functional magnetic resonance imaging has identified extensive abnormalities in the blood-oxygen level-dependent signal in SCZ patients, including alterations in the average signal over the brain-i.e. the "global" signal (GS). It remains unknown, however, if these "global" alterations occur pervasively or follow a spatially preferential pattern. This study presents the first network-by-network quantification of GS topography in healthy subjects and SCZ patients. We observed a nonuniform GS contribution in healthy comparison subjects, whereby sensory areas exhibited the largest GS component. In SCZ patients, we identified preferential GS representation increases across association regions, while sensory regions showed preferential reductions. GS representation in sensory versus association cortices was strongly anti-correlated in healthy subjects. This anti-correlated relationship was markedly reduced in SCZ. Such shifts in GS topography may underlie profound alterations in neural information flow in SCZ, informing development of pharmacotherapies. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  10. Snap evaporation of droplets on smooth topographies.

    Science.gov (United States)

    Wells, Gary G; Ruiz-Gutiérrez, Élfego; Le Lirzin, Youen; Nourry, Anthony; Orme, Bethany V; Pradas, Marc; Ledesma-Aguilar, Rodrigo

    2018-04-11

    Droplet evaporation on solid surfaces is important in many applications including printing, micro-patterning and cooling. While seemingly simple, the configuration of evaporating droplets on solids is difficult to predict and control. This is because evaporation typically proceeds as a "stick-slip" sequence-a combination of pinning and de-pinning events dominated by static friction or "pinning", caused by microscopic surface roughness. Here we show how smooth, pinning-free, solid surfaces of non-planar topography promote a different process called snap evaporation. During snap evaporation a droplet follows a reproducible sequence of configurations, consisting of a quasi-static phase-change controlled by mass diffusion interrupted by out-of-equilibrium snaps. Snaps are triggered by bifurcations of the equilibrium droplet shape mediated by the underlying non-planar solid. Because the evolution of droplets during snap evaporation is controlled by a smooth topography, and not by surface roughness, our ideas can inspire programmable surfaces that manage liquids in heat- and mass-transfer applications.

  11. Ocean Acidification

    Science.gov (United States)

    Ludwig, Claudia; Orellana, Mónica V.; DeVault, Megan; Simon, Zac; Baliga, Nitin

    2015-01-01

    The curriculum module described in this article addresses the global issue of ocean acidification (OA) (Feely 2009; Figure 1). OA is a harmful consequence of excess carbon dioxide (CO[subscript 2]) in the atmosphere and poses a threat to marine life, both algae and animal. This module seeks to teach and help students master the cross-disciplinary…

  12. Functional analysis screening for multiple topographies of problem behavior.

    Science.gov (United States)

    Bell, Marlesha C; Fahmie, Tara A

    2018-04-23

    The current study evaluated a screening procedure for multiple topographies of problem behavior in the context of an ongoing functional analysis. Experimenters analyzed the function of a topography of primary concern while collecting data on topographies of secondary concern. We used visual analysis to predict the function of secondary topographies and a subsequent functional analysis to test those predictions. Results showed that a general function was accurately predicted for five of six (83%) secondary topographies. A specific function was predicted and supported for a subset of these topographies. The experimenters discuss the implication of these results for clinicians who have limited time for functional assessment. © 2018 Society for the Experimental Analysis of Behavior.

  13. Investigations of Surface Topography of Hot Working Tool Steel Manufactured with the Use of 3D Print

    Directory of Open Access Journals (Sweden)

    Grobelny Pawel

    2017-01-01

    Full Text Available The paper presents the possibilities of 3D printing of chosen hot working tool steel for manufacturing ready made parts. Results of examination of the surface topography of material manufactured by the technology Laser CUSING®B (Laser melting with metals on the machine, Concept Laser M1 3D printing of metal parts has the potential to revolutionize the market of manufacturing and supplying parts. It makes it possible to dissipate manufacturing and to produce parts on request at lower cost and less energy consumption. The parameters of the surface topography of the hot working tool steel directly after printing can differ depending on the distance from the base plate. The differences of surface roughness values can amount from 32% to 85% for Ra and from 59% to 85% for Rz in comparison of the sample bottom to its top.

  14. Ocean energies

    International Nuclear Information System (INIS)

    Charlier, R.H.; Justus, J.R.

    1993-01-01

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

  15. The ecology of scattering layer biota around Indian Ocean seamounts and islands

    OpenAIRE

    Boersch-Supan, Philipp Hanno

    2014-01-01

    The waters of the open ocean constitute the largest living space on Earth but despite its obvious significance to the biosphere, the open ocean remains an unexplored frontier. With a regional focus on the Indian Ocean, this thesis investigates (i) the distribution of pelagic biota on basin scales, (ii) the effect of abrupt topography on pelagic biota and their predator-prey relationships, and (iii) the use of genetic techniques to elucidate population connectivity and dispersal of pelag...

  16. X-ray diffraction topography. Stages and tendencies of development

    International Nuclear Information System (INIS)

    Shul'pina, I.L.

    2000-01-01

    The physical foundation of X-ray diffraction topography, its methods, the achievements in image theory, the stages of evolution were described in this review. It was found that modern topography is well along in development associated with the use of third-generation synchrotron radiation and with its adaptation to advance materials and problems of materials science. Some proposals about prospects for X-ray topography progress in the future have been made [ru

  17. Bottom Scour Observed Under Hurricane Ivan

    National Research Council Canada - National Science Library

    Teague, William J; Jarosz, Eva; Keen, Timothy R; Wang, David W; Hulbert, Mark S

    2006-01-01

    Observations that extensive bottom scour along the outer continental shelf under Hurricane Ivan resulted in the displacement of more than 100 million cubic meters of sediment from a 35x15 km region...

  18. Partly standing internal tides in a dendritic submarine canyon observed by an ocean glider

    Science.gov (United States)

    Hall, Rob A.; Aslam, Tahmeena; Huvenne, Veerle A. I.

    2017-08-01

    An autonomous ocean glider is used to make the first direct measurements of internal tides within Whittard Canyon, a large, dendritic submarine canyon system that incises the Celtic Sea continental slope and a site of high benthic biodiversity. This is the first time a glider has been used for targeted observations of internal tides in a submarine canyon. Vertical isopycnal displacement observations at different stations fit a one-dimensional model of partly standing semidiurnal internal tides - comprised of a major, incident wave propagating up the canyon limbs and a minor wave reflected back down-canyon by steep, supercritical bathymetry near the canyon heads. The up-canyon internal tide energy flux in the primary study limb decreases from 9.2 to 2.0 kW m-1 over 28 km (a dissipation rate of 1 - 2.5 ×10-7 Wkg-1), comparable to elevated energy fluxes and internal tide driven mixing measured in other canyon systems. Within Whittard Canyon, enhanced mixing is inferred from collapsed temperature-salinity curves and weakened dissolved oxygen concentration gradients near the canyon heads. It has previously been hypothesised that internal tides impact benthic fauna through elevated near-bottom current velocities and particle resuspension. In support of this, we infer order 20 cm s-1 near-bottom current velocities in the canyon and observe high concentrations of suspended particulate matter. The glider observations are also used to estimate a 1 °C temperature range and 12 μmol kg-1 dissolved oxygen concentration range, experienced twice a day by organisms on the canyon walls, due to the presence of internal tides. This study highlights how a well-designed glider mission, incorporating a series of tide-resolving stations at key locations, can be used to understand internal tide dynamics in a region of complex topography, a sampling strategy that is applicable to continental shelves and slopes worldwide.

  19. Importance of dynamic topography in Himalaya-Tibetan plateau region

    Science.gov (United States)

    Ghosh, A.; Singh, S.

    2017-12-01

    Himalaya-Tibetan plateau region has the highest topography in the world. Various studies have been done to understand the mechanisms responsible for sustaining this high topography. However, the existence of dynamic topography in this region is still uncertain, though there have been some studies exploring the role of channel flow in lower crust leading to some topography. We investigated the role of radial mantle flow in this region by studying the relationship between geoid and topography. High geoid-to-topography ratios (GTR) were observed along the Himalayas suggesting deeper compensation mechanisms. However, further north, the geoid and topography relationship became a lot more complex as high as well as low GTR values were observed. The high GTR regions also coincided with area of high filtered free air gravity anomalies, indicating dynamic support. We also looked at the spectral components of gravity, geoid and topography, and calculated response functions to distinguish between different compensation mechanisms. We estimated the average elastic thickness of the whole region to be around 40 km from coherence and admittance studies. The GTR and admittance-coherence studies suggest deeper mass anomalies playing a role in supporting the topography along Himalayas and the area between Altyn Tagh and Kunlun faults.

  20. Origin of bending in uncoated microcantilever - Surface topography?

    International Nuclear Information System (INIS)

    Lakshmoji, K.; Prabakar, K.; Tripura Sundari, S.; Jayapandian, J.; Tyagi, A. K.; Sundar, C. S.

    2014-01-01

    We provide direct experimental evidence to show that difference in surface topography on opposite sides of an uncoated microcantilever induces bending, upon exposure to water molecules. Examination on opposite sides of the microcantilever by atomic force microscopy reveals the presence of localized surface features on one side, which renders the induced stress non-uniform. Further, the root mean square inclination angle characterizing the surface topography shows a difference of 73° between the opposite sides. The absence of deflection in another uncoated microcantilever having similar surface topography confirms that in former microcantilever bending is indeed induced by differences in surface topography

  1. 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

  2. Bottom production asymmetries at the LHC

    Energy Technology Data Exchange (ETDEWEB)

    Norrbin, E.; Vogt, R.

    1999-01-01

    We present results on bottom hadron production asymmetries at the LHC within both the Lund string fragmentation model and the intrinsic bottom model. The main aspects of the models are summarized and specific predictions for pp collisions at 14 TeV are given. Asymmetries are found to be very small at central rapidities increasing to a few percent at forward rapidities. At very large rapidities intrinsic production could dominate but this region is probably out of reach of any experiment.

  3. Bottom production asymmetries at the LHC

    International Nuclear Information System (INIS)

    Norrbin, E.; Vogt, R.

    1999-01-01

    We present results on bottom hadron production asymmetries at the LHC within both the Lund string fragmentation model and the intrinsic bottom model. The main aspects of the models are summarized and specific predictions for pp collisions at 14 TeV are given. Asymmetries are found to be very small at central rapidities increasing to a few percent at forward rapidities. At very large rapidities intrinsic production could dominate but this region is probably out of reach of any experiment

  4. 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.

  5. Proceedings of oceans '91

    International Nuclear Information System (INIS)

    Anon.

    1991-01-01

    This volume contains the proceedings of the Oceans '91 Conference. Topics addressed include: ocean energy conversion, marine communications and navigation, ocean wave energy conversion, environmental modeling, global climate change, ocean minerals technology, oil spill technology, and submersible vehicles

  6. 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...

  7. Ocean acidification

    International Nuclear Information System (INIS)

    Soubelet, Helene; Veyre, Philippe; Monnoyer-Smith, Laurence

    2017-09-01

    This brief publication first recalls and outlines that ocean acidification is expected to increase, and will result in severe ecological impacts (more fragile coral reefs, migration of species, and so on), and therefore social and economic impacts. This issue is particularly important for France who possesses the second exclusive maritime area in the world. The various impacts of ocean acidification on living species is described, notably for phytoplankton, coral reefs, algae, molluscs, and fishes. Social and economic impacts are also briefly presented: tourism, protection against risks (notably by coral reefs), shellfish aquaculture and fishing. Issues to be addressed by scientific research are evoked: interaction between elements of an ecosystem and between different ecosystems, multi-stress effects all along organism lifetime, vulnerability and adaptability of human societies

  8. Nanoscale surface topographies for structural colors

    DEFF Research Database (Denmark)

    Clausen, Jeppe Sandvik

    The thesis describes and demonstrates the possibilities for utilization of structural colors in mass fabricated plastic products as replacement for or in combination with pigments and inks. The motivation is the possible advantages related to re-cycling and re-use of plastic by limiting the number......-polymer interface is suppressed. This improves the ability to see through a clear plastic in the presence of specular reflection. The tapered nanostructures are also utilized to enhance the chroma of pigmented polymers. Larger tapered structures fabricated in a similar manor are shown to work as color filters....... Through an experimental study is the color of the transmitted light linked directly to the random topography of the surface by use of diffraction theory. The color effects from periodic structures and how these might be employed to create bright colors are investigated. This is done both for opaque...

  9. Relationship between Topography and Some Soil Properties

    Directory of Open Access Journals (Sweden)

    M. J. Pajand

    2016-09-01

    Full Text Available Introduction: Topography is an important and effective property affecting the soil quality. Some researchers demonstrated that degree and aspect of land slope may influence the particle size distribution and gravel. Slope degree affects the surface and subsurface run-off, drainage, soil temperature, stability of soil aggregates and soil erosion. This research was carried out to determine the spatial variation of soil properties in different slope degrees of northern and southern slopes in Khorasan Razavei province, Iran. Material and Methods: This study was performed in Sanganeh research station (longitude 60o 15ʹ60ʺ and latitude 36o 41ʹ 36ʺ, of north-eastern, Khorasan Razavi province of Iran. In order to study the effects of topography on some soil physical and chemical properties, a topo-sequence with the same slope length, parent materials and cover crops was selected. 30 soil samples (0-30 cm depth were collected from different slopes of less than 5, 5-15, 15-30, 30-50 and more than 50 percent of both southern and northern aspects. In this study, the soil particle size distribution (texture was measured by hydrometer method, organic carbon and calcium carbonate were determined by wet oxidation and titration with HCl 6 M, respectively and soil structural stability index, aggregates mean weight diameter and particles fractal dimension were calculated by related equations. Finally, the studied soil properties of 5 slopes (less than 5, 5-15, 15-30, 30-50, and more than 50% and 2 aspects (north and south with 3 replicates were compared by nested experimental design and Tuky test in JMP statistical software. Results and Discussion: The maximum and minimum clay contents as well as fractal dimension and organic carbon contents were found in less than 5% and more than 50% of south slopes, respectively. Clay content and fractal dimension in north aspect were also significantly (P

  10. Mars topography: bulk statistics and spectral scaling

    International Nuclear Information System (INIS)

    Nikora, V.; Goring, D.

    2004-01-01

    In this paper we present a systematic study of the Mars topography focusing on the statistical distributions and maps of the 5 deg.x 5 deg.cell-averaged mean elevations, standard deviations, skewness and kurtosis coefficients, and power spectra. Altogether, the obtained data suggest that at a 5 deg.x 5 deg.cell scale a large portion of the Martian surface may be reasonably considered as a Gaussian random field with a three-range spectrum consisting: (1) a high-energy low-wave-number range (∼0.003 -1 ) where the spectrum may deviate from a power law and attain a maximum; (2) scaling range 1 (∼0.03 -1 ) where the spectrum may be well approximated as S(k)∝k -β 1 ; and (3) scaling range 2 (∼(0.2-0.3) -1 ) where the spectrum may be also approximated as a power function but with a different exponent, i.e., S(k)∝k -β 2 . The most probable values for the exponents are β 1 =(2.2-2.4) and β 2 =3.8. The data show that the separation of these two scaling ranges most frequently occurs at L c ∼3.3 km. At a scale larger than the 5 deg.x 5 deg.cell scale the topography is highly intermittent with patchy spatial distributions of the key statistical moments. This patchiness is superimposed with systematic north-to-south trends in statistical properties, reflecting the crustal dichotomy of the planet and large-scale differences in the surface-forming processes

  11. 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.

  12. 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.

  13. Decoding Dynamic Topography: Geologic and Thermochronologic Constraints From Madagascar

    Science.gov (United States)

    Stephenson, S.; White, N.

    2017-12-01

    Madagascar's topography is characterized by flights of low relief peneplains separated by escarpments. Remarkably, nearly 50% of the landscape is higher than 500 m despite being surrounded by passive margins. Eocene marine limestones crop out at elevations of 400-800 m, staircases of Pleistocene marine terraces fringe the coastline and longitudinal river profiles are disequilibrated. Together, these observations suggest that Madagascar has experienced Neogene epeirogenic uplift. Positive oceanic residual depth anomalies surrounding the island, long wavelength free-air gravity anomalies, Neogene basaltic volcanism and slow sub-plate shear wave velocities show that Neogene uplift is generated by convective circulation within the upper mantle. However, the landscape's erosional response to long wavelength uplift is poorly known. Here, we present 18 apatite fission track and apatite He analyses of granitoid samples from sub-vertical transects in central and northern Madagascar. Apatite fission track ages are 200-250 Ma with mean track lengths of 12 μm. Apatite He ages are highly dispersed in samples from the highlands (i.e. AHe age > 150 Ma) but a narrower, younger range of 30-60 Ma is found on the coastal lowlands. Joint inverse modeling was carried out using the QTQt transdimensional reversible jump Markov Chain Monte Carlo (MCMC) algorithm to determine time-temperature histories. Results show that the coastal lowlands experienced up to 1 km of exhumation during the Neogene Period, whilst the central highlands experienced either very slow or negligible exhumation. This spatial distribution is expected when kinematic waves of incision propagate through a fluvially eroding landscape from coast to interior. Inverse modeling of suites of river profiles and forward landscape simulations support this interpretation. Our results show that the landscape response to modest (i.e. 1 km) regional uplift is diachronous and that thermochronologic observations can be used to

  14. Ocean Striations Detecting and Its Features

    Science.gov (United States)

    Guan, Y. P.; Zhang, Y.; Chen, Z.; Liu, H.; Yu, Y.; Huang, R. X.

    2016-02-01

    Over the past 10 years or so, ocean striations has been one of the research frontiers as reported in many investigators. With suitable filtering subroutines, striations can be revealed from many different types of ocean datasets. It is clear that striations are some types of meso-scale phenomena in the large-scale circulation system, which in the form of alternating band-like structure. We present a comprehensive study on the effectiveness of the different detection approaches to unveiling the striations. Three one-dimensional filtering methods: Gaussian smoothing, Hanning and Chebyshev high-pass filtering. Our results show that all three methods can reveal ocean banded structures, but the Chebyshev filtering is the best choice. The Gaussian smoothing is not a high pass filter, and it can merely bring regional striations, such as those in the Eastern Pacific, to light. The Hanning high pass filter can introduce a northward shifting of stripes, so it is not as good as the Chebyshev filter. On the other hand, striations in the open ocean are mostly zonally oriented; however, there are always exceptions. In particular, in coastal ocean, due to topography constraint and along shore currents, striations can titled in the meridional direction. We examined the band-like structure of striation for some selected regions of the open ocean and the semi-closed sub-basins, such as the South China sea, the Gulf of Mexico, the Mediterranean Sea and the Japan Sea. A reasonable interpretation is given here.

  15. Measurement noise of a point autofocus surface topography instrument

    DEFF Research Database (Denmark)

    Feng, Xiaobing; Quagliotti, Danilo; Maculotti, Giacomo

    Optical instruments for areal topography measurement can be especially sensitive to noise when scanning is required. Such noise has different sources, including those internally generated and external sources from the environment.......Optical instruments for areal topography measurement can be especially sensitive to noise when scanning is required. Such noise has different sources, including those internally generated and external sources from the environment....

  16. Investigating Flow Features Near Abrupt Topography in the Mariana Basin

    Science.gov (United States)

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Investigating Flow Features Near Abrupt Topography in...waves generated by flow over topography and mesoscale eddies generated by flow past islands. Having identified the prime locations in the region for such

  17. Relating Cenozoic North Sea sediments to topography in southern Norway:

    DEFF Research Database (Denmark)

    Anell, Ingrid Anna Margareta; Thybo, Hans; Stratford, Wanda Rose

    2010-01-01

    the Shetland platform continued throughout the Cenozoic while supply from southern Norway increased markedly around the Eocene–Oligocene, coeval with the greenhouse–icehouse transition. Mass balance calculations of sediment and eroded rock volumes suggest that while some topography along the western margin...... that Plio-Pleistocene erosion over-deepened a pre-existing topography....

  18. Cokriging surface elevation and seismic refraction data for bedrock topography

    International Nuclear Information System (INIS)

    Nyquist, J.E.; Doll, W.E.; Davis, R.K.; Hopkins, R.A.

    1992-01-01

    Analysis of seismic refraction data collected at a proposed site of the Advanced Neutron Source (ANS) Facility showed a strong correlation between surface and bedrock topography. By combining seismically determined bedrock elevation data with surface elevation data using cokriging, we were able to significantly improve our map of bedrock topography without collecting additional seismic data

  19. Clinical Validation of Point-Source Corneal Topography in Keratoplasty

    NARCIS (Netherlands)

    Vrijling, A C L; Braaf, B.; Snellenburg, J.J.; de Lange, F.; Zaal, M.J.W.; van der Heijde, G.L.; Sicam, V.A.D.P.

    2011-01-01

    Purpose. To validate the clinical performance of point-source corneal topography (PCT) in postpenetrating keratoplasty (PKP) eyes and to compare it with conventional Placido-based topography. Methods. Corneal elevation maps of the anterior corneal surface were obtained from 20 post-PKP corneas using

  20. Diffusion processes in bombardment-induced surface topography

    International Nuclear Information System (INIS)

    Robinson, R.S.

    1984-01-01

    A treatment is given of the problem of surface diffusion processes occurring during surface topography development, whenever a surface is simultaneously seeded with impurities and ion bombarded. The development of controllable topography and the importance of surface diffusion parameters, which can be obtained during these studies, are also analyzed. 101 refs.; 7 figs.; 2 tabs