GeoSEA: Geodetic Earthquake Observatory on the Seafloor

Science.gov (United States)

Kopp, Heidrun; Lange, Dietrich; Flueh, Ernst R.; Petersen, Florian; Behrmann, Jan-Hinrich; Devey, Colin

2014-05-01

monitor station settlement in two horizontal directions. Data can be acquired and recorded autonomously subsea without system or human intervention for up to 6 years. These data can then be recovered via the integrated high-speed acoustic telemetry link without recovering the seafloor units. When requested to do so, the stored data will be transmitted wirelessly up to the sea surface to the GeoSURF wave glider for onward transmission via a satellite link. Targets for GeoSEA are the marine sector of the North Anatolian fault zone in the Marmara Sea, where a joint French-German array will be installed in late 2014 as well as the central sector of the South America - Nazca convergent plate boundary along the Iquique segment, offshore Northern Chile. Here, the GeoSEA array will be installed in late 2015 to monitor crustal deformation. Mobile autonomous seafloor arrays for continuous measurement of active seafloor deformation in hazard zones have the potential to lead to transformative discoveries of plate boundary/fault zone tectonic processes and address a novel element of marine geophysical research.

Anhydrite precipitation in seafloor hydrothermal systems

Science.gov (United States)

Theissen-Krah, Sonja; Rüpke, Lars H.

2016-04-01

The composition and metal concentration of hydrothermal fluids venting at the seafloor is strongly temperature-dependent and fluids above 300°C are required to transport metals to the seafloor (Hannington et al. 2010). Ore-forming hydrothermal systems and high temperature vents in general are often associated with faults and fracture zones, i.e. zones of enhanced permeabilities that act as channels for the uprising hydrothermal fluid (Heinrich & Candela, 2014). Previous numerical models (Jupp and Schultz, 2000; Andersen et al. 2015) however have shown that high permeabilities tend to decrease fluid flow temperatures due to mixing with cold seawater and the resulting high fluid fluxes that lead to short residence times of the fluid near the heat source. A possible mechanism to reduce the permeability and thereby to focus high temperature fluid flow are mineral precipitation reactions that clog the pore space. Anhydrite for example precipitates from seawater if it is heated to temperatures above ~150°C or due to mixing of seawater with hydrothermal fluids that usually have high Calcium concentrations. We have implemented anhydrite reactions (precipitation and dissolution) in our finite element numerical models of hydrothermal circulation. The initial results show that the precipitation of anhydrite efficiently alters the permeability field, which affects the hydrothermal flow field as well as the resulting vent temperatures. C. Andersen et al. (2015), Fault geometry and permeability contrast control vent temperatures at the Logatchev 1 hydrothermal field, Mid-Atlantic Ridge, Geology, 43(1), 51-54. M. D. Hannington et al. (2010), Modern Sea-Floor Massive Sulfides and Base Metal Resources: Toward an Estimate of Global Sea-Floor Massive Sulfide Potential, in The Challenge of Finding New Mineral Resources: Global Metallogeny, Innovative Exploration, and New Discoveries, edited by R. J. Goldfarb, E. E. Marsh and T. Monecke, pp. 317-338, Society of Economic Geologists

Seafloor identification in sonar imagery via simulations of Helmholtz equations and discrete optimization

Science.gov (United States)

Engquist, Björn; Frederick, Christina; Huynh, Quyen; Zhou, Haomin

2017-06-01

We present a multiscale approach for identifying features in ocean beds by solving inverse problems in high frequency seafloor acoustics. The setting is based on Sound Navigation And Ranging (SONAR) imaging used in scientific, commercial, and military applications. The forward model incorporates multiscale simulations, by coupling Helmholtz equations and geometrical optics for a wide range of spatial scales in the seafloor geometry. This allows for detailed recovery of seafloor parameters including material type. Simulated backscattered data is generated using numerical microlocal analysis techniques. In order to lower the computational cost of the large-scale simulations in the inversion process, we take advantage of a pre-computed library of representative acoustic responses from various seafloor parameterizations.

Airborne electromagnetic detection of shallow seafloor topographic features, including resolution of multiple sub-parallel seafloor ridges

Science.gov (United States)

Vrbancich, Julian; Boyd, Graham

2014-05-01

The HoistEM helicopter time-domain electromagnetic (TEM) system was flown over waters in Backstairs Passage, South Australia, in 2003 to test the bathymetric accuracy and hence the ability to resolve seafloor structure in shallow and deeper waters (extending to ~40 m depth) that contain interesting seafloor topography. The topography that forms a rock peak (South Page) in the form of a mini-seamount that barely rises above the water surface was accurately delineated along its ridge from the start of its base (where the seafloor is relatively flat) in ~30 m water depth to its peak at the water surface, after an empirical correction was applied to the data to account for imperfect system calibration, consistent with earlier studies using the same HoistEM system. A much smaller submerged feature (Threshold Bank) of ~9 m peak height located in waters of 35 to 40 m depth was also accurately delineated. These observations when checked against known water depths in these two regions showed that the airborne TEM system, following empirical data correction, was effectively operating correctly. The third and most important component of the survey was flown over the Yatala Shoals region that includes a series of sub-parallel seafloor ridges (resembling large sandwaves rising up to ~20 m from the seafloor) that branch out and gradually decrease in height as the ridges spread out across the seafloor. These sub-parallel ridges provide an interesting topography because the interpreted water depths obtained from 1D inversion of TEM data highlight the limitations of the EM footprint size in resolving both the separation between the ridges (which vary up to ~300 m) and the height of individual ridges (which vary up to ~20 m), and possibly also the limitations of assuming a 1D model in areas where the topography is quasi-2D/3D.

Nitrogen isotopes in bulk marine sediment: linking seafloor observations with subseafloor records

Directory of Open Access Journals (Sweden)

J.-E. Tesdal

2013-01-01

Full Text Available The stable isotopes of nitrogen offer a unique perspective on changes in the nitrogen cycle, past and present. However, the presence of multiple forms of nitrogen in marine sediments can complicate the interpretation of bulk nitrogen isotope measurements. Although the large-scale global patterns of seafloor δ¹⁵N have been shown to match process-based expectations, small-scale heterogeneity on the seafloor, or alterations of isotopic signals during translation into the subseafloor record, could obscure the primary signals. Here, a public database of nitrogen isotope measurements is described, including both seafloor and subseafloor sediment samples ranging in age from modern to the Pliocene, and used to assess these uncertainties. In general, good agreement is observed between neighbouring seafloor sites within a 100 km radius, with 85% showing differences of < 1‰. There is also a good correlation between the δ¹⁵N of the shallowest (< 5 ka subseafloor sediments and neighbouring seafloor sites within a 100 km radius (R² = 0.83, which suggests a reliable translation of sediments into the buried sediment record. Meanwhile, gradual δ¹⁵N decreases over multiple glacial–interglacial cycles appear to reflect post-depositional alteration in records from the deep sea (below 2000 m. We suggest a simple conceptual model to explain these 100-kyr-timescale changes in well-oxygenated, slowly accumulating sediments, which calls on differential loss rates for pools of organic N with different δ¹⁵N. We conclude that bulk sedimentary nitrogen isotope records are reliable monitors of past changes in the marine nitrogen cycle at most locations, and could be further improved with a better understanding of systematic post-depositional alteration. Furthermore, geochemical or environmental criteria should be developed in order to effectively identify problematic locations and to account for

Observations of seafloor fluid venting along the transform margin between the North American and Pacific plates in the Gulf of California

Science.gov (United States)

Lundsten, E. M.; Anderson, K.; Paull, C. K.; Caress, D. W.; Thomas, H.; Gwiazda, R.; Herguera, J.; McGann, M. L.; Edwards, B. D.; Hinojosa, A.; Mejia Mercado, B.; Sanchez, A.; Conlin, D.; Thompson, D.

2012-12-01

Detailed surveys of the seafloor morphology at nine representative sections of the North American - Pacific Plate boundary on the floor of the Gulf of California were conducted by the Monterey Bay Aquarium Research Institute (MBARI) during a two ship expedition in March and April 2012. One of the objectives of this program was to better understand the distribution and impact of seafloor fluid venting along an active transform fault. At issue is whether the fault itself forms an active fluid flow conduit. An autonomous underwater vehicle (AUV) provided detailed bathymetry of the seafloor, and a remotely operated vehicle (ROV) allowed ground-truth observations and sampling of the surveyed area. The AUV surveys provide high-resolution multibeam bathymetry with a vertical precision of 0.15 m, horizontal resolution of 1.0 and 2-10 kHz CHIRP seismic reflection profiles. The nine surveys captured the morphology of a highly active fault zone in unprecedented detail. Among the features highlighted by these surveys are areas of distinctive seafloor textures. This distinctive morphology commonly occurs on the surface of elevated features that are up to 10 m higher than the surrounding seafloor and is characterized by considerable fine scale surface topography observed in both the AUV and ROV surveys. The surface topography is made up of broken and irregular blocks of methane-derived carbonates, separated by seafloor craters and open cracks that are 1 to 2 m deep and up to 10 m across. Individual patches of this distinctive morphology which are commonly ~100 m across occur within two of the nine survey areas. The presence of active chemosynthetic biological communities in open karst-like cracks show many of these sites are areas of active fluid seepage. In some places methane bubble venting was observed. Seepage was only observed where truncated strata exposed permeable layers adjacent to the fault rather than directly along the fault trace.

Quantitative characterization of abyssal seafloor with transit multibeam backscatter data

Science.gov (United States)

Pockalny, R. A.; Ferrini, V. L.

2014-12-01

The expanding volume of deep-water multibeam echosounder data provides emerging opportunities for the improved characterization of the abyssal seafloor. Nearly 500 cruises criss-cross the oceans with modern wide-swath multibeam systems, and these cruise tracks have imaged a variety of morphologic, tectonic and magmatic environments. The qualitative analysis of the seafloor backscatter data strongly suggests a local and regional variability that correlates with sediment thickness, sediment type and/or depositional environment. We present our initial attempts to develop a method that quantifies this observed seafloor backscatter variability and to explore the causes and potential implications of this variability. Our approach is rooted in the Angular Range Analysis methodology, which utilizes changes in backscatter amplitude observed as a function of grazing angle, to characterize the seafloor. The primary difference in our approach is that we do not invert for geo-acoustical parameters, but rather explores empirical relationships between geological observations and stacked slope and y-intercept values. In addition, we also include the mean and the variance of detrended backscatter measurements. Our initial results indicate intriguing relationships between backscatter parameters and the CaCO3 content of surface sediments. Seafloor regions reported to have high manganese nodule concentrations also tend to have characteristic trends in backscatter parameters. We will present these regional correlations as well as some preliminary statistical analyses of the backscatter parameters and key environmental factors.

Seafloor expression and shallow structure of a fold-and-thrust system, Isfjorden, west Spitsbergen

Directory of Open Access Journals (Sweden)

Maria Blinova

2012-09-01

Full Text Available A detailed map of the structure of the west Spitsbergen fold-and-thrust belt in the Isfjorden area, Spitsbergen, is presented. The map was constructed from a dense grid of two-dimensional multichannel reflection seismic and bathymetric data. Joint interpretation of two data sets allowed a comparison of tectonic structures detected along the uppermost parts of the seismic sections and those reflected in the morphology of the seafloor. Three major, predominantly north-west–south-east striking faults were identified. The westernmost fault (T1 is a hinterland-directed (most likely out of sequence thrust, while the central and easternmost faults (T2 and T3 are foreland-directed (in-sequence thrusts. The thrusts divide Isfjorden into three subareas. Subarea 1 is bounded by thrust faults T1 and T2 and comprises Tertiary rocks surrounded by Jurassic–Cretaceous strata. The structural signature of Subarea 1 is that of a system of hinterland- and foreland-directed thrust faults, resulting in a seafloor relief characterized by parallel ridges and troughs. Subarea 2 is limited by thrust faults T2 and T3 and shows Jurassic–Cretaceous outcrops on the seafloor. Subarea 3 is situated east of the main thrust fault T3 and mainly involves outcrops of Triassic–Jurassic rocks. Together, Subareas 2 and 3 are dominated by foreland-directed, north-west–south-east and NNW–SSE-striking thrusts that are hardly detectable in bathymetric data.

The NGDC Seafloor Sediment Grain Size Database

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NGDC (now NCEI) Seafloor Sediment Grain Size Database contains particle size data for over 17,000 seafloor samples worldwide. The file was begun by NGDC in 1976...

Installation of a seafloor geodetic network offshore northern Chile (GeoSEA)

Science.gov (United States)

Kopp, Heidrun; Lange, Dietrich; Hannemann, Katrin; Petersen, Florian; Contreras-Reyes, Eduardo

2016-04-01

The seafloor stores crucial information on sub-seafloor processes, including stress, elastic strain, and earthquake and tsunami generation. This information may be extracted through the nascent scientific field of seafloor geodesy. The target of the recently installed GeoSEA array (Geodetic Earthquake Observatory on the SEAfloor) is to measure crustal deformation in mm-scale on the marine forearc and outer rise of the South American subduction system around 21°S. This segment of the Nazca-South American plate boundary has last ruptured in an earthquake in 1877 and was identified as a seismic gap prior to the 2014 Iquique/Pisagua earthquake (Mw=8.1). The southern portion of the segment remains unbroken by a recent earthquake. Seafloor geodetic measurements provide a way to monitor crustal deformation at high resolution comparable to the satellite-based GPS technique upon which terrestrial geodesy is largely based. The GeoSEA Network consists of autonomous seafloor transponders installed on 4 m high tripods, which were lowered to the seabed on the deep-sea cable of RV SONNE in December 2015. The transponders within an array intercommunicate via acoustic signals for a period of up to 3.5 years and measure acoustic distance, tilt and pressure. An additional component of the network is GeoSURF, a self-steering autonomous surface vehicle (Wave Glider), which monitors system health and is capable to upload the seafloor data to the sea surface and to transfer it via satellite. We have chosen three areas on the middle and lower slope and the outer rise for the set-up of three sub-arrays. The array in Area 1 on the middle continental slope consists of 8 transponders located in pairs on four topographic ridges, which are surface expressions of faults at depth. Area 2 is located on the outer rise seaward of the trench where 5 stations monitor extension across plate-bending related normal faults. The third area is located at water depth >5000 m on the lower continental slope

Mapping the seafloor, with end users in mind

Science.gov (United States)

Lecours, V.

2017-12-01

In the last 25 years, as more seafloor data and user-friendly analysis tools have become available, the amount and diversity of applications making use of such data have considerably increased. While limitations in the utility of the data caused by the data collection and processing methods may be quite apparent to experts, such limitations may be less obvious to users with different background and expertise. For instance, it has been acknowledged many times in the literature that seafloor data are often treated as true representations of the seafloor rather that as models. This lack of understanding brings hidden dangers to unsuspecting end users misusing data, which may result in misleading outcomes/conclusions for different applications like marine geomorphology, marine habitat mapping, marine conservation, and management of marine resources. In this paper, I identify common practices of both data producers and users that can prevent a proper use of seafloor data. Using seafloor data from a variety of locations and sources, I demonstrate how the choice of soundings interpolator, elements of data quality, scale alterations, and backscatter representation can impact applications. I show how these elements propagate throughout analyses and directly influence outcomes, sometimes in predictable ways (e.g. in marine geomorphology) and sometimes in unpredictable ways (e.g. in marine habitat mapping). Regardless of the final use of seafloor data, better and more transparent error and uncertainty quantification and representation should be implemented at the data collection, processing, and analysis levels. Complete metadata should always be documented, with elements related to data provenance, survey, scale, error and uncertainty quantification, and any other information relevant to further use of seafloor data, in order to create a community of users aware of data quality and limitations. As the number of applications using seafloor data increases, some of the

Quantifying Methane Flux from a Prominent Seafloor Crater with Water Column Imagery Filtering and Bubble Quantification Techniques

Science.gov (United States)

Mitchell, G. A.; Gharib, J. J.; Doolittle, D. F.

2015-12-01

Methane gas flux from the seafloor to atmosphere is an important variable for global carbon cycle and climate models, yet is poorly constrained. Methodologies used to estimate seafloor gas flux commonly employ a combination of acoustic and optical techniques. These techniques often use hull-mounted multibeam echosounders (MBES) to quickly ensonify large volumes of the water column for acoustic backscatter anomalies indicative of gas bubble plumes. Detection of these water column anomalies with a MBES provides information on the lateral distribution of the plumes, the midwater dimensions of the plumes, and their positions on the seafloor. Seafloor plume locations are targeted for visual investigations using a remotely operated vehicle (ROV) to determine bubble emission rates, venting behaviors, bubble sizes, and ascent velocities. Once these variables are measured in-situ, an extrapolation of gas flux is made over the survey area using the number of remotely-mapped flares. This methodology was applied to a geophysical survey conducted in 2013 over a large seafloor crater that developed in response to an oil well blowout in 1983 offshore Papua New Guinea. The site was investigated by multibeam and sidescan mapping, sub-bottom profiling, 2-D high-resolution multi-channel seismic reflection, and ROV video and coring operations. Numerous water column plumes were detected in the data suggesting vigorously active vents within and near the seafloor crater (Figure 1). This study uses dual-frequency MBES datasets (Reson 7125, 200/400 kHz) and ROV video imagery of the active hydrocarbon seeps to estimate total gas flux from the crater. Plumes of bubbles were extracted from the water column data using threshold filtering techniques. Analysis of video images of the seep emission sites within the crater provided estimates on bubble size, expulsion frequency, and ascent velocity. The average gas flux characteristics made from ROV video observations is extrapolated over the number

Where The Wild Seafloor Scientists Are: Using Interactive Picture Books To Educate Children About Sub-seafloor Science

Science.gov (United States)

Kurtz, K.

2015-12-01

Sub-seafloor scientific research has the power to spark the imaginations of elementary age children with its mysterious nature, cutting-edge research, and its connections to kid friendly science topics, such as volcanoes, the extinction of dinosaurs and the search for extraterrestrial life. These factors have been utilized to create two interactive eBooks for elementary students and teachers, integrating high quality science information, highly engaging and age-appropriate illustrations, and rhyming text. One book introduces children to the research and discoveries of the JOIDES Resolution research vessel. The second focuses on the discoveries of microbial life in the sub-seafloor. The eBooks present information as traditional, linear, illustrated children's books, but the eBook format allows the book to be available online for free to anyone and allows teachers to project the book on a classroom screen so all students can easily see the illustrations. The iPad versions also provide an interactive, learner-led educational experience, where cognitively appropriate videos, photos and other forms of information can be accessed with the tap of a finger to answer reader questions and enrich their learning experience. These projects provide an example and model of the products that can result from high level and meaningful partnerships between scientists, educators, artists and writers.

A novel approach to imaging extinct seafloor massive sulphides (eSMS) by using ocean bottom seismometer data from the Blue Mining project

Science.gov (United States)

Gil, A.; Chidlow, K. L.; Vardy, M. E.; Bialas, J.; Schroeder, H.; Stobbs, I. J.; Gehrmann, R. A. S.; North, L. J.; Minshull, T. A.; Petersen, S.; Murton, B. J.

2017-12-01

Seafloor massive sulphide (SMS) deposits have generated great interest regarding their formation and composition, since their discovery in 1977. SMS deposits form through hydrothermal circulation and are therefore commonly found near hydrothermal vent sites. The high base (Cu, Zn) and precious metal (Au, Ag) content has interested mining companies, due to their potentially high economic value. Currently, the possibility of mining extinct seafloor massive sulphides (eSMS) deposits has opened a debate about their environmentally and economically sustainable exploitation. A major goal is the rapid exploration and assessment of deposit structure and volume. This is challenging due to their small dimensions (100s m diameter) and typically great water depths (> 3000 mbsl). Here we present a novel approach combining seismic reflection/refraction forward modelling to data acquired from the TAG hydrothermal field (26ºN, Mid-Atlantic Ridge, 3500mbsl) to image deep-water eSMS deposits. In May 2016, the RV METEOR shot 30, short (Mining' project, n˚ 604500.

Measurement of Seafloor Deformation in the Marine Sector of the Campi Flegrei Caldera (Italy)

Science.gov (United States)

Iannaccone, Giovanni; Guardato, Sergio; Donnarumma, Gian Paolo; De Martino, Prospero; Dolce, Mario; Macedonio, Giovanni; Chierici, Francesco; Beranzoli, Laura

2018-01-01

We present an assessment of vertical seafloor deformation in the shallow marine sector of the Campi Flegrei caldera (southern Italy) obtained from GPS and bottom pressure recorder (BPR) data, acquired over the period April 2016 to July 2017 in the Gulf of Pozzuoli by a new marine infrastructure, MEDUSA. This infrastructure consists of four fixed buoys with GPS receivers; each buoy is connected by cable to a seafloor multisensor module hosting a BPR. The measured maximum vertical uplift of the seafloor is about 4.2 ± 0.4 cm. The MEDUSA data were then compared to the expected vertical displacement in the marine sector according to a Mogi model point source computed using only GPS land measurements. The results show that a single point source model of deformation is able to explain both the GPS land and seafloor data. Moreover, we demonstrate that a network of permanent GPS buoys represents a powerful tool to measure the seafloor vertical deformation field in shallow water. The performance of this system is comparable to on-land high-precision GPS networks, marking a significant achievement and advance in seafloor geodesy and extending volcano monitoring capabilities to shallow offshore areas (up to 100 m depth). The GPS measurements of MEDUSA have also been used to confirm that the BPR data provide an independent measure of the seafloor vertical uplift in shallow water.

Design of a Data Distribution Core Model for Seafloor Observatories in East China Sea

Science.gov (United States)

Chen, H.; Qin, R.; Xu, H.

2017-12-01

High loadings of nutrients and pollutants from agriculture, industries and city waste waters are carried by Changjiang (Yangtze) River and transformed into the foodweb in the river freshwater plume. Understanding these transport and transformation processes is essential for the ecosystem protection, fisheries resources management, seafood safety and human health. As Xiaoqushan Seafloor Observatory and Zhujiajian Seafloor Observatory built in East China Sea, it is an opportunity and a new way for the research of Changjiang River plume. Data collected by seafloor observatory should be accessed conveniently by end users in real time or near real time, which can make it play a better role. Therefore, data distribution is one of major issues for seafloor observatory characterized by long term, real time, high resolution and continuous observation. This study describes a Data Distribution core Model for Seafloor Observatories in East China Sea (ESDDM) containing Data Acquisition Module (DAM), Data Interpretation Module (DIM), Data Transmission Module (DTM) and Data Storage Module (DTM), which enables acquiring, interpreting, transmitting and storing various types of data in real time. A Data Distribution Model Makeup Language (DDML) based on XML is designed to enhance the expansibility and flexibility of the system implemented by ESDDM. Network sniffer is used to acquire data by IP address and port number in DAM promising to release the operating pressure of junction boxes. Data interface, core data processing plugins and common libraries consist of DIM helping it interpret data in a hot swapping way. DTM is an external module in ESDDM transmitting designated raw data packets to Secondary Receiver Terminal. The technology of database connection pool used in DSM facilitates the efficiency of large volumes of continuous data storage. Given a successful scenario in Zhujiajian Seafloor Observatory, the protosystem based on ESDDM running up to 1500h provides a reference for

Observations of Seafloor Roughness in a Tidally Modulated Inlet

Science.gov (United States)

Lippmann, T. C.; Hunt, J.

2014-12-01

The vertical structure of shallow water flows are influenced by the presence of a bottom boundary layer, which spans the water column for long period waves or mean flows. The nature of the boundary is determined in part by the roughness elements that make up the seafloor, and includes sometimes complex undulations associated with regular and irregular shaped bedforms whose scales range several orders of magnitude from orbital wave ripples (10-1 m) to mega-ripples (100 m) and even larger features (101-103) such as sand waves, bars, and dunes. Modeling efforts often parameterize the effects of roughness elements on flow fields, depending on the complexity of the boundary layer formulations. The problem is exacerbated by the transient nature of bedforms and their large spatial extent and variability. This is particularly important in high flow areas with large sediment transport, such as tidally dominated sandy inlets like New River Inlet, NC. Quantification of small scale seafloor variability over large spatial areas requires the use of mobile platforms that can measure with fine scale (order cm) accuracy in wide swaths. The problem is difficult in shallow water where waves and currents are large, and water clarity is often limited. In this work, we present results from bathymetric surveys obtained with the Coastal Bathymetry Survey System, a personal watercraft equipped with a Imagenex multibeam acoustic echosounder and Applanix POS-MV 320 GPS-aided inertial measurement unit. This system is able to measure shallow water seafloor bathymetry and backscatter intensity with very fine scale (10-1 m) resolution and over relatively large scales (103 m) in the presence of high waves and currents. Wavenumber spectra show that the noise floor of the resolved multibeam bathymetry is on the order of 2.5 - 5 cm in amplitude, depending on water depths ranging 2 - 6 m, and about 30 cm in wavelength. Seafloor roughness elements are estimated from wavenumber spectra across the inlet

Mind the seafloor

Science.gov (United States)

Boetius, Antje; Haeckel, Matthias

2018-01-01

As human use of rare metals has diversified and risen with global development, metal ore deposits from the deep ocean floor are increasingly seen as an attractive future resource. Japan recently completed the first successful test for zinc extraction from the deep seabed, and the number of seafloor exploration licenses filed at the International Seabed Authority (ISA) has tripled in the past 5 years. Seafloor-mining equipment is being tested, and industrial-scale production in national waters could start in a few years. We call for integrated scientific studies of global metal resources, the fluxes and fates of metal uses, and the ecological footprints of mining on land and in the sea, to critically assess the risks of deep-sea mining and the chances for alternative technologies. Given the increasing scientific evidence for long-lasting impacts of mining on the abyssal environment, precautionary regulations for commercial deep-sea mining are essential to protect marine ecosystems and their biodiversity.

Seafloor weathering buffering climate: numerical experiments

Science.gov (United States)

Farahat, N. X.; Archer, D. E.; Abbot, D. S.

2013-12-01

Continental silicate weathering is widely held to consume atmospheric CO2 at a rate controlled in part by temperature, resulting in a climate-weathering feedback [Walker et al., 1981]. It has been suggested that weathering of oceanic crust of warm mid-ocean ridge flanks also has a CO2 uptake rate that is controlled by climate [Sleep and Zahnle, 2001; Brady and Gislason, 1997]. Although this effect might not be significant on present-day Earth [Caldeira, 1995], seafloor weathering may be more pronounced during snowball states [Le Hir et al., 2008], during the Archean when seafloor spreading rates were faster [Sleep and Zahnle, 2001], and on waterworld planets [Abbot et al., 2012]. Previous studies of seafloor weathering have made significant contributions using qualitative, generally one-box, models, and the logical next step is to extend this work using a spatially resolved model. For example, experiments demonstrate that seafloor weathering reactions are temperature dependent, but it is not clear whether the deep ocean temperature affects the temperature at which the reactions occur, or if instead this temperature is set only by geothermal processes. Our goal is to develop a 2-D numerical model that can simulate hydrothermal circulation and resulting alteration of oceanic basalts, and can therefore address such questions. A model of diffusive and convective heat transfer in fluid-saturated porous media simulates hydrothermal circulation through porous oceanic basalt. Unsteady natural convection is solved for using a Darcy model of porous media flow that has been extensively benchmarked. Background hydrothermal circulation is coupled to mineral reaction kinetics of basaltic alteration and hydrothermal mineral precipitation. In order to quantify seafloor weathering as a climate-weathering feedback process, this model focuses on hydrothermal reactions that influence carbon uptake as well as ocean alkalinity: silicate rock dissolution, calcium and magnesium leaching

Sedimentological characteristics and seafloor failure offshore SW Taiwan

Directory of Open Access Journals (Sweden)

Chih-Chieh Su

2018-01-01

Full Text Available In this study, analysis results reveal two main deposition zones are located at the flank of upper Gaoping Submarine Canyon and Lower Fangliao Basin offshore SW Taiwan. The non-event related sediments deposited in past 150 years (i.e., 632 Mt km-2 was delivered and transported from Gaoping River by suspension process with tides and coastal currents and gradually spread out offshore. Meanwhile, the total mass of accumulation sediments is 1922 Mt km-2, accounting for 40% Gaoping River’s sediment load and suggesting that the deposition process is mainly controlled by natural hazards. Sedimentation rates in much of the study area, except in the main deposition zones, are less than 0.5 cm yr-1 (5 m kyr-1. Compared with the studies at the instability seafloor caused by high sedimentation rates (~30 m kyr-1, the offshore southwestern Taiwan is relatively stable. In this study, we also discovered a series of sediment waves located on the upper continental slope between Gaoping and Fangliao Submarine Canyons, which is related to the creeping process on seafloor. In summary, our results reveal the fluid activities, existence of weak layers and earthquake triggering are potential factors which might induced seafloor failures offshore southwestern Taiwan.

Beaufort Sea deep-water gas hydrate recovery from a seafloor mound in a region of widespread BSR occurrence

Science.gov (United States)

Hart, Patrick E.; Pohlman, John W.; Lorenson, T.D.; Edwards, Brian D.

2011-01-01

Gas hydrate was recovered from the Alaskan Beaufort Sea slope north of Camden Bay in August 2010 during a U.S. Coast Guard Cutter Healy expedition (USCG cruise ID HLY1002) under the direction of the U.S. Geological Survey (USGS). Interpretation of multichannel seismic (MCS) reflection data collected in 1977 by the USGS across the Beaufort Sea continental margin identified a regional bottom simulating reflection (BSR), indicating that a large segment of the Beaufort Sea slope is underlain by gas hydrate. During HLY1002, gas hydrate was sampled by serendipity with a piston core targeting a steep-sided bathymetric high originally thought to be an outcrop of older, exposed strata. The feature cored is an approximately 1100m diameter, 130 m high conical mound, referred to here as the Canning Seafloor Mound (CSM), which overlies the crest of a buried anticline in a region of sub-parallel compressional folds beneath the eastern Beaufort outer slope. An MCS profile shows a prominent BSR upslope and downslope from the mound. The absence of a BSR beneath the CSM and occurrence of gas hydrate near the summit indicates that free gas has migrated via deep-rooted thrust faults or by structural focusing up the flanks of the anticline to the seafloor. Gas hydrate recovered from near the CSM summit at a subbottom depth of about 5.7 meters in a water depth of 2538 m was of nodular and vein-filling morphology. Although the hydrate was not preserved, residual gas from the core liner contained >95% methane by volume when corrected for atmospheric contamination. The presence of trace C4+hydrocarbons (extrusion contributing to the development of the mound. Blister-like inflation of the seafloor caused by formation and accumulation of shallow hydrate lenses is also a likely factor in CSM growth. Pore water analysis shows the sulfate-methane transition to be very shallow (0-1 mbsf), also supporting an active high-flux interpretation. Pore water with chloride concentrations as low as 160 m

The Skælskør structure in eastern Denmark – wrench-related anticline or primary Late Cretaceous sea-floor topography?

DEFF Research Database (Denmark)

Surlyk, Finn; Boldreel, Lars Ole; Lykke-Andersen, Holger

2010-01-01

seismic studies of the Chalk Group in Øresund and Kattegat have shown that similar highs actually represent topographic highs on the Late Cretaceous – Danian seafloor formed by strong contourparallel bottom currents. Reflection seismic data collected over the Skælskør structure in order to test...... the Ringkøbing Fyn High into the Danish Basin. The elevated position is maintained due to reduced subsidence as compared with the Danish Basin north of the high. The hypothesis of wrench tectonics as origin can be refuted. The seismic data show that the upper part of the Chalk Group is characterised by irregular...

Quantitative prediction process and evaluation method for seafloor polymetallic sulfide resources

Directory of Open Access Journals (Sweden)

Mengyi Ren

2016-03-01

Full Text Available Seafloor polymetallic sulfide resources exhibit significant development potential. In 2011, China received the exploration rights for 10,000 km2 of a polymetallic sulfides area in the Southwest Indian Ocean; China will be permitted to retain only 25% of the area in 2021. However, an exploration of seafloor hydrothermal sulfide deposits in China remains in the initial stage. According to the quantitative prediction theory and the exploration status of seafloor sulfides, this paper systematically proposes a quantitative prediction evaluation process of oceanic polymetallic sulfide resources and divides it into three stages: prediction in a large area, prediction in the prospecting region, and the verification and evaluation of targets. The first two stages of the prediction process have been employed in seafloor sulfides prospecting of the Chinese contract area. The results of stage one suggest that the Chinese contract area is located in the high posterior probability area, which indicates good prospecting potential area in the Indian Ocean. In stage two, the Chinese contract area of 48°–52°E has the highest posterior probability value, which can be selected as the reserved region for additional exploration. In stage three, the method of numerical simulation is employed to reproduce the ore-forming process of sulfides to verify the accuracy of the reserved targets obtained from the three-stage prediction. By narrowing the exploration area and gradually improving the exploration accuracy, the prediction will provide a basis for the exploration and exploitation of seafloor polymetallic sulfide resources.

Spectral reflectance of carbonate sediments and application to remote sensing classification of benthic habitats

Science.gov (United States)

Louchard, Eric Michael

Remote sensing is a valuable tool in marine research that has advanced to the point that images from shallow waters can be used to identify different seafloor types and create maps of benthic habitats. A major goal of this dissertation is to examine differences in spectral reflectance and create new methods of analyzing shallow water remote sensing data to identify different seafloor types quickly and accurately. Carbonate sediments were used as a model system as they presented a relatively uniform, smooth surface for measurement and are a major bottom type in tropical coral reef systems. Experimental results found that sediment reflectance varied in shape and magnitude depending on pigment content, but only varied in magnitude with variations in grain size and shape. Derivative analysis of the reflectance spectra identified wavelength regions that correlate to chlorophyll a and chlorophyllide a as well as accessory pigments, indicating differences in microbial community structure. Derivative peak height also correlated to pigment content in the sediments. In remote sensing data, chlorophyll a, chlorophyllide a, and some xanthophylls were identified in derivative spectra and could be quantified from second derivative peak height. Most accessory pigments were attenuated by the water column, however, and could not be used to quantify pigments in sediments from remote sensing images. Radiative transfer modeling of remote sensing reflectance showed that there was sufficient spectral variation to separate major sediment types, such as ooid shoals and sediment with microbial layers, from different densities of seagrass and pavement bottom communities. Both supervised classification with a spectral library and unsupervised classification with principal component analysis were used to create maps of seafloor type. The results of the experiments were promising; classified seafloor types correlated with ground truth observations taken from underwater video and were

Sea-floor geology in northwestern Block Island Sound, Rhode Island

Science.gov (United States)

McMullen, Katherine Y.; Poppe, Lawrence J.; Ackerman, Seth D.; Blackwood, Dann S.; Woods, D.A.

2014-01-01

Multibeam-echosounder and sidescan-sonar data, collected by the National Oceanic and Atmospheric Administration in a 69-square-kilometer area of northwestern Block Island Sound, are used with sediment samples, and still and video photography of the sea floor, collected by the U.S. Geological Survey at 43 stations within this area, to interpret the sea-floor features and sedimentary environments. Features on the sea floor include boulders, sand waves, scour depressions, modern marine sediments, and trawl marks. Boulders, which are often several meters wide, are found in patches in the shallower depths and tend to be overgrown with sessile flora and fauna. They are lag deposits of winnowed glacial drift, and reflect high-energy environments characterized by processes associated with erosion and nondeposition. Sand waves and megaripples tend to have crests that either trend parallel to shore with 20- to 50-meter (m) wavelengths or trend perpendicular to shore with several-hundred-meter wavelengths. The sand waves reflect sediment transport directions perpendicular to shore by waves, and parallel to shore by tidal or wind-driven currents, respectively. Scour depressions, which are about 0.5 m lower than the surrounding sea floor, have floors of gravel and coarser sand than bounding modern marine sediments. These scour depressions, which are conspicuous in the sidescan-sonar data because of their more highly reflective coarser sediment floors, are likely formed by storm-generated, seaward-flowing currents and maintained by the turbulence in bottom currents caused by their coarse sediments. Areas of the sea floor with modern marine sediments tend to be relatively flat to current-rippled and sandy.

First high-resolution near-seafloor survey of magnetic anomalies of the South China Sea

Science.gov (United States)

Lin, J.; Xu, X.; Li, C.; Sun, Z.; Zhu, J.; Zhou, Z.; Qiu, N.

2013-12-01

We successfully conducted the first high-resolution near-seafloor magnetic survey of the Central, Southwest, and Northern Central Basins of the South China Sea (SCS) during two cruises on board Chinese R/V HaiYangLiuHao in October-November 2012 and March-April 2013, respectively. Measurements of magnetic field were made along four long survey lines, including (1) a NW-SE across-isochron profile transecting the Southwest Basin and covering all ages of the oceanic crust (Line CD); (2) a N-S across-isochron profile transecting the Central Basin (Line AB); and (3) two sub-parallel NE-SW across-isochron profiles transecting the Northern Central Basin of the SCS (Lines D and E). A three-axis magnetometer was mounted on a deep-tow vehicle, flying within 0.6 km above the seafloor. The position of the tow vehicle was provided by an ultra-short baseline navigation system along Lines D and E, while was estimated using shipboard GPS along Lines AB and CD. To investigate crustal magnetization, we first removed the International Geomagnetic Reference Field (IGRF) of 2010 from the measured magnetic data, and then downward continued the resultant magnetic field data to a horizontal plane at a water depth of 4.5 km to correct for variation due to the fishing depth of the deep-tow vehicle. Finally, we calculated magnetic anomalies at various water depths after reduction-to-the-pole corrections. We also constructed polarity reversal block (PRB) models of crustal magnetization by matching peaks and troughs of the observed magnetic field anomaly. Our analysis yielded the following results: (1) The near-bottom magnetic anomaly showed peak-to-trough amplitudes of more than 2,500 nT, which are several times of the anomaly amplitudes at the sea surface, illustrating that deep-tow measurements acquired much higher spatial resolutions. (2) The deep-tow data revealed several distinctive magnetic anomalies with wavelengths of 5-15 km and amplitudes of several hundred nT. These short

Seafloor Geodesy usi­ng Wave Gliders to study Earthquake and Tsunami Hazards at Subduction Zones

Science.gov (United States)

Sathiakumar, S.; Barbot, S.; Hill, E.; Peng, D.; Zerucha, J.; Suhaimee, S.; Chia, G.; Salamena, G. G.; Syahailatua, A.

2016-12-01

Land-based GNSS networks are now in place to monitor most subduction zones of the world. These provide valuable information about the amount of­ geodetic strain accumulated in the region, which in turn gives insight into the seismic potential. However, it is usually impossible to resolve activity on the megathrust near the trench using land-based GNSS data alone, given typical signal-to-noise ratios. Ship-based seafloor geodesy is being used today to fill this observation gap. However, surveys using ships are very expensive, tedious and impractical due to the large areas to be covered. Instead of discrete missions using ships, continuous monitoring of the seafloor using autonomous marine robots would aid in understanding the tectonic setting of the seafloor better at a potentially lower cost, as well as help in designing better warning systems. Thus, we are developing seafloor geodesy capabilities using Wave Gliders, a new class of wave-propelled, persistent marine autonomous vehicle using a combination of acoustic and GNSS technologies. We use GNSS/INS to position the platform, and acoustic ranging to locate the seafloor. The GNSS/INS system to be integrated with the Wave Gliders has stringent requirements of low power, light weight, and high accuracy. All these factors are equally important due to limited power and space in the Wave Gliders and the need for highly accurate and precise measurements. With this hardware setup, a limiting factor is the accuracy of measurement of the sound velocity in the water column. We plan to obtain precise positioning of seafloor by exploring a measurement setup that minimizes uncertainties in sound velocity. This will be achieved by making fine-resolution measurements of the two-way travel time of the acoustic waves underwater using the Wave Gliders, and performing statistical signal processing on this data to obtain more reliable sound velocity measurement. This enhanced seafloor geodetic technique using Wave Gliders should

Multi-angle backscatter classification and sub-bottom profiling for improved seafloor characterization

Science.gov (United States)

Alevizos, Evangelos; Snellen, Mirjam; Simons, Dick; Siemes, Kerstin; Greinert, Jens

2018-06-01

This study applies three classification methods exploiting the angular dependence of acoustic seafloor backscatter along with high resolution sub-bottom profiling for seafloor sediment characterization in the Eckernförde Bay, Baltic Sea Germany. This area is well suited for acoustic backscatter studies due to its shallowness, its smooth bathymetry and the presence of a wide range of sediment types. Backscatter data were acquired using a Seabeam1180 (180 kHz) multibeam echosounder and sub-bottom profiler data were recorded using a SES-2000 parametric sonar transmitting 6 and 12 kHz. The high density of seafloor soundings allowed extracting backscatter layers for five beam angles over a large part of the surveyed area. A Bayesian probability method was employed for sediment classification based on the backscatter variability at a single incidence angle, whereas Maximum Likelihood Classification (MLC) and Principal Components Analysis (PCA) were applied to the multi-angle layers. The Bayesian approach was used for identifying the optimum number of acoustic classes because cluster validation is carried out prior to class assignment and class outputs are ordinal categorical values. The method is based on the principle that backscatter values from a single incidence angle express a normal distribution for a particular sediment type. The resulting Bayesian classes were well correlated to median grain sizes and the percentage of coarse material. The MLC method uses angular response information from five layers of training areas extracted from the Bayesian classification map. The subsequent PCA analysis is based on the transformation of these five layers into two principal components that comprise most of the data variability. These principal components were clustered in five classes after running an external cluster validation test. In general both methods MLC and PCA, separated the various sediment types effectively, showing good agreement (kappa >0.7) with the Bayesian

Semi-Automated Classification of Seafloor Data Collected on the Delmarva Inner Shelf

Science.gov (United States)

Sweeney, E. M.; Pendleton, E. A.; Brothers, L. L.; Mahmud, A.; Thieler, E. R.

2017-12-01

We tested automated classification methods on acoustic bathymetry and backscatter data collected by the U.S. Geological Survey (USGS) and National Oceanic and Atmospheric Administration (NOAA) on the Delmarva inner continental shelf to efficiently and objectively identify sediment texture and geomorphology. Automated classification techniques are generally less subjective and take significantly less time than manual classification methods. We used a semi-automated process combining unsupervised and supervised classification techniques to characterize seafloor based on bathymetric slope and relative backscatter intensity. Statistical comparison of our automated classification results with those of a manual classification conducted on a subset of the acoustic imagery indicates that our automated method was highly accurate (95% total accuracy and 93% Kappa). Our methods resolve sediment ridges, zones of flat seafloor and areas of high and low backscatter. We compared our classification scheme with mean grain size statistics of samples collected in the study area and found that strong correlations between backscatter intensity and sediment texture exist. High backscatter zones are associated with the presence of gravel and shells mixed with sand, and low backscatter areas are primarily clean sand or sand mixed with mud. Slope classes further elucidate textural and geomorphologic differences in the seafloor, such that steep slopes (>0.35°) with high backscatter are most often associated with the updrift side of sand ridges and bedforms, whereas low slope with high backscatter correspond to coarse lag or shell deposits. Low backscatter and high slopes are most often found on the downdrift side of ridges and bedforms, and low backscatter and low slopes identify swale areas and sand sheets. We found that poor acoustic data quality was the most significant cause of inaccurate classification results, which required additional user input to mitigate. Our method worked well

Developments of next generation of seafloor observatories in MARsite project

Science.gov (United States)

Italiano, Francesco; Favali, Paolo; Zaffuto, Alfonso; Zora, Marco; D'Anca, Fabio

2015-04-01

The development of new generation of autonomous sea-floor observatories is among the aims of the EC supersite project MARsite (MARMARA Supersite; FP7 EC-funded project, grant n° 308417). An approach based on multiparameter seafloor observatories is considered of basic importance to better understand the role of the fluids in an active tectonic system and their behaviour during the development of the seismogenesis. To continuously collect geochemical and geophysical data from the immediate vicinity of the submerged North Anatolian Fault Zone (NAFZ) is one of the possibilities to contribute to the seismic hazard minimization of the Marmara area. The planning of next generation of seafloor observatories for geo-hazard monitoring is a task in one of the MARsite Work Packages (WP8). The activity is carried out combining together either the experience got after years of investigating fluids and their interactions with the seafloor and tectonic structures and the long-term experience on the development and management of permanent seafloor observatories in the main frame of the EMSO (European Multidisciplinary Seafloor and water-column Observatory, www.emso-eu.org) Research Infrastructure. The new generation of seafloor observatories have to support the observation of both slow and quick variations, thus allow collecting low and high-frequency signals besides the storage of long-term dataset and/or enable the near-real-time mode data transmission. Improvements of some the seafloor equipments have been done so far within MARsite project in terms of the amount of contemporary active instruments, their interlink with "smart sensor" capacities (threshold detection, triggering), quality of the collected data and power consumption reduction. In order to power the multiparameter sensors the digitizer and the microprocessor, an electronic board named PMS (Power Management System) with multi-master, multi-slave, single-ended, serial bus Inter-Integrated Circuit (I²C) interface

3D Marine MT Modeling for a Topographic Seafloor

Science.gov (United States)

Zhang, B., Sr.; Yin, C.; Ren, X.; Liu, Y.; Huang, X.; Liu, L.

2017-12-01

As an effective geophysical tool, marine magnetotelluric (MMT) exploration has been widely used in offshore oil and gas exploration. Accordingly, the MMT forward modelling has made big progress. However, most of the researches are focused on a flat seafloor. In this paper, we present a 3D finite-element (FE) algorithm for marine MT forward modelling based on unstructured grids that can accurately model the MMT responses for a topographic seafloor. The boundary value problem for the forward modelling is described by an Helmholtz equation together with the boundary conditions derived by assuming the electrical polarizations respectively along the x- and y-direction on the top surface of the modelling domain. Applying the Galerkin method to the boundary value problem and substituting the unstructured finite-element vector shape function into the equation, we derive the final large linear system for the two polarizations, from which the EM fields is obtained for the calculation of impedance apparent resistivities and phases. To verify the effectiveness of our algorithm, we compare our modelling results with those by Key's (2013) 2D marine MT open source code of Scripps Institution of Oceanography (Figure 1). From Figure 1, one sees that the two agree well, implying that our 3D modelling method based unstructured FE is an effective modelling tool for topographic seafloor. From the MMT modelling responses for other topographic seafloor models (not shown here), we further observe that 1) the apparent resistivities have a similar profile pattern to the topography at the seafloor; 2) at the edges of the topography, there exist sharp changes; 3) the seafloor topography may dominate the responses from the abnormal bodies under the seafloor. This paper is supported by Key Program of National Natural Science Foundation of China (41530320), China Natural Science Foundation for Young Scientists (41404093), and Key National Research Project of China (2016YFC0303100, 2017YFC0601900)

Seafloor Litter in the Sinop İnceburun Coast in the Southern Black Sea

Directory of Open Access Journals (Sweden)

Ayşah Öztekin

2017-11-01

Full Text Available In this study, abundance, distribution and type of seafloor litter were determined in the Sinop Inceburun coast which is the northeast point of Turkey. Study was carried out in October 2014 and proposed methods by Guidance on Monitoring of Marine Litter in European Seas’ published by European Marine Strategy Framework Directive Technical Subgroup on Marine Litter section of seafloor litter adopted the region. Seafloor litter density was found mean 808.74±215.02 pieces per km-2. The amount of litter was found maximum in 34 m depth. When results were evaluated in terms of the type of material plastic was found 95.35% and encountered litter items were mainly composed of plastic bags. The size groups were found generally small than 50 cm x 50 cm in the classification according to the size groups. The data obtained from the study demonstrate that the seafloor in the region have highly littered compared to the other studies in the Black Sea. Marine litter pollution is a growing problem in the world all of the world’s oceans and also the Black Sea. Necessary measurements must be taken to solve this problem.

Non-traditional Stable Isotope Systematics of Seafloor Hydrothermal Systems

Science.gov (United States)

Rouxel, O. J.

2009-05-01

Seafloor hydrothermal activity at mid-ocean ridges is one of the fundamental processes controlling the chemistry of the oceans and the altered oceanic crust. Past studies have demonstrated the complexity and diversity of seafloor hydrothermal systems and have highlighted the importance of subsurface environments in controlling the composition of hydrothermal fluids and mineralization types. Traditionally, the behavior of metals in seafloor hydrothermal systems have been investigated by integrating results from laboratory studies, theoretical models, mineralogy and fluid and mineral chemistry. Isotope ratios of various metals and metalloids, such as Fe, Cu, Zn, Se, Cd and Sb have recently provided new approaches for the study of seafloor hydrothermal systems. Despite these initial investigations, the cause of the isotopic variability of these elements remains poorly constrained. We have little understanding of the isotope variations between vent types (black or white smokers) as well as the influence of source rock composition (basalt, felsic or ultrabasic rocks) and alteration types. Here, I will review and present new results of metal isotope systematics of seafloor hydrothermal systems, in particular: (1) determination of empirical isotope fractionation factors for Zn, Fe and Cu-isotopes through isotopic analysis of mono-mineralic sulfide grains lining the internal chimney wall in contact with hydrothermal fluid; (2) comparison of Fe- and Cu-isotope signatures of vent fluids from mid- oceanic and back-arc hydrothermal fields, spanning wide ranges of pH, temperature, metal concentrations and contributions of magmatic fluids enriched in SO2. Ultimately, the use of complementary non-traditional stable isotope systems may help identify and constrain the complex interactions between fluids,minerals, and organisms in seafloor hydrothermal systems.

Seafloor Mapping: We've Come a Long Way - But Still Have Far to Go……

Science.gov (United States)

Mayer, L. A.

2017-12-01

Our ability to map the seafloor has changed radically over the past century. For thousands of years a weight at the end of a rope (or wire) - a lead line - provided the only means to measure depth. By the end of the Second World War, single beam echo sounders had been perfected to the extent that they became common on oceanographic and other vessels providing more rapid but laterally averaged (typically over a distance commensurate with the water depth) measurements of seafloor depths. Towards the end of the 20th Century - two great advances were made in seafloor mapping - the development of techniques to use satellite altimetry to predict seafloor bathymetry and the evolution of multibeam sonar technology from classified military applications to the academic and commercial communities. Satellite-altimetry derived bathymetry provides an unprecedented view of seafloor topography and tremendous insight into tectonic-scale processes but is limited in achievable resolution. Multibeam sonars offer the potential of extremely high-resolution (a function of array size, beam footprint, and water depth), but are typically deployed from manned surface vessels that cover limited amount of seafloor at a relatively high daily cost. We have the technology to map the entire world ocean with multibeam sonar but It has been estimated that to map the world ocean deeper than about 150m (shallow water is very time-consuming and expensive because the coverage swath width is typically 3-5 times water) would take approximately 200 ship years and cost on the order of 3 billion dollars. We have demonstrated our willingness to spend billions to map other planets (e.g. Mars and the Moon) but for some reason, not our own. Recently, however, there has been growing momentum to see the entire world ocean mapped. The Nippon Foundation and GEBCO have recently announced the Seabed 2030 project with a goal of facilitating the mapping of the world ocean by 2030 and international agreements like The

Seafloor observatories a new vision of the Earth from the abyss

CERN Document Server

Favali, Paolo; De Santis, Angelo

2015-01-01

This book addresses the important and apparently simple question: ""How can continuous and reliable monitoring at the seafloor by means of seafloor observatories extend exploration and improve knowledge of our planet?""

The NGDC Seafloor Sediment Geotechnical Database

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NGDC Seafloor Sediment Geotechnical Properties Database contains test engineering properties data coded by students at NGDC from primarily U.S. Naval...

Tectonics and Volcanism During the Cretaceous Normal Superchron Seafloor in the Western Pacific Ocean

Science.gov (United States)

O'Brien, E.

2017-12-01

We have conducted an integration study on the origin and evolution of the tectonics and volcanism of seafloor in the Western Pacific Ocean that took place during the Cretaceous Normal Superchron (CNS) where sparse data has so far precluded detailed investigation. We have compiled the latest satellite-based gravity, gravity gradient, and magnetic grids (EMAG2 v.3) for this region. These crustal-scale high-resolution grids suggest that the CNS seafloor contains fossilized lithospheric morphology possibly attributed to the interaction between Cretaceous supervolcanism activity and Mid-Cretaceous Pacific mid ocean ridge systems that have continuously expanded the Pacific Plate. We recognize previously identified fossilized microplates west of the Magellan Rise, short-lived abandoned propagating rifts and fracture zones, all of which show significant rotation of seafloor fabric. In addition to these large scale observations, we have also compiled marine geological information from previously drilled cores and new data from a Kongsberg Topas PS18 Parametric Sub-Bottom Profiler collected on a transect from Honolulu, Hawaii to Apra, Guam acquired during research cruise SKQ2014S2. In particular, the narrow beam and high bandwidth signal of the Topas PS18 sub-bottom profiler provides sonar data of the seabed with a resolution and depth penetration that is unprecedented compared with previously available surveys in the region. A preliminary assessment of this high resolution Topas data allows us to better characterize sub-seafloor sediment properties and identify features, including the Upper Transparent Layer with identifiable pelagic clay and porcelanite-chert reflectors as well as tectonic features such as the westernmost tip of the Waghenaer Fracture Zone.

EX1608 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1104 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1604 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1101 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1102 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1303 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1106 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX0905 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1301 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1704 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1204 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1403 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1505 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1006 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1703 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1603 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX0903 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX0904 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1201 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1105 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1302 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1206 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1705 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1701 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1702 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

Assessment of impact on seafloor features in INDEX area

Digital Repository Service at National Institute of Oceanography (India)

Sharma, R.

Benthic disturbance,environmental impact,photographic and subbottomdata,seafloor features. Imaging and sounding techniques are effective tools for obtaining first-hand information forassessing the baseline (undisturbed) conditions as well as the impact (disturbed...) conditions onthe seabed,to evaluate the extent and type of efects on the physical environment on the seafloor. This information is also useful for planning the locations and areas for sampling instudies to ases the impact on different parameters.Information...

Assessment of impact on seafloor features in INDEX area

Digital Repository Service at National Institute of Oceanography (India)

Sharma, R.

Marine Georesources and Geotechnology,18:237–250,2000Copyright ©2000 Taylor & Francis1064-119X / 00 $12.00 1 .00 Assessment of Impact on Seafloor Features in INDEX Area RAHUL SHARMANational Institute of Oceanography,Dona Paula,Goa 403004,India...Benthic disturbance,environmental impact,photographic and subbottomdata,seafloor features. Imaging and sounding techniques are effective tools for obtaining first-hand information forassessing the baseline (undisturbed) conditions as well as the impact (disturbed...

Global patterns and predictions of seafloor biomass using random forests.

Directory of Open Access Journals (Sweden)

Chih-Lin Wei

Full Text Available A comprehensive seafloor biomass and abundance database has been constructed from 24 oceanographic institutions worldwide within the Census of Marine Life (CoML field projects. The machine-learning algorithm, Random Forests, was employed to model and predict seafloor standing stocks from surface primary production, water-column integrated and export particulate organic matter (POM, seafloor relief, and bottom water properties. The predictive models explain 63% to 88% of stock variance among the major size groups. Individual and composite maps of predicted global seafloor biomass and abundance are generated for bacteria, meiofauna, macrofauna, and megafauna (invertebrates and fishes. Patterns of benthic standing stocks were positive functions of surface primary production and delivery of the particulate organic carbon (POC flux to the seafloor. At a regional scale, the census maps illustrate that integrated biomass is highest at the poles, on continental margins associated with coastal upwelling and with broad zones associated with equatorial divergence. Lowest values are consistently encountered on the central abyssal plains of major ocean basins The shift of biomass dominance groups with depth is shown to be affected by the decrease in average body size rather than abundance, presumably due to decrease in quantity and quality of food supply. This biomass census and associated maps are vital components of mechanistic deep-sea food web models and global carbon cycling, and as such provide fundamental information that can be incorporated into evidence-based management.

Sea-floor morphology and sedimentary environments in southern Narragansett Bay, Rhode Island

Science.gov (United States)

McMullen, Katherine Y.; Poppe, Lawrence J.; Blackwood, Dann S.; Nardi, Matthew J.; Andring, Matthew A.

2015-09-09

Multibeam echosounder data collected by the National Oceanic and Atmospheric Administration along with sediment samples and still and video photography of the sea floor collected by the U.S. Geological Survey were used to interpret sea-floor features and sedimentary environments in southern Narragansett Bay, Rhode Island, as part of a long-term effort to map the sea floor along the northeastern coast of the United States. Sea-floor features include rocky areas and scour depressions in high-energy environments characterized by erosion or nondeposition, and sand waves and megaripples in environments characterized by coarse-grained bedload transport. Two shipwrecks are also located in the study area. Much of the sea floor is relatively featureless within the resolution of the multibeam data; sedimentary environments in these areas are characterized by processes associated with sorting and reworking. This report releases bathymetric data from the multibeam echosounder, grain-size analyses of sediment samples, and photographs of the sea floor and interpretations of the sea-floor features and sedimentary environments. It provides base maps that can be used for resource management and studies of topics such as benthic ecology, contaminant inventories, and sediment transport.

A framework to quantify uncertainties of seafloor backscatter from swath mapping echosounders

Science.gov (United States)

Malik, Mashkoor; Lurton, Xavier; Mayer, Larry

2018-06-01

Multibeam echosounders (MBES) have become a widely used acoustic remote sensing tool to map and study the seafloor, providing co-located bathymetry and seafloor backscatter. Although the uncertainty associated with MBES-derived bathymetric data has been studied extensively, the question of backscatter uncertainty has been addressed only minimally and hinders the quantitative use of MBES seafloor backscatter. This paper explores approaches to identifying uncertainty sources associated with MBES-derived backscatter measurements. The major sources of uncertainty are catalogued and the magnitudes of their relative contributions to the backscatter uncertainty budget are evaluated. These major uncertainty sources include seafloor insonified area (1-3 dB), absorption coefficient (up to > 6 dB), random fluctuations in echo level (5.5 dB for a Rayleigh distribution), and sonar calibration (device dependent). The magnitudes of these uncertainty sources vary based on how these effects are compensated for during data acquisition and processing. Various cases (no compensation, partial compensation and full compensation) for seafloor insonified area, transmission losses and random fluctuations were modeled to estimate their uncertainties in different scenarios. Uncertainty related to the seafloor insonified area can be reduced significantly by accounting for seafloor slope during backscatter processing while transmission losses can be constrained by collecting full water column absorption coefficient profiles (temperature and salinity profiles). To reduce random fluctuations to below 1 dB, at least 20 samples are recommended to be used while computing mean values. The estimation of uncertainty in backscatter measurements is constrained by the fact that not all instrumental components are characterized and documented sufficiently for commercially available MBES. Further involvement from manufacturers in providing this essential information is critically required.

Geologic Seafloor Mapping Defines Extensive Paleochannel Network Offshore of the Delmarva Peninsula, U.S.A: Implications for Mid-Atlantic Bight Evolution since the Pliocene

Science.gov (United States)

Brothers, L. L.; Foster, D. S.; Pendleton, E. A.; Thieler, E. R.; Baldwin, W. E.; Sweeney, E. M.

2017-12-01

Nearly 10,000 km of geophysical data and seafloor grab samples along with photo and video data from more than 200 seafloor stations are used to interpret seafloor and shallow subsurface geology on the Delmarva Peninsula's inner continental shelf. These USGS data are supplemented with existing National Oceanic Atmospheric Administration hydrographic survey data and Bureau of Ocean Energy Management Wind Energy Area seismic reflection profile data to support one of the most data-rich and extensive inner continental shelf studies on the U.S. Atlantic coast. Using chirp, multi-channel boomer and sparker seismic reflection profile data, we map an extensive paleochannel network from 500 meters to 30 kilometers offshore of the modern Delmarva coastline. Fluvial erosional surfaces relating to six sea-level lowstands are identified at two-way travel times between 0.01 and 0.12 ms. Paleochannels exhibit up to 30 meters of relief and the discrete complexes can be >25 kilometers wide. Based on areal distribution, stratigraphic relationships and amino acid dating results from earlier borehole studies, we interpret the infilled channels as Late Tertiary and Quaternary courses of the Delaware, Susquehanna, Potomac and York Rivers. Our study generates a detailed illustration of major river systems' paleochannel frequency, distribution and geometry and provides new insight into how coastal river systems evolve in low-gradient passive margins.

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.

Rifting-to-drifting transition of the South China Sea: Moho reflection characteristics in continental-ocean transition zone

Science.gov (United States)

Wen, Y.; Li, C.

2017-12-01

Dispute remains on the process of continental rifting to subsequent seafloor spreading in the South China Sea (SCS). Several crust-scale multi-channel seismic reflection profiles acquired in the continent-ocean transition zone (COT) of the SCS provide a detailed overview of Moho and deep crustal reflectors and give key information on rifting-to-drifting transition of the area. Moho has strong but discontinuous seismic reflection in COT. These discontinuities are mainly located in the landward side of continent-ocean boundary (COB), and may own to upwelling of lower crustal materials during initial continental extension, leading to numerous volcanic edifices and volcanic ridges. The continental crust in COT shows discontinuous Moho reflections at 11-8.5 s in two-way travel time (twtt), and thins from 18-20.5 km under the uppermost slope to 6-7 km under the lower slope, assuming an average crustal velocity of 6.0 km/s. The oceanic crust has Moho reflections of moderate to high continuity mostly at 1.8-2.2 s twtt below the top of the igneous basement, which means that the crustal thickness excluding sediment layer in COT is 5.4-6.6 km. Subhorizontal Moho reflections are often abruptly interrupted by large seaward dipping normal faults in southern COT but are more continuous compared with the fluctuant and very discontinuous Moho reflections in northern COT. The thickness of thinned continental crust (4.2-4.8 km) is smaller than that of oceanic crust (5.4-6.0 km) near southern COB, indicating that the continental crust has experienced a long period of rifting before seafloor spreading started. The smaller width of northern COT (0-40 km) than in southern COT (0-60 km), and thinner continental crust in southern COT, all indicate that the continental margin rifting and extension was asymmetric. The COT width in the SCS is narrower than that found in other magma-poor continental margins, indicating a swift transition from the final stage of rifting to the inception of

Characterizing Indian Ocean manganese nodule-bearing seafloor using multi-beam angular backscatter

Digital Repository Service at National Institute of Oceanography (India)

Chakraborty, B.; Kodagali, V.N.

backscattering in delineating seafloor parameters characteristic of nodule-rich sediments. In this paper, processed Hydrosweep multi-beam backscatter data from 45 spot locations in the CIOB (where nodule samples are available) were analysed to estimate seafloor...

Tractive performance evaluation of seafloor tracked trencher based on laboratory mechanical measurements

Directory of Open Access Journals (Sweden)

Meng Wang

2016-03-01

Full Text Available To evaluate the tractive performance of tracked trencher on seafloor surface, a new shear stress-displacement empirical model was proposed for saturated soft-plastic soil (SSP model. To validate the SSP model, a test platform, where track segment shear test can be performed in seafloor soil simulacrum (bentonite water mixture, was built. Series shear tests were carried out. Test results indicate that the SSP model can describe the mechanical behavior of track segment with good approximation in seafloor soil simulacrum. Through analyzing the main external forces applied to seafloor tracked trencher during the uniform linear trenching process, a drawbar pull prediction model was deduced with the SSP model. A tracked walking mechanism of the seafloor tracked trencher prototype was built, and verification tests were carried out. Test results indicate that this prediction model was feasible and effective; moreover, from another side, this conclusion also proved that the SSP model was effective.

Seafloor backscatter signal simulation and classification

Digital Repository Service at National Institute of Oceanography (India)

Mahale, V.; El Dine, W.G.; Chakraborty, B.

. In this model a smooth echo envelope is generated then mixed up with multiplicative and additive noise. Several such echo signals were simulated for three types of seafloor. An Artificial Neural Network based classification technique is conceived to classify...

LiDAR Relative Reflectivity Surface (2011) for Coral Bay, St. John

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a LiDAR (Light Detection & Ranging) 0.3x0.3 meter resolution relative seafloor reflectivity surface for Coral Bay, St. John in the U.S....

LiDAR Relative Reflectivity Surface (2011) for Fish Bay, St. John

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a LiDAR (Light Detection & Ranging) 0.3x0.3 meter resolution relative seafloor reflectivity surface for Fish Bay, St. John in the U.S....

Giant seafloor craters formed by hydrate-controlled large-scale methane expulsion from the Arctic seafloor after ice sheet retreat

Science.gov (United States)

Andreassen, K.; Hubbard, A.; Patton, H.; Vadakkepuliyambatta, S.; Winsborrow, M.; Plaza-Faverola, A. A.; Serov, P.

2017-12-01

Large-scale methane releases from thawing Arctic gas hydrates is a major concern, yet the processes and fluxes involved remain elusive. We present geophysical data indicating two contrasting processes of natural methane emissions from the seafloor of the northern Barents Sea, Polar North Atlantic. Abundant gas flares, acoustically imaged in the water column reveal slow, gradual release of methane bubbles, a process that is commonly documented from nearby areas, elsewhere in the Arctic and along continental margins worldwide. Conversely, giant craters across the study area indicate a very different process. We propose that these are blow-out craters, formed through large-scale, abrupt methane expulsion induced when gas hydrates destabilized after the Barents Sea Ice Sheet retreated from the area. The data reveal over 100 giant seafloor craters within an area of 440 km2. These are up to 1000 m in diameter, 30 m deep and with a semi-circular to elliptical shape. We also identified numerous large seafloor mounds, which we infer to have formed by the expansion of gas hydrate accumulations within the shallow subsurface, so-called gas hydrate pingos. These are up to 1100 m wide and 20 m high. Smaller craters and mounds < 200 m wide and with varying relief are abundant across the study site. The empirical observations and analyses are combined with numerical modelling of ice sheet, isostatic and gas hydrate evolution and indicate that during glaciation, natural gas migrating from underlying hydrocarbon reservoirs was stored as subglacial gas hydrates. On ice sheet retreat, methane from these hydrate reservoirs and underlying free gas built up and abruptly released, forming the giant mounds and craters observed in the study area today. Petroleum basins are abundant beneath formerly and presently glaciated regions. We infer that episodes of subglacial sequestration of gas hydrates and underlying free gas and subsequent abrupt expulsions were common and widespread throughout

Effect of changes in seafloor temperature and sea-level on gas hydrate stability

Energy Technology Data Exchange (ETDEWEB)

Garg, S.K.; Pritchett, W. [Science Applications International Corp., San Diego, CA (United States)

2008-07-01

Natural gas hydrates occur in oceanic sediments and in permafrost regions around the world. As a greenhouse gas, large amounts of methane released from the global hydrate reservoir would have a significant impact on Earth's climate. The role of methane released by hydrate dissociation in climate change is uncertain. However, changes in global climate such as glaciation and warming can destabilize the hydrates. During the last glacial maximum, the sea level dropped about 100 meters. It has been suggested that the sea-level fall was associated with gas hydrate instability and seafloor slumping. This paper investigated the effect of changes in seafloor temperature and sea level on gas hydrate stability and on gas venting at the seafloor. A one-dimensional numerical computer model (simulator) was developed to describe methane hydrate formation, decomposition, reformation, and distribution with depth below the seafloor in the marine environment. The simulator was utilized to model hydrate distributions at two sites, notably Blake Ridge, located offshore South Carolina and Hydrate Ridge, located off the coast of Oregon. The numerical models for the two sites were conditioned by matching the sulfate, chlorinity, and hydrate distribution measurements. The effect of changes in seafloor temperature and sea-level on gas hydrate stability were then investigated. It was concluded that for Blake Ridge, changes in hydrate concentration were small. Both the changes in seafloor temperature and sea-level led to a substantial increase in gas venting at the seafloor for Hydrate Ridge. 17 refs., 8 figs.

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...

Seafloor 2030 - Building a Global Ocean Map through International Collaboration

Science.gov (United States)

Ferrini, V. L.; Wigley, R. A.; Falconer, R. K. H.; Jakobsson, M.; Allen, G.; Mayer, L. A.; Schmitt, T.; Rovere, M.; Weatherall, P.; Marks, K. M.

2016-12-01

With more than 85% of the ocean floor unmapped, a huge proportion of our planet remains unexplored. Creating a comprehensive map of seafloor bathymetry remains a true global challenge that can only be accomplished through collaboration and partnership between governments, industry, academia, research organizations and non-government organizations. The objective of Seafloor 2030 is to comprehensively map the global ocean floor to resolutions that enable exploration and improved understanding of ocean processes, while informing maritime policy and supporting the management of natural marine resources for a sustainable Blue Economy. Seafloor 2030 is the outcome of the Forum for Future of Ocean Floor Mapping held in Monaco in June 2016, which was held under the auspices of GEBCO and the Nippon Foundation of Japan. GEBCO is the only international organization mandated to map the global ocean floor and is guided by the International Hydrographic Organization (IHO) and the Intergovernmental Oceanographic Commission of UNESCO. The task of completely mapping the ocean floor will require new global coordination to ensure that both existing data are identified and that new mapping efforts are coordinated to help efficiently "map the gaps." Fundamental to achieving Seafloor 2030 will be greater access to data, tools and technology, particularly for developing and coastal nations. This includes bathymetric post-processing and analysis software, database technology, computing infrastructure and gridding techniques as well as the latest developments in seafloor mapping methods and emerging crowd-sourced bathymetry initiatives. The key to achieving this global bathymetric map is capacity building and education - including greater coordination between scientific research and industry and the effective engagement of international organizations such as the United Nations.

Sea-Floor geology and character of Eastern Rhode Island Sound West of Gay Head, Massachusetts

Science.gov (United States)

Poppe, L.J.; McMullen, K.Y.; Ackerman, S.D.; Blackwood, D.S.; Irwin, B.J.; Schaer, J.D.; Forrest, M.R.

2011-01-01

Gridded multibeam bathymetry covers approximately 102 square kilometers of sea floor in eastern Rhode Island Sound west of Gay Head, Massachusetts. Although originally collected for charting purposes during National Oceanic and Atmospheric Administration hydrographic survey H11922, these acoustic data and the sea-floor stations subsequently occupied to verify them (1) show the composition and terrain of the seabed, (2) provide information on sediment transport and benthic habitat, and (3) are part of an expanding series of studies that provide a fundamental framework for research and management activities (for example, windfarms and fisheries) along the Massachusetts inner continental shelf. Most of the sea floor in the study area has an undulating to faintly rippled appearance and is composed of bioturbated muddy sand, reflecting processes associated with sediment sorting and reworking. Shallower areas are composed of rippled sand and, where small fields of megaripples are present, indicate sedimentary environments characterized by processes associated with coarse bedload transport. Boulders and gravel were found on the floors of scour depressions and on top of an isolated bathymetric high where erosion has removed the Holocene marine sediments and exposed the underlying relict lag deposits of Pleistocene drift. The numerous scour depressions, which formed during storm-driven events, result in the juxtaposition of sea-floor areas with contrasting sedimentary environments and distinct gravel, sand, and muddy sand textures. This textural heterogeneity in turn creates a complex patchwork of habitats. Our observations of local variations in community structure suggest that this small-scale textural heterogeneity adds dramatically to the sound-wide benthic biological diversity.

Deck41 Surficial Seafloor Sediment Description Database

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Deck41 is a digital summary of surficial sediment composition for 36,401 seafloor samples worldwide. Data include collecting source, ship, cruise, sample id,...

Deformation offshore Northern Chile monitored by a seafloor geodetic network (GeoSEA)

Science.gov (United States)

Hannemann, Katrin; Lange, Dietrich; Kopp, Heidrun; Petersen, Florian; Contreras-Reyes, Eduardo

2017-04-01

The Nazca-South American plate boundary around 21°S has last ruptured in an earthquake in 1877 and was identified as a seismic gap prior to the 2014 Iquique earthquake (Mw=8.1). The southern portion of this segment is still unbroken. The geodetic monitoring of the Chilean subduction zone is crucial to understand the deformation processes in this area. Most geodetic measurements rely on GPS and are therefore limited to onshore campaigns. In December 2015, we installed the GeoSEA (Geodetic Earthquake Observatory on the SEAfloor) array around 21°S of the Nazca-South American plate boundary with RV SONNE to extend the geodetic observations to the offshore areas. The GeoSEA array consists of autonomous acoustic seafloor transponders mounted on 4 m high tripods. These transponders are able to continuously measure the two-way travel time of acoustic signals between station pairs (baselines) and the properties of the sea water (sound speed, temperature and pressure) at each transponder. These measurements are used to retrieve the distances between the transponders and give insights into the deformation of the seafloor. At the Chilean subduction zone, we installed in total 23 transponders in 3 subarrays with interstation distances of up to 2500 m. On the middle continental slope in 2300 m water depth, an array consisting of 8 transponders measures across crustal faults seen in AUV mapping. A second array of 5 stations located on the outer rise monitors extension across normal plate-bending faults. The deepest deployment in 5000 m water depth located on the lower continental slope with 10 stations is designed to measure diffuse strain build-up. The transponders are intended to monitor the seafloor deformation for 3.5 years. In November 2016 during a cruise of RV Langseth, the first 11 months of data were successfully uploaded via an acoustic modem. Furthermore, an additional component of the network, GeoSURF, a self-steering autonomous vehicle (wave glider), was

Similar microbial communities found on two distant seafloor basalts

Directory of Open Access Journals (Sweden)

Esther eSinger

2015-12-01

Full Text Available The oceanic crust forms two thirds of the Earth’s surface and hosts a large phylogenetic and functional diversity of microorganisms. While advances have been made in the sedimentary realm, our understanding of the igneous rock portion as a microbial habitat has remained limited. We present the first comparative metagenomic microbial community analysis from ocean floor basalt environments at the Lō’ihi Seamount, Hawai’i, and the East Pacific Rise (EPR (9˚N. Phylogenetic analysis indicates the presence of a total of 43 bacterial and archaeal mono-phyletic groups, dominated by Alpha- and Gammaproteobacteria, as well as Thaumarchaeota. Functional gene analysis suggests that these Thaumarchaeota play an important role in ammonium oxidation on seafloor basalts. In addition to ammonium oxidation, the seafloor basalt habitat reveals a wide spectrum of other metabolic potentials, including CO2 fixation, denitrification, dissimilatory sulfate reduction, and sulfur oxidation. Basalt communities from Lō’ihi and the EPR show considerable metabolic and phylogenetic overlap down to the genus level despite geographic distance and slightly different seafloor basalt mineralogy.

Pockmark asymmetry and seafloor currents in the Santos Basin offshore Brazil

Science.gov (United States)

Schattner, U.; Lazar, M.; Souza, L. A. P.; ten Brink, Uri S.; Mahiques, M. M.

2016-01-01

Pockmarks form by gas/fluid expulsion into the ocean and are preserved under conditions of negligible sedimentation. Ideally, they are circular at the seafloor and symmetrical in profile. Elliptical pockmarks are more enigmatic. They are associated with seafloor currents while asymmetry is connected to sedimentation patterns. This study examines these associations through morphological analysis of new multibeam data collected across the Santos continental slope offshore Brazil in 2011 (353–865 mbsl). Of 984 pockmarks, 78% are both elliptical and asymmetric. Geometric criteria divide the pockmarks into three depth ranges that correlate with a transition between two currents: the Brazil Current transfers Tropical Water and South Atlantic Central Water southwestwards while the Intermediate Western Boundary Current transfers Antarctic Intermediate Water northeastwards. It is suggested that the velocity of seafloor currents and their persistence dictate pockmark ellipticity, orientation and profile asymmetry. Fast currents (>20 cm/s) are capable of maintaining pockmark flank steepness close to the angle of repose. These morphological expressions present direct evidence for an edge effect of the South Atlantic Subtropical Gyre and, in general, provide a correlation between pockmark geometry and seafloor currents that can be applied at other locations worldwide.

Industry Contributions to Seafloor Mapping: Building Partnerships for Collecting, Sharing, and Compiling Data

Science.gov (United States)

Brumley, K. J.; Mitchell, G. A.; Millar, D.; Saade, E. J.; Gharib, J. J.

2017-12-01

In an effort to map the remaining 85% of the worlds seafloor, The Nippon Foundation and GEBCO have launched Seabed 2030 to provide high-resolution bathymetry for all ocean waters by the year 2030. This ambitious effort will require sharing of bathymetric information to build a global baseline bathymetry database. Multibeam echosounder (MBES) data is a promising source of data for Seabed 2030. These data benefit multiple users which includes not only bathymetric information, but also valuable backscatter data, useful for determining seafloor characteristics), as well as water column data, which can be used to explore other aspects of the marine environment and potentially help constrain some of the ocean's methane flux estimates. Fugro provides global survey services for clients in the oil and gas, telecommunications, infrastructure industries, and state and federal agencies. With a global fleet of survey vessels and autonomous vehicles equipped with state-of-the-art MBES systems, Fugro has performed some of the world's largest offshore surveys over the past several years mapping close to 1,000,000 km2 of seafloor per year with high-resolution MBES data using multi-vessel operational models and new methods for merging datasets from different multibeam sonar systems. Although most of these data are proprietary, Fugro is working with clients in the private-sector to make data available to the Seabed 2030 project at a decimated resolution of 100 m. The company is also contributing the MBES data acquired during transits to survey locations. Fugro has also partnered with Shell Ocean Discovery XPRIZE to support development of new rapid, unmanned, high-resolution ocean mapping technologies that can benefit understanding of the world's oceans. Collaborative approaches such as these are helping to establish a new standard for other industry contributions, and to facilitate a new outlook for data sharing among the public and private sectors. Recognizing the importance of an

Seafloor classification using artificial neural network architecture from central western continental shelf of India

Science.gov (United States)

Mahale, Vasudev; Chakraborty, Bishwajit; Navelkar, Gajanan S.; Prabhu Desai, R. G.

2005-04-01

Seafloor classification studies are carried out at the central western continental shelf of India employing two frequency normal incidence single beam echo-sounder backscatter data. Echo waveform data from different seafloor sediment areas are utilized for present study. Three artificial neural network (ANN) architectures, e.g., Self-Organization Feature Maps (SOFM), Multi-Layer Perceptron (MLP), and Learning Vector Quantization (LVQ) are applied for seafloor classifications. In case of MLP, features are extracted from the received echo signal, on the basis of which, classification is carried out. In the case of the SOFM, a simple moving average echo waveform pre-processing technique is found to yield excellent classification results. Finally, LVQ, which is known as ANN of hybrid architecture is found to be the efficient seafloor classifier especially from the point of view of the real-time application. The simultaneously acquired sediment sample, multi-beam bathymetry and side scan sonar and echo waveform based seafloor classifications results are indicative of the depositional (inner shelf), non-depositional or erosion (outer shelf) environment and combination of both in the transition zone. [Work supported by DIT.

The California Seafloor Mapping Program — Providing science and geospatial data for California's State Waters

Science.gov (United States)

Johnson, S. Y.; Cochrane, G. R.; Golden, N. E.; Dartnell, P.; Hartwell, S. R.; Cochran, S. A.; Watt, J. T.

2017-12-01

The California Seafloor Mapping Program (CSMP) is a collaborative effort to develop comprehensive bathymetric, geologic, and habitat maps and data for California's State Waters, which extend for 1,350 km from the shoreline to 5.6 km offshore. CSMP began in 2007 when the California Ocean Protection Council and NOAA allocated funding for high-resolution bathymetric mapping to support the California Marine Life Protection Act and update nautical charts. Collaboration and support from the USGS and other partners has led to development and dissemination of one of the world's largest seafloor-mapping datasets. CSMP data collection includes: (1) High-resolution bathymetric and backscatter mapping using swath sonar sensors; (2) "Ground-truth" imaging from a sled mounted with video and still cameras; (3) High-resolution seismic-reflection profiling at 1 km line spacing. Processed data are all publicly available. Additionally, 25 USGS map and datasets covering one third of California's coast have been published. Each publication contains 9 to 12 pdf map sheets (1:24,000 scale), an explanatory pamphlet, and a catalog of digital geospatial data layers (about 15 to 25 per map area) with web services. Map sheets display bathymetry, backscatter, perspective views, habitats, groundtruth imagery, seismic profiles, sediment distribution and thickness, and onshore-offshore geology. The CSMP goal is to serve a large constituency, ranging from senior GIS analysts in large agencies, to local governments with limited resources, to non-governmental organizations, the private sector, and concerned citizens. CSMP data and publications provide essential science and data for ocean and coastal management, stimulate and enable research, and raise public education and awareness of coastal and ocean issues. Specific applications include: Delineation and designation of marine protected areas Characterization and modeling of benthic habitats and ecosystems Updating nautical charts Earthquake hazard

Tectonic microplates in a wax model of sea-floor spreading

International Nuclear Information System (INIS)

Katz, Richard F; Ragnarsson, Rolf; Bodenschatz, Eberhard

2005-01-01

Rotating, growing microplates are observed in a wax analogue model of sea-floor spreading. Wax microplates are kinematically similar to sea-floor tectonic microplates in terms of spreading rate and growth rate. Furthermore, their spiral pseudofault geometry is quantitatively consistent with Schouten's oceanic microplate model. These results suggest that Schouten's edge-driven microplate model captures the kinematics of tectonic microplate evolution on Earth. Based on the wax observations, a theory for the nucleation of overlapping spreading centres, the precursors of tectonic microplates, is developed

A Seafloor Benchmark for 3-dimensional Geodesy

Science.gov (United States)

Chadwell, C. D.; Webb, S. C.; Nooner, S. L.

2014-12-01

We have developed an inexpensive, permanent seafloor benchmark to increase the longevity of seafloor geodetic measurements. The benchmark provides a physical tie to the sea floor lasting for decades (perhaps longer) on which geodetic sensors can be repeatedly placed and removed with millimeter resolution. Global coordinates estimated with seafloor geodetic techniques will remain attached to the benchmark allowing for the interchange of sensors as they fail or become obsolete, or for the sensors to be removed and used elsewhere, all the while maintaining a coherent series of positions referenced to the benchmark. The benchmark has been designed to free fall from the sea surface with transponders attached. The transponder can be recalled via an acoustic command sent from the surface to release from the benchmark and freely float to the sea surface for recovery. The duration of the sensor attachment to the benchmark will last from a few days to a few years depending on the specific needs of the experiment. The recovered sensors are then available to be reused at other locations, or again at the same site in the future. Three pins on the sensor frame mate precisely and unambiguously with three grooves on the benchmark. To reoccupy a benchmark a Remotely Operated Vehicle (ROV) uses its manipulator arm to place the sensor pins into the benchmark grooves. In June 2014 we deployed four benchmarks offshore central Oregon. We used the ROV Jason to successfully demonstrate the removal and replacement of packages onto the benchmark. We will show the benchmark design and its operational capabilities. Presently models of megathrust slip within the Cascadia Subduction Zone (CSZ) are mostly constrained by the sub-aerial GPS vectors from the Plate Boundary Observatory, a part of Earthscope. More long-lived seafloor geodetic measures are needed to better understand the earthquake and tsunami risk associated with a large rupture of the thrust fault within the Cascadia subduction zone

EX1503L2 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1205L2 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1202L1 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX0909L2 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1502L2 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1605L1 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1404L3 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1304L2 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1202L2 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1202L3 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1004L2 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1004L1 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1004L4 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1004L3 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1503L1 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1205L1 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1502L1 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1502L3 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1504L1 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1402L2 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1605L3 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1504L2 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1402L3 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

EX1404L1 Seafloor Mapping Products Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Standard suite of multibeam survey mapping products generated by the Okeanos Explorer seafloor mapping team on data collected on NOAA Ship Okeanos Explorer during...

How has the Long Island Sound Seafloor Changed Over Time?

Science.gov (United States)

Mayo, E. C.; Nitsche, F. O.

2016-12-01

The present Long Island Sound (LIS) was mainly shaped by the last glaciation and the sea level transgression that followed. Today the LIS is an important ecosystem that provides a critical habitat to numerous plant and animal species, and is important to the stability of several economies including fishing, boating, and tourism. Determining where erosion, transportation and deposition of sediment is occurring is important for sustainable development in and around the sound. Calculating the rate of change of the seafloor, identifying the hot spots where the most change is occurring, and determining which processes impact the scale of change are important for preserving the economy and ecology that depend on the sound. This is especially true as larger and more frequent storms comparable to hurricane Sandy are anticipated due to climate change. We used older bathymetric data (collected 1990-2001 by the National Oceanic and Atmospheric Administration) and compared those with the more recently collected LIS bathymetric data covering the same areas (collected 2012-2014 by a collaborative LIS mapping project with NOAA, the States of New York and Connecticut). Using Geographic Information Systems (GIS) we analyzed and mapped the differences between these two datasets to determine where and by how much the seafloor has changed. The results show observable changes in the LIS seafloor on the scale of 1-2 meters over this 10-20 year period. The scale and type of these changes varies across the sound. The rates of change observed depends on the area of the sound, as each area has different factors to account for that controls sediment movement. We present results from five areas of the sound that had data from 1990-2001 and 2012-2014 and that highlight different key processes that change the seafloor. Observed changes in tidal inlets are mostly controlled by existing morphology and near shore sediment transport. In areas with strong bottom currents the data show migrating

Estimating Global Seafloor Total Organic Carbon Using a Machine Learning Technique and Its Relevance to Methane Hydrates

Science.gov (United States)

Lee, T. R.; Wood, W. T.; Dale, J.

2017-12-01

Empirical and theoretical models of sub-seafloor organic matter transformation, degradation and methanogenesis require estimates of initial seafloor total organic carbon (TOC). This subsurface methane, under the appropriate geophysical and geochemical conditions may manifest as methane hydrate deposits. Despite the importance of seafloor TOC, actual observations of TOC in the world's oceans are sparse and large regions of the seafloor yet remain unmeasured. To provide an estimate in areas where observations are limited or non-existent, we have implemented interpolation techniques that rely on existing data sets. Recent geospatial analyses have provided accurate accounts of global geophysical and geochemical properties (e.g. crustal heat flow, seafloor biomass, porosity) through machine learning interpolation techniques. These techniques find correlations between the desired quantity (in this case TOC) and other quantities (predictors, e.g. bathymetry, distance from coast, etc.) that are more widely known. Predictions (with uncertainties) of seafloor TOC in regions lacking direct observations are made based on the correlations. Global distribution of seafloor TOC at 1 x 1 arc-degree resolution was estimated from a dataset of seafloor TOC compiled by Seiter et al. [2004] and a non-parametric (i.e. data-driven) machine learning algorithm, specifically k-nearest neighbors (KNN). Built-in predictor selection and a ten-fold validation technique generated statistically optimal estimates of seafloor TOC and uncertainties. In addition, inexperience was estimated. Inexperience is effectively the distance in parameter space to the single nearest neighbor, and it indicates geographic locations where future data collection would most benefit prediction accuracy. These improved geospatial estimates of TOC in data deficient areas will provide new constraints on methane production and subsequent methane hydrate accumulation.

LiDAR Relative Reflectivity Surface (2011) for the St. Thomas East End Reserve, St. Thomas

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a LiDAR (Light Detection & Ranging) 0.3x0.3 meter resolution relative seafloor reflectivity surface for the St. Thomas East End Reserve...

NF-12-01-USVI Characterization of Seafloor Habitats of the U.S. Caribbean (EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The objective of this project is to collect a multibeam bathymetry dataset with 100% seafloor ensonification, along with multibeam backscatter suitable for seafloor...

NF-11-01-USVI Characterization of Seafloor Habitats of the U.S. Caribbean (EK60)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The objective of this project is to collect a multibeam bathymetry dataset with 100% seafloor ensonification, along with multibeam backscatter suitable for seafloor...

CVD molybdenum films of high infrared reflectance

Energy Technology Data Exchange (ETDEWEB)

Carver, G. E.

1979-01-01

Molybdenum thin films of high infrared reflectance have been deposited by pyrolytic decomposition of molybdenum carbonyl (Mo(CO)/sub 6/), and by hydrogen reduction of molybdenum pentachloride (MoCl/sub 5/). Reflectance values within 0.7% of the reflectance of supersmooth bulk molybdenum have been attained by annealing films of lower reflectance in both reducing and non-reducing atmospheres. All depositions and anneals proceed at atmospheric pressure, facilitating a continuous, flow-through fabrication. These reflectors combine the high temperature stability of molybdenum thin films with the infrared reflectance of a material such as aluminum. Deposition from Mo(CO)/sub 6/ under oxidizing conditions, and subsequent anneal in a reducing atmosphere, results in films that combine high solar absorptance with low thermal emittance. If anti-reflected, black molybdenum films can serve as highly selective single layer photothermal converters. Structural, compositional, and crystallographic properties have been measured after both deposition and anneal.

New High-Resolution Multibeam Mapping and Seismic Reflection Imaging of Mudflows on the Mississippi River Delta Front

Science.gov (United States)

Chaytor, J. D.; Baldwin, W. E.; Danforth, W. W.; Bentley, S. J.; Miner, M. D.; Damour, M.

2017-12-01

Mudflows (channelized and unconfined debris flows) on the Mississippi River Delta Front (MRDF) are a recognized hazard to oil and gas infrastructure in the shallow Gulf of Mexico. Preconditioning of the seafloor for failure results from high sedimentation rates coupled with slope over-steepening, under-consolidation, and abundant biogenic gas production. Cyclical loading of the seafloor by waves from passing major storms appears to be a primary trigger, but the role of smaller (more frequent) storms and background oceanographic processes are largely unconstrained. A pilot high-resolution seafloor mapping and seismic imaging study was carried out across portions of the MRDF aboard the R/V Point Sur from May 19-26, 2017, as part of a multi-agency/university effort to characterize mudflow hazards in the area. The primary objective of the cruise was to assess the suitability of seafloor mapping and shallow sub-surface imaging tools in the challenging environmental conditions found across delta fronts (e.g., variably-distributed water column stratification and wide-spread biogenic gas in the shallow sub-surface). More than 600 km of multibeam bathymetry/backscatter/water column data, 425 km of towed chirp data, and > 500 km of multi-channel seismic data (boomer/mini-sparker sources, 32-channel streamer) were collected. Varied mudflow (gully, lobe), pro-delta morphologies, and structural features, some of which have been surveyed more than once, were imaged in selected survey areas from Pass a Loutre to Southwest Pass. The present location of the SS Virginia, which has been moving with one of the mudflow lobes since it was sunk in 1942, was determined and found to be 60 m SW of its 2006 position, suggesting movement not linked to hurricane-induced wave triggering of mudflows. Preliminary versions these data were used to identify sediment sampling sites visited on a cruise in early June 2017 led by scientists from LSU and other university/agency partners.

Seafloor observations indicate spatial separation of coseismic and postseismic slips in the 2011 Tohoku earthquake

Science.gov (United States)

Iinuma, Takeshi; Hino, Ryota; Uchida, Naoki; Nakamura, Wataru; Kido, Motoyuki; Osada, Yukihito; Miura, Satoshi

2016-01-01

Large interplate earthquakes are often followed by postseismic slip that is considered to occur in areas surrounding the coseismic ruptures. Such spatial separation is expected from the difference in frictional and material properties in and around the faults. However, even though the 2011 Tohoku Earthquake ruptured a vast area on the plate interface, the estimation of high-resolution slip is usually difficult because of the lack of seafloor geodetic data. Here using the seafloor and terrestrial geodetic data, we investigated the postseismic slip to examine whether it was spatially separated with the coseismic slip by applying a comprehensive finite-element method model to subtract the viscoelastic components from the observed postseismic displacements. The high-resolution co- and postseismic slip distributions clarified the spatial separation, which also agreed with the activities of interplate and repeating earthquakes. These findings suggest that the conventional frictional property model is valid for the source region of gigantic earthquakes. PMID:27853138

Seismic-Reflection Technology Defines Potential Vertical Bypass in Hydrogeologic Confinement within Tertiary Carbonates of the Southeastern Florida Platform

Science.gov (United States)

Cunningham, K. J.; Walker, C.; Westcott, R. L.

2011-12-01

Continuous improvements in shallow-focused, high-resolution, marine seismic-reflection technology has provided the opportunity to evaluate geologic structures that breach confining units of the Floridan aquifer system within the southeastern Florida Platform. The Floridan aquifer system is comprised mostly of Tertiary platform carbonates. In southeastern Florida, hydrogeologic confinement is important to sustainable use of the Floridan aquifer system, where the saline lower part is used for injection of wastewater and the brackish upper part is an alternative source of drinking water. Between 2007 and 2011, approximately 275 km of 24- and 48-channel seismic-reflection profiles were acquired in canals of peninsular southeastern Florida, Biscayne Bay, present-day Florida shelf margin, and the deeply submerged Miami Terrace. Vertical to steeply dipping offsets in seismic reflections indicate faults, which range from Eocene to possible early Pliocene age. Most faults are associated with karst collapse structures; however, a few tectonic faults of early Miocene to early Pliocene age are present. The faults may serve as a pathway for vertical groundwater flow across relatively low-permeability carbonate strata that separate zones of regionally extensive high-permeability in the Floridan aquifer system. The faults may collectively produce a regional confinement bypass system. In early 2011, twenty seismic-reflection profiles were acquired near the Key Biscayne submarine sinkhole located on the seafloor of the Miami Terrace. Here the water depth is about 365 m. A steeply dipping (eastward) zone of mostly deteriorated quality of seismic-reflection data underlies the sinkhole. Correlation of coherent seismic reflections within and adjacent to the disturbed zone indicates a series of faults occur within the zone. It is hypothesized that upward movement of groundwater within the zone contributed to development of a hypogenic karst system and the resultant overlying sinkhole

Using Interactive eBooks To Educate Children About Sub-seafloor Science

Science.gov (United States)

Kurtz, K.

2016-02-01

Sub-seafloor scientific research has the power to spark the imaginations of elementary age children with its mysterious nature, cutting-edge research, and its connections to kid friendly science topics, such as volcanoes, the extinction of dinosaurs and the search for extraterrestrial life. These factors have been utilized to create two interactive eBooks for elementary students and teachers, integrating high quality science information, highly engaging and age-appropriate illustrations, and rhyming text. The first eBook introduces children to the research and discoveries of the JOIDES Resolution research vessel. The creators were able to build-on the knowledge gained in creating the first eBook to create a second eBook that focuses on the discoveries of microbial life in the sub-seafloor. The eBooks present information as traditional, linear, illustrated children's books, but the eBook format allows the book to be available online for free to anyone and allows teachers to project the book on a classroom screen so all students can easily see the illustrations. The iPad versions also provide an interactive, learner-led educational experience, where cognitively appropriate videos, photos and other forms of information can be accessed with the tap of a finger to answer reader questions and enrich their learning experience. These projects provide an example and model of the products that can result from high level and meaningful partnerships between scientists, educators, artists and writers.

California State Waters Map Series: offshore of Refugio Beach, California

Science.gov (United States)

Johnson, Samuel Y.; Dartnell, Peter; Cochrane, Guy R.; Golden, Nadine E.; Phillips, Eleyne L.; Ritchie, Andrew C.; Krigsman, Lisa M.; Dieter, Bryan E.; Conrad, James E.; Greene, H. Gary; Seitz, Gordon G.; Endris, Charles A.; Sliter, Ray W.; Wong, Florence L.; Erdey, Mercedes D.; Gutierrez, Carlos I.; Yoklavich, Mary M.; East, Amy E.; Hart, Patrick E.; Johnson, Samuel Y.; Cochran, Susan A.

2015-01-01

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within California’s State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 100 m) subsurface geology.

California State Waters Map Series: offshore of San Francisco, California

Science.gov (United States)

Cochrane, Guy R.; Johnson, Samuel Y.; Dartnell, Peter; Greene, H. Gary; Erdey, Mercedes D.; Golden, Nadine E.; Hartwell, Stephen R.; Endris, Charles A.; Manson, Michael W.; Sliter, Ray W.; Kvitek, Rikk G.; Watt, Janet Tilden; Ross, Stephanie L.; Bruns, Terry R.; Cochrane, Guy R.; Cochran, Susan A.

2015-01-01

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within California’s State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 100 m) subsurface geology.

Seafloor classification using echo- waveforms: A method employing hybrid neural network architecture

Digital Repository Service at National Institute of Oceanography (India)

Chakraborty, B.; Mahale, V.; DeSouza, C.; Das, P.

, neural network architecture, seafloor classification, self-organizing feature map (SOFM). I. INTRODUCTION S EAFLOOR classification and characterization using re- mote high-frequency acoustic system has been recognized as a useful tool (see [1...] and references therein). The seafloor’s characteristics are extremely complicated due to variations of the many parameters at different scales. The parameters include sediment grain size, relief height at the water–sediment inter- face, and variations within...

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...

Precise natural radiography of seafloor sedimentary cores by using imaging plate

International Nuclear Information System (INIS)

Sugihara, Makoto; Tsuchiya, Noriyoshi

2007-01-01

The radiation measurement for seafloor sedimentary cores was carried out by using the Imaging Plate (IP). The precise natural radiography was obtained with 48 hours (exposure time) in a shield box. Layered structures of seafloor sediments that have relatively low radioactivity like biogenic matters could be detected by autoradiography, and it was possible to identify optically unclear layers of sediments with differences of radiation characteristics. The detection limit of thickness of suspended particle layers like volcanic ashes might be sub millimeters. It was possible to identify the pinpoint position where radioactive mineral emitted α-rays at the surface of sample. Identification of pinpoint position could be possible suppose radioactive minerals that emits α-ray exposed at the surface of sample. Distribution of dose (PSL value of IP) was related to CT value (X-ray CT), which indicates dose of sedimentary core have relationships with density and atomic number of sediments. The natural radiography for seafloor sediments cores by using the Imaging Plate is considered to be a powerful new tool as a non-destructive core analysis. (author)

Advances in Shallow-Water, High-Resolution Seafloor Mapping: Integrating an Autonomous Surface Vessel (ASV) Into Nearshore Geophysical Studies

Science.gov (United States)

Denny, J. F.; O'Brien, T. F.; Bergeron, E.; Twichell, D.; Worley, C. R.; Danforth, W. W.; Andrews, B. A.; Irwin, B.

2006-12-01

The U.S. Geological Survey (USGS) has been heavily involved in geological mapping of the seafloor since the 1970s. Early mapping efforts such as GLORIA provided broad-scale imagery of deep waters (depths > 400 meters) within the Exclusive Economic Zone (EEZ). In the early 1990's, the USGS research emphasis shifted from deep- to shallow-water environments (inner continental shelf, nearshore, estuaries) to address pertinent coastal issues such as erosion, sediment availability, sediment transport, vulnerability of coastal areas to natural and anthropogenic hazards, and resource management. Geologic framework mapping in these shallow- water environments has provided valuable data used to 1) define modern sediment distribution and thickness, 2) determine underlying stratigraphic and structural controls on shoreline behavior, and 3) enable onshore-to- offshore geologic mapping within the coastal zone when coupled with subaerial techniques such as GPR and topographic LIDAR. Research in nearshore areas presents technological challenges due to the dynamics of the environment, high volume of data collected, and the geophysical limitations of operating in very shallow water. In 2004, the USGS, in collaboration with NOAA's Coastal Services Center, began a multi-year seafloor mapping effort to better define oyster habitats within Apalachicola Bay, Florida, a shallow water estuary along the northern Gulf of Mexico. The bay poses a technological challenge due to its shallow depths (turbidity that prohibits the use of bathymetric LIDAR. To address this extreme shallow water setting, the USGS incorporated an Autonomous Surface Vessel (ASV) into seafloor mapping operations, in June 2006. The ASV is configured with a chirp sub-bottom profiler (4 24 kHz), dual-frequency chirp sidescan-sonar (100/500 kHz), single-beam echosounder (235 kHz), and forward-looking digital camera, and will be used to delineate the distribution and thickness of surficial sediment, presence of oyster beds

Analysis of Backscatter and Seafloor Acoustical Properties across deepwater sandwaves in Cook Strait, New Zealand

Science.gov (United States)

Lurton, X.; Lamarche, G.

2011-12-01

Central Cook Strait, New Zealand presents a variety of geological landforms subjected to intense hydrodynamic conditions. A comprehensive EM300 multibeam coverage of the strait was used to develop a method to objectively characterise the seafloor substrate. Specific post-processing was applied to the backscatter data to correct the signal from sensor bias, and was completed by correlating a quantitative description of backscatter with the field data. The final calibrated Backscattering Strength (BS) provides information on the physical characteristics of the seafloor. The BS imagery was used for both qualitative and quantitative interpretation, and give access to a level of detail higher than with conventional multibeam bathymetry. We developed a functional descriptive model of the physical BS angular response, describing satisfactorily the various typical BS responses met over Cook Strait and providing a first-order interpretation of the substrate composition. The full model needs 6 input parameters, but a practical classification can be obtained with only two (the BS value at 45° and the specular-to-oblique contrast). We analyse the BS angular response of sandwaves and erosional bedforms typically met in the central Cook Strait. The sandwave fields occur in 200-350 m of water depth and exhibit large-scale topographical features (wavelengths 100 - 250 m; vertical amplitudes 2 - 10 m). They are conspicuous in the backscatter imagery, and analysing their BS variations according to topography is specially informative. The BS level has a sharp minimum at the wave crests and is maximal inside the troughs, with a typical dynamics of 6 dB. Such a variation cannot be explained by the dependence on incident angle retrieved from local high-resolution bathymetry. Hence we infer that the reflectivity variations observed on the sandwaves are due to sediment facies changes, from fine to coarse sand in this case. This is corroborated by the fact that some sandwave fields with

Upper crustal structure of the Hawaiian Swell from seafloor compliance measurements

Science.gov (United States)

Doran, A. K.; Laske, G.

2017-12-01

We present new constraints on elastic properties of the marine sediments and crust surrounding the Hawaiian Islands derived from seafloor compliance measurements. We analyze long-period seismic and pressure data collected during the Plume-Lithosphere Undersea Mantle Experiment [Laske et al, 2009], a deployment consisting of nearly 70 broadband ocean-bottom seismometers with an array aperture of over 1000 kilometers. Our results are supported by previous reflection & refraction studies and by direct sampling of the crust from regional drilling logs. We demonstrate the importance of simultaneously modeling density, compressional velocity, and shear velocity, the former two of which are often ignored during compliance investigations. We find variable sediment thickness and composition across the Hawaiian Swell, with the thickest sediments located within the Hawaiian Moat. Improved resolution of near-surface structure of the Hawaiian Swell is crucially important to improve tomographic images of the underlying lithosphere and asthenosphere and to address outstanding questions regarding the size, source, and location of the hypothesized mantle plume.

Sea-floor texture and physiographic zones of the inner continental shelf from Salisbury to Nahant, Massachusetts, including the Merrimack Embayment and Western Massachusetts Bay

Science.gov (United States)

Pendleton, Elizabeth E.; Barnhardt, Walter A.; Baldwin, Wayne E.; Foster, David S.; Schwab, William C.; Andrews, Brian D.; Ackerman, Seth D.

2015-10-26

A series of maps that describe the distribution and texture of sea-floor sediments and physiographic zones of Massachusetts State waters from Nahant to Salisbury, Massachusetts, including western Massachusetts Bay, have been produced by using high-resolution geophysical data (interferometric and multibeam swath bathymetry, lidar bathymetry, backscatter intensity, and seismic reflection profiles), sediment samples, and bottom photographs. These interpretations are intended to aid statewide efforts to inventory and manage coastal and marine resources, link with existing data interpretations, and provide information for research focused on coastal evolution and environmental change. Marine geologic mapping of the inner continental shelf of Massachusetts is a statewide cooperative effort of the U.S. Geological Survey and the Massachusetts Office of Coastal Zone Management.

A Comparison between Oceanographic Parameters and Seafloor Pressures; Measured, Theoretical and Modelled, and Terrestrial Seismic Data

Science.gov (United States)

Donne, Sarah; Bean, Christopher; Craig, David; Dias, Frederic; Christodoulides, Paul

2016-04-01

Microseisms are continuous seismic vibrations which propagate mainly as surface Rayleigh and Love waves. They are generated by the Earth's oceans and there are two main types; primary and secondary microseisms. Primary microseisms are generated through the interaction of travelling surface gravity ocean waves with the seafloor in shallow waters relative to the wavelength of the ocean wave. Secondary microseisms, on the other hand are generated when two opposing wave trains interact and a non-linear second order effect produces a pressure fluctuation which is depth independent. The conditions necessary to produce secondary microseisms are presented in Longuet-Higgins (1950) through the interaction of two travelling waves with the same wave period and which interact at an angle of 180 degrees. Equivalent surface pressure density (p2l) is modelled using the numerical ocean wave model Wavewatch III and this term is considered as the microseism source term. This work presents an investigation of the theoretical second order pressures generated through the interaction of travelling waves with varying wave amplitude, period and angle of incidence. Predicted seafloor pressures calculated off the Southwest coast of Ireland are compared with terrestrially recorded microseism records, measured seafloor pressures and oceanographic parameters. The work presented in this study suggests that a broad set of sea states can generate second order seafloor pressures that are consistent with seafloor pressure measurements. Local seismic arrays throughout Ireland allow us to investigate the temporal covariance of these seafloor pressures with microseism source locations.

California State Waters Map Series: offshore of Tomales Point, California

Science.gov (United States)

Johnson, Samuel Y.; Dartnell, Peter; Golden, Nadine E.; Hartwell, Stephen R.; Greene, H. Gary; Erdey, Mercedes D.; Cochrane, Guy R.; Watt, Janet Tilden; Kvitek, Rikk G.; Manson, Michael W.; Endris, Charles A.; Dieter, Bryan E.; Krigsman, Lisa M.; Sliter, Ray W.; Lowe, Erik N.; Chinn, John L.; Johnson, Samuel Y.; Cochran, Susan A.

2015-01-01

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California’s State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 200 m) subsurface geology.

California State Waters Map Series: offshore of Pacifica, California

Science.gov (United States)

Edwards, Brian D.; Phillips, Eleyne L.; Dartnell, Peter; Greene, H. Gary; Bretz, Carrie K.; Kvitek, Rikk G.; Hartwell, Stephen R.; Johnson, Samuel Y.; Cochrane, Guy R.; Dieter, Bryan E.; Sliter, Ray W.; Ross, Stephanie L.; Golden, Nadine E.; Watt, Janet Tilden; Chinn, John L.; Erdey, Mercedes D.; Krigsman, Lisa M.; Manson, Michael W.; Endris, Charles A.; Cochran, Susan A.; Edwards, Brian D.

2015-01-01

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California’s State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 100 m) subsurface geology. 

Recommendations for improved and coherent acquisition and processing of backscatter data from seafloor-mapping sonars

Science.gov (United States)

Lamarche, Geoffroy; Lurton, Xavier

2018-06-01

Multibeam echosounders are becoming widespread for the purposes of seafloor bathymetry mapping, but the acquisition and the use of seafloor backscatter measurements, acquired simultaneously with the bathymetric data, are still insufficiently understood, controlled and standardized. This presents an obstacle to well-accepted, standardized analysis and application by end users. The Marine Geological and Biological Habitat Mapping group (Geohab.org) has long recognized the need for better coherence and common agreement on acquisition, processing and interpretation of seafloor backscatter data, and established the Backscatter Working Group (BSWG) in May 2013. This paper presents an overview of this initiative, the mandate, structure and program of the working group, and a synopsis of the BSWG Guidelines and Recommendations to date. The paper includes (1) an overview of the current status in sensors and techniques available in seafloor backscatter data from multibeam sonars; (2) the presentation of the BSWG structure and results; (3) recommendations to operators, end-users, sonar manufacturers, and software developers using sonar backscatter for seafloor-mapping applications, for best practice methods and approaches for data acquisition and processing; and (4) a discussion on the development needs for future systems and data processing. We propose for the first time a nomenclature of backscatter processing levels that affords a means to accurately and efficiently describe the data processing status, and to facilitate comparisons of final products from various origins.

Marine litter on the seafloor of the Faial-Pico Passage, Azores Archipelago.

Science.gov (United States)

Rodríguez, Yasmina; Pham, Christopher K

2017-03-15

Plastic pollution in the marine environment attracts much attention from both researchers and the general public. Plastic items and other debris are commonly observed everywhere in the ocean, from the surface down to the deep ocean floor. In this study, we analysed 45.2km of video footage, collected during 56 transects surveying the seafloor of the Faial-Pico Passage in order to quantify the abundance of marine litter and its interactions with benthic fauna. The footage was collected by a Remotely Operated Vehicle (ROV) and a manned submersible at depths ranging between 40 and 525m. The mean litter density in the passage was 0.26±0.03 items·100m -1 (±SE) and was significantly higher between 151 and 250m compared to other depth strata. Overall, derelict fishing gear, mostly made of plastic, were the most common objects found on the seafloor, representing 64% of all items. Although we observed few evidence of direct deleterious effects by the litter, interactions with fauna were observed in more than half of the items. This study makes an important contribution in quantifying the abundance of marine litter on the seafloor of the Azores. The location of the Faial-Pico Passage, close to shore, makes it an appropriate site for long-term monitoring of litter on the seafloor and evaluate the efficiency of upcoming public policies aimed at reducing litter input into the oceans. Copyright © 2017 Elsevier Ltd. All rights reserved.

Shaded seafloor relief, backscatter strength, and surficial geology; German Bank, Scotian Shelf, offshore Nova Scotia

Science.gov (United States)

Todd, B.J.; Valentine, Page C.

2010-01-01

This map is part of a three-map series of German Bank, located on the Scotian Shelf off southern Nova Scotia.  This map is the product of a number of surveys (1997-2003) that used a multibeam sonar system to map 5321 km2 of the seafloor.  Other surveys collected geological data for scientific interpretation.  This map sheet shows the seafloor topography of German Bank in shaded-relief view and seafloor depth (coded by colour) at a scale of 1:1000,000.  Topographic contours generated from the multibeam data are shown (in white) on the colour-coded multibeam topography at a depth interval of 20 m.  Bathymetic contours (in blue) outside the multibeam survey area, presented at a depth interval of 10 m, are from the Natural Resource Map series (Canadian Hydrographic Service, 1967, 1971a, 1971b, 1972). Sheet 2 shows coloured backscatter strength in shaded-relief view.  Sheet 3 shows seafloor topography in shaded-relief view with colour-coded surficial geological units.

GeoTIFF of 3x3 m Relative Reflectivity for St. Thomas & St. John, 2011, UTM 20N NAD83

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a LiDAR (Light Detection & Ranging) 3x3 meter resolution relative seafloor reflectivity surface for an area of shallow seabed surrounding...

GeoTIFF of 3x3 m Relative Reflectivity for Buck Island, St. Croix, 2011, UTM 20N NAD83

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a LiDAR (Light Detection & Ranging) 3x3 meter resolution relative seafloor reflectivity surface for an area including and surrounding Buck...

Development of Deep-tow Autonomous Cable Seismic (ACS) for Seafloor Massive Sulfides (SMSs) Exploration.

Science.gov (United States)

Asakawa, Eiichi; Murakami, Fumitoshi; Tsukahara, Hitoshi; Saito, Shutaro; Lee, Sangkyun; Tara, Kenji; Kato, Masafumi; Jamali Hondori, Ehsan; Sumi, Tomonori; Kadoshima, Kazuyuki; Kose, Masami

2017-04-01

Within the EEZ of Japan, numerous surveys exploring ocean floor resources have been conducted. The exploration targets are gas hydrates, mineral resources (manganese, cobalt or rare earth) and especially seafloor massive sulphide (SMS) deposits. These resources exist in shallow subsurface areas in deep waters (>1500m). For seismic explorations very high resolution images are required. These cannot be effectively obtained with conventional marine seismic techniques. Therefore we have been developing autonomous seismic survey systems which record the data close to the seafloor to preserve high frequency seismic energy. Very high sampling rate (10kHz) and high accurate synchronization between recording systems and shot time are necessary. We adopted Cs-base atomic clock considering its power consumption. At first, we developed a Vertical Cable Seismic (VCS) system that uses hydrophone arrays moored vertically from the ocean bottom to record close to the target area. This system has been successfully applied to SMS exploration. Specifically it fixed over known sites to assess the amount of reserves with the resultant 3D volume. Based on the success of VCS, we modified the VCS system to use as a more efficient deep-tow seismic survey system. Although there are other examples of deep-tow seismic systems, signal transmission cables present challenges in deep waters. We use our autonomous recording system to avoid these problems. Combining a high frequency piezoelectric source (Sub Bottom Profiler:SBP) that automatically shots with a constant interval, we achieve the high resolution deep-tow seismic without data transmission/power cable to the board. Although the data cannot be monitored in real-time, the towing system becomes very simple. We have carried out survey trial, which showed the systems utility as a high-resolution deep-tow seismic survey system. Furthermore, the frequency ranges of deep-towed source (SBP) and surface towed sparker are 700-2300Hz and 10-200Hz

Modeling of methane bubbles released from large sea-floor area: Condition required for methane emission to the atmosphere

OpenAIRE

Yamamoto, A.; Yamanaka, Y.; Tajika, E.

2009-01-01

Massive methane release from sea-floor sediments due to decomposition of methane hydrate, and thermal decomposition of organic matter by volcanic outgassing, is a potential contributor to global warming. However, the degree of global warming has not been estimated due to uncertainty over the proportion of methane flux from the sea-floor to reach the atmosphere. Massive methane release from a large sea-floor area would result in methane-saturated seawater, thus some methane would reach the atm...

Response to Comment on "Sensitivity of seafloor bathymetry to climate-driven fluctuations in mid-ocean ridge magma supply".

Science.gov (United States)

Olive, J-A; Behn, M D; Ito, G; Buck, W R; Escartín, J; Howell, S

2016-07-15

Tolstoy reports the existence of a characteristic 100 thousand year (ky) period in the bathymetry of fast-spreading seafloor but does not argue that sea level change is a first-order control on seafloor morphology worldwide. Upon evaluating the overlap between tectonic and Milankovitch periodicities across spreading rates, we reemphasize that fast-spreading ridges are the best potential recorders of a sea level signature in seafloor bathymetry. Copyright © 2016, American Association for the Advancement of Science.

Analysis of seafloor change around Dauphin Island, Alabama, 1987–2015

Science.gov (United States)

Flocks, James G.; DeWitt, Nancy T.; Stalk, Chelsea A.

2017-09-26

surveys around Dauphin Island using a variety of shallow draft vessels and equipment. More than 95 square kilometers of seafloor was imaged. The data were integrated into a seamless digital elevation model to provide a high-resolution bathymetric map of the seafloor extending 9.5 kilometers seaward from the island’s eastern end and approximately 2 km along the rest of the island on the gulf and sound sides. Water depths range from 0.3 to 15.0 meters (m), with depths greater than 10.0 m constrained to the Mobile ship channel on the extreme eastern flank of the coverage.To measure seafloor change, two periods of historic hydrographic survey data were acquired from the National Oceanic and Atmospheric Administration National Centers for Environmental Information data archive. The two timeframes (1987–1988 and 2005–2007) were selected for their completeness of spatial coverage and because they encompass a period of significant storm impacts to the island. These timeframes were compared to each other and with the 2015 dataset to monitor elevation gain (sediment accretion) and elevation loss (sediment erosion) over time. Sediment dynamics is by far the most significant driver of nearshore elevation change in this area. The Mississippi-Alabama inner shelf is a passive margin, and other influences on elevation change (for example, tectonic adjustment, Holocene subsidence, and eustatic sea-level rise) are neither significant nor variable enough over this time period to have an imprint.

Sensitivity of seafloor bathymetry to climate-driven fluctuations in mid-ocean ridge magma supply.

Science.gov (United States)

Olive, J-A; Behn, M D; Ito, G; Buck, W R; Escartín, J; Howell, S

2015-10-16

Recent studies have proposed that the bathymetric fabric of the seafloor formed at mid-ocean ridges records rapid (23,000 to 100,000 years) fluctuations in ridge magma supply caused by sealevel changes that modulate melt production in the underlying mantle. Using quantitative models of faulting and magma emplacement, we demonstrate that, in fact, seafloor-shaping processes act as a low-pass filter on variations in magma supply, strongly damping fluctuations shorter than about 100,000 years. We show that the systematic decrease in dominant seafloor wavelengths with increasing spreading rate is best explained by a model of fault growth and abandonment under a steady magma input. This provides a robust framework for deciphering the footprint of mantle melting in the fabric of abyssal hills, the most common topographic feature on Earth. Copyright © 2015, American Association for the Advancement of Science.

Global patterns and predictions of seafloor biomass using random forests

Digital Repository Service at National Institute of Oceanography (India)

Wei, Chih-Lin; Rowe, G.T.; Escobar-Briones, E.; Boetius, A; Soltwedel, T.; Caley, M.J.; Soliman, Y.; Huettmann, F.; Qu, F.; Yu, Z.; Pitcher, C.R.; Haedrich, R.L.; Wicksten, M.K.; Rex, M.A; Baguley, J.G.; Sharma, J.; Danovaro, R.; MacDonald, I.R.; Nunnally, C.C.; Deming, J.W.; Montagna, P.; Levesque, M.; Weslawsk, J.M.; Wlodarska-Kowalczuk, M.; Ingole, B.S.; Bett, B.J.; Billett, D.S.M.; Yool, A; Bluhm, B.A; Iken, K.; Narayanaswamy, B.E.

A comprehensive seafloor biomass and abundance database has been constructed from 24 oceanographic institutions worldwide within the Census of Marine Life (CoML) field projects. The machine-learning algorithm, Random Forests, was employed to model...

GeoTIFF of 5x5 m Relative Reflectivity for Salt River Bay, St. Croix, 2011, UTM 20N NAD83

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a LiDAR (Light Detection & Ranging) 5x5 meter resolution relative seafloor reflectivity surface for an area surrounding the mouth of Salt...

Oregon OCS seafloor mapping: Selected lease blocks relevant to renewable energy

Science.gov (United States)

Cochrane, Guy R.; Hemery, Lenaïg G.; Henkel, Sarah K.

2017-05-23

seafloor character raster consists of three substrate classes: soft-flat areas, hard-flat areas, and hard-rugged areas. A Coastal and Marine Ecological Classification Standard (CMECS) geoform and substrate map was also produced using depth, slope, and benthic position index classes to delineate geoform boundaries. Seven geoforms were identified in this process, including ridges, slump scars, slump deposits, basins, and pockmarks.Statistical analysis of the video data for correlations between substrate, depth, and invertebrate assemblages resulted in the identification of seven biomes: three hard-bottom biomes and four softbottom biomes. A similar analysis of vertebrate observations produces a similar set of biomes. The biome between-group dissimilarity was very high or high. Invertebrates alone represent most of the structure of the whole benthic community into different assemblages. A biotope map was generated using the seafloor character raster and the substrate and depth values of the biomes. Hard substrate biotopes were small in size and were located primarily on the ridge and in pockmarks along the pockmark lineation. The soft-bottom bitopes consisted of large contiguous areas delimited by isobaths.

Feasibility of Acoustic Remote Sensing of Large Herring Shoals and Seafloor by Baleen Whales

Directory of Open Access Journals (Sweden)

Dong Hoon Yi

2016-08-01

Full Text Available Recent research has found a high spatial and temporal correlation between certain baleen whale vocalizations and peak herring spawning processes in the Gulf of Maine. These vocalizations are apparently related to feeding activities with suggested functions that include communication, prey manipulation, and echolocation. Here, the feasibility of the echolocation function is investigated. Physical limitations on the ability to detect large herring shoals and the seafloor by acoustic remote sensing are determined with ocean acoustic propagation, scattering, and statistical theories given baleen whale auditory parameters. Detection is found to be highly dependent on ambient noise conditions, herring shoal distributions, baleen whale time-frequency vocalization spectra, and geophysical parameters of the ocean waveguide. Detections of large herring shoals are found to be physically feasible in common Gulf of Maine herring spawning scenarios at up to 10 ± 6 km in range for humpback parameters and 1 ± 1 km for minke parameters but not for blue and fin parameters even at zero horizontal range. Detections of the seafloor are found to be feasible up to 2 ± 1 km for blue and humpback parameters and roughly 1 km for fin and minke parameters, suggesting that the whales share a common acoustic sensation of rudimentary features of the geophysical environment.

Satellite Derived Seafloor Bathymetry and Habitat Mapping on a Shallow Carbonate Platform: Campeche Bank, México.

Science.gov (United States)

Garza-Perez, J. R.; Rankey, E. C.; Rodriguez-Vázquez, R. A.; Naranjo-Garcia, M. J.

2017-12-01

Extensive and consistent high-resolution seafloor mapping is a difficult task involving important financial resources, intensive field work and careful planning; thus there is a paucity of this type of mapping products both in spatial distribution and through time. Remote sensed imagery has supported continuous mapping efforts elsewhere, but extensive seafloor mapping, even in shallow regions keeps being elusive. Challenges to this effort include cloud cover, surface sun-glint, and water turbidity caused by sediment resuspension and primary productivity. Nevertheless, using high-quality satellite imagery (Landsat-8 OLI -30x30m/pixel- and GeoEye-1 -2x2m/pixel) and rigorous pre-processing (atmospheric correction, de-glinting and water-column light extinction compensation), resulting data contribute towards the advancement of seafloor mapping. The Yucatan Peninsula in México is a carbonate ramp devoid of significant orographic features and surface water bodies. Its submerged portion is the Campeche Bank, gently sloping towards the Gulf of Mexico. The bottom features several distinct blankets composed by medium-fine sediment (dominated by pelecypods, gastropods, foraminifera, lithoclasts, calcareous peloids and algal nodules, Halimeda plaques and coralline algae fragments), and a reef unit with several bank-type coral reefs. Outside the coral reefs, biotic cover down to 20 m deep is dominated by macroalgae (red, brown, green), coralline and filamentous algae with sharp seasonal changes in abundance, from almost nil during north-winds (Oct. - Jan.) to high during dry (Feb.- May) and rainy seasons (Jun. - Sept.), with changes of dominance by algae groups between dry and rainy seasons. This bloom is favored by increases in sunlight and nutrients carried by the Caribbean current upwelling washing the Campeche Bank. Beyond 20 m depth, sandy plains dominate the seascape. Corals, octocorals, sponges and tunicates are spatially restricted to bottoms with thin layers of

Sea-floor geology and character offshore of Rocky Point, New York

Science.gov (United States)

Poppe, L.J.; McMullen, K.Y.; Ackerman, S.D.; Blackwood, D.S.; Irwin, B.J.; Schaer, J.D.; Lewit, P.G.; Doran, E.F.

2010-01-01

The U.S. Geological Survey (USGS), the Connecticut Department of Environmental Protection, and the National Oceanic and Atmospheric Administration (NOAA) have been working cooperatively to interpret surficial sea-floor geology along the coast of the Northeastern United States. NOAA survey H11445 in eastern Long Island Sound, offshore of Plum Island, New York, covers an area of about 12 square kilometers. Multibeam bathymetry and sidescan-sonar imagery from the survey, as well as sediment and photographic data from 13 stations occupied during a USGS verification cruise are used to delineate sea-floor features and characterize the environment. Bathymetry gradually deepens offshore to over 100 meters in a depression in the northwest part of the study area and reaches 60 meters in Plum Gut, a channel between Plum Island and Orient Point. Sand waves are present on a shoal north of Plum Island and in several smaller areas around the basin. Sand-wave asymmetry indicates that counter-clockwise net sediment transport maintains the shoal. Sand is prevalent where there is low backscatter in the sidescan-sonar imagery. Gravel and boulder areas are submerged lag deposits produced from the Harbor Hill-Orient Point-Fishers Island moraine segment and are found adjacent to the shorelines and just north of Plum Island, where high backscatter is present in the sidescan-sonar imagery.

GeoTIFF of 3x3 m Relative Reflectivity for St. Thomas & St. John, 2011, UTM 20N NAD83 (NCEI Accession 0131858)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a LiDAR (Light Detection & Ranging) 3x3 meter resolution relative seafloor reflectivity surface for an area of shallow seabed surrounding...

GeoTIFF of 3x3 m Relative Reflectivity for Buck Island, St. Croix, 2011, UTM 20N NAD83 (NCEI Accession 0131858)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a LiDAR (Light Detection & Ranging) 3x3 meter resolution relative seafloor reflectivity surface for an area including and surrounding Buck...

Improved detection and mapping of deepwater hydrocarbon seeps: optimizing multibeam echosounder seafloor backscatter acquisition and processing techniques

Science.gov (United States)

Mitchell, Garrett A.; Orange, Daniel L.; Gharib, Jamshid J.; Kennedy, Paul

2018-02-01

Marine seep hunting surveys are a current focus of hydrocarbon exploration surveys due to recent advances in offshore geophysical surveying, geochemical sampling, and analytical technologies. Hydrocarbon seeps are ephemeral, small, discrete, and therefore difficult to sample on the deep seafloor. Multibeam echosounders are an efficient seafloor exploration tool to remotely locate and map seep features. Geophysical signatures from hydrocarbon seeps are acoustically-evident in bathymetric, seafloor backscatter, midwater backscatter datasets. Interpretation of these signatures in backscatter datasets is a fundamental component of commercial seep hunting campaigns. Degradation of backscatter datasets resulting from environmental, geometric, and system noise can interfere with the detection and delineation of seeps. We present a relative backscatter intensity normalization method and an oversampling acquisition technique that can improve the geological resolvability of hydrocarbon seeps. We use Green Canyon (GC) Block 600 in the Northern Gulf of Mexico as a seep calibration site for a Kongsberg EM302 30 kHz MBES prior to the start of the Gigante seep hunting program to analyze these techniques. At GC600, we evaluate the results of a backscatter intensity normalization, assess the effectiveness of 2X seafloor coverage in resolving seep-related features in backscatter data, and determine the off-nadir detection limits of bubble plumes using the EM302. Incorporating these techniques into seep hunting surveys can improve the detectability and sampling of seafloor seeps.

Improved detection and mapping of deepwater hydrocarbon seeps: optimizing multibeam echosounder seafloor backscatter acquisition and processing techniques

Science.gov (United States)

Mitchell, Garrett A.; Orange, Daniel L.; Gharib, Jamshid J.; Kennedy, Paul

2018-06-01

Marine seep hunting surveys are a current focus of hydrocarbon exploration surveys due to recent advances in offshore geophysical surveying, geochemical sampling, and analytical technologies. Hydrocarbon seeps are ephemeral, small, discrete, and therefore difficult to sample on the deep seafloor. Multibeam echosounders are an efficient seafloor exploration tool to remotely locate and map seep features. Geophysical signatures from hydrocarbon seeps are acoustically-evident in bathymetric, seafloor backscatter, midwater backscatter datasets. Interpretation of these signatures in backscatter datasets is a fundamental component of commercial seep hunting campaigns. Degradation of backscatter datasets resulting from environmental, geometric, and system noise can interfere with the detection and delineation of seeps. We present a relative backscatter intensity normalization method and an oversampling acquisition technique that can improve the geological resolvability of hydrocarbon seeps. We use Green Canyon (GC) Block 600 in the Northern Gulf of Mexico as a seep calibration site for a Kongsberg EM302 30 kHz MBES prior to the start of the Gigante seep hunting program to analyze these techniques. At GC600, we evaluate the results of a backscatter intensity normalization, assess the effectiveness of 2X seafloor coverage in resolving seep-related features in backscatter data, and determine the off-nadir detection limits of bubble plumes using the EM302. Incorporating these techniques into seep hunting surveys can improve the detectability and sampling of seafloor seeps.

Unlocking the Treasures of the Ocean: Current Assessment and Future Perspectives of Seafloor Resources (C.F Gauss Lecture)

Science.gov (United States)

Jegen, Marion

2016-04-01

Oceans cover 70% of the Earth's surface, and there is reason to believe that the wealth of mineral and carbon resources on the seafloor is similar to deposits on land. While off-shore energy resources such as oil and gas are nowadays regarded as conventional, energy resources in form of methane hydrates and seafloor mineral deposits are yet unconventional and at best marginally economic. However, taking into account global population growth, geopolitics and technological development (both in terms of increasing industrialization and possibility to explore and mine seafloor resources), these resources might play a more fundamental role in the future. Resource assessment and understanding of the geological formation process of resources are topics in marine geosciences with broad relevance to society. The lecture presents an overview of the geophysical exploration of the seafloor and its resource potential. Starting from the link of physical parameter anomalies associated with resources, I will explore marine technological developments on how to sense them remotely from the seafloor. Also the question will be addressed of how well we can actually quantify the amount of resources from geophysical data. The process will be illustrated based on theoretical work as well as case studies from around the world.

Duel frequency echo data acquisition system for sea-floor classification

Digital Repository Service at National Institute of Oceanography (India)

Navelkar, G.S.; Desai, R.G.P.; Chakraborty, B.

An echo data acquisition system is designed to digitize echo signal from a single beam shipboard echo-sounder for use in sea-floor classification studies using a 12 bit analog to digital (A/D) card with a maximum sampling frequency of 1 MHz. Both 33...

S-net : Construction of large scale seafloor observatory network for tsunamis and earthquakes along the Japan Trench

Science.gov (United States)

Mochizuki, M.; Uehira, K.; Kanazawa, T.; Shiomi, K.; Kunugi, T.; Aoi, S.; Matsumoto, T.; Sekiguchi, S.; Yamamoto, N.; Takahashi, N.; Nakamura, T.; Shinohara, M.; Yamada, T.

2017-12-01

NIED has launched the project of constructing a seafloor observatory network for tsunamis and earthquakes after the occurrence of the 2011 Tohoku Earthquake to enhance reliability of early warnings of tsunamis and earthquakes. The observatory network was named "S-net". The S-net project has been financially supported by MEXT.The S-net consists of 150 seafloor observatories which are connected in line with submarine optical cables. The total length of submarine optical cable is about 5,500 km. The S-net covers the focal region of the 2011 Tohoku Earthquake and its vicinity regions. Each observatory equips two units of a high sensitive pressure gauges as a tsunami meter and four sets of three-component seismometers. The S-net is composed of six segment networks. Five of six segment networks had been already installed. Installation of the last segment network covering the outer rise area have been finally finished by the end of FY2016. The outer rise segment has special features like no other five segments of the S-net. Those features are deep water and long distance. Most of 25 observatories on the outer rise segment are located at the depth of deeper than 6,000m WD. Especially, three observatories are set on the seafloor of deeper than about 7.000m WD, and then the pressure gauges capable of being used even at 8,000m WD are equipped on those three observatories. Total length of the submarine cables of the outer rise segment is about two times longer than those of the other segments. The longer the cable system is, the higher voltage supply is needed, and thus the observatories on the outer rise segment have high withstanding voltage characteristics. We employ a dispersion management line of a low loss formed by combining a plurality of optical fibers for the outer rise segment cable, in order to achieve long-distance, high-speed and large-capacity data transmission Installation of the outer rise segment was finished and then full-scale operation of S-net has started

3D movies for teaching seafloor bathymetry, plate tectonics, and ocean circulation in large undergraduate classes

Science.gov (United States)

Peterson, C. D.; Lisiecki, L. E.; Gebbie, G.; Hamann, B.; Kellogg, L. H.; Kreylos, O.; Kronenberger, M.; Spero, H. J.; Streletz, G. J.; Weber, C.

2015-12-01

Geologic problems and datasets are often 3D or 4D in nature, yet projected onto a 2D surface such as a piece of paper or a projection screen. Reducing the dimensionality of data forces the reader to "fill in" that collapsed dimension in their minds, creating a cognitive challenge for the reader, especially new learners. Scientists and students can visualize and manipulate 3D datasets using the virtual reality software developed for the immersive, real-time interactive 3D environment at the KeckCAVES at UC Davis. The 3DVisualizer software (Billen et al., 2008) can also operate on a desktop machine to produce interactive 3D maps of earthquake epicenter locations and 3D bathymetric maps of the seafloor. With 3D projections of seafloor bathymetry and ocean circulation proxy datasets in a virtual reality environment, we can create visualizations of carbon isotope (δ13C) records for academic research and to aid in demonstrating thermohaline circulation in the classroom. Additionally, 3D visualization of seafloor bathymetry allows students to see features of seafloor most people cannot observe first-hand. To enhance lessons on mid-ocean ridges and ocean basin genesis, we have created movies of seafloor bathymetry for a large-enrollment undergraduate-level class, Introduction to Oceanography. In the past four quarters, students have enjoyed watching 3D movies, and in the fall quarter (2015), we will assess how well 3D movies enhance learning. The class will be split into two groups, one who learns about the Mid-Atlantic Ridge from diagrams and lecture, and the other who learns with a supplemental 3D visualization. Both groups will be asked "what does the seafloor look like?" before and after the Mid-Atlantic Ridge lesson. Then the whole class will watch the 3D movie and respond to an additional question, "did the 3D visualization enhance your understanding of the Mid-Atlantic Ridge?" with the opportunity to further elaborate on the effectiveness of the visualization.

Seafloor classification using acoustic backscatter echo-waveform - Artificial neural network applications

Digital Repository Service at National Institute of Oceanography (India)

Chakraborty, B.; Mahale, V.; Navelkar, G.S.; Desai, R.G.P.

In this paper seafloor classifications system based on artificial neural network (ANN) has been designed. The ANN architecture employed here is a combination of Self Organizing Feature Map (SOFM) and Linear Vector Quantization (LVQ1). Currently...

Estimation of mean grain size of seafloor sediments using neural network

Digital Repository Service at National Institute of Oceanography (India)

De, C.; Chakraborty, B.

The feasibility of an artificial neural network based approach is investigated to estimate the values of mean grain size of seafloor sediments using four dominant echo features, extracted from acoustic backscatter data. The acoustic backscatter data...

Seafloor characterization using time-dependent acoustic backscatter: Study at Arabian Sea

Digital Repository Service at National Institute of Oceanography (India)

Chakraborty, B.; De, C

This paper presents application of `inversion modeling` technique to echo shape data acquired shallow water regions off Goa. The estimated sediment and seafloor roughness parameter for two different frequencies (33 and 210 kHz) provide comparable...

GeoTIFF of 5x5 m Relative Reflectivity for Salt River Bay, St. Croix, 2011, UTM 20N NAD83 (NCEI Accession 0131858)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a LiDAR (Light Detection & Ranging) 5x5 meter resolution relative seafloor reflectivity surface for an area surrounding the mouth of Salt...

Tectonic reorganization in the Indian Ocean: Evidences from seafloor crenulations

Digital Repository Service at National Institute of Oceanography (India)

Kessarkar, P.M.

these lineaments, oriented in N-S, NW-SE and E-W directions, vary in time and space. A sharp change in nature and orientation of these seafloor lineaments, as well as of magnetic anomalies, occurs along 73~'E long., which appears to act as contact between older...

Impacts on seafloor geology of drilling disturbance in shallow waters.

Science.gov (United States)

Corrêa, Iran C S; Toldo, Elírio E; Toledo, Felipe A L

2010-08-01

This paper describes the effects of drilling disturbance on the seafloor of the upper continental slope of the Campos Basin, Brazil, as a result of the project Environmental Monitoring of Offshore Drilling for Petroleum Exploration--MAPEM. Field sampling was carried out surrounding wells, operated by the company PETROBRAS, to compare sediment properties of the seafloor, including grain-size distribution, total organic carbon, and clay mineral composition, prior to drilling with samples obtained 3 and 22 months after drilling. The sampling grid used had 74 stations, 68 of which were located along 7 radials from the well up to a distance of 500 m. The other 6 stations were used as reference, and were located 2,500 m from the well. The results show no significant sedimentological variation in the area affected by drilling activity. The observed sedimentological changes include a fining of grain size, increase in total organic carbon, an increase in gibbsite, illite, and smectite, and a decrease in kaolinite after drilling took place.

Perturbation of seafloor bacterial community structure by drilling waste discharge.

Science.gov (United States)

Nguyen, Tan T; Cochrane, Sabine K J; Landfald, Bjarne

2018-04-01

Offshore drilling operations result in the generation of drill cuttings and localized smothering of the benthic habitats. This study explores bacterial community changes in the in the upper layers of the seafloor resulting from an exploratory drilling operation at 1400m water depth on the Barents Sea continental slope. Significant restructurings of the sediment microbiota were restricted to the sampling sites notably affected by the drilling waste discharge, i.e. at 30m and 50m distances from the drilling location, and to the upper 2cm of the seafloor. Three bacterial groups, the orders Clostridiales and Desulfuromonadales and the class Mollicutes, were almost exclusively confined to the upper two centimeters at 30m distance, thereby corroborating an observed increase in anaerobicity inflicted by the drilling waste deposition. The potential of these phylogenetic groups as microbial bioindicators of the spatial extent and persistence of drilling waste discharge should be further explored. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Investigation of Active Tectonism Offshore Cide-Sinop, Southern Black Sea by Seismic Reflection and Bathymetric Data

Science.gov (United States)

Alp, Y. I.; Ocakoglu, N.; Kılıc, F.; Ozel, A. O.

2017-12-01

The active tectonism offshore Cide-Sinop at the Southern Black Sea shelf area was first time investigated by multi-beam bathymetric and multi-channel seismic reflection data under the Research Project of The Scientific and Technological Research Council of Turkey (TUBİTAK-ÇAYDAG-114Y057). The multi-channel seismic reflection data of about 700 km length were acquired in 1991 by Turkish Petroleum Company (TP). Multibeam bathymetric data were collected between 2002-2008 by the Turkish Navy, Department of Navigation, Hydrography and Oceanography (TN-DNHO). Conventional data processing steps were applied as follows: in-line geometry definition, shot-receiver static correction, editing, shot muting, gain correction, CDP sorting, velocity analysis, NMO correction, muting, stacking, predictive deconvolution, band-pass filtering, finite-difference time migration, and automatic gain correction. Offshore area is represented by a quite smooth and large shelf plain with an approx. 25 km wide and the water depth of about -100 m. The shelf gently deepens and it is limited by the shelf break with average of -120 m contour. The seafloor morphology is charasterised by an erosional surface. Structurally, E-W trending strike-slip faults with generally compression components and reverse/thrust faults have been regionally mapped for the first time. Most of these faults deform all seismic units and reach the seafloor delimiting the morphological highs and submarine plains. Thus, these faults are intepreted as active faults. These results support the idea that the area is under the active compressional tectonic regime

High {Tc} superconductivity: Symmetries and reflections

International Nuclear Information System (INIS)

Zhang, S.C.

1999-01-01

This is a talk given at the Symposium Symmetries and Reflections, dedicated to Prof. C.N. Yang's retirement. In this talk, the author reflects on his personal interaction with Prof. Yang since his graduate career at SUNY Stony Brook, and his profound impact on his understanding of theoretical physics. He also reviews the SO(5) theory of high T c superconductivity and shows how his collaboration with Prof. Yang in 1990 lead to the foundation of this idea

Surficial geology and shaded seafloor relief of Georges Bank, Fundian Channel and Northeast Channel, Gulf of Maine

Science.gov (United States)

Todd, B.J.; Valentine, Page C.

2015-01-01

Georges Bank is a shallow submarine bank that lies south of Nova Scotia and east of Cape Cod and bounds the seaward side of the Gulf of Maine. The international boundary between Canada and the United States transects the bank, and the eastern part of the bank (~7500 square kilometres) lies in Canadian territory. This map shows the surficial geology of a part of Georges Bank at a scale of 1:50 000. This map has companion topographic and backscatter strength maps. These companion maps provide a basis for interpreting the origin of seafloor features and the nature of materials that form the seafloor. The maps are based on multibeam-sonar surveys conducted in 1999 and 2000 to map 11,965 square kilometres of the seafloor.

Seafloor studies of Mamala Bay, Honolulu, Hawaii

Science.gov (United States)

Torresan, Michael E.

No comprehensive study of the effects of disposal of dredge spoils has been conducted to determine if the environment has suffered. The U.S. Army Corps of Engineers (USACE) has regularly dredged the shipping channels of Honolulu Harbor and Pearl Harbor for commercial and military purposes. The 5-year frequency for new dredging activity has led to the formation of extensive offshore wide deposits of relatively coarse sediments being created in a sedimentary environment that naturally collects much finer-grained materials. At the same time, the rapid growth of Honolulu and its suburban region over the past 3 decades has added nutrient-enriched sewage outfall to the artificially-heavy sediment load. The combined effects of dredge-spoil disposal and contaminant loads are not well-documented, and are poorly understood. The U.S. Geological Survey (USGS) began a comprehensive study to characterize the seafloor of Mamala Bay.In 1993, the USGS initiated a program sponsored by the USACE and the U.S. Environmental Protection Agency that produced a detailed map of the seafloor, especially of the distribution of dredge spoils, and a preliminary analysis of the environmental effects of dredge-spoils disposal and the chemical effects of the introduction of nutrient-rich outfall. Part of the work would involve sediment sampling, biological testing, and evaluation. Of particular interest is tissue sampling and analysis of endemic shrimp to determine the rates of absorption of toxic elements, such as heavy metals, that are easily brought into the food chain.

Exploring the Tectonic Evolution of the Seafloor using Roughness, Covariance, and Anisotropy in Bathymetry and Marine Gravity

Science.gov (United States)

Kalnins, L. M.; Simons, F.

2017-12-01

Between the vastness of the oceans and the technological challenges water poses, data scarcity is frequently a limiting factor in studying the tectonic and morphological evolution of the seafloor. It is therefore essential to extract maximum information from the available gravity and bathymetry data, whilst also retaining realistic estimates of uncertainties. Here, we use a frequency-domain maximum-likelihood procedure to map the roughness structure and the nature of the topographic covariance of the seafloor. Rather than requiring us to assume the covariance is Gaussian or exponential, the flexibility of the Matérn form's parameterisation (variance, range, and differentiability) lets us solve for the shape of the covariance and map out its changes without a priori assumptions.We also examine the relationship between gravity and bathymetry through their coherence and admittance, particularly the anisotropy in the relationship. We extend the robust analysis developed to map anisotropy in lithospheric strength in the continents (Kalnins et al., 2015) to the oceanic domain. This method lets us separate out measurements of anisotropy likely to be linked to anisotropy in the long-term mechanical strength of the lithosphere itself; those aligned with anisotropies in the input gravity and bathymetry data; and those that are mathematically significant, but unexplained. Ultimately, we aim to use the statistical analyses to infer geophysical parameters of interest, such as oceanic spreading rate, level of volcanic activity, and potential for energy dissipation in ocean circulation. Our first results show a general alignment of strong directions ridge-parallel and weak directions ridge-perpendicular, suggesting widespread mechanical anisotropy derived from the lithosphere's highly anisotropic formation at mid-ocean ridges. However, this pattern changes markedly near sites of significant intraplate volcanism, where little to no robust anisotropy in strength is recovered. This

Teacher Reflective Practice in Jesuit High Schools

Science.gov (United States)

Klug, Joseph H.

2010-01-01

Teachers who engage in reflective practice are more effective and may encourage higher student achievement. The purpose of this study is to explore and describe the methods that teachers use in order to engage in reflective practice. Further, it is essential to gain an understanding of how schools, including Jesuit high schools, promote reflective…

Mapping the Gulf of Maine with side-scan sonar: A new bottom-type classification for complex seafloors

Science.gov (United States)

Barnhardt, W.A.; Kelley, J.T.; Dickson, S.M.; Belknap, D.F.

1998-01-01

The bedrock-framed seafloor in the northwestern Gulf of Maine is characterized by extreme changes in bathymetric relief and covered with a wide variety of surficial materials. Traditional methods of mapping cannot accurately represent the great heterogeneity of such a glaciated region. A new mapping scheme for complex seafloors, based primarily on the interpretation of side-scan sonar imagery, utilizes four easily recognized units: rock, gravel, sand and mud. In many places, however, the seafloor exhibits a complicated mixture or extremely 'patchy' distribution of the four basic units, which are too small to map individually. Twelve composite units, each a two-component mixture of the basic units, were established to represent this patchiness at a small scale (1:100,000). Using a geographic information system, these and all other available data (seismic profiles, grab samples, submersible dives and cores) were referenced to a common geographic base, superimposed on bathymetric contours and then integrated into surficial geologic maps of the regional inner continental shelf. This digital representation of the seafloor comprises a multidimensional, interactive model complete with explicit attributes (depth, bottom type) that allow for detailed analysis of marine environments.

In-situ Eh sensor measurement and calibration: application to seafloor observatories

Science.gov (United States)

Ding, K.; Seyfried, W. E.; Tan, C.

2013-12-01

Eh measurement is often used with manned submersible and AUV assets as an effective way to detect and locate seafloor hydrothermal activity. Eh can be fundamentally and sensitively linked to dissolved H 2 , which, in turn, serves as a key constraint on subseafloor redox reactions. Moreover, Eh is now being increasingly relied on for event detection and process monitoring efforts intrinsic to cabled seafloor observatories. Due to seawater interaction with electrochemical components fundamental to the operation of the Eh sensor, however, the quality and reliability of the measurements are often compromised by signal drift, especially when the sensor is used for long term deployment. To solve this problem, a calibration protocol was developed and added to our previously constructed pH 'calibrator'. Thus, the integrated electrochemical system now permits the combined in-situ measurement and calibration of pH and Eh of seafloor hydrothermal fluids. Key aspects of the design for this calibration system are: (1) the sensing electrodes can be kept preserved in fluid of known pH, Eh and NaCl concentration prior to use, thereby preventing deterioration of electrode response characteristics by chemical and biological activity; (2) the system consists of valves and pumps for flow control, and therefore can be operated remotely with power from the seafloor cabled observatory, or as a stand-alone device, using battery power for shorter-term deployments. In both cases, standardization with on-board fluids of known redox, pH, and NaCl activity can be activated at any time, providing enhanced reliability (3) the current development is aimed at deep sea environments, cold seeps, and hydrothermal diffuse flow fluids at the temperatures up to 100°C and depths up to 4500 m. The in-situ operation is especially well-suited for use with cabled observatory for real time intervention and event response owing to enabled power supply and two way communications. Field tests have been

Stable Attitude of Seafloor Geodetic Benchmarks Confirmed Through Diving Surveys After the 2004 Fff-Kii Peninsula Earthquake

Science.gov (United States)

Fujimoto, H.; Tadokoro, K.; Okuda, T.; Matsumoto, Y.; Kido, M.; Osada, Y.; Kurihara, K.

2006-12-01

Tohoku University, Nagoya University, and Japan Coast Guard (JCG) deployed benchmarks for GPS/Acoustic seafloor positioning in Kumano-nada, Central Japan, which detected horizontal crustal deformation caused by the off-Kii Peninsula earthquake M7.4 on September 5, 2004 (Tadokoro et al., 2005; Kido et al., 2006). It would be the first to observe crustal deformation on the seafloor associated with an offshore earthquake. When we, working on the GPS/A seafloor positioning, reported on results of observation, we were often requested to answer the following question: "Can the benchmarks be sunk and tilted due to the shaking of the sedimented seafloor?" Indeed the benchmarks are precision acoustic transponders (PXPs) and we dropped them from the sea surface assuming soft and stable landing on the sediment. Moreover, a branch of the aftershock distribution of the off-Kii Peninsula earthquake extended close to the benchmarks. It would be the first experience for the benchmarks for cm-order seafloor geodesy to be shaked by large earthquakes. We had a chance to carry out diving surveys there by using the ROV "Dolphin 3K" of JAMSTEC during the NT06-07 cruise of the R/V Natsushima to obtain the following results. (1) We observed 10 PXPs (Tohoku 4, Nagoya 3, JCG 3) on the seafloor. All of them stood stably on the flat sedimented bottom with their bases partly sunk in the mud. We could not find any indication that the earthquake changed the attitude of some of the benchmarks. (2) We recovered one of the PXPs, which were deployed by JCG 6 years ago as the first benchmarks around the Japanese Islands. We could confirm little erosion of the instrument made of stainless frames and a glass sphere covered with a hard hut. (3) We could not find any feature on the bottom indicating local crustal deformation. This research was partly supported by the Research Revolution 2002 Program, MEXT, Japan.

High-accuracy measurements of the normal specular reflectance

International Nuclear Information System (INIS)

Voarino, Philippe; Piombini, Herve; Sabary, Frederic; Marteau, Daniel; Dubard, Jimmy; Hameury, Jacques; Filtz, Jean Remy

2008-01-01

The French Laser Megajoule (LMJ) is designed and constructed by the French Commissariata l'Energie Atomique (CEA). Its amplifying section needs highly reflective multilayer mirrors for the flash lamps. To monitor and improve the coating process, the reflectors have to be characterized to high accuracy. The described spectrophotometer is designed to measure normal specular reflectance with high repeatability by using a small spot size of 100 μm. Results are compared with ellipsometric measurements. The instrument can also perform spatial characterization to detect coating nonuniformity

High gain durable anti-reflective coating

Energy Technology Data Exchange (ETDEWEB)

Maghsoodi, Sina; Brophy, Brenor L.; Colson, Thomas E.; Gonsalves, Peter R.; Abrams, Ze' ev R.

2017-06-27

Disclosed herein are polysilsesquioxane-based anti-reflective coating (ARC) compositions, methods of preparation, and methods of deposition on a substrate. In one embodiment, the polysilsesquioxane of this disclosure is prepared in a two-step process of acid catalyzed hydrolysis of organoalkoxysilane followed by addition of tetralkoxysilane that generates silicone polymers with >40 mol % silanol based on Si-NMR. These high silanol siloxane polymers are stable and have a long shelf-life in polar organic solvents at room temperature. Also disclosed are low refractive index ARC made from these compositions with and without additives such as porogens, templates, thermal radical initiator, photo radical initiators, crosslinkers, Si--OH condensation catalyst and nano-fillers. Also disclosed are methods and apparatus for applying coatings to flat substrates including substrate pre-treatment processes, coating processes and coating curing processes including skin-curing using hot-air knives. Also disclosed are coating compositions and formulations for highly tunable, durable, highly abrasion-resistant functionalized anti-reflective coatings.

Occurrence and Magnitude of High Reflectance Materials on the Moon

Science.gov (United States)

Nuno, R. G.; Boyd, A. K.; Robinson, M. S.

2013-12-01

We utilize a Lunar Reconnaissance Orbiter (LRO) Wide Angle Camera (WAC) 643 nm photometrically normalized (30°, 0°, 30°; i, e, g) reflectance map to investigate the occurrence and origin of high reflectance materials on the Moon. Compositional differences (mainly iron and titanium content) and maturity state (e.g. Copernican crater rays and swirls) are the predominant factors affecting reflectance variations observed on the Moon. Therefore, comparing reflectance values of different regions yields insight into the composition and relative exposure age of lunar materials. But an accurate comparison requires precise reflectance values normalized across every region being investigated. The WAC [1] obtains monthly near-global ground coverage, each month's observations acquired with different lighting conditions. Boyd et al. [2] utilized a geologically homogeneous subset [0°N to 90°N, 146°E to 148°E] of the WAC observations to determine an equation that describes how viewing and lighting angles affect reflectance values. A normalized global reflectance map was generated by applying the local empirical solution globally, with photometric angles derived from the WAC Global Lunar Digital Terrain Model (DTM)(GLD100) [3]. The GLD100 enables accurate correction of reflectance differences caused by local topographic undulations at the scale of 300 meters. We compare reflectance values across the Moon within 80°S to 80°N latitude. The features with the highest reflectance are steep crater walls within Copernican aged craters, such as the walls of Giordano Bruno, which have normalized reflectance values up to 0.35. Near-impact ejecta of some craters have high reflectance values, such as Virtanen (0.22). There are also broad relatively flat features with high reflectance, such as the 900-km Thales-Compton region (0.24) and the 600-km extent of Anaxagoras (Copernican age) ejecta (0.20). Since the interior of Anaxagoras contains occurrences of pure anorthosite [4], the high

Preference of echo features for classification of seafloor sediments using neural networks

Digital Repository Service at National Institute of Oceanography (India)

De, C.; Chakraborty, B.

7.0, Neural network Toolbox, The Math Works, Inc., 1984 -2004. Michalopoulou, Z. -H., D. Alexandrou, and C. de Moustier. 1995. Application of neural and statistical classifiers to the problem of seafloor characterization. IEEE Journal of Oceanic...

Exploring Seafloor Volcanoes in Cyberspace: NOAA's "Ocean Explorer" Inspires Inquiry

Science.gov (United States)

Hjelm, Elizabeth

2011-01-01

Seafloor exploration being done by scientists is an ideal way to introduce students to technology as a tool for inquiry. The same technology that allows scientists to share data in near real time can also provide students the tools to become researchers. NOAA's Ocean Explorer Explorations website is a rich research data bank that can be used by…

Fault zone controlled seafloor methane seepage in the rupture area of the 2010 Maule Earthquake, Central Chile

OpenAIRE

Geersen, Jacob; Scholz, Florian; Linke, Peter; Schmidt, Mark; Lange, Dietrich; Behrmann, Jan H.; Völker, David; Hensen, Christian

2016-01-01

Seafloor seepage of hydrocarbon-bearing fluids has been identified in a number of marine forearcs. However, temporal variations in seep activity and the structural and tectonic parameters that control the seepage often remain poorly constrained. Subduction-zone earthquakes for example, are often discussed to trigger seafloor seepage but causal links that go beyond theoretical considerations have not yet been fully established. This is mainly due to the inaccessibility of offshore epicentral a...

High-resolution bathymetry as a primary exploration tool for seafloor massive sulfide deposits - lessons learned from exploration on the Mid-Atlantic and Juan de Fuca Ridges, and northern Lau Basin

Science.gov (United States)

Jamieson, J. W.; Clague, D. A.; Petersen, S.; Yeo, I. A.; Escartin, J.; Kwasnitschka, T.

2016-12-01

High-resolution, autonomous underwater vehicle (AUV)-derived multibeam bathymetry is increasingly being used as an exploration tool for delineating the size and extent of hydrothermal vent fields and associated seafloor massive sulfide deposits. However, because of the limited amount of seafloor that can be surveyed during a single dive, and the challenges associated with distinguishing hydrothermal chimneys and mounds from other volcanic and tectonic features using solely bathymetric data, AUV mapping surveys have largely been employed as a secondary exploration tool once hydrothermal sites have been discovered using other exploration methods such as plume, self-potential and TV surveys, or ROV and submersible dives. Visual ground-truthing is often required to attain an acceptable level of confidence in the hydrothermal origin of features identified in AUV-derived bathymetry. Here, we present examples of high-resolution bathymetric surveys of vent fields from a variety of tectonic environments, including slow- and intermediate-rate mid-ocean ridges, oceanic core complexes and back arc basins. Results illustrate the diversity of sulfide deposit morphologies, and the challenges associated with identifying hydrothermal features in different tectonic environments. We present a developing set of criteria that can be used to distinguish hydrothermal deposits in bathymetric data, and how AUV surveys can be used either on their own or in conjunction with other exploration techniques as a primary exploration tool.

Quantitative estimation of seafloor features from photographs and their application to nodule mining

Digital Repository Service at National Institute of Oceanography (India)

Sharma, R.

Methods developed for quantitative estimation of seafloor features from seabed photographs and their application for estimation of nodule sizes, coverage, abundance, burial, sediment thickness, extent of rock exposure, density of benthic organisms...

Revisiting Seafloor-Spreading in the Red Sea: Basement Nature, Transforms and Ocean-Continent Boundary

Science.gov (United States)

Tapponnier, P.; Dyment, J.; Zinger, M. A.; Franken, D.; Afifi, A. M.; Wyllie, A.; Ali, H. G.; Hanbal, I.

2013-12-01

A new marine geophysical survey on the Saudi Arabian side of the Red Sea confirms early inferences that ~ 2/3 of the eastern Red Sea is floored by oceanic crust. Most seismic profiles south of 24°N show a strongly reflective, landward-deepening volcanic basement up to ~ 100 km east of the axial ridge, beneath thick evaporitic deposits. This position of the Ocean-Continent Boundary (OCB) is consistent with gravity measurements. The low amplitudes and long wavelengths of magnetic anomalies older than Chrons 1-3 can be accounted for by low-pass filtering due to thick sediments. Seafloor-spreading throughout the Red Sea started around 15 Ma, as in the western Gulf of Aden. Its onset was coeval with the activation of the Aqaba/Levant transform and short-cutting of the Gulf of Suez. The main difference between the southern and northern Red Sea lies not in the nature of the crust but in the direction and modulus of the plate motion rate. The ~ 30° counterclockwise strike change and halving of the spreading rate (~ 16 to ~ 8 mm/yr) between the Hermil (17°N) and Suez triple junctions results in a shift from slow (≈ North Atlantic) to highly oblique, ultra-slow (≈ Southwest Indian) ridge type. The obliquity of spreading in the central and northern basins is taken up by transform discontinuities that stop ~ 40 km short of the coastline, at the OCB. Three large transform fault systems (Jeddah, Zabargad, El Akhawein) nucleated as continental transfer faults reactivating NNE-trending Proterozoic shear zones. The former two systems divide the Red Sea into three main basins. Between ~15 and ~5 Ma, for about 10 million years, thick evaporites were deposited directly on top of oceanic crust in deep water, as the depositional environment, modulated by climate, became restricted by the Suez and Afar/Bab-el-Mandeb volcano-tectonic 'flood-gates.' The presence of these thick deposits (up to ~ 8 km) suffices to account for the difference between the Red Sea and the Gulf of Aden

Gondwana subduction-modified mantle domain prevents magmatic seafloor generation in the Central Indian Ridge

Science.gov (United States)

Morishita, T.; Nakamura, K.; Senda, R.; Suzuki, K.; Kumagai, H.; Sato, H.; Sato, T.; Shibuya, T.; Minoguchi, K.; Okino, K.

2013-12-01

The creation of oceanic crust at mid-ocean ridges is essential to understanding the genesis of oceanic plate and the evolution of the Earth. Detailed bathymetric measurements coupled with dense sample recovery at mid-ocean ridge revealed a wide range of variations in the ridge and seafloor morphologies, which cannot be simply explained by a spreading rate, but also by ridge geometry, mantle compositions and thermal structure (Dick et al., 2003 Nature; Cannat et al. 2006 Geology). It is now widely accepted that very limited magmatic activity with tectonic stretching generates oceanic core complex and/or smooth seafloor surface in the slow to ultraslow-spreading ridges, where serpentinized peridotite and gabbros are expected to be exposed associated with detachment faults (Cann et al., 1997 Nature; Cannat et al., 2006), although magmatism might be an essential role for the formation of oceanic core complexes (Buck et al., 2005 Nature; Tucholke et al 2008 JGR). A rising question is why magmatic activity is sometimes prevented during the oceanic plate formation. Ancient melting domain, that are too refractory to melt even in adiabatically upwelling to the shallow upper mantle, might cause the amagmatic spreading ridges (Harvey et al., 2006 EPSL, Liu et al.,2008 Nature). Its origin and effect on seafloor generations are, however, not well understood yet. We report an oceanic hill as an example of an ancient subduction-modified mantle domain, probably formed at continental margin of the Gondwanaland~Pangea supercontinent, existing beneath the Central Indian Ridge. This domain is the most likely to have prevented magmatic seafloor generation, resulting in creation of very deep oceanic valley and serpentine diaper (now the studied oceanic hill) at the present Central Indian ridge.

A 1.4-Billion Pixel Map of the Seafloor: BOEM's Mission to Visualize Dynamic Geology and Identify Natural Seep Sites in the Gulf of Mexico

Science.gov (United States)

Kramer, K.; Shedd, W. W.

2017-12-01

In May, 2017, the U.S. Department of the Interior's Bureau of Ocean Energy Management (BOEM) published a high-resolution seafloor map of the northern Gulf of Mexico region. The new map, derived from 3-D seismic surveys, provides the scientific community with enhanced resolution and reveals previously undiscovered and poorly resolved geologic features of the continental slope, salt minibasin province, abyssal plain, Mississippi Fan, and the Florida Shelf and Escarpment. It becomes an even more powerful scientific tool when paired with BOEM's public database of 35,000 seafloor features, identifying natural hydrocarbon seeps, hard grounds, mud volcanoes, sediment flows, pockmarks, slumps, and many others. BOEM has mapped the Gulf of Mexico seafloor since 1998 in a regulatory mission to identify natural oil and gas seeps and protect the coral and chemosynthetic communities growing at those sites. The nineteen-year mapping effort, still ongoing, resulted in the creation of the 1.4-billion pixel map and the seafloor features database. With these tools and continual collaboration with academia, professional scientific institutions, and the offshore energy industry, BOEM will continue to incorporate new data to update and expand these two resources on a regular basis. They can be downloaded for free from BOEM's website at https://www.boem.gov/Gulf-of-Mexico-Deepwater-Bathymetry/ and https://www.boem.gov/Seismic-Water-Bottom-Anomalies-Map-Gallery/.

Estimating deep seafloor interface and volume roughness parameters using the multibeam-hydrosweep system

Digital Repository Service at National Institute of Oceanography (India)

Chakraborty, B.; Schenke, H.W.; Kodagali, V.N.; Hagen, R.

composite roughness model, including water-sediment interface roughness and sediment volume roughness parameters the data was modeled. The model effectively uses the near normal incidence angle backscatter to determine the seafloor interface roughness...

Interannual changes in seafloor surficial geology at an artificial reef site on the inner continental shelf

Science.gov (United States)

Raineault, Nicole A.; Trembanis, Arthur C.; Miller, Douglas C.; Capone, Vince

2013-04-01

The influence of reef structures on seafloor surface sediments has implications for marine spatial planning and coastal development, including use of the coastal zone for offshore wind energy. We present results of interannual changes in seafloor surficial geology at the Redbird artificial reef site, located on the continental shelf offshore of Delaware Bay. The Redbird reef is composed of NYC subway cars, barges, tugboats, and other sunken objects. Since objects were added sporadically between 1996 and 2009, the survey area acts as a natural laboratory to study the evolution of the surrounding seafloor at a structural reef habitat through time. Annual side-scan surveys from 2008 through 2011, and one bathymetric survey in 2010 provide information about surface geology and morphology. Local wave and current data for this time period were analyzed to determine the main morphological agents. Automated backscatter segmentation show that three bottom types dominate and that these large-scale (>10 m) surface sediment patterns persist from year to year. Grab samples reveal that the bottom types are silty sand with clay and sandy gravel. Clear sediment and biological patterns emerged revealing the influence of the objects on the seafloor. Comet-shaped moats of sandy gravel surround single objects and grow to form large-scale coalesced patches around groups of objects. Alignment of sediment patches suggests the periodic hydrodynamic influence of seasonal storms. The abundance and diversity of organisms increases with decreasing clay/silt content. Evidence of scour includes the removal of fine sediments, the formation of moats 1-30 m in diameter and 0.5-1 m deep around the reef objects, and the >1 m settling of objects into the seafloor. Data suggest subway cars reached equilibrium with the environment in 6-7 years, but that larger objects or clusters of objects take a longer time to equilibrate and have farther-reaching effects. Knowledge of local wave and current climate

High-precision reflectivity measurements: improvements in the calibration procedure

Science.gov (United States)

Jupe, Marco; Grossmann, Florian; Starke, Kai; Ristau, Detlev

2003-05-01

The development of high quality optical components is heavily depending on precise characterization procedures. The reflectance and transmittance of laser components are the most important parameters for advanced laser applications. In the industrial fabrication of optical coatings, quality management is generally insured by spectral photometric methods according to ISO/DIS 15386 on a medium level of accuracy. Especially for high reflecting mirrors, a severe discrepancy in the determination of the absolute reflectivity can be found for spectral photometric procedures. In the first part of the CHOCLAB project, a method for measuring reflectance and transmittance with an enhanced precision was developed, which is described in ISO/WD 13697. In the second part of the CHOCLAB project, the evaluation and optimization for the presented method is scheduled. Within this framework international Round-Robin experiment is currently in progress. During this Round-Robin experiment, distinct deviations could be observed between the results of high precision measurement facilities of different partners. Based on the extended experiments, the inhomogeneity of the sample reflectivity was identified as one important origin for the deviation. Consequently, this inhomogeneity is also influencing the calibration procedure. Therefore, a method was developed that allows the calibration of the chopper blade using always the same position on the reference mirror. During the investigations, the homogeneity of several samples was characterized by a surface mapping procedure for 1064 nm. The measurement facility was extended to the additional wavelength 532 nm and a similar set-up was assembled at 10.6 μm. The high precision reflectivity procedure at the mentioned wavelengths is demonstrated for exemplary measurements.

Feasibility of Ocean Acoustic Waveguide Remote Sensing (OAWRS of Atlantic Cod with Seafloor Scattering Limitations

Directory of Open Access Journals (Sweden)

Ankita D. Jain

2013-12-01

Full Text Available Recently reported declines in the population of Atlantic cod have led to calls for additional survey methods for stock assessments. In combination with conventional line-transect methods that may have ambiguities in sampling fish populations, Ocean Acoustic Waveguide Remote Sensing (OAWRS has been shown to have a potential for providing accurate stock assessments (Makris N.C., et al. Science 2009, 323, 1,734–1,737; 54th Northeast Regional Stock Assessment Workshop (54th SAW US Department of Commerce, Northeast Fisheries Science Center, 2012. The use of OAWRS technology enables instantaneous wide-area sensing of fish aggregations over thousands of square kilometers. The ratio of the intensity of scattered returns from fish versus the seafloor in any resolution cell typically determines the maximum fish detection range of OAWRS, which then is a function of fish population density, scattering amplitude and depth distribution, as well as the level of seafloor scattering. With the knowledge of oceanographic parameters, such as bathymetry, sound speed structure and attenuation, we find that a Rayleigh–Born volume scattering approach can be used to efficiently and accurately estimate seafloor scattering over wide areas. From hundreds of OAWRS measurements of seafloor scattering, we determine the Rayleigh–Born scattering amplitude of the seafloor, which we find has a ƒ2,4 frequency dependence below roughly 2 kHz in typical continental shelf environments along the US northeast coast. We then find that it is possible to robustly detect cod aggregations across frequencies at and near swim bladder resonance for observed spawningconfigurations along the U.S. northeast coast, roughly the two octave range 150–600 Hzfor water depths up to roughly 100 m. This frequency range is also optimal for long-rangeocean acoustic waveguide propagation, because it enables multimodal acoustic waveguidepropagation with minimal acoustic absorption and forward

Constraining climate sensitivity and continental versus seafloor weathering using an inverse geological carbon cycle model.

Science.gov (United States)

Krissansen-Totton, Joshua; Catling, David C

2017-05-22

The relative influences of tectonics, continental weathering and seafloor weathering in controlling the geological carbon cycle are unknown. Here we develop a new carbon cycle model that explicitly captures the kinetics of seafloor weathering to investigate carbon fluxes and the evolution of atmospheric CO 2 and ocean pH since 100 Myr ago. We compare model outputs to proxy data, and rigorously constrain model parameters using Bayesian inverse methods. Assuming our forward model is an accurate representation of the carbon cycle, to fit proxies the temperature dependence of continental weathering must be weaker than commonly assumed. We find that 15-31 °C (1σ) surface warming is required to double the continental weathering flux, versus 3-10 °C in previous work. In addition, continental weatherability has increased 1.7-3.3 times since 100 Myr ago, demanding explanation by uplift and sea-level changes. The average Earth system climate sensitivity is  K (1σ) per CO 2 doubling, which is notably higher than fast-feedback estimates. These conclusions are robust to assumptions about outgassing, modern fluxes and seafloor weathering kinetics.

Seismic reflection results of the GYRE 1997 Cruise at the Bryant Canyon of the Louisiana Gulf Coast

Science.gov (United States)

Nealon, Jeffrey W.; Dillon, William P.; Twichell, David

2000-01-01

The TexasLouisiana continental slope is one of the few remaining frontiers for hydrocarbon exploration within the US Exclusive Economic Zone.  This area has a complex seafloor morphology and highly discontinuous shallow stratigraphy that are the result of deformation by the highly mobile Louann salt that underlies much of this margin shoreward of the Sigsbee Escarpment.Gas hydrates exist both on the sea floor and at depth throughout the gas hydrate stability zone which extends to several hundred meters beneath the sea floor at greater water depths.  Multibeam bathymetry, GLORIA sidescan sonar imagery, and site-specific studies have identified the presence of faults, mass-wasting deposits, variable sediment types, and gas hydrates exposed on the seafloor.  The expression of these features on the seafloor suggests a tectonically active area.  The distribution of these different processes and their relation to the subsurface stratigraphy and tectonic setting are not well understood, yet an understanding of these issues is essential as exploration extends into this deep-water area.To address the questions of surficial processes and their connection with deeper structures underlying this continental margin, a three-week cruise was conducted by the USGS in April, 1997 aboard the RV GYRE. The study area focussed on Bryant Canyon, a former submarine canyon, through which turbidity currents transported sands from a shelf-edge delta upslope of the study area to the Bryant Fan on the rise seaward of the base of the slope.  The cruise was divided into two parts.  The first part was devoted to collecting seismic-reflection profiles across parts of the canyon system to define the shallow stratigraphy and to determine the presence and distribution of gas hydrates in this area.  Approximately 555 km of single-channel seismic-reflection data were collected during this first part of the cruise.  A track map showing the locations of the profiles, low-resolution images of the

Scales of seafloor sediment resuspension in the northern Gulf of Mexico

Directory of Open Access Journals (Sweden)

Arne-R. Diercks

2018-04-01

Full Text Available Seafloor sediment resuspension events of different scales and magnitudes and the resulting deep (>1,000 m benthic nepheloid layers were investigated in the northern Gulf of Mexico during Fall 2012 to Summer 2013. Time-series data of size-specific 'in-situ' settling speeds of marine snow in the benthic nepheloid layer (moored flux cameras, particle size distributions (profiling camera, currents (various current meters and stacked time-series flux data (sediment traps were combined to recognize resuspension events ranging from small-scale local, to small-scale far-field to hurricane-scale. One small-scale local resuspension event caused by inertial currents was identified based on local high current speeds (>10 cm s–1 and trap data. Low POC content combined with high lithogenic silica flux at 30 m above bottom (mab compared to the flux at 120 mab, suggested local resuspension reaching 30 mab, but not 120 mab. Another similar event was detected by the changes in particle size distribution and settling speeds of particles in the benthic nepheloid layer. Flux data indicated two other small-scale events, which occurred at some distance, rather than locally. Inertia-driven resuspension of material in shallower areas surrounding the traps presumably transported this material downslope leaving a resuspension signal at 120 mab, but not at 30 mab. The passage of hurricane Isaac left a larger scale resuspension event that lasted a few days and was recorded in both traps. Although hurricanes cause large-scale events readily observable in sediment trap samples, resuspension events small in temporal and spatial scale are not easily recognizable in trapped material as they tend to provide less material and become part of the background signal in the long-term averaged trap samples. We suggest that these small-scale resuspension events, mostly unnoticed in conventional time-series sampling, play an important role in the redistribution and ultimate fate of

Archive of Digital Boomer and CHIRP Seismic Reflection Data Collected During USGS Field Activity 08LCA03 in Lake Panasoffkee, Florida, May 2008

Science.gov (United States)

Harrison, Arnell S.; Dadisman, Shawn V.; McBride, W. Scott; Flocks, James G.; Wiese, Dana S.

2009-01-01

for CHIRP), '##' is a 2-digit number representing a specific track, and 'a' is a letter representing the section of a line if recording was prematurely terminated or rerun for quality or acquisition problems. The boomer plate is an acoustic energy source that consists of capacitors charged to a high voltage and discharged through a transducer in the water. The transducer is towed on a sled floating on the water surface and, when discharged, emits a short acoustic pulse, or shot, which propagates through the water, sediment column, or rock beneath. The acoustic energy is reflected at density boundaries (such as the seafloor, sediment, or rock layers beneath the seafloor), detected by the receiver, and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (for example, 0.5 s) and recorded for specific intervals of time (for example, 100 ms). In this way, a two-dimensional (2-D) vertical profile of the shallow geologic structure beneath the ship track is produced. Figure 1 displays the boomer acquisition geometry. The EdgeTech SB-424 CHIRP system used for this survey has a vertical resolution of 4 - 8 cm, a penetration depth that is usually less than 2 m beneath the seafloor, and uses a signal of continuously varying frequency. The towfish is a sound source and receiver, which is typically towed 2 - 5 m above the seafloor. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the seafloor), detected by a receiver, and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (for example, 0.125 s) and recorded for specific intervals of time (for example, 50 ms); the resulting profile is a two-dimensional vertical image of the shallow geologic structure beneath the ship track. Figure 2 displays the acquisition geometry for the CHIRP system. Refer to table 1 for a summary of acquisition parameters and table 2 for trackline statistics.

Seafloor geological studies of active gas chimneys offshore Egypt (central Nile Fan).

NARCIS (Netherlands)

Dupre, S.; Woodside, J.M.; Foucher, J.-P.; de Lange, G.; Mascle, J.; Boetius, A.; Mastalerz, V.; Stadnitskaia, A.; Ondreas, H.; Huguen, C.; Harmegnies, F.; Gontharet, S.; Loncke, L; Deville, E.; Niemann, H.; Omoregie, E.; Olu-Le Roy, K; Fiala-Medioni, A.; Dahlmann, A.; Caprais, J.-C.; Prinzhofer, A.; Sibuet, M.; Pierre, C.

2007-01-01

Four mud volcanoes of several kilometres diameter named Amon, Osiris, Isis, and North Alex and located above gas chimneys on the Central Nile Deep Sea Fan, were investigated for the first time with the submersible Nautile. One of the objectives was to characterize the seafloor morphology and the

Bathymetry & Geomorphology - A New Seafloor Mapping of the Israeli Exclusive Economic Zone

Science.gov (United States)

Tibor, G.; Hall, J. K.; Kanari, M.; Sade, R. A.; Sade, H.; Amit, G.; Gur-Arie, L.; Ketter, T.

2017-12-01

Recent extensive activities of oil and gas exploration and production companies in the Israeli Exclusive Economic Zone (EEZ) raised the need for an up-to-date baseline mapping of the seafloor to assist policy makers. The baseline mapping focused on bathymetry, geomorphology, geology, biodiversity, infauna and habitat in order to compile a sensitivity map for the Petroleum Commissioner in the Ministry of Energy in the bid for opening the sea to new natural gas and oil explorations. The Israeli EEZ covers an area of 25,950 sq. km. and reaches a maximum water depth of 2,100 m. It is located within the Levantine Basin, a zone of compression and strike-slip tectonics as Africa pushes into Eurasia. These forces operate on a half kilometer thick of Messinian evaporates and over a dozen kilometers of Pliocene and Pleistocene sediments to produce a complex seafloor morphology. The margin is cut by numerous slumps and canyons, while the basin is traversed by deep sea channels emptying into the moat around Eratosthenes Seamount farther north. The bathymetric and geomorphological mapping was done in three phases using Kongsberg and Elac multibeam sonars installed on different research vessels. The last phase (Aug.-Sept., 2016) covering depths from 1,400 to 2,100 m used the Kongsberg EM302 sonar installed on our new governmental research vessel Bat Galim. It has "state of the art" capabilities to map, sample and analyze the water column, seafloor and sub-bottom from water depths of 10m to 7,000 m. These mapping capabilities are unique in our region, the Eastern Mediterranean and the Red Sea, so we hope to promote research collaborations with our neighbors.

Low-Temperature Alteration of the Seafloor: Impacts on Ocean Chemistry

Science.gov (United States)

Coogan, Laurence A.; Gillis, Kathryn M.

2018-05-01

Over 50% of Earth is covered by oceanic crust, the uppermost portion of which is a high-permeability layer of basaltic lavas through which seawater continuously circulates. Fluid flow is driven by heat lost from the oceanic lithosphere; the global fluid flux is dependent on plate creation rates and the thickness and distribution of overlying sediment, which acts as a low-permeability layer impeding seawater access to the crust. Fluid-rock reactions in the crust, and global chemical fluxes, depend on the average temperature in the aquifer, the fluid flux, and the composition of seawater. The average temperature in the aquifer depends largely on bottom water temperature and, to a lesser extent, on the average seafloor sediment thickness. Feedbacks between off-axis chemical fluxes and their controls may play an important role in modulating ocean chemistry and planetary climate on long timescales, but more work is needed to quantify these feedbacks.

Model-based seafloor characterization employing multi-beam angular backscatter data - A comparative study with dual-frequency single beam

Digital Repository Service at National Institute of Oceanography (India)

Haris, K.; Chakraborty, B.; De, C.; Desai, R.G.P.; Fernandes, W.A.

developed by Jackson et al., 3 has been extensively applied to this approach. 4-6 In this work, characterization of seafloor sediments is achieved by employing a MB system (Simrad EM 1002) operable at 95 kHz. Here, the seafloor parameters are estimated... pre-formed beams data were acquired during two cruises using the EM1002 echo-sounding system installed onboard CRV Sagar Sukti (cruises: SASU-108 and 134). 13,14 Besides calculating the angular backscatter strengths using the MB system, the modeled...

Assessment of the Influence of Dredge Spoil Dumping on the Seafloor Geological Integrity

Directory of Open Access Journals (Sweden)

Joonas J. Virtasalo

2018-04-01

Full Text Available The European Marine Strategy Framework Directive requires the development of suitable indicators for regular reporting on the environmental state and achievement of a good environmental status of EU's marine waters by 2020. The development of indicators for determining seafloor integrity and its possible disturbance by human activities have so far largely ignored the geological properties of seafloor. This paper presents a study of Vuosaari and Uusikaupunki-D offshore dumping sites in Finland, the northern Baltic Sea. Full coverage multibeam bathymetry and relative backscatter data, and a number of sediment cores were collected over the sites. The areas covered by dumped dredge spoil stand out in the multibeam images because of their irregular surface and elevated backscatter. The short gravity cores were studied for lithology, and in 1-cm slices for 137Cs activity, organic content, and grain size distribution. The dumped material is represented in the cores by the gravelly mud lithofacies with massive texture and angular coarse particles. The dumped material is coarser, less sorted and has higher kurtosis compared to natural sediment due to the admixing of blasted rock during the dredging activities, and limited sorting during fall through the water column upon dumping. Dispersed dredge spoil, which was suspended in the water column during the dumping activities or reworked from the dumped material mounds and redistributed along the seafloor soon thereafter, was deposited over a wide area as a thin layer that is not necessarily readily identifiable by visual inspection in the cores. Cesium activity helped distinguish the dumped material from the 137Cs-enriched natural sediments deposited after the 1986 Chernobyl disaster. Considering that the dumped material at many of the coring sites in the Vuosaari dumping area is covered by natural sediment, it probably is largely stable. In contrast, dumped material at the shallower Uusikaupunki-D site has

EMSO: European Multidisciplinary Seafloor Observatory

Science.gov (United States)

Favali, P.; Partnership, Emso

2009-04-01

EMSO, a Research Infrastructure listed within ESFRI (European Strategy Forum on Research Infrastructures) Roadmap), is the European-scale network of multidisciplinary seafloor observatories from the Arctic to the Black Sea with the scientific objective of long-term real-time monitoring of processes related to geosphere/biosphere/hydrosphere interactions. EMSO will enhance our understanding of processes through long time series appropriate to the scale of the phenomena, constituting the new frontier of studying Earth interior, deep-sea biology and chemistry and ocean processes. EMSO will reply also to the need expressed in the frame of GMES (Global Monitoring for Environment and Security) to develop a marine segment integrated in the in situ and satellite global monitoring system. The EMSO development relays upon the synergy between the scientific community and the industry to improve the European competitiveness with respect to countries like USA/Canada, NEPTUNE, VENUS and MARS projects, Taiwan, MACHO project, and Japan, DONET project. In Europe the development of an underwater network is based on previous EU-funded projects since early '90, and presently supported by EU initiatives. The EMSO infrastructure will constitute the extension to the sea of the land-based networks. Examples of data recorded by seafloor observatories will be presented. EMSO is presently at the stage of Preparatory Phase (PP), funded in the EC FP7 Capacities Programme. The project has started in April 2008 and will last 4 years with the participation of 12 Institutions representing 12 countries. EMSO potential will be significantly increased also with the interaction with other Research Infrastructures addressed to Earth Science. 2. IFREMER-Institut Français de Recherche pour l'exploitation de la mer (France, ref. Roland Person); KDM-Konsortium Deutsche Meeresforschung e.V. (Germany, ref. Christoph Waldmann); IMI-Irish Marine Institute (Ireland, ref. Michael Gillooly); UTM-CSIC-Unidad de

More losers than winners in a century of future Southern Ocean seafloor warming

Science.gov (United States)

Griffiths, Huw J.; Meijers, Andrew J. S.; Bracegirdle, Thomas J.

2017-10-01

The waters of the Southern Ocean are projected to warm over the coming century, with potential adverse consequences for native cold-adapted organisms. Warming waters have caused temperate marine species to shift their ranges poleward. The seafloor animals of the Southern Ocean shelf have long been isolated by the deep ocean surrounding Antarctica and the Antarctic Circumpolar Current, with little scope for southward migration. How these largely endemic species will react to future projected warming is unknown. By considering 963 invertebrate species, we show that within the current century, warming temperatures alone are unlikely to result in wholesale extinction or invasion affecting Antarctic seafloor life. However, 79% of Antarctica's endemic species do face a significant reduction in suitable temperature habitat (an average 12% reduction). Our findings highlight the species and regions most likely to respond significantly (negatively and positively) to warming and have important implications for future management of the region.

Paleothermal structure of the Nankai inner accretionary wedge estimated from vitrinite reflectance of cuttings

Science.gov (United States)

Fukuchi, Rina; Yamaguchi, Asuka; Yamamoto, Yuzuru; Ashi, Juichiro

2017-08-01

The paleothermal structure and tectonic evolution of an accretionary prism is basic information for understanding subduction zone seismogenesis. To evaluate the entire paleotemperature profile of the Integrated Ocean Drilling Program (IODP) Site C0002 located in the off-Kumano region of the Nankai Trough and penetrate the inner accretionary wedge down to 3058.5 m below the seafloor (mbsf), we performed a vitrinite reflectance analysis for cuttings and core samples during IODP expeditions 338 and 348: Nankai Trough seismogenic zone experiment. Although vitrinite reflectance values (Ro) tend to increase with depth, two reversals of these values suggested the existence of thrust fault zones with sufficient displacements to offset the paleothermal structure. The estimated maximum paleotemperatures are 42-70°C at 1200-1300 mbsf, 44-100°C at 1600-2400 mbsf, and 56-115°C at 2600-3000 mbsf, respectively. These temperatures roughly coincide with estimated modern temperatures; however, at a smaller scale, the reconstructed partial paleogeothermal gradient (˜60-150°C/km) recorded at the hanging- and footwall of the presumed thrust fault zone is higher than the modern geothermal gradient (˜30-40°C/km). This high paleogeothermal gradient was possibly obtained prior to subduction, reflecting the large heat flow of the young Philippine Sea Plate.

Coupled seismoacoustic modes on the seafloor

Science.gov (United States)

Butler, Rhett; Lomnitz, Cinna

2002-05-01

Wave-to-wave coupling arises when an acoustic pulse selects a Rayleigh mode of the same speed and both travel together swapping energy across an interface [Ewing et al., 1957]. A distinctive signal is observed at the Hawaii-2 Observatory for purely oceanic paths from earthquakes on the Blanco and Mendocino Fracture Zones, off the coast of North America. The signal appears to be a composite of undispersed higher Rayleigh modes propagating along the ocean floor both in the sediments and in the water. The new coupled modes are identified by their frequency composition and their phase and group velocities. Seismoacoustic coupling at the seafloor is conditioned on (a) the presence of a low-velocity interface at the ocean floor, and (b) the wavelength of the Rayleigh component being shorter than the depth of the water layer.

Further Interpretation of the Relationship between Faunal Community and Seafloor Geology at Southern Hydrate Ridge, Cascadia Margin: Exploring Machine Learning

Science.gov (United States)

Bigham, K.; Kelley, D. S.; Marburg, A.; Delaney, J. R.

2017-12-01

In 2011, high-resolution, georeferenced photomoasiacs were taken of Einstein's Grotto, an active methane hydrate seep within the field at Southern Hydrate Ridge located 90 km west of Newport, Oregon at a water depth of 800 m. Methods used to analyze the relationships between the seep site, seafloor geology, and the spatial distribution and abundances of microbial and macrofaunal communities at Einstein's Grotto were expanded to three other sites over the 200 by 300 m active seep field. These seeps were documented in the same survey in 2011 conducted by the remotely operated vehicle ROPOS on board the R/V Thompson. Over 10,000 high definition images allowed for the further quantification and characterization of the diversity and structure of the faunal community at this seep field. The new results support the study's initial findings of high variability in the distribution and abundance of seep organisms across the field, with correlation to seafloor geology. The manual classification of organisms was also used to train a series of convolutional neural networks in Nvidia DIGITS and Google Tensorflow environments for automated identification. The developed networks proved highly accurate at background/non-background segmentation ( 96%) and slightly less reliable for fauna identification ( 89%). This study provides a baseline for the faunal community at the Southern Hydrate Ridge methane seeps and a more efficient computer assisted method for processing follow on studies.

NEMO-SN-1 the first 'real-time' seafloor observatory of ESONET

International Nuclear Information System (INIS)

Favali, Paolo; Beranzoli, Laura; D'Anna, Giuseppe; Gasparoni, Francesco; Gerber, Hans W.

2006-01-01

The fruitful collaboration between Italian Research Institutions, particularly Istituto Nazionale di Fisica Nucleare (INFN) and Istituto Nazionale di Geofisica e Vulcanologia (INGV) together with Marine Engineering Companies, led to the development of NEMO-SN-1, the first European cabled seafloor multiparameter observatory. This observatory, deployed at 2060 m w.d. about 12 miles off-shore the Eastern coasts of Sicily (Southern Italy), is in real-time acquisition since January 2005 and addressed to different set of measurements: geophysical and oceanographic. In particular the SN-1 seismological data are integrated in the INGV land-based national seismic network, and they arrive in real-time to the Operative Centre in Rome. In the European Commission (EC) European Seafloor Observatory NETwork (ESONET) project, in connection to the Global Monitoring for Environment and Security (GMES) action plan, the NEMO-SN-1 site has been proposed as an European key area, both for its intrinsic importance for geo-hazards and for the availability of infrastructure as a stepwise development in GMES program. Presently, NEMO-SN-1 is the only ESONET site operative. The paper gives a description of SN-1 observatory with examples of data

Analysis of calibrated seafloor backscatter for habitat classification methodology and case study of 158 spots in the Bay of Biscay and Celtic Sea

Science.gov (United States)

Fezzani, Ridha; Berger, Laurent

2018-06-01

An automated signal-based method was developed in order to analyse the seafloor backscatter data logged by calibrated multibeam echosounder. The processing consists first in the clustering of each survey sub-area into a small number of homogeneous sediment types, based on the backscatter average level at one or several incidence angles. Second, it uses their local average angular response to extract discriminant descriptors, obtained by fitting the field data to the Generic Seafloor Acoustic Backscatter parametric model. Third, the descriptors are used for seafloor type classification. The method was tested on the multi-year data recorded by a calibrated 90-kHz Simrad ME70 multibeam sonar operated in the Bay of Biscay, France and Celtic Sea, Ireland. It was applied for seafloor-type classification into 12 classes, to a dataset of 158 spots surveyed for demersal and benthic fauna study and monitoring. Qualitative analyses and classified clusters using extracted parameters show a good discriminatory potential, indicating the robustness of this approach.

Methods for measuring the spectral reflectivity of advanced materials at high temperature

International Nuclear Information System (INIS)

Salikhov, T.P.; Kan, V.V.

1993-01-01

For investigation in the domain of advanced materials as well as for new technologies there is an urgent need for knowledge of the spectral reflectivity of the materials specially at high temperatures. However the methods available are mostly intended for measuring the model materials with specular or diffuse reflection surface. This is not quite correct since advanced materials have mixed specular diffuse reflection surfaces. New methods for reflectivity measurements of materials in the visible, near and middle infrared range at high temperature, regardless of surface texture, have been developed. The advantages of the methods proposed are as flows: (a) the facility of performing the reflectivity measurements for materials with mixed specular diffuse reflectance; (b) wide spectral range 0,38-8 micro m; (c) wide temperature range 300-3000 K; (d) high accuracy and rapid measurements. The methods are based on the following principals (i) Diffuse irradiation of the sample surface and the use of Helkholtz reciprocity principle to determine the directional hemispherical reflectivity ii) Pulse polychromatic probing of the sample by additional light source. The first principle excludes the influence of the angular reflection distribution of sample surface on data obtained. The second principle gives the possibility of simultaneous measurements of the reflectivity. The second principle gives the possibility of simultaneous measurements of the reflectivity in wide spectral range. On the basis of these principles for high temperature reflectometers have been developed and discussed here. (author)

A seafloor electromagnetic receiver for marine magnetotellurics and marine controlled-source electromagnetic sounding

Science.gov (United States)

Chen, Kai; Wei, Wen-Bo; Deng, Ming; Wu, Zhong-Liang; Yu, Gang

2015-09-01

In planning and executing marine controlled-source electromagnetic methods, seafloor electromagnetic receivers must overcome the problems of noise, clock drift, and power consumption. To design a receiver that performs well and overcomes the abovementioned problems, we performed forward modeling of the E-field abnormal response and established the receiver's characteristics. We describe the design optimization and the properties of each component, that is, low-noise induction coil sensor, low-noise Ag/AgCl electrode, low-noise chopper amplifier, digital temperature-compensated crystal oscillator module, acoustic telemetry modem, and burn wire system. Finally, we discuss the results of onshore and offshore field tests to show the effectiveness of the developed seafloor electromagnetic receiver and its performance: typical E-field noise of 0.12 nV/m/rt(Hz) at 0.5 Hz, dynamic range higher than 120 dB, clock drift lower than 1 ms/day, and continuous operation of at least 21 days.

Human activities on the deep seafloor in the North East Atlantic: an assessment of spatial extent.

Directory of Open Access Journals (Sweden)

Angela R Benn

Full Text Available BACKGROUND: Environmental impacts of human activities on the deep seafloor are of increasing concern. While activities within waters shallower than 200 m have been the focus of previous assessments of anthropogenic impacts, no study has quantified the extent of individual activities or determined the relative severity of each type of impact in the deep sea. METHODOLOGY: The OSPAR maritime area of the North East Atlantic was chosen for the study because it is considered to be one of the most heavily impacted by human activities. In addition, it was assumed data would be accessible and comprehensive. Using the available data we map and estimate the spatial extent of five major human activities in the North East Atlantic that impact the deep seafloor: submarine communication cables, marine scientific research, oil and gas industry, bottom trawling and the historical dumping of radioactive waste, munitions and chemical weapons. It was not possible to map military activities. The extent of each activity has been quantified for a single year, 2005. PRINCIPAL FINDINGS: Human activities on the deep seafloor of the OSPAR area of the North Atlantic are significant but their footprints vary. Some activities have an immediate impact after which seafloor communities could re-establish, while others can continue to make an impact for many years and the impact could extend far beyond the physical disturbance. The spatial extent of waste disposal, telecommunication cables, the hydrocarbon industry and marine research activities is relatively small. The extent of bottom trawling is very significant and, even on the lowest possible estimates, is an order of magnitude greater than the total extent of all the other activities. CONCLUSIONS/SIGNIFICANCE: To meet future ecosystem-based management and governance objectives for the deep sea significant improvements are required in data collection and availability as well as a greater awareness of the relative impact of

Temporal Characterization of Hydrates System Dynamics beneath Seafloor Mounds. Integrating Time-Lapse Electrical Resistivity Methods and In Situ Observations of Multiple Oceanographic Parameters

Energy Technology Data Exchange (ETDEWEB)

Lutken, Carol [Univ. of Mississippi, Oxford, MS (United States); Macelloni, Leonardo [Univ. of Mississippi, Oxford, MS (United States); D' Emidio, Marco [Univ. of Mississippi, Oxford, MS (United States); Dunbar, John [Univ. of Mississippi, Oxford, MS (United States); Higley, Paul [Univ. of Mississippi, Oxford, MS (United States)

2015-01-31

This study was designed to investigate temporal variations in hydrate system dynamics by measuring changes in volumes of hydrate beneath hydrate-bearing mounds on the continental slope of the northern Gulf of Mexico, the landward extreme of hydrate occurrence in this region. Direct Current Resistivity (DCR) measurements were made contemporaneously with measurements of oceanographic parameters at Woolsey Mound, a carbonate-hydrate complex on the mid-continental slope, where formation and dissociation of hydrates are most vulnerable to variations in oceanographic parameters affected by climate change, and where changes in hydrate stability can readily translate to loss of seafloor stability, impacts to benthic ecosystems, and venting of greenhouse gases to the water-column, and eventually, the atmosphere. We focused our study on hydrate within seafloor mounds because the structurally-focused methane flux at these sites likely causes hydrate formation and dissociation processes to occur at higher rates than at sites where the methane flux is less concentrated and we wanted to maximize our chances of witnessing association/dissociation of hydrates. We selected a particularly well-studied hydrate-bearing seafloor mound near the landward extent of the hydrate stability zone, Woolsey Mound (MC118). This mid-slope site has been studied extensively and the project was able to leverage considerable resources from the team’s research experience at MC118. The site exhibits seafloor features associated with gas expulsion, hydrates have been documented at the seafloor, and changes in the outcropping hydrates have been documented, photographically, to have occurred over a period of months. We conducted observatory-based, in situ measurements to 1) characterize, geophysically, the sub-bottom distribution of hydrate and its temporal variability, and 2) contemporaneously record relevant environmental parameters (temperature, pressure, salinity, turbidity, bottom currents) to

Long-Term Seafloor Electromagnetic Observation in the Northwest Pacific May Detect the Vector Geomagnetic Secular Variation

Directory of Open Access Journals (Sweden)

H Toh

2010-03-01

Full Text Available Sea Floor ElectroMagnetic Stations (SFEMSs are now operating at two deep seafloor sites called the 'WPB' and the 'NWP' in the West Philippine Basin and the Northwest Pacific Basin, respectively. One of the main objectives of the SFEMSs is to detect the geomagnetic secular variations on the deep seafloor where long-term geomagnetic observations have not so far been achieved. SFEMSs can measure the absolute geomagnetic total force as well as the geomagnetic vector field with precise attitude monitoring systems. The vector geomagnetic time-series that was observed for more than 5 years revealed that the westward drift of the equatorial dipole dominates in the geomagnetic secular variation at the NWP.

KIGAM Seafloor Observation System (KISOS) for the baseline study in monitoring of gas hydrate test production in the Ulleung Basin, Korea

Science.gov (United States)

Lee, Sung-rock; Chun, Jong-hwa

2013-04-01

For the baseline study in the monitoring gas hydrate test production in the Ulleung Basin, Korea Institute of Geoscience and Mineral Resources (KIGAM) has developed the KIGAM Seafloor Observation System (KISOS) for seafloor exploration using unmanned remotely operated vehicle connected with a ship by a cable. The KISOS consists of a transponder of an acoustic positioning system (USBL), a bottom finding pinger, still camera, video camera, water sampler, and measuring devices (methane, oxygen, CTD, and turbidity sensors) mounted on the unmanned ROV, and a sediment collecting device collecting sediment on the seafloor. It is very important to monitoring the environmental risks (gas leakage and production water/drilling mud discharge) which may be occurred during the gas hydrate test production drilling. The KISOS will be applied to solely conduct baseline study with the KIGAM seafloor monitoring system (KIMOS) of the Korean gas hydrate program in the future. The large scale of environmental monitoring program includes the environmental impact assessment such as seafloor disturbance and subsidence, detection of methane gas leakage around well and cold seep, methane bubbles and dissolved methane, change of marine environments, chemical factor variation of water column and seabed, diffusion of drilling mud and production water, and biological factors of biodiversity and marine habitats before and after drilling test well and nearby areas. The design of the baseline survey will be determined based on the result of SIMAP simulation in 2013. The baseline survey will be performed to provide the gas leakage and production water/drilling mud discharge before and after gas hydrate test production. The field data of the baseline study will be evaluated by the simulation and verification of SIMAP simulator in 2014. In the presentation, the authors would like introduce the configuration of KISOS and applicability to the seafloor observation for the gas hydrate test production in

Reflection measurement of waveguide-injected high-power microwave antennas.

Science.gov (United States)

Yuan, Chengwei; Peng, Shengren; Shu, Ting; Zhang, Qiang; Zhao, Xuelong

2015-12-01

A method for reflection measurements of High-power Microwave (HPM) antennas excited with overmoded waveguides is proposed and studied systemically. In theory, principle of the method is proposed and the data processing formulas are developed. In simulations, a horn antenna excited by a TE11 mode exciter is examined and its reflection is calculated by CST Microwave Studio and by the method proposed in this article, respectively. In experiments, reflection measurements of two HPM antennas are conducted, and the measured results are well consistent with the theoretical expectations.

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

High resolution multibeam and hydrodynamic datasets of tidal channels and inlets of the Venice Lagoon

Science.gov (United States)

Madricardo, Fantina; Foglini, Federica; Kruss, Aleksandra; Ferrarin, Christian; Pizzeghello, Nicola Marco; Murri, Chiara; Rossi, Monica; Bajo, Marco; Bellafiore, Debora; Campiani, Elisabetta; Fogarin, Stefano; Grande, Valentina; Janowski, Lukasz; Keppel, Erica; Leidi, Elisa; Lorenzetti, Giuliano; Maicu, Francesco; Maselli, Vittorio; Mercorella, Alessandra; Montereale Gavazzi, Giacomo; Minuzzo, Tiziano; Pellegrini, Claudio; Petrizzo, Antonio; Prampolini, Mariacristina; Remia, Alessandro; Rizzetto, Federica; Rovere, Marzia; Sarretta, Alessandro; Sigovini, Marco; Sinapi, Luigi; Umgiesser, Georg; Trincardi, Fabio

2017-09-01

Tidal channels are crucial for the functioning of wetlands, though their morphological properties, which are relevant for seafloor habitats and flow, have been understudied so far. Here, we release a dataset composed of Digital Terrain Models (DTMs) extracted from a total of 2,500 linear kilometres of high-resolution multibeam echosounder (MBES) data collected in 2013 covering the entire network of tidal channels and inlets of the Venice Lagoon, Italy. The dataset comprises also the backscatter (BS) data, which reflect the acoustic properties of the seafloor, and the tidal current fields simulated by means of a high-resolution three-dimensional unstructured hydrodynamic model. The DTMs and the current fields help define how morphological and benthic properties of tidal channels are affected by the action of currents. These data are of potential broad interest not only to geomorphologists, oceanographers and ecologists studying the morphology, hydrodynamics, sediment transport and benthic habitats of tidal environments, but also to coastal engineers and stakeholders for cost-effective monitoring and sustainable management of this peculiar shallow coastal system.

New insights into the geodiversity of the southeast Indian Ocean seafloor revealed by Malaysia Airlines flight MH370 search data

Science.gov (United States)

Picard, K.; Brooke, B. B.; Harris, P. T.; Siwabessy, J. P. W.; Coffin, M. F.; Tran, M.; Spinoccia, M.; Weales, J.; Macmillan-Lawler, M.; Sullivan, J.

2017-12-01

A large multibeam echo sounder (MBES) dataset (710, 000 km2, inclusive of transit data) was acquired in the SE Indian Ocean to assist the search for Malaysia Airlines Flight 370 (MH370). Here, we present the results of a geomorphic analysis of this new data and compare with the Global Seafloor Geomorphic Features Map (GSFM) that is based on coarser resolution satellite-derived bathymetry data. The analyses show that abyssal plains and basins are significantly more rugged than their representation in the GSFM, with a 20% increase in the extent of hills and mountains. The new model also reveals four times more seamounts than presented in the GSFM, suggesting a greater number of these features than previously estimated for the broader region and indeed globally. This is important considering the potential ecological significance of these high-relief structures. Analyses of the new data also enabled knolls, fans, valleys, canyons, troughs and holes to be identified, doubling the number of discrete features mapped and revealing the true geodiversity of the deep ocean in this area. This high-resolution mapping of the seafloor also provides new insights into the geological evolution of the region, both in terms of structural, tectonic, and sedimentary processes. For example, sub-parallel ridges extend over approximately 20% of the area mapped and their form and alignment provide valuable insight into Southeast Indian Ridge seafloor spreading processes. Rifting is recorded along the Broken Ridge - Diamantina Escarpment, with rift blocks and well-bedded sedimentary bedrock exposures discernible down to 2,400 m water depth. Ocean floor sedimentary processes are represented in sediment mass transport features, especially along and north of Broken Ridge, and pockmarks (the finest-scale features mapped) south of Diamantina Trench. The new MBES data highlight the complexity of the search area and serve to demonstrate how little we know about the 85-90% of the ocean floor that

Can neap-spring tidal cycles modulate biogeochemical fluxes in the abyssal near-seafloor water column?

Science.gov (United States)

Turnewitsch, Robert; Dale, Andrew; Lahajnar, Niko; Lampitt, Richard S.; Sakamoto, Kei

2017-05-01

Before particulate matter that settles as 'primary flux' from the interior ocean is deposited into deep-sea sediments it has to traverse the benthic boundary layer (BBL) that is likely to cover almost all parts of the seafloor in the deep seas. Fluid dynamics in the BBL differ vastly from fluid dynamics in the overlying water column and, consequently, have the potential to lead to quantitative and compositional changes between primary and depositional fluxes. Despite this potential and the likely global relevance very little is known about mechanistic and quantitative aspects of the controlling processes. Here, results are presented for a sediment-trap time-series study that was conducted on the Porcupine Abyssal Plain in the abyssal Northeast Atlantic, with traps deployed at 2, 40 and 569 m above bottom (mab). The two bottommost traps were situated within the BBL-affected part of the water column. The time series captured 3 neap and 4 spring tides and the arrival of fresh settling material originating from a surface-ocean bloom. In the trap-collected material, total particulate matter (TPM), particulate inorganic carbon (PIC), biogenic silica (BSi), particulate organic carbon (POC), particulate nitrogen (PN), total hydrolysable amino acids (AA), hexosamines (HA) and lithogenic material (LM) were determined. The biogeochemical results are presented within the context of time series of measured currents (at 15 mab) and turbidity (at 1 mab). The main outcome is evidence for an effect of neap/spring tidal oscillations on particulate-matter dynamics in BBL-affected waters in the deep sea. Based on the frequency-decomposed current measurements and numerical modelling of BBL fluid dynamics, it is concluded that the neap/spring tidal oscillations of particulate-matter dynamics are less likely due to temporally varying total free-stream current speeds and more likely due to temporally and vertically varying turbulence intensities that result from the temporally varying

Angle-resolved reflection spectroscopy of high-quality PMMA opal crystal

Science.gov (United States)

Nemtsev, Ivan V.; Tambasov, Igor A.; Ivanenko, Alexander A.; Zyryanov, Victor Ya.

2018-02-01

PMMA opal crystal was prepared by a simple hybrid method, which includes sedimentation, meniscus formation and evaporation. We investigated three surfaces of this crystal by angle-resolved reflective light spectroscopy and SEM study. The angle-resolved reflective measurements were carried out in the 400-1100 nm range. We have determined the high-quality ordered surface of the crystal region. Narrow particle size distribution of the surface has been revealed. The average particle diameter obtained with SEM was nearly 361 nm. The most interesting result was that reflectivity of the surface turned out up to 98% at normal light incidence. Using a fit of dependences of the maximum reflectivity wavelength from an angle based on the Bragg-Snell law, the wavelength of maximum 0° reflectivity, the particle diameter and the fill factor have been determined. For the best surface maximum reflectivity wavelength of a 0° angle was estimated to be 869 nm. The particle diameter and fill factor were calculated as 372 nm and 0.8715, respectively. The diameter obtained by fitting is in excellent agreement with the particle diameter obtained with SEM. The reflectivity maximum is assumed to increase significantly when increasing the fill factor. We believe that using our simple approach to manufacture PMMA opal crystals will significantly increase the fabrication of high-quality photonic crystal templates and thin films.

Identification of seafloor provinces - specific applications at the deep-sea Hà ¥kon Mosby Mud Volcano and the North Sea

OpenAIRE

Jerosch, Kerstin

2006-01-01

The identification of distinct provinces is currently an emphasis of marine research geosciences. Typological approaches for the Hà ¥kon Mosby Mud Volcano and the North Sea combining geological, biological and chemical properties are accomplished by geostatistical, multivariate statistical, and GIS techniques. Besides scientific needs seafloor provinces support management decisions related to upcoming economic use of the seafloor and bear up to model spatio-temporal connections and changes o...

Semi-automated high-efficiency reflectivity chamber for vacuum UV measurements

Science.gov (United States)

Wiley, James; Fleming, Brian; Renninger, Nicholas; Egan, Arika

2017-08-01

This paper presents the design and theory of operation for a semi-automated reflectivity chamber for ultraviolet optimized optics. A graphical user interface designed in LabVIEW controls the stages, interfaces with the detector system, takes semi-autonomous measurements, and monitors the system in case of error. Samples and an optical photodiode sit on an optics plate mounted to a rotation stage in the middle of the vacuum chamber. The optics plate rotates the samples and diode between an incident and reflected position to measure the absolute reflectivity of the samples at wavelengths limited by the monochromator operational bandpass of 70 nm to 550 nm. A collimating parabolic mirror on a fine steering tip-tilt motor enables beam steering for detector peak-ups. This chamber is designed to take measurements rapidly and with minimal oversight, increasing lab efficiency for high cadence and high accuracy vacuum UV reflectivity measurements.

Harnessing Multiple Internal Reflections to Design Highly Absorptive Acoustic Metasurfaces

Science.gov (United States)

Shen, Chen; Cummer, Steven A.

2018-05-01

The rapid development of metasurfaces has enabled numerous intriguing applications with acoustically thin sheets. Here we report the theory and experimental realization of a nonresonant sound-absorbing strategy using metasurfaces by harnessing multiple internal reflections. We theoretically and numerically show that the higher-order diffraction of thin gradient-index metasurfaces is tied to multiple internal reflections inside the unit cells. Highly absorbing acoustic metasurfaces can be realized by enforcing multiple internal reflections together with a small amount of loss. A reflective gradient-index acoustic metasurface is designed based on the theory, and we further experimentally verify the performance using a three-dimensional printed prototype. Measurements show over 99% energy absorption at the peak frequency and a 95% energy absorption bandwidth of around 600 Hz. The proposed mechanism provides an alternative route for sound absorption without the necessity of high absorption of the individual unit cells.

Repeat Mapping in Upper Monterey Canyon Captures the Effect of Sediment Transport Events of Known Magnitude and Duration on the Seafloor Morphology

Science.gov (United States)

Lundsten, E. M.; Anderson, K.; Caress, D. W.; Thomas, H. J.; Paull, C. K.; Maier, K. L.; Gwiazda, R.; Gales, J. A.; Talling, P.; Xu, J.; Parsons, D. R.

2017-12-01

As part of a multi-institution submarine canyon study, the Coordinated Canyon Experiment (CCE), high-resolution multibeam bathymetric surveys of the floor of Monterey Canyon, offshore California, were conducted to capture the changes in seafloor morphology directly related to the passage of sediment density flows documented during the study. The goals of this study were to monitor the passage of sediment density flows as they move through the axis of a submarine canyon in order to understand the velocity structure of these flows and to document the associated changes in seafloor morphology and the resultant deposits. The CCE consisted of an array of moorings and sensors deployed on the canyon floor during the 18-month period between October 2015 and April 2017. In addition, a mapping AUV (Autonomous Underwater Vehicle) repeatedly surveyed two sites along the canyon during the study. Differencing the repeat grids quantified the morphological changes directly related to specifically documented, individual flow events. The AUV carried a Reson 7125 multibeam echosounder (vertical precision of 0.15 m and horizontal resolution of 1.0 m). An inertial navigation system combined with a Doppler velocity logger allowed the AUV to fly pre-programmed grids at 3 knots while maintaining an altitude of 50 m above the seafloor and obtain a nominal line spacing of 130 m. The axial channel between 200 and 540 m water depth was surveyed six times. At least fifteen density flow events were captured by the array of CCE instruments within this AUV survey area. These events caused moorings as well as several large and small instruments to move down canyon significant distances at least 30 times. Difference grids show the canyon experienced erosion and deposition of up to +/- 3 m between surveys. The pair of surveys that straddle a sediment transport event on December 1, 2015 show the seafloor was altered only down to 420 m water depth, consistent with the observations on the CCE

Analysis of seafloor change at Breton Island, Gosier Shoals, and surrounding waters, 1869–2014, Breton National Wildlife Refuge, Louisiana

Science.gov (United States)

Flocks, James G.; Terrano, Joseph F.

2016-08-01

Characterizing bathymetric change in coastal environments is an important component in understanding shoreline evolution, especially along barrier island platforms. Bathymetric change is a function of the regional sediment budget, long-term wave and current patterns, and episodic impact from high-energy events such as storms. Human modifications may also cause changes in seafloor elevation. This study, conducted by the U.S. Geological Survey in collaboration with the U.S. Fish and Wildlife Service, evaluates bathymetric and volumetric change and sediment characteristics around Breton Island and Gosier Shoals located offshore of the Mississippi River Delta in Louisiana. This area has been affected by significant storm events such as Hurricane Katrina in 2005. Sedimentation patterns at Breton Island and offshore have also been modified by the excavation of a shipping channel north of the island. Four time periods are considered that encompass these episodes and include long-term change and short-term storm recovery: 1869–2014, 1869–1920, 1920–2014, and 2007–2014. Finally, sediment characteristics are reported in the context of seafloor elevation.

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

Virtual Seafloor Reduces Internal Wave Generation by Tidal Flow

Science.gov (United States)

Zhang, Likun; Swinney, Harry L.

2014-03-01

Our numerical simulations of tidal flow of a stratified fluid over periodic knife-edge ridges and random topography reveal that the time-averaged tidal energy converted into internal gravity wave radiation arises only from the section of a ridge above a virtual seafloor. The average radiated power is approximated by the power predicted by linear theory if the height of the ridge is measured relative to the virtual floor. The concept of a virtual floor can extend the applicability of linear theory to global predictions of the conversion of tidal energy into internal wave energy in the oceans.

The high resolution shear wave seismic reflection technique

International Nuclear Information System (INIS)

Johnson, W.J.; Clark, J.C.

1991-04-01

This report presents the state-of-the-art of the high resolution S-wave reflection technique. Published and unpublished literature has been reviewed and discussions have been held with experts. Result is to confirm that the proposed theoretical and practical basis for identifying aquifer systems using both P- and S-wave reflections is sound. Knowledge of S-wave velocity and P-wave velocity is a powerful tool for assessing the fluid characteristics of subsurface layers. Material properties and lateral changes in material properties such as change from clay to sand, can be inferred from careful dual evaluation of P and S-wave records. The high resolution S-wave reflection technique has seen its greatest application to date as part of geotechnical studies for building foundations in the Far East. Information from this type of study has been evaluated and will be incorporated in field studies. In particular, useful information regarding S-wave sources, noise suppression and recording procedures will be incorporated within the field studies. Case histories indicate that the best type of site for demonstrating the power of the high resolution S-wave technique will be in unconsolidated soil without excessive structural complexities. More complex sites can form the basis for subsequent research after the basic principles of the technique can be established under relatively uncomplicated conditions

Effect of thermal non-equilibrium, seafloor topography and fluid advection on BSR-derived geothermal gradient

Digital Repository Service at National Institute of Oceanography (India)

Mandal, R.; Dewangan, P.; Ramprasad, T.; Kumar, B.J.P.; Vishwanath, K.

The seafloor and bottom simulating reflectors (BSRs) are interpreted from the 3D seismic data acquired in Krishna–Godavari (KG) offshore basin in the vicinity of sites drilled/cored during National Gas Hydrate Program (NGHP) Expedition-01...

Using bathymetry and reflective seismic profiles to tests a suspected link between melt flux and cumulative fault heave at mid-ocean ridges

Science.gov (United States)

Haughton, G.; Murton, B. J.; Le Bas, T.; Henstock, T.

2017-12-01

The interplay between magma supply and spreading rate is believed to play a major role in determining large scale seafloor morphology. Here we use bathymetry to test this relationship in areas with similar spreading rates and differing magma supplies. By using open source bathymetry data we have developed a repeatable, automated method for categorising seafloor cumulative fault heave and then attempt to identify the controlling variables. We measure the total apparent fault heave along axis and off-axis at 29°N and 60°N on the Mid-Atlantic Ridge then compare this to proxies for deformation and magma supply. Two approaches are adopted for identifying faults: one using bathymetry and the other spreading-parallel seismic reflection data. The first re-examines the orthogonally spreading Broken Spur segment (26°N) spreading at 23 mm yr-1 (full rate). The other examines the Reykjanes Ridge (60°N) spreading obliquely at 21 mm yr-1 (full rate), which may be influenced by the Icelandic hotspot. Each have contrasting residual depth and structure, with the former being typical of slow spreading ridges, with marked axial valleys, whereas the latter is more typical of fast spreading ridge morphology, with smooth axial rise. We find that high total heave (indicating high tectonic spreading) on the Broken Spur segment does not correlate with high mantle Bouguer anomalies (indicating thin crust and low melt flux). From this we hypothesise that total heave on the large scale at the Broken Spur segment is not controlled by crustal thickness or melt supply. At the Raykjanes Ridge, V-shaped ridges have thicker crust (measured seismically) which converge south of Iceland. These are thought to reflect transient (every 4-6 Myrs) pulses of hot mantle radiating away from the Iceland plume. We find ridge-symmetrical variation in fault heave but with a lower frequency (6-8 Myrs) and longer wavelength (3-7 Myrs) than the V-shaped ridges. Our analysis shows that plume pulses do not

Application of artificial neural networks to segmentation and classification of topographic profiles of ridge-flank seafloor

Digital Repository Service at National Institute of Oceanography (India)

Chakraborty, B.; Lourenco, E.; Kodagali, V.N.; Baracho, J.

In this paper, we have utilized Artificial Neural Networks (ANN) for seafloor topographic data segmentation and roughness classification using the multibeam- Hydrosweep system (installed onboard ocean research vessel Sagar Kanya) data. Bathymetric...

Archive of Geosample Data and Information from the Woods Hole Oceanographic Institution (WHOI) Seafloor Samples Laboratory

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Woods Hole Oceanographic Institution (WHOI) Seafloor Samples Laboratory is a partner in the Index to Marine and Lacustrine Geological Samples (IMLGS) database,...

Comparative analyses of the bacterial community of hydrothermal deposits and seafloor sediments across Okinawa Trough

Science.gov (United States)

Wang, Long; Yu, Min; Liu, Yan; Liu, Jiwen; Wu, Yonghua; Li, Li; Liu, Jihua; Wang, Min; Zhang, Xiao-Hua

2018-04-01

As an ideal place to study back-arc basins and hydrothermal eco-system, Okinawa Trough has attracted the interests of scientists for decades. However, there are still no in-depth studies targeting the bacterial community of the seafloor sediments and hydrothermal deposits in Okinawa Trough. In the present study, we reported the bacterial community of the surface deposits of a newly found hydrothermal field in the southern Okinawa Trough, and the horizontal and vertical variation of bacterial communities in the sediments of the northern Okinawa Trough. The hydrothermal deposits had a relatively high 16S rRNA gene abundance but low bacterial richness and diversity. Epsilonproteobacteria and Bacteroidetes were predominant in hydrothermal deposits whereas Deltaproteobacteria, Gammaproteobacteria and Chloroflexi were abundant across all samples. The bacterial distribution in the seafloor of Okinawa Trough was significantly correlated to the content of total nitrogen, and had consistent relationship with total carbon. Gradual changes of sulfur-oxidizing bacteria were found with the distance away from hydrothermal fields, while the hydrothermal activity did not influence the distribution of the major clades of sulfate-reducing bacteria. Higher abundance of the sulfur cycle related genes (aprA and dsrB), and lower abundance of the bacterial ammonia-oxidizing related gene (amoA) were quantified in hydrothermal deposits. In addition, the present study also compared the inter-field variation of Epsilonproteobacteria among multi-types of hydrothermal vents, revealing that the proportion and diversity of this clade were quite various.

Seismic-reflection surveys of the Blake Ridge, R/V Cape Hatteras, 1992 and 1995; data acquisition, navigation and processing

Science.gov (United States)

Taylor, Michael H.; Dillon, William P.; Anton, Christopher H.; Danforth, William W.

1999-01-01

As part of an ongoing study, seismic-reflection profiles were collected over the Blake Ridge in 1992 and 1995, in order to map the volume and distribution of methane hydrate. Faulting and seafloor instabilities appear to be related to methane hydrate processes at the Blake Ridge. Seismic profiles display a prominent collapse structure at the crest, which is inferred to have resulted from the mobilization of sediment that was associated with methane hydrate dissociation.

Challenge to image the stagnant slab beneath the Philippine Sea by seafloor electromagnetic survey

Science.gov (United States)

Utada, H.; Baba, K.; Goto, T.; Kasaya, T.; Ichikita, T.; Tada, N.; Shimizu, H.; Koyama, T.; Uyeshima, M.

2007-12-01

We have run a seafloor electromagnetic survey project in the Philippine Sea in order to image the deep mantle slab stagnating in the transition zone and surrounding mantle in three dimensions. Seafloor observations at every 500 km or so is necessary to resolve the geometry of the slab because existing data sets are based on the observations by land geomagnetic stations and submarine cables, which are distributed coarsely and unevenly. Although it is difficult to establish a bunch of nearly permanent observation stations at seafloor, iterative maneuver observations using ocean bottom electromagnetometers (OBEMs) can acquire the data required to probe down to the mantle transition zone. The project iterates one-year-long deployment three times. Earthquake Research Institute, University of Tokyo and Institute for Research on Earth Evolution (IFREE), Japan Agency for Marine-Earth Science and Technology (JAMSTEC) have resourced the project with the OBEMs. In the first phase, we deployed 11 OBEMs in October, 2005 and recovered all of them successfully in November, 2006. R/V Kairei of JAMSTEC was utilized for both cruises. In the second cruise, we deployed another 12 OBEMs and started the second phase. The recovery of the OBEMs and the third initiation will be done in November, 2007. The quality of the first phase data is quite good except for the electric field at one site. The MT responses are estimated at 10 sites in the period range of from about 300 to 60,000 seconds. The geomagnetic transfer functions are also estimated at all the 11 sites in the range of about 300 to 1,000,000 seconds. The responses at the period longer than 100,000 seconds are somewhat inaccurate and the improvement is expected by further data collection in the second and third phases. These responses will be analyzed together with the responses which were obtained by past experiments in the Philippine Sea. The features of the responses may be classified by basins composing the Philippine Sea

Seafloor spreading anomalies and crustal ages of the Clarion-Clipperton Zone

OpenAIRE

Udo Barckhausen; Meike Bagge; Douglas S. Wilson

2013-01-01

The Clarion-Clipperton Zone (CCZ) of the central Pacific is one of the few regions in the world’s oceans that are still lacking full coverage of reliable identifications of seafloor spreading anomalies. This is mainly due to the geometry of the magnetic lineations’ strike direction sub-parallel to the Earth’s magnetic field vector near the equator resulting in low amplitude magnetic anomalies, and the remoteness of the region which has hindered systematic surveying in the past. Following rece...

Seafloor multibeam backscatter calibration experiment: comparing 45°-tilted 38-kHz split-beam echosounder and 30-kHz multibeam data

Science.gov (United States)

Ladroit, Yoann; Lamarche, Geoffroy; Pallentin, Arne

2018-06-01

Obtaining absolute seafloor backscatter measurements from hydrographic multibeam echosounders is yet to be achieved. We propose a low-cost experiment to calibrate the various acquisition modes of a 30-kHz Kongsberg EM 302 multibeam echosounder in a range of water depths. We use a 38-kHz Simrad EK60 calibrated fisheries split-beam echosounder mounted at 45° angle on the vessel's hull as a reference for the calibration. The processing to extract seafloor backscatter from the EK60 requires bottom detection, ray tracing and motion compensation to obtain acceptable geo-referenced backscatter measurements from this non-hydrographic system. Our experiment was run in Cook Strait, New Zealand, on well-known seafloor patches in shallow, mid, and deep-water depths. Despite acquisition issues due to weather, our results demonstrate the strong potential of such an approach to obtain system's absolute calibration which is required for quantitative use of backscatter strength data.

Classification of sea-floor features associated with methane seeps along the Gulf of Cádiz continental margin

Science.gov (United States)

León, Ricardo; Somoza, Luis; Medialdea, Teresa; Maestro, Adolfo; Díaz-del-Río, Victor; Fernández-Puga, María del Carmen

2006-06-01

Based on recently gathered swath-bathymetry, high- to ultra-high-resolution seismic, and underwater camera data, along with dredging and coring samples, this paper examines the relationship between sea-floor features and the nature of hydrocarbon-enriched fluid and gas leaks from degassing of deeply buried sediments along the continental margin of the Gulf of Cádiz (eastern Central Atlantic). A classification into three main groups is proposed on the basis of the morphology and nature of deposits: (1) mud volcanoes, (2) methane-derived authigenic carbonates (MDAC) mounds, and (3) crater-like pockmarks. Mud volcanoes are, topographically, cone-shaped sea-floor edifices, built up from catastrophic mud and fluid degassing, intercalated with periods of inactivity. So far more than 25 mud volcanoes have been discovered in the Gulf of Cádiz, named in memory of deceased colleagues (e.g., Ginsburg and Baraza), or researchers' birth places (e.g. Faro, Cibeles, Almazán, San Petersburgh, Yuma, Rabat, Bonjardim, Coruña, Gades). These structures range from 800 to 2500 m in diameter and tower 150-300 m above the seabed. The volcanoes consistently feature a well-defined outer ring or circular terrace and an inner dome. All mud volcanoes are built up of episodes of mud-breccia flows, intercalated with deep-current deposits, with evident indications of gas saturation: degassing structures, a strong H 2S smell, and chemosynthetic fauna (such as Pogonophora sp. tube worms and Calyptogena sp.). Commonly observed carbonate crusts and slabs overlying some mud volcanoes are thought to have been formed by slow, diffuse venting during periods of inactivity or slower rates of fluid venting following the ejection of mud. A "fermentation" process, the result of microbial-mediated oxidation of hydrocarbon-enriched fluids, seems to play an important role in the growth of large deep-water carbonate mounds and chimneys during periods of low methane-seep fluid pressure. More than 400 crater

Evaluating the earliest traces of Archean sub-seafloor life by NanoSIMS

Science.gov (United States)

Mcloughlin, N.; Grosch, E. G.; Kilburn, M.; Wacey, D.

2012-12-01

The Paleoarchean sub-seafloor has been proposed as an environment for the emergence of life with titanite microtextures in pillow lavas argued to be the earliest traces of microbial micro-tunneling (Furnes et al. 2004). Here we use a nano-scale ion microprobe (NanoSIMS) to evaluate possible geochemical traces of life in 3.45 Ga pillow lavas of the Barberton Greenstone Belt, South Africa. We investigated both surface and drill core samples from the original "Biomarker" outcrop in the Hooggenoeg Fm. Pillow lava metavolcanic glass contain clusters of segmented microcrystalline titanite filaments, ~4μm across and sedimentary sulfides (δ34S = +8 to -23‰). We propose that the Hooggenoeg sulfides probably formed during early fluid-rock-microbe interaction involving sulfate-reducing microbes (c.f. Rouxel et al. 2008). The pillow lavas were then metamorphosed, the glass transformed to a greenschist facies assemblage and titanite growth encapsulated the microbial sulfides. In summary, the extreme sulfur isotope fractionations reported here independently point towards the potential involvement of microbes in the alteration of Archean volcanic glass. In situ sulfur isotope analysis of basalt-hosted sulfides may provide an alternative approach to investigating the existence of an Archean sub-seafloor biosphere that does not require the mineralization of early microbial microborings with organic linings.

New Approaches to the Sea-Floor Mapping: Results From the GEBCO-NF Alumni Team's Technique Developments in Preparation to the Shell Ocean Discovery XPRIZE 2017.

Science.gov (United States)

Bazhenova, E.; Zarayskaya, Y.; Wigley, R. A.; Anderson, R.; Falconer, R. K. H.; Kearns, T.; Martin, T.; Minami, H.; Roperez, J.; Rosedee, A.; Sade, H.; Seeboruth, S.; Simpson, B.; Sumiyoshi, M.; Tinmouth, N.; Zwolak, K.

2017-12-01

In preparation for the XPRIZE 2017 Round 1, a new sea-floor mapping system has been assembled based on an Unmanned Surface Vessel (USV) coupled with an Autonomous Underwater Vehicle (AUV). USV operation allows reducing logistics costs, while the AUV provides enhanced maneuverability and high accuracy of stabilization for the mapping missions. The AUV is equipped with a high-resolution interferometric synthetic aperture sonar (HISAS) and a multibeam sonar (MBES), covering a wide bathymetry swath and the nadir, respectively. Typically operating at 20 to 40 m altitude, the HISAS is capable of providing SAS imagery with 4 x 4 cm resolution and bathymetry with 40 x 40 cm resolution throughout the swath. Smaller areas of interest (50 x 50 m) can be further examined using the Spot processing technique, to produce SAS imagery with 2 x 2 cm resolution and high- resolution SAS bathymetry with 5 x 5 cm resolution. This allows multi-aspect imaging and examination of seabed geological features at different scales. Advanced data post-processing can be performed to produce 3D images of objects and explore their structure using the shadow contrast and shape. Being an interferometric system, the HISAS collects data for both imagery and bathymetry in the same swath. This improves the robustness for SAS in areas with significant relief. In the standard survey mode, the HISAS can typically collect SAS data at 2.6 km2/hr over relatively flat ground. Another limiting factor to the HISAS data coverage and quality is the vehicle stability influenced by downslope and cross currents and the resulting vehicle's speed. From experience, the best coverage occurs at a vehicle speed of around 2 m/s. At slower speeds the vehicle starts to lose steerage leading to degradation of tracking and navigation performance, which harms the focusing algorithm that creates the SAS data. For the AUV mission planning in unknown areas or in case of highly variable conditions at the study site, MBES

High-Reflectivity Multi-Layer Coatings for the CLASP Sounding Rocket Project

Science.gov (United States)

Narukage, Noriyuki; Kano, Ryohei; Bando, Takamasa; Ishikawa, Ryoko; Kubo, Masahito; Katsukawa, Yukio; Ishikawa, Shin-nosuke; Kobiki, Toshihiko; Giono, Gabriel; Auchere, Frederic;

Abyssal ocean overturning shaped by seafloor distribution

Science.gov (United States)

de Lavergne, C.; Madec, G.; Roquet, F.; Holmes, R. M.; McDougall, T. J.

2017-11-01

The abyssal ocean is broadly characterized by northward flow of the densest waters and southward flow of less-dense waters above them. Understanding what controls the strength and structure of these interhemispheric flows—referred to as the abyssal overturning circulation—is key to quantifying the ocean’s ability to store carbon and heat on timescales exceeding a century. Here we show that, north of 32° S, the depth distribution of the seafloor compels dense southern-origin waters to flow northward below a depth of about 4 kilometres and to return southward predominantly at depths greater than 2.5 kilometres. Unless ventilated from the north, the overlying mid-depths (1 to 2.5 kilometres deep) host comparatively weak mean meridional flow. Backed by analysis of historical radiocarbon measurements, the findings imply that the geometry of the Pacific, Indian and Atlantic basins places a major external constraint on the overturning structure.

Nitrogen Concentrations and Isotopic Compositions of Seafloor-Altered Terrestrial Basaltic Glass: Implications for Astrobiology

Science.gov (United States)

Banerjee, N.R.; Izawa, M.R.M.; Kobayashi, K.; Lazzeri, K.; Ranieri, L.A.; Nakamura, E.

2018-01-01

Abstract Observed enrichments of N (and the δ15N of this N) in volcanic glasses altered on Earth's modern and ancient seafloor are relevant in considerations of modern global N subduction fluxes and ancient life on Earth, and similarly altered glasses on Mars and other extraterrestrial bodies could serve as valuable tracers of biogeochemical processes. Palagonitized glasses and whole-rock samples of volcanic rocks on the modern seafloor (ODP Site 1256D) contain 3–18 ppm N with δ15Nair values of up to +4.5‰. Variably altered glasses from Mesozoic ophiolites (Troodos, Cyprus; Stonyford volcanics, USA) contain 2–53 ppm N with δ15N of −6.3 to +7‰. All of the more altered glasses have N concentrations higher than those of fresh volcanic glass (for MORB, smectite, illite) in both the palagonitized cracks and the microtubules. These phyllosilicates (particularly illite), and possibly also zeolites, are the likely hosts for N in these glasses. Key Words: Nitrogen—Nitrogen isotope—Palagonite—Volcanic glass—Mars. Astrobiology 18, 330–342. PMID:29106312

Distinct bacterial communities in surficial seafloor sediments following the 2010 Deepwater Horizon blowout

Directory of Open Access Journals (Sweden)

Tingting Yang

2016-09-01

Full Text Available A major fraction of the petroleum hydrocarbons discharged during the 2010 Macondo oil spill became associated with and sank to the seafloor as marine snow flocs. This sedimentation pulse induced the development of distinct bacterial communities. Between May 2010 and July 2011, full-length 16S rRNA gene clone libraries demonstrated bacterial community succession in oil-polluted sediment samples near the wellhead area. Libraries from early May 2010, before the sedimentation event, served as the baseline control. Freshly deposited oil-derived marine snow was collected on the surface of sediment cores in September 2010, and was characterized by abundantly detected members of the marine Roseobacter cluster within the Alphaproteobacteria. Samples collected in mid-October 2010 closest to the wellhead contained members of the sulfate-reducing, anaerobic bacterial families Desulfobacteraceae and Desulfobulbaceae within the Deltaproteobacteria, suggesting that the oil-derived sedimentation pulse triggered bacterial oxygen consumption and created patchy anaerobic microniches that favored sulfate-reducing bacteria. Phylotypes of the polycyclic aromatic hydrocarbon-degrading genus Cycloclasticus, previously found both in surface oil slicks and the deep hydrocarbon plume, were also found in oil-derived marine snow flocs sedimenting on the seafloor in September 2010, and in surficial sediments collected in October and November 2010, but not in any of the control samples. Due to the relative recalcitrance and stability of polycyclic aromatic compounds, Cycloclasticus represents the most persistent microbial marker of seafloor hydrocarbon deposition that we could identify in this dataset. The bacterial imprint of the DWH oil spill had diminished in late November 2010, when the bacterial communities in oil-impacted sediment samples collected near the Macondo wellhead began to resemble their pre-spill counterparts and spatial controls. Samples collected in summer

Global seafloor geomorphic features map: applications for ocean conservation and management

Science.gov (United States)

Harris, P. T.; Macmillan-Lawler, M.; Rupp, J.; Baker, E.

2013-12-01

Seafloor geomorphology, mapped and measured by marine scientists, has proven to be a very useful physical attribute for ocean management because different geomorphic features (eg. submarine canyons, seamounts, spreading ridges, escarpments, plateaus, trenches etc.) are commonly associated with particular suites of habitats and biological communities. Although we now have better bathymetric datasets than ever before, there has been little effort to integrate these data to create an updated map of seabed geomorphic features or habitats. Currently the best available global seafloor geomorphic features map is over 30 years old. A new global seafloor geomorphic features map (GSGM) has been created based on the analysis and interpretation of the SRTM (Shuttle Radar Topography Mission) 30 arc-second (~1 km) global bathymetry grid. The new map includes global spatial data layers for 29 categories of geomorphic features, defined by the International Hydrographic Organisation. The new geomorphic features map will allow: 1) Characterization of bioregions in terms of their geomorphic content (eg. GOODS bioregions, Large Marine Ecosystems (LMEs), ecologically or biologically significant areas (EBSA)); 2) Prediction of the potential spatial distribution of vulnerable marine ecosystems (VME) and marine genetic resources (MGR; eg. associated with hydrothermal vent communities, shelf-incising submarine canyons and seamounts rising to a specified depth); and 3) Characterization of national marine jurisdictions in terms of their inventory of geomorphic features and their global representativeness of features. To demonstrate the utility of the GSGM, we have conducted an analysis of the geomorphic feature content of the current global inventory of marine protected areas (MPAs) to assess the extent to which features are currently represented. The analysis shows that many features have very low representation, for example fans and rises have less than 1 per cent of their total area

Environmental security of the coastal seafloor in the sea ports and waterways of the Mediterranean region

Energy Technology Data Exchange (ETDEWEB)

Obhodas, Jasmina, E-mail: jobhodas@irb.h [Institute Ruder Boskovic, Bijenicka c.54, 10000 Zagreb (Croatia); Valkovic, Vladivoj [A.C.T.d.o.o., Prilesje 4, 10000 Zagreb (Croatia); Sudac, Davorin [Institute Ruder Boskovic, Bijenicka c.54, 10000 Zagreb (Croatia); Matika, Dario [Institute for Researches and Development of Defense Systems, Ilica 256b, 10000 Zagreb (Croatia); Pavic, Ivica [Ministry of Defense, Croatian Navy, Dubrovacka 49, 21000 Split (Croatia); Kollar, Robert [A.C.T.d.o.o., Prilesje 4, 10000 Zagreb (Croatia)

2010-07-21

The Mediterranean coastal seafloor is littered with man-made objects and materials, including a variety of ammunition in many areas. In addition, sediments in ports, harbors and marinas are contaminated with elevated concentrations of chemicals used as biocides in antifouling paints. In order to reach a satisfactory level of environmental security of the coastal sea areas, fast neutron activation analysis with detection of associated alpha particles and energy dispersive X-ray fluorescence, both in laboratory and inside an autonomous underwater vehicle for in-situ measurements, has been used for the characterization of the objects on the seafloor. Measurements have shown that gamma ray spectra are able to distinguish threat material from the surrounding material. Analysis of more than 700 coastal sea sediment samples has resulted in concentration distribution maps indicating the locations of 'hot spots', which might interfere with threat material identification.

Estimation of seafloor impact from demersal trawls, seines and dredges based on gear design and dimensions

DEFF Research Database (Denmark)

Eigaard, Ole Ritzau; Bastardie, Francois; Breen, Michael

a different approach using the gear itself (design and dimensions) for understanding and estimation of the physical interactions with the seafloor at the individual fishing operation level. With reference to the métier groupings of EU logbooks, we defined 17 distinct towed gear groups in European waters (11...... otter trawl groups, 3 beam trawl groups, 2 demersal seine groups, and 1 dredge group), for which we established seafloor “footprints”. The footprint of a gear was defined as the relative contribution from individual larger gear components, such as the trawl doors, sweeps and ground gear, to the total...... types based on a review of the scientific literature. For each defined gear group a vessel-size (kW or total length) – gear size (total gear width or circumference) relationship was estimated to enable the prediction of gear footprint area and sediment penetration from vessel size. The implications...

Sea-floor drainage features of Cascadia Basin and the adjacent continental slope, northeast Pacific Ocean

Science.gov (United States)

Hampton, M.A.; Karl, Herman A.; Kenyon, Neil H.

1989-01-01

Sea-floor drainage features of Cascadia Basin and the adjacent continental slope include canyons, primary fan valleys, deep-sea valleys, and remnant valley segments. Long-range sidescan sonographs and associated seismic-reflection profiles indicate that the canyons may originate along a mid-slope escarpment and grow upslope by mass wasting and downslope by valley erosion or aggradation. Most canyons are partly filled with sediment, and Quillayute Canyon is almost completely filled. Under normal growth conditions, the larger canyons connect with primary fan valleys or deep-sea valleys in Cascadia Basin, but development of accretionary ridges blocks or re-routes most canyons, forcing abandonment of the associated valleys in the basin. Astoria Fan has a primary fan valley that connects with Astoria Canyon at the fan apex. The fan valley is bordered by parallel levees on the upper fan but becomes obscure on the lower fan, where a few valley segments appear on the sonographs. Apparently, Nitinat Fan does not presently have a primary fan valley; none of the numerous valleys on the fan connect with a canyon. The Willapa-Cascadia-Vancouver-Juan de Fuca deep-sea valley system bypasses the submarine fans and includes deeply incised valleys to broad shallow swales, as well as within-valley terraces and hanging-valley confluences. ?? 1989.

Ultrastructure and potential sub-seafloor evidence of bacteriogenic iron oxides from Axial Volcano, Juan de Fuca Ridge, north-east Pacific Ocean.

Science.gov (United States)

Kennedy, C B; Scott, S D; Ferris, F G

2003-03-01

Iron oxides from the caldera of Axial Volcano, a site of hydrothermal vent activity along the Juan de Fuca Ridge, were found to consist predominantly of microbial structures in hydrated whole mounts examined using an environmental scanning electron microscope. Novel observations were made of the iron oxides revealing the spatial relationships of the bacteria within to be more consistent with microbial mats than mineral precipitates. The bacterial structures are attributed to the sheaths of Leptothrix ochracea, the stalks of Gallionella ferruginea, and the filaments of a novel iron oxidizing PV-1 strain, based on the distinctive morphological characteristics of these three bacteria. Energy dispersive X-ray spectroscopy revealed the presence and distribution of Fe, Si, and Cl on the bacterial sheaths, stalks and filaments. The iron oxides were identified by X-ray diffraction to be two-line ferrihydrite, a poorly ordered iron oxyhydroxide. Adsorption of Si in particular to two-line ferrihydrite likely contributes to its stability on the seafloor, and might also be a preservation mechanism creating microfossils of the bacterial structures encrusted with ferrihydrite. Presumptive evidence of the sub-seafloor presence of L. ochracea, G. ferruginea and PV-1 at Axial Volcano was obtained from the presence of these bacteria on a trap that had been placed within an active vent, and also in a vent fluid sample. If indeed these bacteria are present in the sub-seafloor, it may be an indication that the surface expression of iron oxide deposits at Axial Volcano is minimal in comparison to what exists beneath the seafloor.

Seafloor Backscatter Image of North of Santa Rosa Island, Channel Islands National Marine Sanctuary (8m resolution tif)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This image represents an 8 meter resolution backscatter of the seafloor south of Santa Rosa Island in Channel Islands National Marine Sanctuary. It was acquired...

Seafloor Backscatter Image of South of Santa Rosa Island, Channel Islands National Marine Sanctuary (8m resolution tif)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This image represents an 8 meter resolution backscatter of the seafloor south of Santa Rosa Island in Channel Islands National Marine Sanctuary. It was acquired...

Assessing the distribution and abundance of seabed minerals from seafloor photographic data in the Central Indian Ocean Basin

Digital Repository Service at National Institute of Oceanography (India)

Sharma, R.; Khadge, N.H.; JaiSankar, S.

Distribution characteristics of deep-sea mineral resources such as polymetallic nodules and ferromanganese crusts are often influenced by local seafloor features such as the topographic undulations and sediment thickness. Qualitative as well as semi...

High-reflective colorful films fabricated by all-solid multi-layer cholesteric structures

Science.gov (United States)

Li, Y.; Luo, D.

2018-02-01

We demonstrate all-solid-state film with high-reflectivity based on cholesteric template. The adhesive (NOA81) is both filler and an adhesive, which can be avoids interfacial losses. The reflected right- and left-circularly polarized light has been developed by roll-to-roll method, and the reflectance of the films is more than 78%. Here, the all-solid film was used in distribute feedback laser with dye-doped. In addition, this films also used in include flexible reflective display, color pixels in digital photographs, printing and colored cladding of variety of objects.

Low reflectance high power RF load

Science.gov (United States)

Ives, R. Lawrence; Mizuhara, Yosuke M.

2016-02-02

A load for traveling microwave energy has an absorptive volume defined by cylindrical body enclosed by a first end cap and a second end cap. The first end cap has an aperture for the passage of an input waveguide with a rotating part that is coupled to a reflective mirror. The inner surfaces of the absorptive volume consist of a resistive material or are coated with a coating which absorbs a fraction of incident RF energy, and the remainder of the RF energy reflects. The angle of the reflector and end caps is selected such that reflected RF energy dissipates an increasing percentage of the remaining RF energy at each reflection, and the reflected RF energy which returns to the rotating mirror is directed to the back surface of the rotating reflector, and is not coupled to the input waveguide. Additionally, the reflector may have a surface which generates a more uniform power distribution function axially and laterally, to increase the power handling capability of the RF load. The input waveguide may be corrugated for HE11 mode input energy.

Seafloor Bathymetry Image of South of Santa Rosa Island, Channel Islands National Marine Sanctuary (8m resolution tif)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This image represents an 8 meter resolution bathymetry of the seafloor south of Santa Rosa Island in Channel Islands National Marine Sanctuary. It was acquired using...

Seafloor Bathymetry Image of North of Santa Rosa Island, Channel Islands National Marine Sanctuary (8m resolution tif)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This image represents an 8 meter resolution bathymetry of the seafloor north of Santa Rosa Island in Channel Islands National Marine Sanctuary. It was acquired using...

Pore-level determination of spectral reflection behaviors of high-porosity metal foam sheets

Science.gov (United States)

Li, Yang; Xia, Xin-Lin; Ai, Qing; Sun, Chuang; Tan, He-Ping

2018-03-01

Open cell metal foams are currently attracting attention and their radiative behaviors are of primary importance in high temperature applications. The spectral reflection behaviors of high-porosity metal foam sheets, bidirectional reflectance distribution function (BRDF) and directional-hemispherical reflectivity were numerically investigated. A set of realistic nickel foams with porosity from 0.87 to 0.97 and pore density from 10 to 40 pores per inch were tomographied to obtain their 3-D digital cell network. A Monte Carlo ray-tracing method was employed in order to compute the pore-level radiative transfer inside the network within the limit of geometrical optics. The apparent reflection behaviors and their dependency on the textural parameters and strut optical properties were comprehensively computed and analysed. The results show a backward scattering of the reflected energy at the foam sheet surface. Except in the cases of large incident angles, an energy peak is located almost along the incident direction and increases with increasing incident angles. Through an analytical relation established, the directional-hemispherical reflectivity can be related directly to the porosity of the foam sheet and to the complex refractive index of the solid phase as well as the specularity parameter which characterizes the local reflection model. The computations show that a linear decrease in normal-hemispherical reflectivity occurs with increasing porosity. The rate of this decrease is directly proportional to the strut normal reflectivity. In addition, the hemispherical reflectivity increases as a power function of the incident angle cosine.

ROV seafloor surveys combining 5-cm lateral resolution multibeam bathymetry with color stereo photographic imagery

Science.gov (United States)

Caress, D. W.; Hobson, B.; Thomas, H. J.; Henthorn, R.; Martin, E. J.; Bird, L.; Rock, S. M.; Risi, M.; Padial, J. A.

2013-12-01

The Monterey Bay Aquarium Research Institute is developing a low altitude, high-resolution seafloor mapping capability that combines multibeam sonar with stereo photographic imagery. The goal is to obtain spatially quantitative, repeatable renderings of the seafloor with fidelity at scales of 5 cm or better from altitudes of 2-3 m. The initial test surveys using this sensor system are being conducted from a remotely operated vehicle (ROV). Ultimately we intend to field this survey system from an autonomous underwater vehicle (AUV). This presentation focuses on the current sensor configuration, methods for data processing, and results from recent test surveys. Bathymetry data are collected using a 400-kHz Reson 7125 multibeam sonar. This configuration produces 512 beams across a 135° wide swath; each beam has a 0.5° acrosstrack by 1.0° alongtrack angular width. At a 2-m altitude, the nadir beams have a 1.7-cm acrosstrack and 3.5 cm alongtrack footprint. Dual Allied Vision Technology GX1920 2.8 Mpixel color cameras provide color stereo photography of the seafloor. The camera housings have been fitted with corrective optics achieving a 90° field of view through a dome port. Illumination is provided by dual 100J xenon strobes. Position, depth, and attitude data are provided by a Kearfott SeaDevil Inertial Navigation System (INS) integrated with a 300 kHz RDI Doppler velocity log (DVL). A separate Paroscientific pressure sensor is mounted adjacent to the INS. The INS Kalman filter is aided by the DVL velocity and pressure data, achieving navigational drift rates less than 0.05% of the distance traveled during surveys. The sensors are mounted onto a toolsled fitted below MBARI's ROV Doc Ricketts with the sonars, cameras and strobes all pointed vertically down. During surveys the ROV flies at a 2-m altitude at speeds of 0.1-0.2 m/s. During a four-day R/V Western Flyer cruise in June 2013, we successfully collected multibeam and camera survey data from a 2-m altitude

Expressions for tidal conversion at seafloor topography using physical space integrals

International Nuclear Information System (INIS)

Schorghofer, Norbert

2010-01-01

The barotropic tide interacts with seafloor topography to generate internal gravity waves. Equations for streamfunction and power conversion are derived in terms of integrals over the topography in spatial coordinates. The slope of the topography does not need to be small. Explicit equations are derived up to second order in slope for general topography, and conversion by a bell-shaped topography is calculated analytically to this order. A concise formalism using Hilbert transforms is developed, the minimally converting topographic shape is discussed, and a numerical scheme for the evaluation of power conversion is designed that robustly deals with the singular integrand.

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...

Slippiń and Slidiń: Capturing the Earth in Motion below the Seafloor

Science.gov (United States)

Strasser, M.

2017-12-01

Since the beginning of ocean drilling, sampling and dating seismically imaged tectono-stratigraphic sections and recovering rocks from active faults of marine plate-boundary systems has advanced our understanding of subduction zone structures and evolution. It further evidenced the dynamic nature of deformation, fluid flow and fluxes within such systems. With the advancement in developing borehole observatories, monitoring data is increasingly becoming available to analyze and quantify the dynamic processes, such as those leading to and resulting from earthquakes, slides and tsunamis. Combined with knowledge gained from seismological studies, IODP drilling efforts at Costa Rica, Hikurangi, Japan Trench, Nankai and Sumatra margins contribute invaluable observatory data and core samples, the analyses and derived research results of which are fundamentally changing the way fault slip behavior, seafloor instability and tsunamigenesis are understood. Short instrumental records, however, limit our perspective of maximum magnitude and recurrence of such submarine geohazard processes. Examining past events expressed as sedimentary or geochemical perturbations preserved in the marine record provides IODP the key to address this challenge: Recent efforts included sampling mass-transport deposits to study causes and consequences of submarine slides. For the Nankai accretionary margin, we documented the submarine landslide history spanning ˜2.5 million years. The modes and scales of slides were linked to the different morphotectonic settings in which they occurred. The timing of major slides hints at climate preconditioning for sediment instability and reveals that margin destabilization does not occur systematically during all megathrust earthquakes. However, new observation after recent earthquakes and studies using lakes as model basins discovered a new mode of dynamic earthquake ground motion response for surficial (<5-10 cm) seafloor sediments. This can trigger

High-resolution reflection spectroscopy

International Nuclear Information System (INIS)

Ducloy, Martial

1997-01-01

In this article some recent developments in selective reflection spectroscopy is reviewed and the various ways to extend Doppler free techniques to this spectroscopic field is discussed. Its main feature is to probe atomic gas close to the cell boundaries

Impact of lower plate structure on upper plate deformation at the NW Sumatran convergent margin from seafloor morphology

Digital Repository Service at National Institute of Oceanography (India)

Graindorge, D.; Klingelhoefer, F.; Sibuet, J-C; McNeill, L.; Henstock, T.J; Dean, S.; Gutscher, M-A.; Dessa, J; Permana, H.; Singh, S.C; Leau, H.; White, N.; Carton, H.; Malod, J.A.; Rangin, C.; Aryawan, K.G.; Chaubey, A.K.; Chauhan, A.; Galih, D.R.; Greenroyd, C.J; Laesanpura, A.; Prihantono, J.; Royle, G.; Shankar, U.

forearc from the Sunda trench to the submarine volcanic arc just north of Sumatra. A slope gradient analysis of the combined dataset accurately highlights those portions of the seafloor shaped by active tectonic, depositional and/or erosional processes...

Cellular content of biomolecules in sub-seafloor microbial communities

DEFF Research Database (Denmark)

Braun, Stefan; Morono, Yuki; Becker, Kevin W.

2016-01-01

the lifetime of their microbial sources. Here we provide for the first time measurements of the cellular content of biomolecules in sedimentary microbial cells. We separated intact cells from sediment matrices in samples from surficial, deeply buried, organic-rich, and organic-lean marine sediments by density...... content. We find that the cellular content of biomolecules in the marine subsurface is up to four times lower than previous estimates. Our approach will facilitate and improve the use of biomolecules as proxies for microbial abundance in environmental samples and ultimately provide better global estimates......Microbial biomolecules, typically from the cell envelope, can provide crucial information about distribution, activity, and adaptations of sub-seafloor microbial communities. However, when cells die these molecules can be preserved in the sediment on timescales that are likely longer than...

Seep Detection using E/V Nautilus Integrated Seafloor Mapping and Remotely Operated Vehicles on the United States West Coast

Science.gov (United States)

Gee, L. J.; Raineault, N.; Kane, R.; Saunders, M.; Heffron, E.; Embley, R. W.; Merle, S. G.

2017-12-01

Exploration Vessel (E/V) Nautilus has been mapping the seafloor off the west coast of the United States, from Washington to California, for the past three years with a Kongsberg EM302 multibeam sonar. This system simultaneously collects bathymetry, seafloor and water column backscatter data, allowing an integrated approach to mapping to more completely characterize a region, and has identified over 1,000 seafloor seeps. Hydrographic multibeam sonars like the EM302 were designed for mapping the bathymetry. It is only in the last decade that major mapping projects included an integrated approach that utilizes the seabed and water column backscatter information in addition to the bathymetry. Nautilus mapping in the Eastern Pacific over the past three years has included a number of seep-specific expeditions, and utilized and adapted the preliminary mapping guidelines that have emerged from research. The likelihood of seep detection is affected by many factors: the environment: seabed geomorphology, surficial sediment, seep location/depth, regional oceanography and biology, the nature of the seeps themselves: size variation, varying flux, depth, and transience, the detection system: design of hydrographic multibeam sonars limits use for water column detection, the platform: variations in the vessel and operations such as noise, speed, and swath overlap. Nautilus integrated seafloor mapping provided multiple indicators of seep locations, but it remains difficult to assess the probability of seep detection. Even when seeps were detected, they have not always been located during ROV dives. However, the presence of associated features (methane hydrate and bacterial mats) serve as evidence of potential seep activity and reinforce the transient nature of the seeps. Not detecting a seep in the water column data does not necessarily indicate that there is not a seep at a given location, but with multiple passes over an area and by the use of other contextual data, an area may

An improved method to estimate reflectance parameters for high dynamic range imaging

Science.gov (United States)

Li, Shiying; Deguchi, Koichiro; Li, Renfa; Manabe, Yoshitsugu; Chihara, Kunihiro

2008-01-01

Two methods are described to accurately estimate diffuse and specular reflectance parameters for colors, gloss intensity and surface roughness, over the dynamic range of the camera used to capture input images. Neither method needs to segment color areas on an image, or to reconstruct a high dynamic range (HDR) image. The second method improves on the first, bypassing the requirement for specific separation of diffuse and specular reflection components. For the latter method, diffuse and specular reflectance parameters are estimated separately, using the least squares method. Reflection values are initially assumed to be diffuse-only reflection components, and are subjected to the least squares method to estimate diffuse reflectance parameters. Specular reflection components, obtained by subtracting the computed diffuse reflection components from reflection values, are then subjected to a logarithmically transformed equation of the Torrance-Sparrow reflection model, and specular reflectance parameters for gloss intensity and surface roughness are finally estimated using the least squares method. Experiments were carried out using both methods, with simulation data at different saturation levels, generated according to the Lambert and Torrance-Sparrow reflection models, and the second method, with spectral images captured by an imaging spectrograph and a moving light source. Our results show that the second method can estimate the diffuse and specular reflectance parameters for colors, gloss intensity and surface roughness more accurately and faster than the first one, so that colors and gloss can be reproduced more efficiently for HDR imaging.

Wave exposure as a predictor of benthic habitat distribution on high energy temperate reefs

Directory of Open Access Journals (Sweden)

Alex eRattray

2015-02-01

Full Text Available The new found ability to measure physical attributes of the marine environment at high resolution across broad spatial scales has driven the rapid evolution of benthic habitat mapping as a field in its own right. Improvement of the resolution and ecological validity of seafloor habitat distribution models has, for the most part, paralleled developments in new generations of acoustic survey tools such as multibeam echosounders. While sonar methods have been well demonstrated to provide useful proxies of the relatively static geophysical patterns that reflect distribution of benthic species and assemblages, the spatially and temporally variable influence of hydrodynamic energy on habitat distribution have been less well studied. Here we investigate the role of wave exposure on patterns of distribution of near-shore benthic habitats. A high resolution spectral wave model was developed for a 624 km2 site along Cape Otway, a major coastal feature of western Victoria, Australia. Comparison of habitat classifications implemented using the Random Forests algorithm established that significantly more accurate estimations of habitat distribution were obtained by including a fine-scale numerical wave model, extended to the seabed using linear wave theory, than by using depth and seafloor morphology information alone. Variable importance measures and map interpretation indicated that the spatial variation in wave induced bottom orbital velocity was most influential in discriminating habitat the classes containing canopy forming kelp Ecklonia radiata, a foundation kelp species that affects biodiversity and ecological functioning on shallow reefs across temperate Australasia. We demonstrate that hydrodynamic models reflecting key environmental drivers on wave exposed coastlines are important in accurately defining distributions of benthic habitats.

EMSO: European multidisciplinary seafloor observatory

Science.gov (United States)

Favali, Paolo; Beranzoli, Laura

2009-04-01

EMSO has been identified by the ESFRI Report 2006 as one of the Research Infrastructures that European members and associated states are asked to develop in the next decades. It will be based on a European-scale network of multidisciplinary seafloor observatories from the Arctic to the Black Sea with the aim of long-term real-time monitoring of processes related to geosphere/biosphere/hydrosphere interactions. EMSO will enhance our understanding of processes, providing long time series data for the different phenomenon scales which constitute the new frontier for study of Earth interior, deep-sea biology and chemistry, and ocean processes. The development of an underwater network is based on past EU projects and is supported by several EU initiatives, such as the on-going ESONET-NoE, aimed at strengthening the ocean observatories' scientific and technological community. The EMSO development relies on the synergy between the scientific community and industry to improve European competitiveness with respect to countries such as USA, Canada and Japan. Within the FP7 Programme launched in 2006, a call for Preparatory Phase (PP) was issued in order to support the foundation of the legal and organisational entity in charge of building up and managing the infrastructure, and coordinating the financial effort among the countries. The EMSO-PP project, coordinated by the Italian INGV with participation by 11 institutions from as many European countries, started in April 2008 and will last four years.

GANSEKI: JAMSTEC Deep Seafloor Rock Sample Database Emerging to the New Phase

Science.gov (United States)

Tomiyama, T.; Ichiyama, Y.; Horikawa, H.; Sato, Y.; Soma, S.; Hanafusa, Y.

2013-12-01

Japan Agency for Marine-Earth Science and Technology (JAMSTEC) collects a lot of substantial samples as well as various geophysical data using its research vessels and submersibles. These samples and data, which are obtained by spending large amounts of human and physical resources, are precious wealth of the world scientific community. For the better use of these samples and data, it is important that they are utilized not only for initial purpose of each cruse but also for other general scientific and educational purposes of second-hand users. Based on the JAMSTEC data and sample handling policies [1], JAMSTEC has systematically stored samples and data obtained during research cruises, and provided them to domestic/foreign activities on research, education, and public relation. Being highly valued for second-hand usability, deep seafloor rock samples are one of the most important types of samples obtained by JAMSTEC, as oceanic biological samples and sediment core samples are. Rock samples can be utilized for natural history sciences and other various purposes; some of these purposes are connected to socially important issues such as earthquake mechanisms and mineral resource developments. Researchers and educators can access to JAMSTEC rock samples and associated data through 'GANSEKI [2]', the JAMSTEC Deep Seafloor Rock Sample Database. GANSEKI was established on the Internet in 2006 and its contents and functions have been continuously enriched and upgraded since then. GANSEKI currently provides 19 thousands of sample metadata, 9 thousands of collection inventory data and 18 thousands of geochemical data. Most of these samples are recovered from the North-western Pacific Ocean, although samples from other area are also included. The major update of GANSEKI held in May 2013 involved a replacement of database core system and a redesign of user interface. In the new GANSEKI, users can select samples easily and precisely using multi-index search, numerical

Same pattern, different mechanism: Locking onto the role of key species in seafloor ecosystem process.

Science.gov (United States)

Woodin, Sarah Ann; Volkenborn, Nils; Pilditch, Conrad A; Lohrer, Andrew M; Wethey, David S; Hewitt, Judi E; Thrush, Simon F

2016-05-27

Seafloor biodiversity is a key mediator of ecosystem functioning, but its role is often excluded from global budgets or simplified to black boxes in models. New techniques allow quantification of the behavior of animals living below the sediment surface and assessment of the ecosystem consequences of complex interactions, yielding a better understanding of the role of seafloor animals in affecting key processes like primary productivity. Combining predictions based on natural history, behavior of key benthic species and environmental context allow assessment of differences in functioning and process, even when the measured ecosystem property in different systems is similar. Data from three sedimentary systems in New Zealand illustrate this. Analysis of the behaviors of the infaunal ecosystem engineers in each system revealed three very different mechanisms driving ecosystem function: density and excretion, sediment turnover and surface rugosity, and hydraulic activities and porewater bioadvection. Integrative metrics of ecosystem function in some cases differentiate among the systems (gross primary production) and in others do not (photosynthetic efficiency). Analyses based on behaviors and activities revealed important ecosystem functional differences and can dramatically improve our ability to model the impact of stressors on ecosystem and global processes.

Mid Ocean Ridge Processes at Very Low Melt Supply : Submersible Exploration of Smooth Ultramafic Seafloor at the Southwest Indian Ridge, 64 degree E

Science.gov (United States)

Cannat, M.; Agrinier, P.; Bickert, M.; Brunelli, D.; Hamelin, C.; Lecoeuvre, A.; Lie Onstad, S.; Maia, M.; Prampolini, M.; Rouméjon, S.; Vitale Brovarone, A.; Besançon, S.; Assaoui, E. M.

2017-12-01

Mid-ocean ridges are the Earth's most extensive and active volcanic chains. They are also, particularly at slow spreading rates, rift zones, where plate divergence is in part accommodated by faults. Large offset normal faults, also called detachments, are characteristic of slow-spreading ridges, where they account for the widespread emplacement of mantle-derived rocks at the seafloor. In most cases, these detachments occur together with ridge magmatism, with melt injection and faulting interacting to shape the newly formed oceanic lithosphere. Here, we seek to better understand these interactions and their effects on oceanic accretion by studying the end-member case of a ridge where magmatism is locally almost absent. The portion of the Southwest Indian ridge we are studying has an overal low melt supply, focused to discrete axial volcanoes, leaving almost zero melt to intervening sections of the axial valley. One of these nearly amagmatic section of the ridge, located at 64°E, has been the focus of several past cruises (sampling, mapping and seismic experiments). Here we report on the most recent cruise to the area (RV Pourquoi Pas? with ROV Victor; dec-jan 2017), during which we performed high resolution mapping, submersible exploration and sampling of the ultramafic seafloor and of sparse volcanic formations. Our findings are consistent with the flip-flop detachment hypothesis proposed for this area by Sauter et al. (Nature Geosciences, 2013; ultramafic seafloor forming in the footwall of successive detachment faults, each cutting into the footwall of the previous fault, with an opposite polarity). Our observations also document the extent and geometry of deformation in the footwall of a young axial detachment, the role of mass-wasting for the evolution of this detachment, and provide spectacular evidence for serpentinization-related hydrothermal circulation and for spatial links between faults and volcanic eruptions.

Real-time defect detection on highly reflective curved surfaces

Science.gov (United States)

Rosati, G.; Boschetti, G.; Biondi, A.; Rossi, A.

2009-03-01

This paper presents an automated defect detection system for coated plastic components for the automotive industry. This research activity came up as an evolution of a previous study which employed a non-flat mirror to illuminate and inspect high reflective curved surfaces. According to this method, the rays emitted from a light source are conveyed on the surface under investigation by means of a suitably curved mirror. After the reflection on the surface, the light rays are collected by a CCD camera, in which the coating defects appear as shadows of various shapes and dimensions. In this paper we present an evolution of the above-mentioned method, introducing a simplified mirror set-up in order to reduce the costs and the complexity of the defect detection system. In fact, a set of plane mirrors is employed instead of the curved one. Moreover, the inspection of multiple bend radius parts is investigated. A prototype of the machine vision system has been developed in order to test this simplified method. This device is made up of a light projector, a set of plane mirrors for light rays reflection, a conveyor belt for handling components, a CCD camera and a desktop PC which performs image acquisition and processing. Like in the previous system, the defects are identified as shadows inside a high brightness image. At the end of the paper, first experimental results are presented.

Determination of the distribution of shallow-water seagrass and drift algae communities with acoustic seafloor discrimination.

Science.gov (United States)

Riegl, B; Moyer, R P; Morris, L; Virnstein, R; Dodge, R E

2005-05-01

The spatial distribution of seagrass and algae communities can be difficult to determine in large, shallow lagoon systems where high turbidity prevents the use of optical methods like aerial photography or satellite imagery. Further complications can arise when algae are not permanently attached to the substratum and drift with tides and currents. A study using acoustic seafloor discrimination was conducted in the Indian River Lagoon (Florida, USA) to determine the extent of drift algae and seagrass. Acoustic surveys using the QTC View V system based on 50 and 200 kHz transducers were conducted near Sebastian Inlet. Results indicate that areas of seagrass can be identified, and are mixed with a high abundance of drift algae. Nearest-neighbor extrapolation was used to fill in spaces between survey lines and thus obtain spatially cohesive maps. These maps were then ground-truthed using data from towed video and compared using confusion matrices, The maps showed a high level of agreement (60%) with the actual distribution of algae, however some confusion existed between bare sand and algae as well as seagrass.

High resolution shear wave reflection surveying for hydrogeological investigations

International Nuclear Information System (INIS)

Johnson, W.J.; Clark, J.C.

1992-08-01

The high resolution S-wave method has been developed to be a powerful tool in mapping subsurface lithology and in conducting groundwater investigations. The research has demonstrated that the resolution obtainable using S-waves in a Coastal Plain environment is more than double than that obtained using conventional reflection, which already offers a higher resolution than any other surface method. Where the mapping of thin clay layers functioning as aquitards or thin sand layers functioning as aquifers are critical to the understanding of groundwater flow, S-wave reflections offer unparalleled possibilities for nondestructive exploration. The field experiment at Cooke Crossroads, South Carolina enabled the detection and mapping of beds in the thickness range of one to three feet. The S-wave reflection technique, in combination with conventional P-wave reflection, has potential to directly detect confined and unconfined aquifers. This is a breakthrough technology that still requires additional research before it can be applied on a commercial basis. Aquifer systems were interpreted from the test data at Cooke Crossroads consistent with theoretical model. Additional research is need in assessing the theoretical response of P- and S-waves to subsurface interfaces within unconsolidated sediments of varying moisture content and lithology. More theoretical modeling and in situ testing are needed to bring our knowledge of these phenomena to the level that oil and gas researchers have done for fluids in sandstones

Seafloor Age-Stacking Reveals No Evidence for Milankovitch Cycle Influence on Abyssal Hills at Intermediate, Fast and Super-Fast Spreading Rates

Science.gov (United States)

Goff, J.; Zahirovic, S.; Müller, D.

2017-12-01

Recently published spectral analyses of seafloor bathymetry concluded that abyssal hills, highly linear ridges that are formed along seafloor spreading centers, exhibit periodicities that correspond to Milankovitch cycles - variations in Earth's orbit that affect climate on periods of 23, 41 and 100 thousand years. These studies argue that this correspondence could be explained by modulation of volcanic output at the mid-ocean ridge due to lithostatic pressure variations associated with rising and falling sea level. If true, then the implications are substantial: mapping the topography of the seafloor with sonar could be used as a way to investigate past climate change. This "Milankovitch cycle" hypothesis predicts that the rise and fall of abyssal hills will be correlated to crustal age, which can be tested by stacking, or averaging, bathymetry as a function of age; stacking will enhance any age-dependent signal while suppressing random components, such as fault-generated topography. We apply age-stacking to data flanking the Southeast Indian Ridge ( 3.6 cm/yr half rate), northern East Pacific Rise ( 5.4 cm/yr half rate) and southern East Pacific Rise ( 7.8 cm/yr half rate), where multibeam bathymetric coverage is extensive on the ridge flanks. At the greatest precision possible given magnetic anomaly data coverage, we have revised digital crustal age models in these regions with updated axis and magnetic anomaly traces. We also utilize known 2nd-order spatial statistical properties of abyssal hills to predict the variability of the age-stack under the null hypothesis that abyssal hills are entirely random with respect to crustal age; the age-stacked profile is significantly different from zero only if it exceeds this expected variability by a large margin. Our results indicate, however, that the null hypothesis satisfactorily explains the age-stacking results in all three regions of study, thus providing no support for the Milankovitch cycle hypothesis. The

Spreading rate dependent seafloor deformation in response to India-Eurasia collision: results of a hydrosweep survey in the Central Indian Ocean basin

Digital Repository Service at National Institute of Oceanography (India)

Mukhopadhyay, R.; George, P.; Ranade, G.

) on the topography of this area. Lack of detailed bathymetric data was a deterrent for such a com- prehensive study. We present here a high-reso- lution multibeam seafloor bathymetry map of an area of more than 56,000 km-’ in the CIOB (Figs. lb, 2), to document... (Fig. 2) an effort was made to understand the basinal geomorphology of the area, in terms of compressive and tensional stress. For this purpose bathymetry data along 64 short pro- files, covering more than 1219 km length, were computed. Due...

Stochastic formalism-based seafloor feature discrimination using multifractality of time-dependent acoustic backscatter

Digital Repository Service at National Institute of Oceanography (India)

Haris, K.; Chakraborty, B.

Nonlin. Processes Geophys., 21, 101–113, 2014 www.nonlin-processes-geophys.net/21/101/2014/ doi:10.5194/npg-21-101-2014 © Author(s) 2014. CC Attribution 3.0 License. Nonlinear Processes in Geophysics O pen A ccess Stochastic formalism-based seafloor... shifted in time to align with the selected feature (Fig. 2). The aligned echo envelopes were averaged to obtain stable acoustic signals to Nonlin. Processes Geophys., 21, 101–113, 2014 www.nonlin-processes-geophys.net/21/101/2014/ K. Haris and B...

Development from the seafloor to the sea surface of the cabled NEMO-SN1 observatory in the Western Ionian Sea

Science.gov (United States)

Sparnocchia, Stefania; Beranzoli, Laura; Borghini, Mireno; Durante, Sara; Favali, Paolo; Giovanetti, Gabriele; Italiano, Francesco; Marinaro, Giuditta; Meccia, Virna; Papaleo, Riccardo; Riccobene, Giorgio; Schroeder, Katrin

2015-04-01

implementation of new measurement capabilities at seafloor and along the water column with sensors for measurements of physical-chemical (pressure, temperature, salinity, dissolved oxygen, turbidity, pCO2, currents) and geophysical (magnetometer, seismometer and gravity meter) parameters. An imaging system for deep sea fauna will be deployed very soon at TSS. Furthermore, the data acquisition/elaboration system will be enhanced, and data will be shared in near real time through the Catania node of the high-speed telecommunication network for University and Scientific Research. An Open Access policy is adopted to favour the access of the international scientific community. According to the EMSO business plan and EC recommendations, the enhanced infrastructure will be open to scientists, companies and public actors on excellence research basis, for the development of innovative scientific and technological research products. The existing seafloor module is already offering this service under the TNA program of FixO3 EC Project (www.fixo3.eu). The ongoing development of NEMO-SN1 will strengthen its capabilities to monitor long-term variability of key physical, geophysical and biogeochemical parameters, with applications, for example, in studies on modifications of the properties of water masses and the marine circulation, changes in marine chemistry, with particular emphasis on the carbon system and its role in ocean acidification, evolving trends in global sea level, and to address geo-hazards issues, such as earthquake and tsunami risks, volcanic risk, instability and collapse of the slopes.

High-resolution seismic reflection study, Vacherie Dome

International Nuclear Information System (INIS)

1984-06-01

A high-resolution seismic reflection study, consisting of recording, processing, and interpreting four seismic reflection lines, was made at Vacherie Dome, Louisiana. The presumed shape of the dome, as pictured in the geologic area characterization report by Law Engineering Testing Company in 1982, was based largely on interpretation of gravity data, constrained by a few wells and exploration-type seismic profiles. The purpose of the study was to obtain refined profiles of the dome above -914 m (-3000 ft) elevation. Additional study had been recommended by Louisiana State University in 1967 and the Office of Nuclear Waste Isolation in 1981 because the interpreted size of Vacherie Dome was based on limited seismic and gravity data. Forty-eight traces of seismic data were recorded each time shots were made to generate energy. Twelve-fold, common-depth-point data were obtained using geophone stations spaced at 15-m (50-ft) intervals with shots at 30-m (100-ft) intervals. The time-sampling interval used was 1 ms. Processing intended to enhance resolution included iterative static corrections, deconvolution before stacking, and both time- and depth-migration. The locations of the steep dome sides were inferred primarily from terminations of strong reflections (migrated) from strata near the top of the upper and lower Cretaceous sections. This interpretation agrees closely with the presumed shape from the top of the dome to about -610 m (-2000 ft) elevation, but below this on three of the profiles, this interpretation indicates a steeper salt face than the presumed shape. The area reduction at -914 m (-3000 ft) elevation is estimated to be on the order of 20 percent. 10 references, 11 figures, 4 tables

The New Seafloor Observatory (OBSEA) for Remote and Long-Term Coastal Ecosystem Monitoring

Science.gov (United States)

Aguzzi, Jacopo; Mànuel, Antoni; Condal, Fernando; Guillén, Jorge; Nogueras, Marc; del Rio, Joaquin; Costa, Corrado; Menesatti, Paolo; Puig, Pere; Sardà, Francesc; Toma, Daniel; Palanques, Albert

2011-01-01

A suitable sampling technology to identify species and to estimate population dynamics based on individual counts at different temporal levels in relation to habitat variations is increasingly important for fishery management and biodiversity studies. In the past two decades, as interest in exploring the oceans for valuable resources and in protecting these resources from overexploitation have grown, the number of cabled (permanent) submarine multiparametric platforms with video stations has increased. Prior to the development of seafloor observatories, the majority of autonomous stations were battery powered and stored data locally. The recently installed low-cost, multiparametric, expandable, cabled coastal Seafloor Observatory (OBSEA), located 4 km off of Vilanova i la Gertrú, Barcelona, at a depth of 20 m, is directly connected to a ground station by a telecommunication cable; thus, it is not affected by the limitations associated with previous observation technologies. OBSEA is part of the European Multidisciplinary Seafloor Observatory (EMSO) infrastructure, and its activities are included among the Network of Excellence of the European Seas Observatory NETwork (ESONET). OBSEA enables remote, long-term, and continuous surveys of the local ecosystem by acquiring synchronous multiparametric habitat data and bio-data with the following sensors: Conductivity-Temperature-Depth (CTD) sensors for salinity, temperature, and pressure; Acoustic Doppler Current Profilers (ADCP) for current speed and direction, including a turbidity meter and a fluorometer (for the determination of chlorophyll concentration); a hydrophone; a seismometer; and finally, a video camera for automated image analysis in relation to species classification and tracking. Images can be monitored in real time, and all data can be stored for future studies. In this article, the various components of OBSEA are described, including its hardware (the sensors and the network of marine and land nodes

The New Seafloor Observatory (OBSEA for Remote and Long-Term Coastal Ecosystem Monitoring

Directory of Open Access Journals (Sweden)

Albert Palanques

2011-05-01

Full Text Available A suitable sampling technology to identify species and to estimate population dynamics based on individual counts at different temporal levels in relation to habitat variations is increasingly important for fishery management and biodiversity studies. In the past two decades, as interest in exploring the oceans for valuable resources and in protecting these resources from overexploitation have grown, the number of cabled (permanent submarine multiparametric platforms with video stations has increased. Prior to the development of seafloor observatories, the majority of autonomous stations were battery powered and stored data locally. The recently installed low-cost, multiparametric, expandable, cabled coastal Seafloor Observatory (OBSEA, located 4 km off of Vilanova i la Gertrú, Barcelona, at a depth of 20 m, is directly connected to a ground station by a telecommunication cable; thus, it is not affected by the limitations associated with previous observation technologies. OBSEA is part of the European Multidisciplinary Seafloor Observatory (EMSO infrastructure, and its activities are included among the Network of Excellence of the European Seas Observatory NETwork (ESONET. OBSEA enables remote, long-term, and continuous surveys of the local ecosystem by acquiring synchronous multiparametric habitat data and bio-data with the following sensors: Conductivity-Temperature-Depth (CTD sensors for salinity, temperature, and pressure; Acoustic Doppler Current Profilers (ADCP for current speed and direction, including a turbidity meter and a fluorometer (for the determination of chlorophyll concentration; a hydrophone; a seismometer; and finally, a video camera for automated image analysis in relation to species classification and tracking. Images can be monitored in real time, and all data can be stored for future studies. In this article, the various components of OBSEA are described, including its hardware (the sensors and the network of marine and

The new Seafloor Observatory (OBSEA) for remote and long-term coastal ecosystem monitoring.

Science.gov (United States)

Aguzzi, Jacopo; Mànuel, Antoni; Condal, Fernando; Guillén, Jorge; Nogueras, Marc; del Rio, Joaquin; Costa, Corrado; Menesatti, Paolo; Puig, Pere; Sardà, Francesc; Toma, Daniel; Palanques, Albert

2011-01-01

A suitable sampling technology to identify species and to estimate population dynamics based on individual counts at different temporal levels in relation to habitat variations is increasingly important for fishery management and biodiversity studies. In the past two decades, as interest in exploring the oceans for valuable resources and in protecting these resources from overexploitation have grown, the number of cabled (permanent) submarine multiparametric platforms with video stations has increased. Prior to the development of seafloor observatories, the majority of autonomous stations were battery powered and stored data locally. The recently installed low-cost, multiparametric, expandable, cabled coastal Seafloor Observatory (OBSEA), located 4 km off of Vilanova i la Gertrú, Barcelona, at a depth of 20 m, is directly connected to a ground station by a telecommunication cable; thus, it is not affected by the limitations associated with previous observation technologies. OBSEA is part of the European Multidisciplinary Seafloor Observatory (EMSO) infrastructure, and its activities are included among the Network of Excellence of the European Seas Observatory NETwork (ESONET). OBSEA enables remote, long-term, and continuous surveys of the local ecosystem by acquiring synchronous multiparametric habitat data and bio-data with the following sensors: Conductivity-Temperature-Depth (CTD) sensors for salinity, temperature, and pressure; Acoustic Doppler Current Profilers (ADCP) for current speed and direction, including a turbidity meter and a fluorometer (for the determination of chlorophyll concentration); a hydrophone; a seismometer; and finally, a video camera for automated image analysis in relation to species classification and tracking. Images can be monitored in real time, and all data can be stored for future studies. In this article, the various components of OBSEA are described, including its hardware (the sensors and the network of marine and land nodes

The enigmatic ultra-long run-out of seafloor density driven flows

Science.gov (United States)

Dorrell, R. M.

2017-12-01

Dilute, particulate-laden, density-driven flows - turbidity currents - are a predominant mechanism for transporting sediment from source to sink in deep marine environments. These flows sculpt channels on the seafloor and, as evidenced by a wealth of bathymetric data, can travel for >1000km, forming some of the largest sedimentary landforms on the planet. For turbidity currents to travel such large dsitances, sediment must be self-maintained in suspension, i.e., be in a state of autosuspension. It has been shown that such self-maintained sediment suspensions can only occur whilst inertial forces are greater than gravitational forces, entailing supercritical flow. This conclusion is paradoxical, as inertia dominated flows rapidly entrain fluid, thereby thickening and slowing to become subcritical. However, current theory can only truly be applied to the proximal upper slope regions of seafloor channels where incised flows are fully confined. This contrasts with the distal reaches of long run out turbidity current systems, where the flow is only partially confined through self-channelization. Here it is shown that overspill of partially confined flow has a significant effect on the hydro- and morphodynamics of turbidity current systems. A new model is derived that shows that channel overspill acts to negate the effects of ambient fluid entrainment: a dynamic balance that limits increases in flow depth and maintains supercritical flow throughout the channel. In the new model mass, momentum and energy conservation is modulated by flow overspill onto channel banks, necessarily requiring description of the vertical structure of the flow. Analysis of continuously stratified steady state flow dynamics shows that the integration of overspill and stratification is necessary to enable maintained autosuspension and thus predict the ultra-long run-out of turbidity currents.

X-ray reflectivity measurements of liquid/solid interfaces under high hydrostatic pressure conditions.

Science.gov (United States)

Wirkert, Florian J; Paulus, Michael; Nase, Julia; Möller, Johannes; Kujawski, Simon; Sternemann, Christian; Tolan, Metin

2014-01-01

A high-pressure cell for in situ X-ray reflectivity measurements of liquid/solid interfaces at hydrostatic pressures up to 500 MPa (5 kbar), a pressure regime that is particularly important for the study of protein unfolding, is presented. The original set-up of this hydrostatic high-pressure cell is discussed and its unique properties are demonstrated by the investigation of pressure-induced adsorption of the protein lysozyme onto hydrophobic silicon wafers. The presented results emphasize the enormous potential of X-ray reflectivity studies under high hydrostatic pressure conditions for the in situ investigation of adsorption phenomena in biological systems.

From the surface to the seafloor: How giant larvaceans transport microplastics into the deep sea

Science.gov (United States)

Katija, Kakani; Choy, C. Anela; Sherlock, Rob E.; Sherman, Alana D.; Robison, Bruce H.

2017-01-01

Plastic waste is a pervasive feature of marine environments, yet little is empirically known about the biological and physical processes that transport plastics through marine ecosystems. To address this need, we conducted in situ feeding studies of microplastic particles (10 to 600 μm in diameter) with the giant larvacean Bathochordaeus stygius. Larvaceans are abundant components of global zooplankton assemblages, regularly build mucus “houses” to filter particulate matter from the surrounding water, and later abandon these structures when clogged. By conducting in situ feeding experiments with remotely operated vehicles, we show that giant larvaceans are able to filter a range of microplastic particles from the water column, ingest, and then package microplastics into their fecal pellets. Microplastics also readily affix to their houses, which have been shown to sink quickly to the seafloor and deliver pulses of carbon to benthic ecosystems. Thus, giant larvaceans can contribute to the vertical flux of microplastics through the rapid sinking of fecal pellets and discarded houses. Larvaceans, and potentially other abundant pelagic filter feeders, may thus comprise a novel biological transport mechanism delivering microplastics from surface waters, through the water column, and to the seafloor. Our findings necessitate the development of tools and sampling methodologies to quantify concentrations and identify environmental microplastics throughout the water column. PMID:28835922

Dispersion of dissolved tracers released at the seafloor

International Nuclear Information System (INIS)

Kupferman, S.L.; Moore, D.E.

1983-01-01

The authors present scenarios that describe the temporal and spatial development of a concentration field of a dissolved tracer released at the seafloor for one Pacific and two Atlantic study areas. The scenarios are closely tied to available data by means of simple analytical models, and they proceed in stages from short time and space scales in the immediate vicinity of a release point to those scales characteristic of entire ocean basins. They introduce and discuss the concepts of internal mixing time and residence time in the benthic mixed layer, which are useful for developing an intuitive feeling for the behavior of a tracer. They 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. In addition they urgently need more information that relates isopycnal structure and bottom topography to local near-bottom circulation

Reflective Writing for a Better Understanding of Scientific Concepts in High School

Science.gov (United States)

El-Helou, Joseph; Kalman, Calvin S.

2018-02-01

Science teachers can always benefit from efficient tools that help students to engage with the subject and understand it better without significantly adding to the teacher's workload nor requiring too much of class time to manage. Reflective writing is such a low-impact, high-return tool. What follows is an introduction to reflective writing, and more on its usefulness for teachers is given in the last part of this article.

High resolution tsunami inversion for 2010 Chile earthquake

Directory of Open Access Journals (Sweden)

T.-R. Wu

2011-12-01

Full Text Available We investigate the feasibility of inverting high-resolution vertical seafloor displacement from tsunami waveforms. An inversion method named "SUTIM" (small unit tsunami inversion method is developed to meet this goal. In addition to utilizing the conventional least-square inversion, this paper also enhances the inversion resolution by Grid-Shifting method. A smooth constraint is adopted to gain stability. After a series of validation and performance tests, SUTIM is used to study the 2010 Chile earthquake. Based upon data quality and azimuthal distribution, we select tsunami waveforms from 6 GLOSS stations and 1 DART buoy record. In total, 157 sub-faults are utilized for the high-resolution inversion. The resolution reaches 10 sub-faults per wavelength. The result is compared with the distribution of the aftershocks and waveforms at each gauge location with very good agreement. The inversion result shows that the source profile features a non-uniform distribution of the seafloor displacement. The highly elevated vertical seafloor is mainly concentrated in two areas: one is located in the northern part of the epicentre, between 34° S and 36° S; the other is in the southern part, between 37° S and 38° S.

High resolution tsunami inversion for 2010 Chile earthquake

Science.gov (United States)

Wu, T.-R.; Ho, T.-C.

2011-12-01

We investigate the feasibility of inverting high-resolution vertical seafloor displacement from tsunami waveforms. An inversion method named "SUTIM" (small unit tsunami inversion method) is developed to meet this goal. In addition to utilizing the conventional least-square inversion, this paper also enhances the inversion resolution by Grid-Shifting method. A smooth constraint is adopted to gain stability. After a series of validation and performance tests, SUTIM is used to study the 2010 Chile earthquake. Based upon data quality and azimuthal distribution, we select tsunami waveforms from 6 GLOSS stations and 1 DART buoy record. In total, 157 sub-faults are utilized for the high-resolution inversion. The resolution reaches 10 sub-faults per wavelength. The result is compared with the distribution of the aftershocks and waveforms at each gauge location with very good agreement. The inversion result shows that the source profile features a non-uniform distribution of the seafloor displacement. The highly elevated vertical seafloor is mainly concentrated in two areas: one is located in the northern part of the epicentre, between 34° S and 36° S; the other is in the southern part, between 37° S and 38° S.

Development of a Long-Life-Cycle, Highly Water-Resistant Solar Reflective Retrofit Roof Coating

Energy Technology Data Exchange (ETDEWEB)

Polyzos, Georgios [ORNL; Hunter, Scott Robert [ORNL; Sharma, Jaswinder K [ORNL; Cheng, Mengdawn [ORNL; Chen, Sharon S [Lawrence Berkeley National Laboratory (LBNL); Demarest, Victoria [Dow Chemical Company; Fabiny, William [Dow Chemical Company; Destaillats, Hugo [Lawrence Berkeley National Laboratory (LBNL); Levinson, Ronnen [Lawrence Berkeley National Laboratory (LBNL)

2016-03-04

Highly water-resistant and solar-reflective coatings for low-slope roofs are potentially among the most economical retrofit approaches to thermal management of the building envelope. Therefore, they represent a key building technology research program within the Department of Energy. Research efforts in industry and the Department of Energy are currently under way to increase long-term solar reflectance on a number of fronts. These include new polymer coatings technologies to provide longer-lasting solar reflectivity and improved test methodologies to predict long-term soiling and microbial performance. The focus on long-term improvements in soiling and microbial resistance for maximum reflectance does not address the single most important factor impacting the long-term sustainability of low-slope roof coatings: excellent water resistance. The hydrophobic character of asphaltic roof products makes them uniquely suitable for water resistance, but their low albedo and poor exterior durability are disadvantages. A reflective coating that maintains very high water resistance with increased long-term resistance to soiling and microbial activity would provide additional energy savings and extend roof service life.

Source-driven noise analysis measurements with neptunium metal reflected by high enriched uranium

International Nuclear Information System (INIS)

Valentine, Timothy E.; Mattingly, John K.

2003-01-01

Subcritical noise analysis measurements have been performed with neptunium ( 237 Np) sphere reflected by highly enriched uranium. These measurements were performed at the Los Alamos Critical Experiment Facility in December 2002 to provide an estimate of the subcriticality of 237 Np reflected by various amounts of high-enriched uranium. This paper provides a description of the measurements and presents some preliminary results of the analysis of the measurements. The measured and calculated spectral ratios differ by 15% whereas the 'interpreted' and calculated k eff values differ by approximately 1%. (author)

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

Comment on "Sensitivity of seafloor bathymetry to climate-driven fluctuations in mid-ocean ridge magma supply".

Science.gov (United States)

Tolstoy, Maya

2016-07-15

Olive et al (Reports, 16 October 2015, p. 310) and Goff (Technical Comment, 4 September 2015, p. 1065) raise important concerns with respect to recent findings of Milankovitch cycles in seafloor bathymetry. However, their results inherently support that the Southern East Pacific Rise is the optimum place to look for such signals and, in fact, models match those observations quite closely. Copyright © 2016, American Association for the Advancement of Science.

Sea-floor morphology and sedimentary environments of western Block Island Sound, northeast of Gardiners Island, New York

Science.gov (United States)

McMullen, Katherine Y.; Poppe, Lawrence J.; Danforth, William W.; Blackwood, Dann S.; Clos, Andrew R.; Parker, Castle E.

2014-01-01

Multibeam-echosounder data, collected during survey H12299 by the National Oceanic and Atmospheric Administration in a 162-square-kilometer area of Block Island Sound, northeast of Gardiners Island, New York, are used along with sediment samples and bottom photography, collected at 37 stations in this area by the U.S. Geological Survey during cruise 2013-005-FA, to interpret sea-floor features and sedimentary environments. These data and interpretations provide important base maps for future studies of the sea floor, focused, for example, on benthic ecology and resource management. The features and sedimentary environments on the sea floor are products of the glacial history and modern tidal regime. Features include bedforms such as sand waves and megaripples, boulders, a large current-scoured depression, exposed glaciolacustrine sediments, and areas of modern marine sediment. Sand covers much of the study area and is often in the form of sand waves and megaripples, which indicate environments characterized by coarse-grained bedload transport. Boulders and gravelly lag deposits, which indicate environments of erosion or nondeposition, are found off the coast of Gardiners Island and on bathymetric highs, probably marking areas where deposits associated with recessional ice-front positions, the northern flank of the terminal moraine, or coastal-plain sediments covered with basal till are exposed. Bottom photographs and video of boulders show that they are commonly covered with sessile fauna. Strong tidal currents have produced the deep scour depression along the northwestern edge of the study area. The eastern side of this depression is armored with a gravel lag. Sea-floor areas characterized by modern marine sediments appear featureless at the 2-meter resolution of the bathymetry and flat to current rippled in the photography. These modern environments are indicative of sediment sorting and reworking.

Intra-Cavity Total Reflection For High Sensitivity Measurement Of Optical Properties

Science.gov (United States)

Pipino, Andrew Charles Rule

1999-11-16

An optical cavity resonator device is provided for conducting sensitive murement of optical absorption by matter in any state with diffraction-limited spatial resolution through utilization of total internal reflection within a high-Q (high quality, low loss) optical cavity. Intracavity total reflection generates an evanescent wave that decays exponentially in space at a point external to the cavity, thereby providing a localized region where absorbing materials can be sensitively probed through alteration of the Q-factor of the otherwise isolated cavity. When a laser pulse is injected into the cavity and passes through the evanescent state, an amplitude loss resulting from absorption is incurred that reduces the lifetime of the pulse in the cavity. By monitoring the decay of the injected pulse, the absorption coefficient of manner within the evanescent wave region is accurately obtained from the decay time measurement.

Below the surface: Twenty-five years of seafloor litter monitoring in coastal seas of North West Europe (1992–2017)

NARCIS (Netherlands)

Maes, Thomas; Leslie, H.A.; Barry, Jon; Vethaak, A.D.; Nicolaus, E.E.M.; Law, R.J.; Lyons, B.P.; Martinez, R.; Harley, B.; Thain, J.E.

2018-01-01

Marine litter presents a global problem, with increasing quantities documented in recent decades. The distribution and abundance of marine litter on the seafloor off the United Kingdom's (UK) coasts were quantified during 39 independent scientific surveys conducted between 1992 and 2017. Widespread

Measuring third year undergraduate nursing students' reflective thinking skills and critical reflection self-efficacy following high fidelity simulation: A pilot study.

Science.gov (United States)

Tutticci, Naomi; Lewis, Peter A; Coyer, Fiona

2016-05-01

Critical reflection underpins critical thinking, a highly desirable generic nursing graduate capability. To improve the likelihood of critical thinking transferring to clinical practice, reflective thinking needs to be measured within the learning space of simulation. This study was divided into two phases to address the reliability and validity measures of previously untested surveys. Phase One data was collected from individuals (n = 6) using a 'think aloud' approach and an expert panel to review content validity, and verbatim comment analysis was undertaken. The Reflective Thinking Instrument and Critical Reflection Self-Efficacy Visual Analogue Scale items were contextualised to simulation. The expert review confirmed these instruments exhibited content validity. Phase Two data was collected through an online survey (n = 58). Cronbach's alpha measured internal consistency and was demonstrated by all subscales and the Instrument as a whole (.849). There was a small to medium positive correlation between critical reflection self-efficacy and general self-efficacy (r = .324, n = 56, p = .048). Participant responses were positive regarding the simulation experience. The research findings demonstrated that the Reflective Thinking and Simulation Satisfaction survey is reliable. Further development of this survey to establish validity is recommended to make it viable. Copyright © 2016 Elsevier Ltd. All rights reserved.

Preliminary hard and soft bottom seafloor substrate map derived from gridded sidescan and bathymetry derivatives at Apra Harbor, Guam U.S. Territory.

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Preliminary hard and soft seafloor substrate map classified from sidescan data and bathymetric derivatives at Apra Harbor, Guam U.S. Territory. The dataset was...

Highly Reflecting, Broadband Deformable Membrane Mirror for Wavefront Control Applications, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This Phase I STTR project will develop a highly reflecting, broadband, radiation resistant, low-stress and lightweight, membrane integrated into an electrostatically...

High-efficiency dual-modes vortex beam generator with polarization-dependent transmission and reflection properties.

Science.gov (United States)

Tang, Shiwei; Cai, Tong; Wang, Guang-Ming; Liang, Jian-Gang; Li, Xike; Yu, Jiancheng

2018-04-23

Vortex beam is believed to be an effective way to extend communication capacity, but available efforts suffer from the issues of complex configurations, fixed operation mode as well as low efficiency. Here, we propose a general strategy to design dual-modes vortex beam generator by using metasurfaces with polarization-dependent transmission and reflection properties. Combining the focusing and vortex functionalities, we design/fabricate a type of compact dual-modes vortex beam generator operating at both reflection/transmission sides of the system. Experimental results demonstrate that the designed metadevice can switch freely and independently between the reflective vortex with topological charge m 1  = 2 and transmissive vortex with m 2  = 1. Moreover, the metadevice exhibits very high efficiencies of 91% and 85% for the reflective and transmissive case respectively. Our findings open a door for multifunctional metadevices with high performances, which indicate wide applications in modern integration-optics and wireless communication systems.

Highly reflective Bragg gratings in slightly etched step-index polymer optical fiber.

Science.gov (United States)

Hu, Xuehao; Pun, Chi-Fung Jeff; Tam, Hwa-Yaw; Mégret, Patrice; Caucheteur, Christophe

2014-07-28

During the past few years, a strong progress has been made in the photo-writing of fiber Bragg gratings (FBGs) in polymer optical fibers (POFs), animated by the constant wish to enhance the grating reflectivity and improve the sensing performances. In this paper, we report the photo-inscription of highly reflective gratings in step-index POFs, obtained thanks to a slight etching of the cladding. We demonstrate that a cladding diameter decrease of ~12% is an ideal trade-off to produce highly reflective gratings with enhanced axial strain sensitivity, while keeping almost intact their mechanical resistance. For this, we make use of Trans-4-stilbenemethanol-doped photosensitive step-index poly(methyl methacrylate) (PMMA) POFs. FBGs are inscribed at ~1550 nm by the scanning phase mask technique in POFs of different external diameters. Reflectivity reaching 97% is achieved for 6 mm long FBGs, compared to 25% for non-etched POFs. We also report that a cladding decrease enhances the FBG axial tension while keeping unchanged temperature and surrounding refractive index sensitivities. Finally and for the first time, a measurement is conducted in transmission with polarized light, showing that a photo-induced birefringence of 7 × 10(-6) is generated (one order of magnitude higher than the intrinsic fiber birefringence), which is similar to the one generated in silica fiber using ultra-violet laser.

Seismic reflection profile of the Blake Ridge near sites 994, 995, and 997: Chapter 4

Science.gov (United States)

Dillon, William P.; Hutchinson, Deborah R.; Drury, Rebecca M.

1996-01-01

Seismic reflection profiles near Sites 994, 995, and 997 were collected with seismic sources that provide maximum resolution with adequate power to image the zone of gas hydrate stability and the region direction beneath it. The overall structure of the sediment drift deposit that constitutes the Blake Ridge consists of southwestward-dipping strata. These strata are approximately conformal to the seafloor on the southwest side of the ridge and are truncated by erosion on the northeast side. A bottom-simulating reflection (BSR) marks the velocity contrast between gas hydrate-bearing sediment and regions containing free gas beneath the zone of gas hydrate stability. The BSR is strong and continuous near the ridge crest but becomes discontinuous on the flanks, where concentration of gas is reduced and dipping strata pass through the level of the base o fgas hydrate stability or the strata are disrupted by faults. Seismic reflection amplitudes appear to be reduced in the region of gas hydrate formation compared to normal amplitudes. A faulted zone ~0.5-0.6 s thick parallels reflections from strata. We infer that this may represent a formerly gas hydrate-bearing zone that was faulted because of a breakdown of hydrate near its phase limit (at the base of the zone). Strong reflections at the top of the faulted zone are caused by free-gas acccumulation at Site 994. Similar strong reflections probably are caused by free-gas accumulations where the top of the faulted zone rises above the BSR, although this would require local free gas within the hydrate-stable zone.

Low Reflectivity and High Flexibility of Tin-Doped Indium Oxide Nanofiber Transparent Electrodes

KAUST Repository

Wu, Hui

2011-01-12

Tin-doped indium oxide (ITO) has found widespread use in solar cells, displays, and touch screens as a transparent electrode; however, two major problems with ITO remain: high reflectivity (up to 10%) and insufficient flexibility. Together, these problems severely limit the applications of ITO films for future optoelectronic devices. In this communication, we report the fabrication of ITO nanofiber network transparent electrodes. The nanofiber networks show optical reflectivity as low as 5% and high flexibility; the nanofiber networks can be bent to a radius of 2 mm with negligible changes in the sheet resistance. © 2010 American Chemical Society.

VISIONS At-Sea Telepresence (VAST): Educating in Real Time, Seafloor to Shore

Science.gov (United States)

Sautter, L. R.; Fundis, A. T.; Kelley, D. S.; Delaney, J. R.; McNichol, E.; Stoermer, M.; Glenn, S. M.

2012-12-01

The University of Washington (UW) has recently led the VISIONS 2011 and 2012 cruises aboard the R/V Thompson to Axial Seamount on the Juan de Fuca Ridge, part of the NSF Ocean Observatory Initiative. During each cruise the VISIONS At-Sea Telepresence, or VAST Program was piloted, consisting of several live 30-60 minute shipboard broadcasts highlighted by streaming live HD video from the ROV ROPOS documenting investigations of the seamount's hydrothermal vents and recent lava flows. Broadcasts also included short lectures and pre-taped documentaries and seafloor video narrated live by shipboard scientists and students. Pilot audiences at UW, the College of Charleston and Rutgers University included undergraduate marine geology, oceanography and education students, high school students, graduate students and teachers. Multiple public audiences were also recipients of VAST programming, and all broadcasts were viewable in standard definition to any web users. Question/answer interactivity via Twitter and Skype were promoted throughout the broadcasts. To supplement live broadcasts with additional content, a VAST Program website was created on UW's Interactive Oceans site, providing a wealth of hyperlinked online resources covering six program themes, as well as a college-level online laboratory exercise, "Characterizing Lava Flow Morphologies." The online resources are primarily suited to inform a high school and older audience, and thus serves to reach a vast audience. The VAST Program was very successful at engaging and educating both formal and informal audiences. Preliminary VAST results documented by user surveys will be presented.

Characterization, optical properties and laser ablation behavior of epoxy resin coatings reinforced with high reflectivity ceramic particles

Science.gov (United States)

Li, Wenzhi; Kong, Jing; Wu, Taotao; Gao, Lihong; Ma, Zhuang; Liu, Yanbo; Wang, Fuchi; Wei, Chenghua; Wang, Lijun

2018-04-01

Thermal damage induced by high power energy, especially high power laser, significantly affects the lifetime and performance of equipment. High-reflectance coating/film has attracted considerable attention due to its good performance in the damage protection. Preparing a high-reflectance coating with high reaction endothermal enthalpy will effectively consume a large amount of incident energy and in turn protect the substrate from thermal damage. In this study, a low temperature process was used to prepare coatings onto substrate with complex shape and avoid thermal effect during molding. An advanced high reflection ceramic powder, La1‑xSrxTiO3+δ , was added in the epoxy adhesive matrix to improve the reflectivity of coating. The optical properties and laser ablation behaviors of coatings with different ceramic additive ratio of La1‑xSrxTiO3+δ and modified epoxy-La1‑xSrxTiO3+δ with ammonium polyphosphate coatings were investigated, respectively. We found that the reflectivity of coatings is extremely high due to mixed high-reflection La1‑xSrxTiO3+δ particles, up to 96% at 1070 nm, which can significantly improve the laser resistance. In addition, the ammonium polyphosphate modifies the residual carbon structure of epoxy resin from discontinuous fine particles structure to continuous and porous structure, which greatly enhances the thermal-insulation property of coating. Furthermore, the laser ablation threshold is improved obviously, which is from 800 W cm‑2 to 1000 W cm‑2.

Reflective Optical Chopper Used in NIST High-Power Laser Measurements

Directory of Open Access Journals (Sweden)

Cromer, Chris

2008-11-01

Full Text Available For the past ten years, NIST has used high-reflectivity, optical choppers as beamsplitters and attenuators when calibrating the absolute responsivity and response linearity of detectors used with high-power CW lasers. The chopper-based technique has several advantages over the use of wedge-shaped transparent materials (usually crystals often used as beam splitters in this type of measurement system. We describe the design, operation and calibration of these choppers. A comparison between choppers and transparent wedge beampslitters is also discussed.

Multifunctional high-reflective and antireflective layer systems with easy-to-clean properties

International Nuclear Information System (INIS)

Gloess, D.; Frach, P.; Gottfried, C.; Klinkenberg, S.; Liebig, J.-S.; Hentsch, W.; Liepack, H.; Krug, M.

2008-01-01

High-reflective (HR) and even more antireflective (AR) layer systems are in use for widespread applications. Multifunctional layer systems providing high optical functionality with an easy-to-clean or a self-cleaning behaviour would be preferable for many applications to avoid soiling of the surface. In this paper, the feasibility of fabrication by highly productive pulse magnetron sputtering in an in-line coating plant is investigated. Easy-to-clean properties are achieved by a top layer of photocatalytic and photoinduced hydrophilic TiO 2 . Multifunctional HR layer systems were successfully deposited on glass and polyethylene terephthalate (PET) substrates at a low deposition temperature of 150 deg. C, demonstrating the possibility of coating certain polymer materials. Double-sided multifunctional AR layer systems with a single-sided photoinduced hydrophilic TiO 2 top coating have a resulting reflectivity of about 3% and transmittance of about 97% in the visible range of light

From the Seafloor to the Pool: Teaching Science in Idaho Using GIS and Lessons from the Undersea

Science.gov (United States)

Dodds, J.; Glickson, D.; Robigou, V.

2006-12-01

My selection for the NSF-funded 2005 REVEL* Project provided me an opportunity to become a member of the scientific team on an international, deep-sea research cruise in the N.E. Pacific Ocean. REVEL is a professional development program for K-12 teachers ready for the challenge of bringing discovery in the classroom and inquiry into science teaching and learning through the practice of oceanographic research. I was chosen to be aboard the R/V Thompson during the VISIONS '05, an interdisciplinary research cruise that used the Jason 2 remotely-operated vehicle and the autonomous vehicle ABE to collect co-registered geological, chemical, biological, and physical observations of the seafloor. In collaboration with scientists, I analyzed and interpreted high-resolution bathymetric data and dive observations collected in the Main Endeavour hydrothermal vent field of the Juan de Fuca Ridge. I will present the results obtained during Jason 2 dive 177, which visited several sites in the field. After analyzing the bathymetric data in ArcGIS, I used the ArcMap application to overlay the well-navigated dive 177. I precisely documented 15 hours of new geological observations, fluid and biology sampling, and instrument deployments and spatially associated them with the co-registered high-resolution bathymetric and morphologic data.This research project supports my exploration of spatial conceptualization in geography and geology. Although my students in Idaho do not have access to the sea, they can utilize the skills they gain from seafloor studies to collect data in our local environment, and make their own observations and interpretations of the landscape and its geological history. In addition, this work supports the mission of researchers, who need accurately-located, co-registered data sets to best plan integrative science to better understand the interaction between geological, chemical, physical and biological processes in deep-sea, remote, volcanic environments. During

Discrimination between discrete and continuum scattering from the sub-seafloor.

Science.gov (United States)

Holland, Charles W; Steininger, Gavin; Dosso, Stan E

2015-08-01

There is growing evidence that seabed scattering is often dominated by heterogeneities within the sediment volume as opposed to seafloor roughness. From a theoretical viewpoint, sediment volume heterogeneities can be described either by a fluctuation continuum or by discrete particles. In at-sea experiments, heterogeneity characteristics generally are not known a priori. Thus, an uninformed model selection is generally made, i.e., the researcher must arbitrarily select either a discrete or continuum model. It is shown here that it is possible to (acoustically) discriminate between continuum and discrete heterogeneities in some instances. For example, when the spectral exponent γ3>4, the volume scattering cannot be described by discrete particles. Conversely, when γ3≤2, the heterogeneities likely arise from discrete particles. Furthermore, in the range 2discrete vs continuum heterogeneities via acoustic remote sensing may lead to improved observations and concomitant increased understanding of the marine benthic environment.

Mid-ocean ridge serpentinite in the Puerto Rico Trench: Accretion, alteration, and subduction of Cretaceous seafloor in the Atlantic Ocean

Science.gov (United States)

Klein, F.; Marschall, H.; Bowring, S. A.; Horning, G.

2016-12-01

Serpentinite is believed to be one of the main carriers of water and fluid mobile elements into subduction zones, but direct evidence for serpentinite subduction has been elusive. The Antilles island arc is one of only two subduction zones worldwide that recycles slow-spreading oceanic lithosphere where descending serpentinite is both exposed by faulting and directly accessible on the seafloor. Here we examined serpentinized peridotites dredged from the North Wall of the Puerto Rico Trench (NWPRT) to assess their formation and alteration history and discuss geological ramifications resulting from their emplacement and subduction. Lithospheric accretion and serpentinization occurred, as indicated by U-Pb geochronology of hydrothermally altered zircon, at the Cretaceous Mid-Atlantic Ridge (CMAR). In addition to lizardite-rich serpentinites with pseudomorphic textures after olivine and pyroxene typical for static serpentinization at slow spreading mid-ocean ridges, recovered samples include non-pseudomorphic antigorite-rich serpentinites that are otherwise typically associated with peridotite at convergent plate boundaries. Antigorite-serpentinites have considerably lower Fe(III)/Fetot and lower magnetic susceptibilities than lizardite-serpentinites with comparable Fetot contents. Rare earth element (REE) contents of lizardite-serpentinites decrease linearly with increasing Fe(III)/Fetot of whole rock samples, suggesting that oxidation during seafloor weathering of serpentinite releases REEs to seawater. Serpentinized peridotites recorded multifaceted igneous and high- to low-temperature hydrothermal processes that involved extensive chemical, physical, and mineralogical modifications of their peridotite precursors with strong implications for our understanding of the accretion, alteration, and subduction of slow-spreading oceanic lithosphere.

Multisource multibeam backscatter data: developing a strategy for the production of benthic habitat maps using semi-automated seafloor classification methods

Science.gov (United States)

Lacharité, Myriam; Brown, Craig J.; Gazzola, Vicki

2018-06-01

The establishment of multibeam echosounders (MBES) as a mainstream tool in ocean mapping has facilitated integrative approaches towards nautical charting, benthic habitat mapping, and seafloor geotechnical surveys. The bathymetric and backscatter information generated by MBES enables marine scientists to present highly accurate bathymetric data with a spatial resolution closely matching that of terrestrial mapping, and can generate customized thematic seafloor maps to meet multiple ocean management needs. However, when a variety of MBES systems are used, the creation of objective habitat maps can be hindered by the lack of backscatter calibration, due for example, to system-specific settings, yielding relative rather than absolute values. Here, we describe an approach using object-based image analysis to combine 4 non-overlapping and uncalibrated (backscatter) MBES coverages to form a seamless habitat map on St. Anns Bank (Atlantic Canada), a marine protected area hosting a diversity of benthic habitats. The benthoscape map was produced by analysing each coverage independently with supervised classification (k-nearest neighbor) of image-objects based on a common suite of 7 benthoscapes (determined with 4214 ground-truthing photographs at 61 stations, and characterized with backscatter, bathymetry, and bathymetric position index). Manual re-classification based on uncertainty in membership values to individual classes—especially at the boundaries between coverages—was used to build the final benthoscape map. Given the costs and scarcity of MBES surveys in offshore marine ecosystems—particularly in large ecosystems in need of adequate conservation strategies, such as in Canadian waters—developing approaches to synthesize multiple datasets to meet management needs is warranted.

SRTM15_PLUS: Data fusion of Shuttle Radar Topography Mission (SRTM) land topography with measured and estimated seafloor topography (NCEI Accession 0150537)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — To provide an improved mapping of the seafloor fabric globally, we have used available sounding data along with an improved global marine gravity model to develop at...

Key factors influencing rates of heterotrophic sulfate reduction in active seafloor hydrothermal massive sulfide deposits

Directory of Open Access Journals (Sweden)

Kiana Laieikawai Frank

2015-12-01

Full Text Available Hydrothermal vents are thermally and geochemically dynamic habitats, and the organisms therein are subject to steep gradients in temperature and chemistry. To date, the influence of these environmental dynamics on microbial sulfate reduction has not been well constrained. Here, via multivariate experiments, we evaluate the effects of key environmental variables (temperature, pH, H2S, SO42-, DOC on sulfate reduction rates and metabolic energy yields in material recovered from a hydrothermal flange from the Grotto edifice in the Main Endeavor Field, Juan de Fuca Ridge. Sulfate reduction was measured in batch reactions across a range of physico-chemical conditions. Temperature and pH were the strongest stimuli, and maximum sulfate reduction rates were observed at 50 °C and pH 6, suggesting that the in situ community of sulfate-reducing organisms in Grotto flanges may be most active in a slightly acidic and moderate thermal/chemical regime. At pH 4, sulfate reduction rates increased with sulfide concentrations most likely due to the mitigation of metal toxicity. While substrate concentrations also influenced sulfate reduction rates, energy-rich conditions muted the effect of metabolic energetics on sulfate reduction rates. We posit that variability in sulfate reduction rates reflect the response of the active microbial consortia to environmental constraints on in situ microbial physiology, toxicity, and the type and extent of energy limitation. These experiments help to constrain models of the spatial contribution of heterotrophic sulfate reduction within the complex gradients inherent to seafloor hydrothermal deposits.

Orbital- to Sub-Orbital-Scale Cyclicity in Seismic Reflections and Sediment Character in Early to Middle Pleistocene Mudstone, Santa Barbara Basin, California

Science.gov (United States)

Peterson, C. D.; Behl, R. J.; Nicholson, C.; Lisiecki, L. E.; Sorlien, C. C.

2009-12-01

High-resolution seismic reflection records and well logs from the Santa Barbara Channel suggest that large parts of the Pleistocene succession records climate variability on orbital to sub-orbital scales with remarkable sensitivity, much like the well-studied sediments of the last glacial cycle (ODP Site 893). Spectral analysis of seismic reflection data and gamma ray logs from stratigraphically similar Pleistocene sections finds similar cyclic character and shifts through the section. This correlation suggests that acoustic impedance and physical properties of sediment are linked by basin-scale, likely climatically-driven, oscillations in lithologic composition and fabric during deposition, and that seismic profiling can provide a method for remote identification and correlation of orbital- and sub-orbital-scale sedimentary cyclicity. Where it crops out along the northern shelf of the central Santa Barbara Channel, the early to middle Pleistocene succession (~1.8-1.2 Ma) is a bathyal hemipelagic mudstone with remarkably rhythmic planar bedding, finely laminated fabric, and well-preserved foraminifera, none of which have been significantly altered, or obscured by post-depositional diagenesis or tectonic deformation. Unlike the coarser, turbiditic successions in the central Ventura and Los Angeles basins, this sequence has the potential to record Quaternary global climate change at high resolution. Seismic reflection data (towed chirp) collected on the R/V Melville 2008 Cruise (MV08) penetrate 10's of meters below seafloor into a ~1 km-long sequence of south-dipping seismic reflectors. Sampling parallel to the seafloor permits acquisition of consistent signal amplitude for similar reflectors without spreading loss. Based on established age ranges for this section, sedimentation rates may range from 0.4 to 1.4 meters/kyr, therefore suggesting that the most powerful cycles are orbital- to sub-orbital-scale. Discrete sets of cycles with high power show an abrupt shift

Experimental reconstruction of a highly reflecting fiber Bragg grating by using spectral regularization and inverse scattering.

Science.gov (United States)

Rosenthal, Amir; Horowitz, Moshe; Kieckbusch, Sven; Brinkmeyer, Ernst

2007-10-01

We demonstrate experimentally, for the first time to our knowledge, a reconstruction of a highly reflecting fiber Bragg grating from its complex reflection spectrum by using a regularization algorithm. The regularization method is based on correcting the measured reflection spectrum at the Bragg zone frequencies and enables the reconstruction of the grating profile using the integral-layer-peeling algorithm. A grating with an approximately uniform profile and with a maximum reflectivity of 99.98% was accurately reconstructed by measuring only its complex reflection spectrum.

High reflectance Cr/C multilayer at 250 eV for soft X-ray polarimetry

Energy Technology Data Exchange (ETDEWEB)

Wen, Mingwu; Jiang, Li; Zhang, Zhong; Huang, Qiushi [MOE Key Laboratory of Advanced Micro-Structured Materials, Institute of Precision Optical Engineering (IPOE), School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Wang, Zhanshan, E-mail: wangzs@tongji.edu.cn [MOE Key Laboratory of Advanced Micro-Structured Materials, Institute of Precision Optical Engineering (IPOE), School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); She, Rui; Feng, Hua [Department of Engineering Physics, Tsinghua University, Beijing (China); Wang, Hongchang [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom)

2015-10-01

X-ray reflection near 45° via multilayer mirrors can be used for astronomical polarization measurements. A Cr/C multilayer mirror (designed for X-ray polarimetry at 250 eV), with a period thickness of 3.86 nm and a bi-layer number of 100, was fabricated using direct current magnetron sputtering. Grazing incidence X-ray reflectometry at 8 keV and transmission electron microscopy were used to investigate the multilayer structure. Different models were introduced to fit the hard X-ray reflectivity curve, which indicates that the layer thickness of two materials slightly drifts from the bottom to the top of the stack. Both the chromium and carbon layers are amorphous with asymmetric interfaces, while the Cr-on-C interface is slightly wider. Based on the good quality of the multilayer structure, a high reflectivity of 21.8% for the s-polarized light was obtained at 250 eV at a grazing incidence angle of 40.7°. The fabricated Cr/C multilayer mirror exhibits high reflectivity and polarization levels in the energy region of 240 eV–260 eV. - Highlights: • We fabricated Cr/C multilayer with 3.8 nm d-spacing. • X-ray reflectometry was used to determine the exact structure of Cr/C multilayer. • A high reflectivity of 21.8% for the s-polarized light was obtained at 250 eV. • Both Cr and C were found to be amorphous with slightly asymmetric interfaces. • A 4-layer model was used to fit and explain the results.

GEBCO-NF Alumni Team's entry for Shell Ocean Discovery XPRIZE. An innovative seafloor mapping system of an AUV integrated with the newly designed USV SEA-KIT.

Science.gov (United States)

Wigley, R. A.; Anderson, R.; Bazhenova, E.; Falconer, R. K. H.; Kearns, T.; Martin, T.; Minami, H.; Roperez, J.; Rosedee, A.; Ryzhov, I.; Sade, H.; Seeboruth, S.; Simpson, B.; Sumiyoshi, M.; Tinmouth, N.; Zarayskaya, Y.; Zwolak, K.

2017-12-01

The international team of Nippon Foundation/GEBCO Alumni was formed to compete in the Shell Ocean Discovery XPRIZE competition. The aim of the Team is to build an innovative seafloor mapping system, not only to successfully compete in the XPRIZE challenge, but also to make a step towards autonomously mapping the complex global seafloor at resolutions not achievable by standard surface mapping systems. This new technology is linked to goals of the recently announced Nippon Foundation-GEBCO Seabed 2030 Project, aiming in highest possible resolution bathymetric mapping of global World Ocean floor by 2030. The mapping system is composed of three main elements: an Unmanned Surface Vessel (USV), an Autonomous Underwater Vehicle (AUV) and an on-shore control station. A newly designed, USV, called SEA-KIT, was be built to interact with any AUV, acting as remote surface access to the deep ocean. The major function of the SEA-KIT in the system design is 1) the potential transportation of a commercially available AUV to and from the launch site to the survey site and 2) the deployment and recovery of the AUV. In further development stages, options for AUV charging and data transfer are considered. Additionally, the SEA-KIT will offer a positioning solution during AUV operations, utilizing an Ultra Short Base Line (USBL) acoustic system. The data acquisition platform (AUV) is equipped with a high-end technology interferometric sonar with synthetic aperture options, providing the possibility of collecting bathymetric data co-registered with seafloor object imagery. An automated data processing workflow is highly desirable due to the large amount of data collected during each mission. The processing workflow is being designed to be as autonomous as possible and an algorithm for automated data processing onboard are being considered to reduce the time of data processing and make a final products available as soon as possible after the completion of data collection. No human

The optical constants and spectral specular reflectivity of highly oriented pyrolytic graphite (HOPG)

International Nuclear Information System (INIS)

Havstad, M.A.; Schildbach, M.A.; McLean, W. II.

1993-08-01

Measurements of the specular reflectivity and the optical constants of highly ordered pyrolytic graphite (HOPG) have been made using two independent optical systems. The first measures reflectance (at 1.06 μm and 293 K) by comparing the intensity of a laser beam before and after reflecting off the sample. The second determines the complex index of raft-action (from 0.55 to 8.45 μm, with sample temperatures of 293, 480, 900 and 1300 K) by ellipsometry. Agreement between the two methods is good. Moderate reflectivities are observed over the full spectral range of measurement: the spectral directional-hemispherical reflectivity at normal incidence varies from 0.41 at 0.55 μm to 0.74 at 8.45 μm. The components of the complex index of refraction increase smoothly with wavelength. The index of refraction increases from 3.10 at 0.55 μm to 7.84 at 8.45 μm. The extinction coefficient varies from 2.01 to 6.66 over the same range

Episodic normal faulting and magmatism during the syn-spreading stage of the Baiyun sag in Pearl River Mouth Basin: response to the multi-phase seafloor spreading of the South China Sea

Science.gov (United States)

Deng, Peng; Mei, Lianfu; Liu, Jun; Zheng, Jinyun; Liu, Minghui; Cheng, Zijie; Guo, Fengtai

2018-03-01

Considerable post-breakup extensional deformation is recorded in the continental margins of the South China Sea (SCS). To recognize the nature and origin of the significant deformation during the syn-spreading stage (32-15.5 Ma) in the SCS, we comprehensively analyzed the geometry and kinematics of the faults and contemporaneous magmas in the Baiyun sag, northern margin of the SCS, using high-resolution regional three-dimensional seismic data. The kinematic analyses indicate that the faults in the Baiyun sag are recently formed following the onset of seafloor spreading in the SCS. The faults exhibit multiple episodes of growth history, with three active episodes, 32-29, 23.8-21 and 18.5-16.5 Ma, separated by periods of inactivity. Four volcanic groups comprising 98 volcanic mounds have been identified and described, located separately in the northwestern, the central, the southeastern and the northern slope areas. The occurrence of multiple palaeo-seafloors, complemented by the biostratigraphic and K-Ar dating data, reveals multiple extrusive events of the syn-spreading magmas in the Baiyun sag, with three active periods of 23.8-21, 18.5-17.5 and 17.5-16.5 Ma. This study confirms that the normal faulting has a shared genetic origin with the contemporaneous magmatism during the syn-spreading stage in the deep-offshore Baiyun sag, northern margin of the SCS. The episodic fault growth and magmatic extrusive events reveal that the Baiyun sag has undergone at least three episodic tectonic events during the syn-spreading stage, which evolved in response to the multi-stage seafloor spreading of the SCS.

Morphodynamics of supercritical high-density turbidity currents

NARCIS (Netherlands)

Cartigny, M.

2012-01-01

Seafloor and outcrop observations combined with numerical and physical experiments show that turbidity currents are likely 1) to be in a supercritical flow state and 2) to carry high sediment concentrations (being of high-density). The thesis starts with an experimental study of bedforms

A Long Gravity-Piston Corer Developed for Seafloor Gas Hydrate Coring Utilizing an In Situ Pressure-Retained Method

Directory of Open Access Journals (Sweden)

Lin-Yi Gu

2013-07-01

Full Text Available A corer, which can obtain long in situ pressure-retained sediments of up to 30 m core containing gas hydrates, has been applied in the South China Sea (SCS dozens of times. The corer presented in this paper is a convenient, efficient and economical long in situ pressure-retained coring and research tool for submarine sediments, that can applied to completely cope with all sediments close to the seafloor ranging from shallow waters to the deep sea depths of 6000 m. This article mainly presents the overall structure, working principles, key pressure-retained components, coring mechanism, sea trials and outlook of the corer. The analyses found that the coring ability was affected by formation characteristics, the outer diameter of the core barrels and inner diameter of the core liners, the shapes of the cutter and the dead weight of the corer. This study can provide the practical basis for the structural optimization of this type of corer and designs for corers with greater penetrability. Sea trials showed that the developed corer presented in this paper can support the in situ pressure of the seafloor sediment core, which is an improvement over the conventional piston corer.

Seafloor geomorphology of western Antarctic Peninsula bays: a signature of ice flow behaviour

Science.gov (United States)

Munoz, Yuribia P.; Wellner, Julia S.

2018-01-01

Glacial geomorphology is used in Antarctica to reconstruct ice advance during the Last Glacial Maximum and subsequent retreat across the continental shelf. Analogous geomorphic assemblages are found in glaciated fjords and are used to interpret the glacial history and glacial dynamics in those areas. In addition, understanding the distribution of submarine landforms in bays and the local controls exerted on ice flow can help improve numerical models by providing constraints through these drainage areas. We present multibeam swath bathymetry from several bays in the South Shetland Islands and the western Antarctic Peninsula. The submarine landforms are described and interpreted in detail. A schematic model was developed showing the features found in the bays: from glacial lineations and moraines in the inner bay to grounding zone wedges and drumlinoid features in the middle bay and streamlined features and meltwater channels in the outer bay areas. In addition, we analysed local variables in the bays and observed the following: (1) the number of landforms found in the bays scales to the size of the bay, but the geometry of the bays dictates the types of features that form; specifically, we observe a correlation between the bay width and the number of transverse features present in the bays. (2) The smaller seafloor features are present only in the smaller glacial systems, indicating that short-lived atmospheric and oceanographic fluctuations, responsible for the formation of these landforms, are only recorded in these smaller systems. (3) Meltwater channels are abundant on the seafloor, but some are subglacial, carved in bedrock, and some are modern erosional features, carved on soft sediment. Lastly, based on geomorphological evidence, we propose the features found in some of the proximal bay areas were formed during a recent glacial advance, likely the Little Ice Age.

Analysis of seismic reflectivity and AVO pattern of BSR using OBS data in the southwestern offshore region of Taiwan

Energy Technology Data Exchange (ETDEWEB)

Cheng, W.B.; Yang, H.R. [Jinwen Univ. of Science and Technology, Hsintien City, Taipei County, Taiwan (China). Dept. of Environment and Property Management; Schnurle, P.; Liu, C.S. [National Taiwan Univ., Taipei, Taiwan (China). Inst. of Oceanography; Lee, C.S. [National Taiwan Ocean Univ., Keelung, Taiwan (China). Inst. of Applied Earth Science; Wang, Y.; Chung, S.H.; Chen, S.C. [Ministry of Economic Affairs, Taiwan (China). Central Geological Survey

2008-07-01

Regional multi-channel seismic reflection profiles that were conducted in Taiwan from 2003 to 2006 resulted in the identification of a gas hydrate-related bottom simulating reflector (BSR) in the broad southwestern offshore region of Taiwan. In order to understand the regional distribution of methane hydrate bearing layers and explore concentrated hydrate bearing layers, this paper presented a comprehensive analysis of reflection coefficient and amplitude-versus-offset (AVO) pattern of BSR using ocean bottom seismographs (OBSs) seismic data acquired in the southwestern offshore region of Taiwan. The study focused on the analysis and interpretation of airgun array signals recorded by OBSs during 2004 and 2006. Ten profiles of seismic reflection/refraction with a total length of about 140 km and recorded by 50 recovered OBSs were acquired on the active and passive margins in offshore southwestern Taiwan. Amplitudes of the direct water arrival, the multiple, and the BSR were picked interactively for all the OBS lines. A quantitative representation of reflector strength was provided by calculation of reflection coefficients. In general, the seafloor reflection coefficients for the active and passive margins were estimated as 0.1-0.25. The paper presented the data and analysis as well as the results of the study. It was concluded that the results of calculated reflection coefficient of the BSR in offshore southwest Taiwan suggested that inferred hydrate concentration for the passive margin profiles was relatively higher than that for the active margin profiles. 4 refs.

Enhancement of phase-conjugate reflectivity using Zeeman coherence in highly degenerate molecular systems

International Nuclear Information System (INIS)

Mukherjee, Nandini

2010-01-01

A comprehensive theoretical analysis is developed for the vectorial phase conjugation using resonant four-wave mixing (FWM) in a highly degenerate rotational vibrational molecular system. The dynamic Stark shifts, saturation, and Doppler broadening are included for a realistic analysis. It is shown that the electromagnetically induced multilevel coherence controls the nonlinear wave mixing yielding interesting results for the phase conjugate (PC) reflectivity. It turns out that the efficiency of the PC reflectivity is decided by the relative phase of the Zeeman coherence and the population grating. When these two contributions are aligned in phase by a small detuning of the pump frequency, a large PC reflectivity (∼20%) is obtained with moderate pump intensity (∼500 mW/cm 2 ).

Characteristics and processing of seismic data collected on thick, floating ice: Results from the Ross Ice Shelf, Antarctica

Science.gov (United States)

Beaudoin, Bruce C.; ten Brink, Uri S.; Stern, Tim A.

1992-01-01

Coincident reflection and refraction data, collected in the austral summer of 1988/89 by Stanford University and the Geophysical Division of the Department of Scientific and Industrial Research, New Zealand, imaged the crust beneath the Ross Ice Shelf, Antarctica. The Ross Ice Shelf is a unique acquisition environment for seismic reflection profiling because of its thick, floating ice cover. The ice shelf velocity structure is multilayered with a high velocity‐gradient firn layer constituting the upper 50 to 100 m. This near surface firn layer influences the data character by amplifying and frequency modulating the incoming wavefield. In addition, the ice‐water column introduces pervasive, high energy seafloor, intra‐ice, and intra‐water multiples that have moveout velocities similar to the expected subseafloor primary velocities. Successful removal of these high energy multiples relies on predictive deconvolution, inverse velocity stack filtering, and frequency filtering. Removal of the multiples reveals a faulted, sedimentary wedge which is truncated at or near the seafloor. Beneath this wedge the reflection character is diffractive to a two‐way traveltime of ∼7.2 s. At this time, a prominent reflection is evident on the southeast end of the reflection profile. This reflection is interpreted as Moho indicating that the crust is ∼21-km thick beneath the profile. These results provide seismic evidence that the extensional features observed in the Ross Sea region of the Ross Embayment extend beneath the Ross Ice Shelf.

Si-Metasomatism During Serpentinization of Jurassic Ultramafic Sea-floor: a Comparative Study

Science.gov (United States)

Vogel, M.; Frueh-Green, G. L.; Boschi, C.; Schwarzenbach, E. M.

2014-12-01

The Bracco-Levanto ophiolitic complex (northwestern Italy) represents one of the largest and better-exposed ophiolitic successions in the Northern Apennines. It is considered to be a fragment of heterogeneous Jurassic lithosphere that records tectono-magmatic and alteration histories similar to those documented along the Mid-Atlantic Ridge (MAR), such as at the 15°20'N area and the Atlantis Massif at 30°N. Structural and petrological studies on these rocks provide constraints on metamorphic/deformation processes during formation and hydrothermal alteration of the Jurassic oceanic lithosphere. We present a petrological and geochemical study of serpentinization processes and fluid-rock interaction in the Bracco-Levanto ophiolitic complex and compare these to published data from modern oceanic hydrothermal systems, such as the Lost City hydrothermal field hosted in serpentinites on the Atlantis Massif. Major element and mineral compositional data allow us to distinguish a multiphase history of alteration characterized by: (1) widespread Si-metasomatism during progressive serpentinization, and (2) multiple phases of veining and carbonate precipitation associated with circulation of seawater in the shallow ultramafic-dominated portions of the Jurassic seafloor, resulting in the formation of ophicalcites. In detail, regional variations in Si, Mg and Al content are observed in zones of ophicalcite formation, indicating metasomatic reactions and Si-Al transport during long-lived fluid-rock interaction and channelling of hydrothermal fluids. Rare earth element and isotopic analysis indicate that the Si-rich fluids are derived from alteration of pyroxenes to talc and tremolite in ultramafic rocks at depth. Comparison with serpentinites from the Atlantis Massif and 15°20'N indicates a similar degree of Si-enrichment in the modern seafloor and suggests that Si-metasomatism may be a fundamental process associated with serpentinization at slow-spreading ridge environments

Characterization of the Navy Fan Channel-to-Lobe Transition: Geomorphology, Gradient, and Structure Imaged through High-Resolution AUV Bathymetry

Science.gov (United States)

Carvajal, C.; Paull, C. K.; Caress, D. W.; Anderson, K.; Lundsten, E. M.; Gwiazda, R.; Fildani, A.; Dykstra, M.; McGann, M.; Maier, K. L.; Herguera, J. C.

2016-12-01

Channel to lobe transition zones (CLTZ) are elusive sectors of the seafloor. They record complex interactions between sediment-gravity flows, flow confinement, and gradient that can result in contrasting geomorphologies. If present, structural controls can add additional intricacies. We illustrate such complexities in the Navy Fan CLTZ offshore California/Mexico using AUV-collected high-resolution (1x1x0.25 m) bathymetry and chirp profiles. The AUV bathymetry images the fine scale details of the seafloor, otherwise unresolved in surface-ship-mounted multibeam bathymetry. Three morphological areas standout that in a direction transverse to sediment transport are: 1) An unconfined area with variable but overall steep gradients (0.5o-1.7o), and considerable erosion shown by numerous large scours that truncate underlying strata. These scours are elongate (turbidity currents due to high gradients, which resulted from relief along the San Clemente Fault and probably from differential seafloor aggradation. In the moderate confinement area, the smoother and gentler seafloor may be related to more efficient sediment dispersal able to transfer/deposit sediment to heal structural relief (though not completely) while avoiding significant local aggradation, hence preventing major gradient build up. In the faulted area, the steep and prominent structure reroutes the sediments. The findings of this study have broad application to any seafloor areas with rapid changes of gradient.

Where the Wild Microbes Are: Education and Outreach on Sub-Seafloor Microbes

Science.gov (United States)

Cooper, S. K.; Kurtz, K.; Orcutt, B.; Strong, L.; Collins, J.; Feagan, A.

2014-12-01

Sub-seafloor microbiology has the power to spark the imaginations of children, students and the general public with its mysterious nature, cutting-edge research, and connections to the search for extraterrestrial life. These factors have been utilized to create a number of educational and outreach products to bring subsurface microbes to non-scientist audiences in creative and innovative ways. The Adopt a Microbe curriculum for middle school students provides hands-on activities and investigations for students to learn about microbes and the on-going research about them, and provides opportunities to connect with active expeditions. A new series of videos engages non-scientists with stories about research expeditions and the scientists themselves. A poster and associated activities explore the nature of science using a microbiologist and her research as examples. A new e-book for young children will engage them with age-appropriate text and illustrations. These projects are multidisciplinary, involve science and engineering practices, are available to all audiences and provide examples of high level and meaningful partnerships between scientists and educators and the kinds of products that can result. Subseafloor microbiology projects such as these, aimed at K-12 students and the general public, have the potential to entice the interest of the next generation of microbe scientists and increase general awareness of this important science.

High-accuracy self-mixing interferometer based on multiple reflections using a simple external reflecting mirror

Science.gov (United States)

Wang, Xiu-lin; Wei, Zheng; Wang, Rui; Huang, Wen-cai

2018-05-01

A self-mixing interferometer (SMI) with resolution twenty times higher than that of a conventional interferometer is developed by multiple reflections. Only by employing a simple external reflecting mirror, the multiple-pass optical configuration can be constructed. The advantage of the configuration is simple and easy to make the light re-injected back into the laser cavity. Theoretical analysis shows that the resolution of measurement is scalable by adjusting the number of reflections. The experiment shows that the proposed method has the optical resolution of approximate λ/40. The influence of displacement sensitivity gain ( G) is further analyzed and discussed in practical experiments.

Seafloor age dependence of Rayleigh wave phase velocities in the Indian Ocean

Science.gov (United States)

Godfrey, Karen E.; Dalton, Colleen A.; Ritsema, Jeroen

2017-05-01

Variations in the phase velocity of fundamental-mode Rayleigh waves across the Indian Ocean are determined using two inversion approaches. First, variations in phase velocity as a function of seafloor age are estimated using a pure-path age-dependent inversion method. Second, a two-dimensional parameterization is used to solve for phase velocity within 1.25° × 1.25° grid cells. Rayleigh wave travel time delays have been measured between periods of 38 and 200 s. The number of measurements in the study area ranges between 4139 paths at a period of 200 s and 22,272 paths at a period of 40 s. At periods Rodriguez Triple Junction and the Australian-Antarctic Discordance and anomalously low velocities immediately to the west of the Central Indian Ridge.

Seafloor geomorphology and geology of the Kingman Reef-Palmyra Atoll region, Central Pacific Ocean

Science.gov (United States)

Eakins, Barry; Barth, Ginger; Scheirer, Dan; Mosher, Dave; Armstrong, Andy

2017-04-01

Kingman Reef and Palmyra Atoll are the exposed summits of two seamounts within the Line Islands Volcanic Chain in the Central Pacific Ocean. Both are U.S. Territories, and the Exclusive Economic Zone around the islands was partially surveyed in 1991 with GLORIA sidescan sonar and seismic reflection profiling. New multibeam swath sonar surveys were conducted in 2010, 2015, and 2016 around the islands, in support of U.S. Extended Continental Shelf investigations. Numerous transits through the region by research vessels have collected additional multibeam swath sonar data. We present new, detailed maps of bathymetry, sidescan sonar imagery, geology, and sediment isopachs of the seafloor surrounding the islands, and how these have informed our understanding of the islands' margins. The islands are the last subaerial remnants of a complex, horse-shoe-shaped volcanic platform spanning roughly 200 km in diameter. The elevated platform from which the seamounts arise comprises at least 10 individual volcanic centers that have heights exceeding 3000m above the nearby abyssal plains. Gravity modeling suggests that the elevated platform is compensated by thickened crust. Strong carbonate caps and voluminous sediment accumulations flanking the platform indicate that the volcanoes were once shallow-water or emergent systems. These systems produced vast quantities of carbonate sediment that were shed to a deep interior basin to the east of Palmyra Atoll, and to nearby abyssal plains. The identification of mass failures, sediment reworking and bedforms, and channel networks provide evidence for extensive sedimentary processes around these volcanic centers. Analysis of the seamounts atop the elevated platform and in the seamount province to the northwest shows that flat-topped seamounts ("guyots") are principally found at depths shallower than 1300 meters, while peaked seamounts are almost exclusively found at greater depths. This constrains the amount of regional subsidence that

Preliminary hard and soft bottom seafloor substrate map derived from an unsupervised classification of gridded backscatter and bathymetry derivatives of Ni'ihau Island, Hawaii, USA.

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Preliminary hard and soft seafloor substrate map derived from an unsupervised classification of multibeam backscatter and bathymety derivatives of Ni'ihau Island,...

Evidences of intraplate deformation in the West Madeira Abyssal Plain (eastern North Atlantic) from seismic reflection and multibeam swath bathymetry data

Science.gov (United States)

Roque, C.; Simões, M.; Lourenço, N.; Pinto de Abreu, M.

2009-04-01

Late Cretaceous oceanic basement. This basement is outcropping in some places originating small highs, which top is placed at 4700-4800 m water depth, about 500 m above the surrounding flat abyssal plain. The acoustic facies shown by the sedimentary record suggests the presence of a great thickness of turbidites within the sedimentary succession. The sismostratigraphy interpretation allowed the identification of four distinctive seismic units named from bottom to top U1 to U4. A theoretical stratigraphic correlation model between these seismic units and the ODP 157 data (Sites 950, 951 and 952) is proposed in the present work. The oldest seismic units U1 and U2 rest above the oceanic basement and could be correlated with the Late Cretaceous to Early Miocene sediments drilled during ODP 157. The youngest seismic units U3 and U4 show a succession of very continuous and parallel reflections alternating between low and high amplitude. Such type of seismic facies could be correlated with alternating turbidites and pelagic sediments possibly of Middle-Upper Miocene to Pleistocene age considering the ODP 157 data. The Cenozoic sedimentary succession is cut by several normal faults, close spaced, possibly related to compaction and dewatering processes. The acoustic record suggests the occurrence of fluid circulation along these faults, which are rooted in the oceanic basement. In some places these faults cut though the entire sedimentary sequence, almost reaching the seafloor. Evidences of recent compressional deformation are shown by reverse faults that affected the sedimentary sequence and also deform the seafloor by buckling and high amplitude folding. A large pop-up structure is recognized, generating a seafloor high, suggesting the occurrence of recent compressional events in the West Madeira Abyssal Plain region.

High-resolution seismic reflection surveying with a land streamer

Science.gov (United States)

Cengiz Tapırdamaz, Mustafa; Cankurtaranlar, Ali; Ergintav, Semih; Kurt, Levent

2013-04-01

In this study, newly designed seismic reflection data acquisition array (land streamer) is utilized to image the shallow subsurface. Our acquisition system consist of 24 geophones screwed on iron plates with 2 m spacing, moving on the surface of the earth which are connected with fire hose. Completely original, 4.5 Kg weight iron plates provides satisfactory coupling. This land-streamer system enables rapid and cost effective acquisition of seismic reflection data due to its operational facilities. First test studies were performed using various seismic sources such as a mini-vibro truck, buffalo-gun and hammer. The final fieldwork was performed on a landslide area which was studied before. Data acquisition was carried out on the line that was previously measured by the seismic survey using 5 m geophone and shot spacing. This line was chosen in order to re-image known reflection patterns obtained from the previous field study. Taking penetration depth into consideration, a six-cartridge buffalo-gun was selected as a seismic source to achieve high vertical resolution. Each shot-point drilled 50 cm for gunshots to obtain high resolution source signature. In order to avoid surface waves, the offset distance between the source and the first channel was chosen to be 50 m and the shot spacing was 2 m. These acquisition parameters provided 12 folds at each CDP points. Spatial sampling interval was 1 m at the surface. The processing steps included standard stages such as gain recovery, editing, frequency filtering, CDP sorting, NMO correction, static correction and stacking. Furthermore, surface consistent residual static corrections were applied recursively to improve image quality. 2D F-K filter application was performed to suppress air and surface waves at relatively deep part of the seismic section. Results show that, this newly designed, high-resolution land seismic data acquisition equipment (land-streamer) can be successfully used to image subsurface. Likewise

Application of hybrid techniques (self-organizing map and fuzzy algorithm) using backscatter data for segmentation and fine-scale roughness characterization of seepage-related seafloor along the western continental margin of India

Digital Repository Service at National Institute of Oceanography (India)

Chakraborty, B.; Menezes, A.A.A.; Dandapath, S.; Fernandes, W.A.; Karisiddaiah, S.M.; Haris, K.; Gokul, G.S.

density. 2 I. INTRODUCTION Echo-sounding systems, single beam (SBES) and multi-beam (MBES), allow coincident acquisition of high-resolution seafloor backscatter and bathymetric data [1], [2], which enormously sustains the marine exploration..., the SOM can be utilized to formulate a decision regarding the number of data classes during the online data acquisition, that are then used as an input to the fuzzy C-means (FCM) algorithms for data segmentation [12]. The FCM will require initial...

Preliminary hard and soft bottom seafloor substrate map derived from an unsupervised classification of gridded backscatter and bathymetry derivatives at Tutuila Island, American Samoa, South Pacific.

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Preliminary hard and soft seafloor substrate map derived from an unsupervised classification of multibeam backscatter and bathymety derivatives at Tutuila Island,...

Development of a High Resolution BRDF/Albedo Product by Fusing Airborne CASI Reflectance with MODIS Daily Reflectance in the Oasis Area of the Heihe River Basin, China

Directory of Open Access Journals (Sweden)

Dongqin You

2015-05-01

Full Text Available A land-cover-based linear BRDF (bi-directional reflectance distribution function unmixing (LLBU algorithm based on the kernel-driven model is proposed to combine the compact airborne spectrographic imager (CASI reflectance with the moderate resolution imaging spectroradiometer (MODIS daily reflectance product to derive the BRDF/albedo of the two sensors simultaneously in the foci experimental area (FEA of the Heihe Watershed Allied Telemetry Experimental Research (HiWATER, which was carried out in the Heihe River basin, China. For each land cover type, an archetypal BRDF, which characterizes the shape of its anisotropic reflectance, is extracted by linearly unmixing from the MODIS reflectance with the assistance of a high-resolution classification map. The isotropic coefficients accounting for the differences within a class are derived from the CASI reflectance. The BRDF is finally determined by the archetypal BRDF and the corresponding isotropic coefficients. Direct comparisons of the cropland archetypal BRDF and CASI albedo with in situ measurements show good agreement. An indirect validation which compares retrieved BRDF/albedo with that of the MCD43A1 standard product issued by NASA and aggregated CASI albedo also suggests reasonable reliability. LLBU has potential to retrieve the high spatial resolution BRDF/albedo product for airborne and spaceborne sensors which have inadequate angular samplings. In addition, it can shorten the timescale for coarse spatial resolution product like MODIS.

Ultra-wideband high-efficiency reflective linear-to-circular polarization converter based on metasurface at terahertz frequencies.

Science.gov (United States)

Jiang, Yannan; Wang, Lei; Wang, Jiao; Akwuruoha, Charles Nwakanma; Cao, Weiping

2017-10-30

The polarization conversion of electromagnetic (EM) waves, especially linear-to-circular (LTC) polarization conversion, is of great significance in practical applications. In this study, we propose an ultra-wideband high-efficiency reflective LTC polarization converter based on a metasurface in the terahertz regime. It consists of periodic unit cells, each cell of which is formed by a double split resonant square ring, dielectric layer, and fully reflective gold mirror. In the frequency range of 0.60 - 1.41 THz, the magnitudes of the reflection coefficients reach approximately 0.7, and the phase difference between the two orthogonal electric field components of the reflected wave is close to 90° or -270°. The results indicate that the relative bandwidth reaches 80% and the efficiency is greater than 88%, thus, ultra-wideband high-efficiency LTC polarization conversion has been realized. Finally, the physical mechanism of the polarization conversion is revealed. This converter has potential applications in antenna design, EM measurement, and stealth technology.

Serpentinization and fluid-rock interaction in Jurassic mafic and ultramafic sea-floor: constraints from Ligurian ophiolite sequences

Science.gov (United States)

Vogel, Monica; Früh-Green, Gretchen L.; Boschi, Chiara; Schwarzenbach, Esther M.

2014-05-01

The Bracco-Levanto ophiolitic complex (Eastern Liguria) represents one of the largest and better-exposed ophiolitic successions in the Northern Apennines. It is considered to be a fragment of heterogeneous Jurassic lithosphere that records tectono-magmatic and alteration histories similar to those documented along the Mid-Atlantic Ridge, such as at the 15°20'N area and the Atlantis Massif at 30°N. Structural and petrological studies on these rocks provide constraints on metamorphic/deformation processes during formation and hydrothermal alteration of the Jurassic oceanic lithosphere. We present a petrological and geochemical study of deformation processes and fluid-rock interaction in the Bracco-Levanto ophiolitic complex and compare these to modern oceanic hydrothermal systems, such as the Lost City Hydrothermal Field hosted in ultramafic rocks on the Atlantis Massif. A focus is on investigating mass transfer and fluid flow paths during high and low temperature hydrothermal activity, and on processes leading to hydrothermal carbonate precipitation and the formation of ophicalcites, which are characteristic of the Bracco-Levanto sequences. Major element and mineral compositional data allow us to distinguish a multiphase history of alteration characterized by: (1) widespread SiO2 metasomatism during progressive serpentinization, and (2) multiple phases of veining and carbonate precipitation associated with circulation of seawater and high fluid-rock ratios in the shallow ultramafic-dominated portions of the Jurassic seafloor. We observe regional variations in MgO, SiO2 and Al2O3, suggesting Si-flux towards stratigraphically higher units. In general, the ophicalcites have higher Si, Al and Fe concentrations and lower Mg than the serpentinite basement rocks or serpentinites with minimal carbonate veins. Bulk rock trace element data and Sr isotope ratios indicate seawater reacting with rocks of more mafic composition, then channeled towards stratigraphically higher

Petrological evolution of subducted rodingite from seafloor metamorphism to dehydration of enclosing antigorite-serpentinite (Cerro del Almirez massif, southern Spain)

Science.gov (United States)

Laborda-López, Casto; López Sánchez-Vizcaíno, Vicente; Marchesi, Claudio; Gómez-Pugnaire, María Teresa; Garrido, Carlos J.; Jabaloy-Sánchez, Antonio; Padrón-Navarta, José Alberto

2016-04-01

Rodingites are common rocks associated with serpentinites in exhumed terrains that experienced subduction and high pressure metamorphism. However, the response of these rocks to devolatilization and redox reactions in subduction settings is not well constrained. In the Cerro del Almirez ultramafic massif (southern Spain) rodingites constitute about 1-2% of the total volume of exposed rocks. Metarodingites are enclosed in antigorite-serpentinite and chlorite-harzburgite separated by a transitional zone that represents the front of prograde serpentinite-dehydration in a paleo-subduction setting (Padrón-Navarta et al., 2011). Metarodingites occur as boudin lenses, 1 to 20 m in length and 30 cm to 2 m in thickness. During serpentinization of peridotite host rocks, dolerites and basalts precursor of rodingites underwent intense seafloor metasomatism, causing the enrichment in Ca and remobilization of Na and K. Subsequent metamorphism during subduction transformed the original igneous and seafloor metamorphic mineralogy into an assemblage of garnet (Ti-rich hydrogrossular), diopside, chlorite, and epidote. During prograde metamorphism, garnet composition changed towards higher andradite contents. High-pressure transformation of enclosing antigorite-serpentinite to chlorite-harzburgite released fluids which induced breakdown of garnet to epidote in metarodingites. Ti liberation by this latter reaction produced abundant titanite. Released fluids also triggered the formation of amphibole by alkalis addition. Highly recrystallized metarodingites in chlorite-harzburgite present a new generation of idiomorphic garnet with composition equal to 10-30% pyrope, 30-40% grossular and 35-55% almandine + spessartine. This garnet has titanite inclusions in the core and rutile inclusions in the rim. The contact between metarodingites and ultramafic rocks consists of a metasomatic zone (blackwall) with variable thickness (7 to 40 cm) constituted by chlorite, diopside, and titanite

Cool seafloor hydrothermal springs reveal global geochemical fluxes

Science.gov (United States)

Wheat, C. Geoffrey; Fisher, Andrew T.; McManus, James; Hulme, Samuel M.; Orcutt, Beth N.

2017-10-01

We present geochemical data from the first samples of spring fluids from Dorado Outcrop, a basaltic edifice on 23 M.y. old seafloor of the Cocos Plate, eastern Pacific Ocean. These samples were collected from the discharge of a cool hydrothermal system (CHS) on a ridge flank, where typical reaction temperatures in the volcanic crust are low (2-20 °C) and fluid residence times are short. Ridge-flank hydrothermal systems extract 25% of Earth's lithospheric heat, with a global discharge rate equivalent to that of Earth's river discharge to the ocean; CHSs comprise a significant fraction of this global flow. Upper crustal temperatures around Dorado Outcrop are ∼15 °C, the calculated residence time is V, U, Mg, phosphate, Si and Li are different. Applying these observed differences to calculated global CHS fluxes results in chemical fluxes for these ions that are ≥15% of riverine fluxes. Fluxes of K and B also may be significant, but better analytical resolution is required to confirm this result. Spring fluids also have ∼50% less dissolved oxygen (DO) than bottom seawater. Calculations of an analytical model suggest that the loss of DO occurs primarily (>80%) within the upper basaltic crust by biotic and/or abiotic consumption. This calculation demonstrates that permeable pathways within the upper crust can support oxic water-rock interactions for millions of years.

High reflectivity YDH/SiO2 distributed Bragg reflector for UV-C wavelength regime

KAUST Repository

Alias, Mohd Sharizal

2018-02-15

A distributed Bragg reflector (DBR) composed of Y2O3-doped HfO2 (YDH)/SiO2 layers with high reflectivity spectrum centered at a wavelength of ~240 nm is deposited using radio-frequency magnetron sputtering. Before the DBR deposition, optical properties for a single layer of YDH, SiO2, and HfO2 thin films were studied using spectroscopic ellipsometry and spectrophotometry. To investigate the performance of YDH as a material for the high refractive index layer in the DBR, a comparison of its optical properties was made with HfO2 thin films. Due to larger optical bandgap, the YDH thin films demonstrated higher transparency, lower extinction coefficient, and lower absorption coefficient in the UV-C regime (especially for wavelengths below 250 nm) compared to the HfO2 thin films. The deposited YDH/SiO2 DBR consisting of 15 periods achieved a reflectivity higher than 99.9% at the wavelength of ~240 nm with a stopband of ~50 nm. The high reflectivity and broad stopband of YDH/SiO2 DBRs will enable further advancement of various photonic devices such as vertical-cavity surface-emitting lasers, resonant-cavity light-emitting diodes, and resonant-cavity photodetectors operating in the UV-C wavelength regime.

Seafloor geomorphology of western Antarctic Peninsula bays: a signature of ice flow behaviour

Directory of Open Access Journals (Sweden)

Y. P. Munoz

2018-01-01

Full Text Available Glacial geomorphology is used in Antarctica to reconstruct ice advance during the Last Glacial Maximum and subsequent retreat across the continental shelf. Analogous geomorphic assemblages are found in glaciated fjords and are used to interpret the glacial history and glacial dynamics in those areas. In addition, understanding the distribution of submarine landforms in bays and the local controls exerted on ice flow can help improve numerical models by providing constraints through these drainage areas. We present multibeam swath bathymetry from several bays in the South Shetland Islands and the western Antarctic Peninsula. The submarine landforms are described and interpreted in detail. A schematic model was developed showing the features found in the bays: from glacial lineations and moraines in the inner bay to grounding zone wedges and drumlinoid features in the middle bay and streamlined features and meltwater channels in the outer bay areas. In addition, we analysed local variables in the bays and observed the following: (1 the number of landforms found in the bays scales to the size of the bay, but the geometry of the bays dictates the types of features that form; specifically, we observe a correlation between the bay width and the number of transverse features present in the bays. (2 The smaller seafloor features are present only in the smaller glacial systems, indicating that short-lived atmospheric and oceanographic fluctuations, responsible for the formation of these landforms, are only recorded in these smaller systems. (3 Meltwater channels are abundant on the seafloor, but some are subglacial, carved in bedrock, and some are modern erosional features, carved on soft sediment. Lastly, based on geomorphological evidence, we propose the features found in some of the proximal bay areas were formed during a recent glacial advance, likely the Little Ice Age.

Use of high-dimensional spectral data to evaluate organic matter, reflectance relationships in soils

Science.gov (United States)

Henderson, T. L.; Baumgardner, M. F.; Coster, D. C.; Franzmeier, D. P.; Stott, D. E.

1990-01-01

Recent breakthroughs in remote sensing technology have led to the development of a spaceborne high spectral resolution imaging sensor, HIRIS, to be launched in the mid-1990s for observation of earth surface features. The effects of organic carbon content on soil reflectance over the spectral range of HIRIS, and to examine the contributions of humic and fulvic acid fractions to soil reflectance was evaluated. Organic matter from four Indiana agricultural soils was extracted, fractionated, and purified, and six individual components of each soil were isolated and prepared for spectral analysis. The four soils, ranging in organic carbon content from 0.99 percent, represented various combinations of genetic parameters such as parent material, age, drainage, and native vegetation. An experimental procedure was developed to measure reflectance of very small soil and organic component samples in the laboratory, simulating the spectral coverage and resolution of the HIRIS sensor. Reflectance in 210 narrow (10 nm) bands was measured using the CARY 17D spectrophotometer over the 400 to 2500 nm wavelength range. Reflectance data were analyzed statistically to determine the regions of the reflective spectrum which provided useful information about soil organic matter content and composition. Wavebands providing significant information about soil organic carbon content were located in all three major regions of the reflective spectrum: visible, near infrared, and middle infrared. The purified humic acid fractions of the four soils were separable in six bands in the 1600 to 2400 nm range, suggesting that longwave middle infrared reflectance may be useful as a non-destructive laboratory technique for humic acid characterization.

Integrated hard and soft bottom seafloor substrate map of Ofu-Olosega, American Samoa, combining NOAA Pacific Island Fisheries Science Center Coral Reef Ecosystem Division hard-soft substrate map with NOAA Center for Coastal Monitoring and Assessment Biogeography Program shallow-water benthic habitat map of American Samoa.

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Hard and soft seafloor substrate map, derived from integrating two existing map products: hard and soft seafloor substrate map derived from an unsupervised...

Self-Reflection of Video-Recorded High-Fidelity Simulations and Development of Clinical Judgment.

Science.gov (United States)

Bussard, Michelle E

2016-09-01

Nurse educators are increasingly using high-fidelity simulators to improve prelicensure nursing students' ability to develop clinical judgment. Traditionally, oral debriefing sessions have immediately followed the simulation scenarios as a method for students to connect theory to practice and therefore develop clinical judgment. Recently, video recording of the simulation scenarios is being incorporated. This qualitative, interpretive description study was conducted to identify whether self-reflection on video-recorded high-fidelity simulation (HFS) scenarios helped prelicensure nursing students to develop clinical judgment. Tanner's clinical judgment model was the framework for this study. Four themes emerged from this study: Confidence, Communication, Decision Making, and Change in Clinical Practice. This study indicated that self-reflection of video-recorded HFS scenarios is beneficial for prelicensure nursing students to develop clinical judgment. [J Nurs Educ. 2016;55(9):522-527.]. Copyright 2016, SLACK Incorporated.

Deposition of talc - kerolite-smectite - smectite at seafloor hydrothermal vent fields: Evidence from mineralogical, geochemical and oxygen isotope studies

Science.gov (United States)

Dekov, V.M.; Cuadros, J.; Shanks, Wayne C.; Koski, R.A.

2008-01-01

Talc, kerolite-smectite, smectite, chlorite-smectite and chlorite samples from sediments, chimneys and massive sulfides from six seafloor hydrothermal areas have been analyzed for mineralogy, chemistry and oxygen isotopes. Samples are from both peridotite- and basalt-hosted hydrothermal systems, and basaltic systems include sediment-free and sediment-covered sites. Mg-phyllosilicates at seafloor hydrothermal sites have previously been described as talc, stevensite or saponite. In contrast, new data show tri-octahedral Mg-phyllosilicates ranging from pure talc and Fe-rich talc, through kerolite-rich kerolite-smectite to smectite-rich kerolite-smectite and tri-octahedral smectite. The most common occurrence is mixed-layer kerolite-smectite, which shows an almost complete interstratification series with 5 to 85% smectitic layers. The smectite interstratified with kerolite is mostly tri-octahedral. The degree of crystal perfection of the clay sequence decreases generally from talc to kerolite-smectite with lower crystalline perfection as the proportion of smectite layers in kerolite-smectite increases. Our studies do not support any dependence of the precipitated minerals on the type/subtype of hydrothermal system. Oxygen isotope geothermometry demonstrates that talc and kerolite-smectite precipitated in chimneys, massive sulfide mounds, at the sediment surface and in open cracks in the sediment near seafloor are high-temperature (> 250????C) phases that are most probably the result of focused fluid discharge. The other end-member of this tri-octahedral Mg-phyllosilicate sequence, smectite, is a moderate-temperature (200-250????C) phase forming deep within the sediment (??? 0.8??m). Chlorite and chlorite-smectite, which constitute the alteration sediment matrix around the hydrothermal mounds, are lower-temperature (150-200????C) phases produced by diffuse fluid discharge through the sediment around the hydrothermal conduits. In addition to temperature, other two

Separation and reconstruction of high pressure water-jet reflective sound signal based on ICA

Science.gov (United States)

Yang, Hongtao; Sun, Yuling; Li, Meng; Zhang, Dongsu; Wu, Tianfeng

2011-12-01

The impact of high pressure water-jet on the different materials target will produce different reflective mixed sound. In order to reconstruct the reflective sound signals distribution on the linear detecting line accurately and to separate the environment noise effectively, the mixed sound signals acquired by linear mike array were processed by ICA. The basic principle of ICA and algorithm of FASTICA were described in detail. The emulation experiment was designed. The environment noise signal was simulated by using band-limited white noise and the reflective sound signal was simulated by using pulse signal. The reflective sound signal attenuation produced by the different distance transmission was simulated by weighting the sound signal with different contingencies. The mixed sound signals acquired by linear mike array were synthesized by using the above simulated signals and were whitened and separated by ICA. The final results verified that the environment noise separation and the reconstruction of the detecting-line sound distribution can be realized effectively.

Does Using E-Portfolios for Reflective Writing Enhance High School Students' Self-Regulated Learning?

Science.gov (United States)

Chang, Chi-Cheng; Liang, Chaoyun; Shu, Kuen-Ming; Tseng, Kuo-Hung; Lin, Chun-Yu

2016-01-01

The study aims to examine whether reflective writing using e-portfolios enhances high school students' self-regulated learning. Participants included two classes of eighth-graders majoring in Information Processing and taking a course called "Website Design" at a vocational high school in Taiwan. There were 41 students, with 18 males and…

Geostatistical and multivariate modelling for large scale quantitative mapping of seafloor sediments using sparse datasets, a case study from the Cleaverbank area (the Netherlands)

NARCIS (Netherlands)

Alevizos, Evangelos; Siemes, K.; Janmaat, J.; Snellen, M.; Simons, D.G.; Greinert, J

2016-01-01

Quantitative mapping of seafloor sediment properties (eg. grain size) requires the input of comprehensive Multi-Beam Echo Sounder (MBES) datasets along with adequate ground truth for establishing a functional relation between them. MBES surveys in extensive shallow shelf areas can be a rather

Introduction to the special issue on submarine geohazard records and potential seafloor instability

Directory of Open Access Journals (Sweden)

Song-Chuen Chen Jia-Jyun Dong

2018-01-01

Full Text Available Submarine landslides frequently occur in passive continental margins or active margins (Hampton et al. 1996; Wynn et al. 2000; Mienert et al. 2002; Korup et al. 2007; Twichell et al. 2009; Cukur et al. 2016. Submarine landslides have been studied extensively not only for scientific research but also for submarine geohazards. Submarine landslides could jeopardize marine infrastructures, such as offshore drilling platforms or submarine telecommunication cables, and could even trigger disastrous tsunamis (Bondevik et al. 2005; Harbitz et al. 2006; Hornbach et al. 2007, 2008; Hsu et al. 2008; Su et al. 2012; Tappin et al. 2014; Li et al. 2015. For instance, one disastrous tsunami hitting the coastal area of southwestern Taiwan in 1781 or 1782 was reported (Chen 1830; Hsu 1983; the tsunami event was probably generated by submarine landslides in the offshore area of southwestern Taiwan (Li et al. 2015. Moreover, several submarine landslides triggered by the 2006 Pingtung earthquake have induced turbidity currents off southwest Taiwan and destroyed about 14 submarine telecommunication cables off SW Taiwan (Hsu et al. 2008. The area of southwest Taiwan currently has a dense population (more than 3 million people in total, one deep-water Kaohsiung Port, several tanks of liquefied natural gas and a nuclear power plant on the coast (Fig. 1. Numerous submarine telecommunication cables exist off SW Taiwan. If a considerable tsunami event would hit again the costal area of SW Taiwan, the damage could very serious. Likewise, there are two nuclear power plants on the coast of northern Taiwan (Fig. 2, and the population in northern Taiwan has more than 10 million people. Submarine telecommunication cables also exist off northern Taiwan. In any case, it is important to understand the status of seafloor stability in the offshore areas of SW and NE Taiwan. For that, this special issue of submarine geohazard records and potential seafloor instability is aimed to

Integration of seafloor point data in usSEABED

Science.gov (United States)

Reid, Jane A.; Williams, S. Jeffress; Zimmermann, Mark; Jenkins, Chris; Golden, Nadine E.

2007-01-01

Sediments of the beach, nearshore, and continental shelves record a complex interplay of processes including wave energy and direction , currents, beach erosion or accretion, bluff or cliff retreat, fluvial input, sediment longshore and cross-shelf transport processes, contaminant content and transport, sediment sources and sinks, and others. In turn, sediments and rocks modify wave patterns, affect recreation and tourism, and provide habitat for fish, epifauna, and infauna. Character of the surficial seafloor also influences navigation, commercial and recreational fishing and gathering of other food sources, communication, piplines, national defense, and provides geologic resources including sand and gravel aggregates, minerals, and real or potential energy sources. The beaches, nearshore, and continental margins fall under overlapping levels of managerial responsibility between Federal, State, regional, and local government agencies and consortia. In addition, universities and other academic institutions investigate these places for pure or applied scientific reasons. Mapping is usually the first step in understanding any issue and is often comprised of remotely gathered geophysical data such as bathymetry and backscatter imagery, and groundtruthing; that is, the collection of physical and virtual samples to tie the remotely gathered data to reality. The physical samples are described and (or) carefully analyzed for grain-size information -- which records both the site's physical conditions and geologic past -- and commonly, for constituent components such as mineral and rock types (to determine onland sources and in situ chemical processes), carbonate and organic content and microfossils (for biological and oceanographic influences), and structure such as layering and bioturbation (for physical influences). The samples may also be subjected to physical tests such as comp[action analyses, liquefaction or plasticity limits, ans other parameters important when

Preliminary hard and soft bottom seafloor substrate map derived from an unsupervised classification of gridded backscatter and bathymetry derivatives at Swains Island, Territory of American Samoa, USA.

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Preliminary hard and soft seafloor substrate map derived from an unsupervised classification of multibeam backscatter and bathymetry derivatives at Swains Island,...

Evidence for small-scale convection in the Pacific and Atlantic upper mantle from joint analysis of surface wave phase velocity and seafloor bathymetry

Science.gov (United States)

Ma, Z.; Dalton, C. A.

2017-12-01

It has been long observed that the rate of seafloor subsidence in the Pacific Ocean is lower than predicted by half-space cooling at ages older than 70 Myr. The magnitude, geographical distribution, onset time, and physical origin of the flattening are fundamental to our understanding of the evolution of oceanic lithosphere, and give important constraints on the Earth's heat budget and ocean volume throughout its history. However, none of these quantities is well established even after a long history of debates. Here, we present evidence from bathymetry and seismic tomography for the wide-scale operation of small-scale convection in the Pacific and Atlantic upper mantle. We track the temporal evolution of surface wave phase velocity and seafloor topography along age trajectories, which connect each piece of seafloor with the ridge segment that created it. The half-space cooling model (HSCM) and plate cooling model are used to predict the age dependence of phase velocity and bathymetry and to identify, for each age trajectory, the age at which the HSCM fails to explain the observations. The phase velocity and bathymetry are analyzed independently and yet yield identical results for more than 80% of points. We observe a wide range of ages at which the HSCM fails in the Atlantic and a much narrower range in the Pacific. We find that the age at which the HSCM fails is anti-correlated with the present-day depth of the ridge axis, with younger failure ages corresponding to deeper ridge axes and therefore colder mantle beneath the ridge.Such dependence is best explained by the small-scale convection model in which the effective viscosity of the lithosphere is regulated by the dehydration process that happens at the mid-ocean ridges. Decompression melting at a ridge removes water from the mantle and generates a depleted, dehydrated, and viscous layer. Since high mantle potential temperatures cause decompression melting to begin at greater depths, the thickness of the

Late Cretaceous and Cenozoic seafloor and oceanic basement roughness: Spreading rate, crustal age and sediment thickness correlations

Science.gov (United States)

Bird, Robert T.; Pockalny, Robert A.

1994-05-01

Single-channel seismic data from the South Australian Basin and Argentine Basin, and bathymetry data from the flanks of the Mid-Atlantic Ridge, East Pacific Rise and Southwest Indian Ridge are analysed to determine the root-mean-square (RMS) roughness of the seafloor and oceanic basement created at seafloor spreading rates ranging from 3 to 80 km/Ma (half-rate). For these data, crustal ages range from near zero to 85 Ma and sediment thicknesses range from near zero to over 2 km. Our results are consistent with a negative correlation of basement roughness and spreading rate where roughness decreases dramatically through the slow-spreading regime (oceanic basement roughness and spreading rate appears to have existed since the late Cretaceous for slow and intermediate spreading rates, suggesting that the fundamental processes creating abyssal hill topography may have remained the same for this time period. Basement roughness does not appear to decrease (smooth) with increasing crustal age, and therefore off-ridge degradation of abyssal hill topography by mass wasting is not detected by our data. Seismic data reveal that sediment thickness increases with increasing crustal age in the South Australian Basin and Argentine Basin, but not monotonically and with significant regional variation. We show that minor accumulations of sediment can affect roughness significantly. Average sediment accumulations of less that 50 m (for our 100 km long sample seismic profiles and half-spreading rates ocean ridges.

Reflection-type hologram for atoms

International Nuclear Information System (INIS)

Shimizu, Fujio; Fujita, Jun-ichi

2002-01-01

A cold metastable neon atomic beam was manipulated with a reflective amplitude hologram that was encoded on a silicon surface. A black-and-white pattern of atoms was reconstructed on a microchannel plate detector. The hologram used the enhanced quantum reflection developed by authors and was made of a two-dimensional array of rectangular low and high reflective cells. The surface of the high reflective cell was composed of regularly spaced roof-shaped ridges, while the low reflective cell was simply a flat surface. The hologram was the first demonstration of reflective atom-optical elements that used universal interaction between a neutral atom and solid surface

Ephemeral seafloor sedimentation during dam removal: Elwha River, Washington

Science.gov (United States)

Foley, Melissa M.; Warrick, Jonathan

2017-01-01

The removal of the Elwha and Glines Canyon dams from the Elwha River in Washington, USA, resulted in the erosion and transport of over 10 million m3 of sediment from the former reservoirs and into the river during the first two years of the dam removal process. Approximately 90% of this sediment was transported through the Elwha River and to the coast at the Strait of Juan de Fuca. To evaluate the benthic dynamics of increased sediment loading to the nearshore, we deployed a tripod system in ten meters of water to the east of the Elwha River mouth that included a profiling current meter and a camera system. With these data, we were able to document the frequency and duration of sedimentation and turbidity events, and correlate these events to physical oceanographic and river conditions. We found that seafloor sedimentation occurred regularly during the heaviest sediment loading from the river, but that this sedimentation was ephemeral and exhibited regular cycles of deposition and erosion caused by the strong tidal currents in the region. Understanding the frequency and duration of short-term sediment disturbance events is instrumental to interpreting the ecosystem-wide changes that are occurring in the nearshore habitats around the Elwha River delta.

Ephemeral seafloor sedimentation during dam removal: Elwha River, Washington

Science.gov (United States)

Foley, Melissa M.; Warrick, Jonathan A.

2017-11-01

The removal of the Elwha and Glines Canyon dams from the Elwha River in Washington, USA, resulted in the erosion and transport of over 10 million m3 of sediment from the former reservoirs and into the river during the first two years of the dam removal process. Approximately 90% of this sediment was transported through the Elwha River and to the coast at the Strait of Juan de Fuca. To evaluate the benthic dynamics of increased sediment loading to the nearshore, we deployed a tripod system in ten meters of water to the east of the Elwha River mouth that included a profiling current meter and a camera system. With these data, we were able to document the frequency and duration of sedimentation and turbidity events, and correlate these events to physical oceanographic and river conditions. We found that seafloor sedimentation occurred regularly during the heaviest sediment loading from the river, but that this sedimentation was ephemeral and exhibited regular cycles of deposition and erosion caused by the strong tidal currents in the region. Understanding the frequency and duration of short-term sediment disturbance events is instrumental to interpreting the ecosystem-wide changes that are occurring in the nearshore habitats around the Elwha River delta.

CRED Preliminary hard and soft bottom seafloor substrate map derived from an unsupervised classification of gridded backscatter and bathymetry derivatives at the U.S. Territory of Guam.

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Preliminary hard and soft seafloor substrate map derived from an unsupervised classification of multibeam backscatter and bathymety derivatives at the U.S. Territory...

Volcanic eruption of the mid-ocean ridge along the East Pacific Rise crest at 9°45-52'N: direct submersible observations of seafloor phenomena associated with an eruption event in April, 1991

Science.gov (United States)

Haymon, R.M.; Fornari, D.J.; Von Damm, Karen L.; Lilley, M.D.; Perfit, M.R.; Edmond, J.M.; Shanks, Wayne C.; Lutz, R.A.; Grebmeier, J.M.; Carbotte, S.; Wright, D.; McLaughlin, E.; Smith, M.; Beedle, N.; Olson, E.

1993-01-01

In April, 1991, we witnessed from the submersible Alvin a suite of previously undocumented seafloor phenomena accompanying an in-progress eruption of the mid-ocean ridge on the East Pacific Rise crest at 9°45′N–52′N. The volume of the eruption could not be precisely determined, although comparison of pre- and post-eruption SeaBeam bathymetry indicate that any changes in ridge crest morphology resulting from the eruption were < 10 m high.

Does high antibiotic consumption still reflect bad practices?

Science.gov (United States)

Levent, T; Delfosse, F; Lambiotte, F; Dezorzi, S; Gosteau, L; Vasseur, M

2012-07-01

The authors had for aim to assess the quality of antibiotic prescription in an intensive care unit because of their high rate of consumption. A prospective 5-month study was made of the first 50 prescriptions of ciprofloxacin, levofloxacin, teicoplanin, vancomycin, and imipenem. Treatment was considered adequate at day 5 if the indication was relevant, with the right doses, and if the prescription was adapted to the antibiogram. Fifty treatments were evaluated (38 patients included). Eighty-four percent (42/50) was adequate at day 5. Glycopeptides and fluoroquinolones accounted for 2/3 of prescriptions. The absence of de-escalation was the most common mistake. The severity of presentations was evident with a mean SSI at 68 (22-113), and a mean BMI at 28 (18.5 - 50). Eighty-four percent (32/38) of patients were exposed to invasive devices, 47% died in the ICU. Most prescriptions were adequate. The patient profile could explain the high rate of antibiotic consumption. Bacteriological monitoring revealed an increased prevalence of resistant bacteria, which could explain a high rate of consumption along with adaptation of the dose to overweight. De-escalation, using aminosides more frequently, and shorter prescribed courses of fluoroquinolones should improve consumption rates does not always reflect bad practices, but may be adequate when considering bacterial ecology and patient profile. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

Impact of Offshore Wind Energy Plants on the Soil Mechanical Behaviour of Sandy Seafloors

Science.gov (United States)

Stark, Nina; Lambers-Huesmann, Maria; Zeiler, Manfred; Zoellner, Christian; Kopf, Achim

2010-05-01

capacities (qsbc.) mainly ranging from 39 - 69 kPa (Nimrod: mass of ~ 13 kg, impact velocity of ~ 8 m/s). There was no evidence for layering in results of both in-situ instruments. After construction, most of the positions show changes in sediment strength ranging from 10 % up to 100 % compared to the results prior to windmill construction. Extreme changes (> 50 %) occur above all close to the foundations. Furthermore, patterns of relatively soft zones (qsbc.: 50 - 80 kPa) and hard zones (qsbc. > 100 kPa) were mapped during the high-resolution surveys close to the foundation. Beside that, a very soft sediment layer (0.03 - 0.05 m) drapes most of the soft zones. This may be recently eroded and re-deposited sediment, whereas the hard zones may indicate areas of sediment erosion where looser material has been carried away. Reasons for sediment remobilization and changes in geotechnical properties may be scouring as a consequence of the changed hydrodynamics in the vicinity of the windmills. Besides first developments of scour, the side scan sonar results show relicts of the wind turbine erection (e.g., footprints of jack-up-platforms). First multibeam-echosounder measurements confirm sediment re-deposition due to scour in the lee of the main current direction and show traces of wind turbine erection equipment in the same areas where also the penetrometer measurements took place. In summary, a local impact of the wind turbines on the soil mechanical properties of the seafloor is attested from this initial post-erection survey. Future cruises (every 6 months) will complement those data, which will eventually allow us a comparison to, or even refinement of long-term scouring models.

Sea-floor morphology and sedimentary environments in western Block Island Sound, offshore of Fishers Island, New York

Science.gov (United States)

McMullen, Katherine Y.; Poppe, Lawrence J.; Danforth, William W.; Blackwood, Dann S.; Winner, William G.; Parker, Castle E.

2015-01-01

Multibeam-bathymetric and sidescan-sonar data, collected by the National Oceanic and Atmospheric Administration in a 114-square-kilometer area of Block Island Sound, southeast of Fishers Island, New York, are combined with sediment samples and bottom photography collected by the U.S. Geological Survey from 36 stations in this area in order to interpret sea-floor features and sedimentary environments. These interpretations and datasets provide base maps for studies on benthic ecology and resource management. The geologic features and sedimentary environments on the sea floor are products of the area’s glacial history and modern processes. These features include bedrock, drumlins, boulders, cobbles, large current-scoured bathymetric depressions, obstacle marks, and glaciolacustrine sediments found in high-energy sedimentary environments of erosion or nondeposition; and sand waves and megaripples in sedimentary environments characterized by coarse-grained bedload transport. Trawl marks are preserved in lower energy environments of sorting and reworking. This report releases the multibeam-bathymetric, sidescan-sonar, sediment, and photographic data and interpretations of the features and sedimentary environments in Block Island Sound, offshore Fishers Island.

A low-frequency asymptotic model of seismic reflection from a high-permeability layer

Energy Technology Data Exchange (ETDEWEB)

Silin, Dmitriy; Goloshubin, Gennady

2009-03-01

Analysis of compression wave propagation through a high-permeability layer in a homogeneous poroelastic medium predicts a peak of reflection in the low-frequency end of the spectrum. An explicit formula expresses the resonant frequency through the elastic moduli of the solid skeleton, the permeability of the reservoir rock, the fluid viscosity and compressibility, and the reservoir thickness. This result is obtained through a low-frequency asymptotic analysis of the Biot's model of poroelasticity. A new physical interpretation of some coefficients of the classical poroelasticity is a result of the derivation of the main equations from the Hooke's law, momentum and mass balance equations, and the Darcy's law. The velocity of wave propagation, the attenuation factor, and the wave number, are expressed in the form of power series with respect to a small dimensionless parameter. The latter is equal to the product of the kinematic reservoir fluid mobility, an imaginary unit, and the frequency of the signal. Retaining only the leading terms of the series leads to explicit and relatively simple expressions for the reflection and transmission coefficients for a planar wave crossing an interface between two permeable media, as well as wave reflection from a thin highly-permeable layer (a lens). The practical implications of the theory developed here are seismic modeling, inversion, and attribute analysis.

Non-Deforming, High-Reflectance X-ray Coatings for Lynx and Other Future Missions

Science.gov (United States)

Windt, David

The overarching challenge addressed by this proposal is the development of highreflectance, high-resolution X-ray mirrors, to be used for the construction of lightweight X-ray telescopes for future NASA astronomy missions such as Lynx and others. The proposal's two specific aims are: 1) the development of optimized iridium-based interference coatings for the 0.1–10 keV band; and 2) the development of methods to mitigate coating-stress-induced substrate deformations in thin-shell glass and Si mirror segments. These goals will be achieved by building on established film deposition techniques and metrology infrastructure for X-ray optics that have been developed and advanced by the PI through APRA funding since 1999. Specific Aim #1: Interference Coatings for the 0.1–10 keV Energy Band Telescope effective area can be maximized by using Ir-based reflective coatings that exploit optical interference to provide higher reflectance than Ir alone. However, only preliminary investigations of such coatings have been conducted thus far; more research is required to fully optimize these coatings for maximum performance, to experimentally determine the coating designs that are feasible, and to determine the achievable X-ray reflectance, film stress, surface roughness, and thermal and temporal stability. The first specific aim of this proposal is to reach these very goals through a comprehensive research program. Demonstration of the achievable reflectance, stress, and roughness in stable, optimized coatings will in turn facilitate global telescope design optimization, by identifying the best coating for each mirror shell based on incidence angle, and on telescope effective-area and field-of-view requirements. The research has the potential to greatly increase the effective area of future X-ray telescopes. Specific Aim #2: Mitigation of Coating-Stress-Induced Substrate Deformations High-quality films of Ir and other candidate materials (e.g., B4C) to be investigated for the 0

A thermoelectric cap for seafloor hydrothermal vents

International Nuclear Information System (INIS)

Xie, Yu; Wu, Shi-jun; Yang, Can-jun

2016-01-01

Highlights: • We developed a thermoelectric cap (TC) to harvest hydrothermal energy. • The TC was deployed at a hydrothermal vent site near Kueishantao islet, Taiwan. • The TC monitored the temperature of the hydrothermal fluids during the field test. • The TC could make the thermal energy of hydrothermal fluids a viable power source. - Abstract: Long-term in situ monitoring is crucial to seafloor scientific investigations. One of the challenges of operating sensors in seabed is the lifespan of the sensors. Such sensors are commonly powered by batteries when other alternatives, such as tidal or solar energy, are unavailable. However, the batteries have a limited lifespan and must be recharged or replaced periodically, which is costly and impractical. A thermoelectric cap, which harvests the thermal energy of hydrothermal fluids through a conduction pipe and converts the heat to electrical energy by using thermoelectric generators, was developed to avoid these inconveniences. The thermoelectric cap was combined with a power and temperature measurement system that enables the thermoelectric cap to power a light-emitting diode lamp, an electronic load (60 Ω), and 16 thermocouples continuously. The thermoelectric cap was field tested at a shallow hydrothermal vent site near Kueishantao islet, which is located offshore of northeastern Taiwan. By using the thermal gradient between hydrothermal fluids and seawater, the thermoelectric cap obtained a sustained power of 0.2–0.5 W during the field test. The thermoelectric cap successfully powered the 16 thermocouples and recorded the temperature of the hydrothermal fluids during the entire field test. Our results show that the thermal energy of hydrothermal fluids can be an alternative renewable power source for oceanographic research.

Quantifying the Uncertainty in High Spatial and Temporal Resolution Synthetic Land Surface Reflectance at Pixel Level Using Ground-Based Measurements

Science.gov (United States)

Kong, J.; Ryu, Y.

2017-12-01

Algorithms for fusing high temporal frequency and high spatial resolution satellite images are widely used to develop dense time-series land surface observations. While many studies have revealed that the synthesized frequent high spatial resolution images could be successfully applied in vegetation mapping and monitoring, validation and correction of fused images have not been focused than its importance. To evaluate the precision of fused image in pixel level, in-situ reflectance measurements which could account for the pixel-level heterogeneity are necessary. In this study, the synthetic images of land surface reflectance were predicted by the coarse high-frequency images acquired from MODIS and high spatial resolution images from Landsat-8 OLI using the Flexible Spatiotemporal Data Fusion (FSDAF). Ground-based reflectance was measured by JAZ Spectrometer (Ocean Optics, Dunedin, FL, USA) on rice paddy during five main growth stages in Cheorwon-gun, Republic of Korea, where the landscape heterogeneity changes through the growing season. After analyzing the spatial heterogeneity and seasonal variation of land surface reflectance based on the ground measurements, the uncertainties of the fused images were quantified at pixel level. Finally, this relationship was applied to correct the fused reflectance images and build the seasonal time series of rice paddy surface reflectance. This dataset could be significant for rice planting area extraction, phenological stages detection, and variables estimation.

Bending Back To Move Forward: Using Reflective Practice To Develop a High School Civic Education/Aikido Course.

Science.gov (United States)

Miller-Lane, Jonathan

This paper describes the development of a high school social studies course, Citizenship and World Affairs. Course development involved two forms of reflection: deliberative and personalistic. The author's deliberative reflection, reported in part one of the paper, began as he reviewed research regarding how teachers should foster citizenship…

Comparative Roughness Characteristics of the Subducting Seafloor and Statistical Relationships with Seismogenic Potential, with Special Emphasis on Great Earthquakes

Science.gov (United States)

Lallemand, S.; Peyret, M.; van Rijsingen, E.; Arcay, D.

2017-12-01

Do some topographic features or morphological characteristics promote earthquake nucleation, large coseismic slip or creep ? To answer this question, we have developed a new database called "SubRough" which provides few roughness parameters at selected spatial wavelengths. Since the currently subducting topography is generally unknown, we assume that the bathymetry of the oceanic plates, a few hundreds of km seaward of the trench, is a reasonable proxy for determining the roughness of the subduction interface. Given the selected wavelengths in our roughness study (detailed below), we do not expect major changes when entering the subduction zone, even though the presence of a subduction channel or significant sediment offscrapping may alter it. Morphological objects characterized by high spatial frequencies (isolated seamounts or fracture zones) are likely to play a role in large events initiation or termination. Similarly, wide "smooth" areas may likely favor rupture propagation and thus large events, while ridges or plateaus may also play a specific role in seismic behavior. Consequently, we only retain the roughness components Rsw and Rlw that are comprised respectively within 2 wavelength bands: [12-20 km] and [80-100 km]. The choice of these wavelengths is constrained by the resolution of the bathymetry, the size of the studied area and the characteristic wavelengths of the seafloor topography. This new morphological information is then statistically analyzed to better understand how topographic features are modeled by roughness data. From a worldwide statistical point of view, fracture zones show similar amplitudes as mean seafloor at both wavelengths, which indicates that it is not possible to distinguish them from the background signal. Conversely, seamounts show roughness amplitudes about two times larger than the averaged ones at both wavelengths. Ridges and plateaus show Rlw amplitudes similar to seamounts but lower Rsw than seamounts. Finally, the

Effect of highly reflective roofing sheet on building thermal loads for a school in Osaka

Directory of Open Access Journals (Sweden)

Yuan Jihui

2017-01-01

Full Text Available Currently, urban heat island (UHI phenomenon and building energy consumptions are becoming serious. Strategies to mitigate UHI and reduce building energy consumptions are implemented worldwide. In Japan, as an effective means of mitigating UHI and saving energy of buildings, highly reflective (HR and green roofs are increasingly used. In order to evaluate the effect of roofs with high reflection and thermal insulation on the energy conservation of buildings, we investigated the roof solar reflectivity of the subject school in Osaka, in which the HR roofing sheet was installed on the roof from 2010. Thermal loads, including cooling and heating loads of the top floor of school, were calculated using the thermal load calculation software, New HASP/ACLD-β. Comparing the thermal loads after HR roofing sheet installation to previous, the annual thermal load decreased about 25 MJ/m2-year and the cooling load decreased about 112 MJ/m2-year. However, the heating load increased about 87 MJ/m2-year in winter. To minimize the annual thermal load, thermal insulation of the roof was also considered be used together with HR roofing sheet in this study. The results showed that the combination of HR roofing sheet and high thermal insulation is more effective to reduce the annual thermal load.

Production of a diffuse very high reflectivity material for light collection in nuclear detectors

CERN Document Server

Pichler, B J; Mirzoyan, R; Weiss, L; Ziegler, S I

2000-01-01

A diffuse very high reflectivity material, based on polytetrafluorethylene (PTFE) for optimization of light-collection efficiency has been developed. PTFE powder was used to produce reflector block material. The powder was pressed with 525 kPa in a form and sintered at 375 deg. C. The reflectivity was above 98% within the spectral range from 350 to 1000 nm. The blocks of this material are machinable with saws, drilling and milling machines. The reflector is used as a housing for scintillating crystals in a nuclear medicine application (small animal positron emission tomograph). It is also used as a light collector in very high-energy gamma-ray astrophysicas experiments, HEGRA and MAGIC. The application of this inexpensive, easy to make diffuse reflector may allow the optimization of light collection in a wide range of low-level light-detector configurations.

Integrated hard and soft bottom seafloor substrate map derived from an unsupervised classification of gridded backscatter, World-View 2 imagery and bathymetry derivatives of Ni'ihau Island, Hawaii, USA.

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Preliminary hard and soft seafloor substrate map derived from an unsupervised classification of multibeam backscatter, bathymety derivatives, and bathymetry derived...

Preliminary hard and soft bottom seafloor substrate map derived from an unsupervised classification of gridded backscatter and bathymetry derivatives at Saipan Island, Commonwealth of the Northern Mariana Islands (CNMI).

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Preliminary hard and soft seafloor substrate map derived from an unsupervised classification of multibeam backscatter and bathymety derivatives at Saipan Island,...

Combining Multicomponent Seismic Attributes, New Rock Physics Models, and In Situ Data to Estimate Gas-Hydrate Concentrations in Deep-Water, Near-Seafloor Strata of the Gulf of Mexico

Energy Technology Data Exchange (ETDEWEB)

Bureau of Economic Geology

2009-04-30

The Bureau of Economic Geology was contracted to develop technologies that demonstrate the value of multicomponent seismic technology for evaluating deep-water hydrates across the Green Canyon area of the Gulf of Mexico. This report describes the methodologies that were developed to create compressional (P-P) and converted-shear (P-SV) images of near-seafloor geology from four-component ocean-bottom-cable (4C OBC) seismic data and the procedures used to integrate P-P and P-SV seismic attributes with borehole calibration data to estimate hydrate concentration across two study areas spanning 16 and 25 lease blocks (or 144 and 225 square miles), respectively. Approximately 200 km of two-dimensional 4C OBC profiles were processed and analyzed over the course of the 3-year project. The strategies we developed to image near-seafloor geology with 4C OBC data are unique, and the paper describing our methodology was peer-recognized with a Best Paper Award by the Society of Exploration Geophysicists in the first year of the project (2006). Among the valuable research findings demonstrated in this report, the demonstrated ability to image deep-water near-seafloor geology with sub-meter resolution using a standard-frequency (10-200 Hz) air gun array on the sea surface and 4C sensors on the seafloor has been the accomplishment that has received the most accolades from professional peers. Our study found that hydrate is pervasive across the two study areas that were analyzed but exists at low concentrations. Although our joint inversion technique showed that in some limited areas, and in some geologic units across those small areas, hydrates occupied up to 40-percent of the sediment pore space, we found that when hydrate was present, hydrate concentration tended to occupy only 10-percent to 20-percent of the pore volume. We also found that hydrate concentration tended to be greater near the base of the hydrate stability zone than it was within the central part of the stability

Preliminary hard and soft bottom seafloor substrate map derived from an unsupervised classification of gridded backscatter and bathymetry derivatives at Tinian Island, Commonwealth of the Northern Mariana Islands (CNMI).

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Preliminary hard and soft seafloor substrate map derived from an unsupervised classification of multibeam backscatter and bathymety derivatives at Tinian Islands and...

Preliminary hard and soft bottom seafloor substrate map derived from an unsupervised classification of gridded backscatter and bathymetry derivatives at Ofu and Olosega Islands, Territory of American Samoa, USA.

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Preliminary hard and soft seafloor substrate map derived from an unsupervised classification of multibeam backscatter and bathymety derivatives at Ofu and Olosega...

High reflectivity YDH/SiO2 distributed Bragg reflector for UV-C wavelength regime

KAUST Repository

Alias, Mohd Sharizal; Alatawi, Abdullah; Wong, Ka Chun; Tangi, Malleswararao; Holguin Lerma, Jorge Alberto; Stegenburgs, Edgars; Shakfa, Mohammad Khaled; Ng, Tien Khee; Rahman, Abdul; Alyamani, Ahmed; Ooi, Boon S.

2018-01-01

A distributed Bragg reflector (DBR) composed of Y2O3-doped HfO2 (YDH)/SiO2 layers with high reflectivity spectrum centered at a wavelength of ~240 nm is deposited using radio-frequency magnetron sputtering. Before the DBR deposition, optical

Seafloor mapping at Olkiluoto western coast of Finland

International Nuclear Information System (INIS)

Ilmarinen, K.; Leinikki, J.; Oulasvirta, P.

2009-02-01

The objective of the study was to investigate the seafloor of shallow areas around Olkiluoto island, western Finland. The surveys were carried out by Alleco Ltd. Posiva will use the data for modeling purposes. The investigations included bathymetric surveys, sediment sampling and assessment of benthic macrophytes and macrozoobenthos in the underwater parts of six pre-defined survey transects extending from land to the sea. Sediment sampling and the assessment of benthic organisms were done by SCUBA diving. The study area showed a great variation in environmental conditions. Olkiluoto stands between almost open sea and extremely sheltered river mouth area of Lapinjoki. Two of the transects were more than 7 meters deep and included both hard and soft sand bottom. Whereas rest of the transects were shallow with mostly soft clay, mud and silt bottom. Altogether 27 species of algae including five species of stoneworts (Charophyta), one species of water moss (Bryophyta) and 16 species of vascular plants (Tracheophyta) were found. The most abundant group was vascular plants, between the other groups of macroalgae big differences in the abundance were not seen. Furthermore altogether 43 species of macrozoobenthos (Invertebrata) were found, of which six species were sessile bottom fauna (permanently attached fauna). The most abundant groups in the bottom samples were bivalves (Lamellibranchiata) (996 individuals per m 2 ), snails (Gastropoda) (739 individuals per m 2 ) and polychaetes (Polychaeta) (542 individuals per m 2 ). The total abundance of macrozoobenthos on all transects was 2 899 individuals per m 2 . The biggest groups by biomass were bivalves (fresh weight 87 054 mg per m 2 ) and polychaetes (fresh weight 12 983 mg per m 2 ). Transect 1 was the richest in number of species of the deep and exposed transects 1 and 2. The transect 5 had the highest diversity of all the shallow soft bottom transects 3, 4, 5 and 5a. The high diversity of the transect 1 and 5 may be

Seafloor mapping at Olkiluoto western coast of Finland

Energy Technology Data Exchange (ETDEWEB)

Ilmarinen, K.; Leinikki, J.; Oulasvirta, P. (Alleco Oy, Helsinki (Finland))

2009-02-15

The objective of the study was to investigate the seafloor of shallow areas around Olkiluoto island, western Finland. The surveys were carried out by Alleco Ltd. Posiva will use the data for modeling purposes. The investigations included bathymetric surveys, sediment sampling and assessment of benthic macrophytes and macrozoobenthos in the underwater parts of six pre-defined survey transects extending from land to the sea. Sediment sampling and the assessment of benthic organisms were done by SCUBA diving. The study area showed a great variation in environmental conditions. Olkiluoto stands between almost open sea and extremely sheltered river mouth area of Lapinjoki. Two of the transects were more than 7 meters deep and included both hard and soft sand bottom. Whereas rest of the transects were shallow with mostly soft clay, mud and silt bottom. Altogether 27 species of algae including five species of stoneworts (Charophyta), one species of water moss (Bryophyta) and 16 species of vascular plants (Tracheophyta) were found. The most abundant group was vascular plants, between the other groups of macroalgae big differences in the abundance were not seen. Furthermore altogether 43 species of macrozoobenthos (Invertebrata) were found, of which six species were sessile bottom fauna (permanently attached fauna). The most abundant groups in the bottom samples were bivalves (Lamellibranchiata) (996 individuals per m2), snails (Gastropoda) (739 individuals per m2) and polychaetes (Polychaeta) (542 individuals per m2). The total abundance of macrozoobenthos on all transects was 2 899 individuals per m2. The biggest groups by biomass were bivalves (fresh weight 87 054 mg per m2) and polychaetes (fresh weight 12 983 mg per m2). Transect 1 was the richest in number of species of the deep and exposed transects 1 and 2. The transect 5 had the highest diversity of all the shallow soft bottom transects 3, 4, 5 and 5a. The high diversity of the transect 1 and 5 may be explained by

SEAFLOOR SEDIMENT CHARACTERISTICS AND HEAVY MINERAL OCCURENCES AT BETUMPAK CAPE AND ADJACENT AREA, BANGKA STRAIT, BANGKA BELITUNG PROVINCE

Directory of Open Access Journals (Sweden)

Rohendi Rohendi

2017-07-01

Full Text Available Thirty seafloor of sediment samples have been taken by using gravity corer and grab sampler at Betumpak Cape, and adjacent area of Bangka Belitung. The result of grain size analyses show that there are four sediment units: gravelly sand, gravelly muddy sand, silt and silty sand. Identification of Scanning Electron Microscope (SEM image on several samples shows the presence of clay mineral such as smectite, alunite, chlorite etc., may resulted from plagioclase weathering of granite. Based on heavy mineral analyses, its highest content is found at MTK-27 (northwest of Betumpak Cape. High content of apatite (0.94% wt and 1.07% wt is found on coarse sand fractions (115-170 mesh at MTK-29 (northeast Ular Cape and MTK-30 (north of Ular Cape. Generally, the heavy mineral accumulation is occurred on medium sand fraction (60-80 mesh as magnetite (7.86% wt, ilmenite (4.9% wt and zircon (1.32% wt. Based on these data, it shows that heavy mineral is accumulated on medium to coarse sand.

Highly reflective polymeric substrates functionalized utilizing atomic layer deposition

Science.gov (United States)

Zuzuarregui, Ana; Coto, Borja; Rodríguez, Jorge; Gregorczyk, Keith E.; Ruiz de Gopegui, Unai; Barriga, Javier; Knez, Mato

2015-08-01

Reflective surfaces are one of the key elements of solar plants to concentrate energy in the receivers of solar thermal electricity plants. Polymeric substrates are being considered as an alternative to the widely used glass mirrors due to their intrinsic and processing advantages, but optimizing both the reflectance and the physical stability of polymeric mirrors still poses technological difficulties. In this work, polymeric surfaces have been functionalized with ceramic thin-films by atomic layer deposition. The characterization and optimization of the parameters involved in the process resulted in surfaces with a reflection index of 97%, turning polymers into a real alternative to glass substrates. The solution we present here can be easily applied in further technological areas where seemingly incompatible combinations of polymeric substrates and ceramic coatings occur.

Highly reflective polymeric substrates functionalized utilizing atomic layer deposition

Energy Technology Data Exchange (ETDEWEB)

Zuzuarregui, Ana, E-mail: a.zuzuarregui@nanogune.eu; Gregorczyk, Keith E. [CIC Nanogune Consolider, de Tolosa Hiribidea 76, 20018 San Sebastián (Spain); Coto, Borja; Ruiz de Gopegui, Unai; Barriga, Javier [IK4-Tekniker, Iñaki Goenaga 5, 20600 Eibar (Spain); Rodríguez, Jorge [Torresol Energy (SENER Group), Avda. de Zugazarte 61, 48930 Las Arenas (Spain); Knez, Mato [CIC Nanogune Consolider, de Tolosa Hiribidea 76, 20018 San Sebastián (Spain); IKERBASQUE Basque Foundation for Science, Maria Diaz de Haro 3, 48013 Bilbao (Spain)

2015-08-10

Reflective surfaces are one of the key elements of solar plants to concentrate energy in the receivers of solar thermal electricity plants. Polymeric substrates are being considered as an alternative to the widely used glass mirrors due to their intrinsic and processing advantages, but optimizing both the reflectance and the physical stability of polymeric mirrors still poses technological difficulties. In this work, polymeric surfaces have been functionalized with ceramic thin-films by atomic layer deposition. The characterization and optimization of the parameters involved in the process resulted in surfaces with a reflection index of 97%, turning polymers into a real alternative to glass substrates. The solution we present here can be easily applied in further technological areas where seemingly incompatible combinations of polymeric substrates and ceramic coatings occur.

Highly reflective polymeric substrates functionalized utilizing atomic layer deposition

International Nuclear Information System (INIS)

Zuzuarregui, Ana; Gregorczyk, Keith E.; Coto, Borja; Ruiz de Gopegui, Unai; Barriga, Javier; Rodríguez, Jorge; Knez, Mato

2015-01-01

Reflective surfaces are one of the key elements of solar plants to concentrate energy in the receivers of solar thermal electricity plants. Polymeric substrates are being considered as an alternative to the widely used glass mirrors due to their intrinsic and processing advantages, but optimizing both the reflectance and the physical stability of polymeric mirrors still poses technological difficulties. In this work, polymeric surfaces have been functionalized with ceramic thin-films by atomic layer deposition. The characterization and optimization of the parameters involved in the process resulted in surfaces with a reflection index of 97%, turning polymers into a real alternative to glass substrates. The solution we present here can be easily applied in further technological areas where seemingly incompatible combinations of polymeric substrates and ceramic coatings occur

Development of High-Reflectivity Optical Coatings for the Vacuum Ultraviolet and Verification on a Sounding Rocket Flight

Data.gov (United States)

National Aeronautics and Space Administration — We desire to develop new thin film coatings of fluorides to utilize the high intrinsic reflectivity of aluminum. Highly controllable thickness of fluorides can be...

The phase transition of methane caused by pressure change during its seeping up from seepage, revealed by video observation and acoustic reflection data

Science.gov (United States)

Aoyama, C.

2017-12-01

Methane plumes often exist in the vicinity sea area where shallow type methane hydrates are extracted and they are observed as images displayed on monitors of multi-beam sonar and echo sounder onboard, where methane hydrates are expected at sea bottom on ROV observation data. The hydrates are generally considered to be generated in shallow depths below the sea floor. In this study, author examined annual amount of methane dissolving into seawater by measuring the amount of plume in order to make a quantification of dissolving methane from seafloor. Measurement procedure is plume exploration using multi-beam and quantitative echo sounder , submerge ROV to gushing point at seafloor , calculate the rising speed of methane plumes and examine the phases by monitoring seeping plumes from seafloor with high-definition camera. Components of seeping plumes were defined as methane hydrate particles based on the result by measuring water temperature. From this procedure, it can be concluded that the minimum rising speed of methane hydrate particles from gushing point is 1.6×10-1(m/s) and the maximum of 2.0×10-1(m/s) indicating a difference of more than ten times the gaseous theoretical value of 2.74(m/s). This speed is theoretically closer to the solid speed of the material with physical property similar to hydrates, which is 3.05×10-1 (m/s). Therefore, it can be determined that those particles are in the solid state, immediately above seafloor. To measure the amount of plumes seeping from gushing points funnel-shaped instruments with 20cm diameter opening were used to collect methane plumes in this sea area. This was performed in three different gushing points. As a result, 300ml of methane plume was collected in 643 seconds. Assuming that gushing points exist evenly in the sea area, the annual amount of methane gas seeping from these points will be 7.7×105m3 /per m2. Result shows a large quantity of methane seeping from seafloor into the water. This data is an important

Preliminary hard and soft bottom seafloor substrate map (40m grid) derived from an unsupervised classification of gridded backscatter and bathymetry derivatives at Rose Atoll, Territory of American Samoa, USA.

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Preliminary hard and soft seafloor substrate map derived from an unsupervised classification of multibeam backscatter and bathymetry derivatives at Rose Atoll,...

Scientific Discoveries in the Central Arctic Ocean Based on Seafloor Mapping Carried out to Support Article 76 Extended Continental Shelf Claims (Invited)

Science.gov (United States)

Jakobsson, M.; Mayer, L. A.; Marcussen, C.

2013-12-01

Despite the last decades of diminishing sea-ice cover in the Arctic Ocean, ship operations are only possible in vast sectors of the central Arctic using the most capable polar-class icebreakers. There are less than a handful of these icebreakers outfitted with modern seafloor mapping equipment. This implies either fierce competition between those having an interest in using these icebreakers for investigations of the shape and properties of Arctic Ocean seafloor or, preferably, collaboration. In this presentation examples will be shown of scientific discoveries based on mapping data collected during Arctic Ocean icebreaker expeditions carried out for the purpose of substantiating claims for an extended continental shelf under United Nations Convention of the Law of the Sea (UNCLOS) Article 76. Scientific results will be presented from the suite of Lomonosov Ridge off Greenland (LOMROG) expeditions (2007, 2009, and 2012), shedding new light on Arctic Ocean oceanography and glacial history. The Swedish icebreaker Oden was used in collaboration between Sweden and Denmark during LOMROG to map and sample portions of the central Arctic Ocean; specifically focused on the Lomonosov Ridge north of Greenland. While the main objective of the Danish participation was seafloor and sub-seabed mapping to substantiate their Article 76 claim, LOMROG also included several scientific components, with scientists from both countries involved. Other examples to be presented are based on data collected using US Coast Guard Cutter Healy, which for several years has carried out mapping in the western Arctic Ocean for the US continental shelf program. All bathymetric data collected with Oden and Healy have been contributed to the International Bathymetric Chart of the Arctic Ocean (IBCAO). This is also the case for bathymetric data collected by Canadian Coast Guard Ship Louis S. St-Laurent for Canada's extended continental shelf claim. Together, the bathymetric data collected during these

Cavity ring-down technique for measurement of reflectivity of high ...

Indian Academy of Sciences (India)

Laser & Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 400 085,. India. *Corresponding author. E-mail: gsridhar@barc.gov.in. Abstract. A simple, accurate and reliable method for measuring the reflectivity of laser- ... Keywords. Cavity ring-down method; reflectivity measurement; optical resonator.

Experimental design for reflection measurements of highly reactive liquid or solid substances with application to liquid sodium

International Nuclear Information System (INIS)

Chan, S.H.; Gossler, A.A.

1980-01-01

A versatile goniometer system with associated electronic components and mechanical instruments has been assembled. It is designed to measure spectral, specular reflectances of highly reactive liquid or solid substances over a spectral range of 0.3 to 9 μ and incidence angles of 12 to 30 0 off the normal direction. The capability of measuring reflectances of liquid substances clearly distinguishes this experimental design from conventional systems which are applicable only to solid substances. This design has been used to measure the spectral, specular reflectance of liquid sodium and preliminary results obtained are compared with those of solid sodium measured by other investigators

High quality broadband spatial reflections of slow Rayleigh surface acoustic waves modulated by a graded grooved surface

KAUST Repository

Xu, Yanlong

2015-01-21

We report high quality broadband spatial reflections of Rayleigh surface acoustic waves (SAWs) through a graded grooved surface. High quality means that no wave is allowed to transmit and the incident wave is nearly all reflected to the input side. The graded grooved surface is structured by drilling one dimensional array of graded grooves with increased depths on a flat surface. We investigate SAW dispersion relations, wave field distribution at several typical SAW wavelengths, and time evolution of a Gaussian pulse through the graded grooved surface. Results show that the input broadband Rayleigh SAWs can be slowed, spatially enhanced and stopped, and finally reflected to the input side. The study suggests that engraving the flat surface can be used as an efficient and economical way to manipulate Rayleigh SAWs, which has potential application in novel SAW devices such as filters, reflectors, sensors, energy harvesters, and diodes.

Quantitative seafloor characterization using angular backscatter data of the multi-beam echo-sounding system - Use of models and model free techniques

Digital Repository Service at National Institute of Oceanography (India)

Chakraborty, B.

processing gain, bottom slope corrections, and bottom insonification area normalisation were proposed to generate angular backscattering strength for modelling to infer bottom roughness parameters. A software package (NORGCOR) for similar purpose... bottom backscatter data from multibeam system. For each seafloor area, processed backscatter strength values [presented in Fig.: I(c)], are binned at intervals of 1° from --45° to +45°, and averaged over the entire dataset (approximately around 100...

NOAA TIFF Image - 2m Multibeam Bathymetry, W00217 USVI 2011, Seafloor Characterization of the US Caribbean - Nancy Foster - NF-11-1 (2011), UTM 20N NAD83

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains a GeoTIFF with 2x2 meter cell size representing the bathymetry of a broad portion of seafloor south of St. Thomas, USVI, derived from data...

NOAA TIFF Image - 2m Multibeam Bathymetry, W00216 USVI 2011, Seafloor Characterization of the US Caribbean - Nancy Foster - NF-11-1 (2011), UTM 20N NAD83

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains a GeoTIFF with 2x2 meter cell size representing the bathymetry of a sharply sloping swath of the St. John Shelf, a selected portion of seafloor...

NOAA TIFF Image - 4m Multibeam Bathymetry , W00216 USVI 2011 , Seafloor Characterization of the US Caribbean - Nancy Foster - NF-11-1 (2011), UTM 20N NAD83

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains a GeoTIFF with 4x4 meter cell size representing the bathymetry of a sharply sloping swath of the St. John Shelf, a selected portion of seafloor...

NOAA TIFF Image - 8m Multibeam Bathymetry , W00216 USVI 2011 , Seafloor Characterization of the US Caribbean - Nancy Foster - NF-11-1 (2011), UTM 20N NAD83

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains a GeoTIFF with 8x8 meter cell size representing the bathymetry of a sharply sloping swath of the St. John Shelf, a selected portion of seafloor...

Reviews and syntheses: to the bottom of carbon processing at the seafloor

Science.gov (United States)

Middelburg, Jack J.

2018-01-01

Organic carbon processing at the seafloor is studied by biogeochemists to quantify burial and respiration, by organic geochemists to elucidate compositional changes and by ecologists to follow carbon transfers within food webs. Here I review these disciplinary approaches and discuss where they agree and disagree. It will be shown that the biogeochemical approach (ignoring the identity of organisms) and the ecological approach (focussing on growth and biomass of organisms) are consistent on longer timescales. Secondary production by microbes and animals is identified to potentially impact the composition of sedimentary organic matter. Animals impact sediment organic carbon processing by microbes in multiple ways: by governing organic carbon supply to sediments, by aeration via bio-irrigation and by mixing labile organic matter to deeper layers. I will present an inverted microbial loop in which microbes profit from bioturbation rather than animals profiting from microbial processing of otherwise lost dissolved organic resources. Sediments devoid of fauna therefore function differently and are less efficient in processing organic matter with the consequence that more organic matter is buried and transferred from Vernadsky's biosphere to the geosphere.

Preliminary hard and soft bottom seafloor substrate map (5m grid) derived from an unsupervised classification of gridded backscatter and bathymetry derivatives at Rose Atoll Lagoon, Territory of American Samoa, USA.

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Preliminary hard and soft seafloor substrate map derived from an unsupervised classification of multibeam backscatter and bathymetry derivatives at Rose Atoll...

Fabrication of high-resolution reflective scale grating for an optical encoder using a patterned self-assembly process

International Nuclear Information System (INIS)

Fan, Shanjin; Jiang, Weitao; Li, Xuan; Yu, Haoyu; Lei, Biao; Shi, Yongsheng; Yin, Lei; Chen, Bangdao; Liu, Hongzhong

2016-01-01

Steel tape scale grating of a reflective incremental linear encoder has a key impact on the measurement accuracy of the optical encoder. However, it is difficult for conventional manufacturing processes to fabricate scale grating with high-resolution grating strips, due to process and material problems. In this paper, self-assembly technology was employed to fabricate high-resolution steel tape scale grating for a reflective incremental linear encoder. Graphene oxide nanoparticles were adopted to form anti-reflective grating strips of steel tape scale grating. They were deposited in the tape, which had a hydrophobic and hydrophilic grating pattern when the dispersion of the nanoparticles evaporated. A standard lift-off process was employed to fabricate the hydrophobic grating strips on the steel tape. Simultaneously, the steel tape itself presents a hydrophilic property. The hydrophobic and hydrophilic grating pattern was thus obtained. In this study, octafluorocyclobutane was used to prepare the hydrophobic grating strips, due to its hydrophobic property. High-resolution graphene oxide steel tape scale grating with a pitch of 20 μ m was obtained through the self-assembly process. The photoelectric signals of the optical encoder containing the graphene oxide scale grating and conventional scale grating were tested under the same conditions. Comparison test results showed that the graphene oxide scale grating has a better performance in its amplitude and harmonic components than that of the conventional steel tape scale. A comparison experiment of position errors was also conducted, demonstrating an improvement in the positioning error of the graphene oxide scale grating. The comparison results demonstrated the applicability of the proposed self-assembly process to fabricate high-resolution graphene oxide scale grating for a reflective incremental linear encoder. (paper)

An accuracy assessment of realtime GNSS time series toward semi- real time seafloor geodetic observation

Science.gov (United States)

Osada, Y.; Ohta, Y.; Demachi, T.; Kido, M.; Fujimoto, H.; Azuma, R.; Hino, R.

2013-12-01

Large interplate earthquake repeatedly occurred in Japan Trench. Recently, the detail crustal deformation revealed by the nation-wide inland GPS network called as GEONET by GSI. However, the maximum displacement region for interplate earthquake is mainly located offshore region. GPS/Acoustic seafloor geodetic observation (hereafter GPS/A) is quite important and useful for understanding of shallower part of the interplate coupling between subducting and overriding plates. We typically conduct GPS/A in specific ocean area based on repeated campaign style using research vessel or buoy. Therefore, we cannot monitor the temporal variation of seafloor crustal deformation in real time. The one of technical issue on real time observation is kinematic GPS analysis because kinematic GPS analysis based on reference and rover data. If the precise kinematic GPS analysis will be possible in the offshore region, it should be promising method for real time GPS/A with USV (Unmanned Surface Vehicle) and a moored buoy. We assessed stability, precision and accuracy of StarFireTM global satellites based augmentation system. We primarily tested for StarFire in the static condition. In order to assess coordinate precision and accuracy, we compared 1Hz StarFire time series and post-processed precise point positioning (PPP) 1Hz time series by GIPSY-OASIS II processing software Ver. 6.1.2 with three difference product types (ultra-rapid, rapid, and final orbits). We also used difference interval clock information (30 and 300 seconds) for the post-processed PPP processing. The standard deviation of real time StarFire time series is less than 30 mm (horizontal components) and 60 mm (vertical component) based on 1 month continuous processing. We also assessed noise spectrum of the estimated time series by StarFire and post-processed GIPSY PPP results. We found that the noise spectrum of StarFire time series is similar pattern with GIPSY-OASIS II processing result based on JPL rapid orbit

Critical metals in manganese nodules from the Cook Islands EEZ, abundances and distributions

Science.gov (United States)

Hein, James R.; Spinardi, Francesca; Okamoto, Nobuyuki; Mizell, Kira; Thorburn, Darryl; Tawake, Akuila

2015-01-01

The Cook Islands (CIs) Exclusive Economic Zone (EEZ) encompasses 1,977,000 km2 and includes the Penrhyn and Samoa basins abyssal plains where manganese nodules flourish due to the availability of prolific nucleus material, slow sedimentation rates, and strong bottom currents. A group of CIs nodules was analyzed for mineralogical and chemical composition, which include many critical metals not before analyzed for CIs nodules. These nodules have varying sizes and nuclei material; however all are composed predominantly of δ-MnO2 and X-ray amorphous iron oxyhydroxide. The mineralogy, Fe/Mn ratios, rare earth element contents, and slow growth rates (mean 1.9 mm/106 years) reflect formation primarily by hydrogenetic precipitation. The paucity of diagenetic input can be explained by low primary productivity at the surface and resultant low organic matter content in seafloor sediment, producing oxic seafloor and sub-seafloor environments. The nodules contain high mean contents of Co (0.41%), Ni (0.38%), Ti (1.20%), and total rare earth elements plus yttrium (REY; 0.167%), and also high contents of Mo, Nb, V, W, and Zr.

EMSO: European Multidisciplinary Seafloor Observatory

Science.gov (United States)

Favali, Paolo

2010-05-01

EMSO, a Research Infrastructure listed within ESFRI (European Strategy Forum on Research Infrastructures) Roadmap (Report 2006, http://cordis.europa.eu/esfri/roadmap.htm), is the European-scale network of multidisciplinary seafloor observatories from the Arctic to the Black Sea with the scientific objective of long-term real-time monitoring of processes related to geosphere/biosphere/hydrosphere interactions. EMSO will enhance our understanding of processes through long time series appropriate to the scale of the phenomena, constituting the new frontier of studying Earth interior, deep-sea biology and chemistry and ocean processes. The development of an underwater network is based on previous EU-funded projects since early '90 and is being supported by several EU initiatives, as the on-going ESONET-NoE, coordinated by IFREMER (2007-2011, http://www.esonet-emso.org/esonet-noe/), and aims at gathering together the Research Community of the Ocean Observatories. In 2006 the FP7 Capacities Programme launched a call for Preparatory Phase (PP) projects, that will provide the support to create the legal and organisational entities in charge of managing the infrastructures, and coordinating the financial effort among the countries. Under this call the EMSO-PP project was approved in 2007 with the coordination of INGV and the participation of other 11 Institutions of 11 countries. The project has started in April 2008 and will last 4 years. The EMSO is a key-infrastructure both for Ocean Sciences and for Solid Earth Sciences. In this respect it will enhance and complement profitably the capabilities of other European research infrastructures such as EPOS, ERICON-Aurora Borealis, and SIOS. The perspective of the synergy among EMSO and other ESFRI Research Infrastructures will be outlined. EMSO Partners: IFREMER-Institut Français de Recherche pour l'exploitation de la mer (France, ref. Roland Person); KDM-Konsortium Deutsche Meeresforschung e.V. (Germany, ref. Christoph

High Reflectance Nanoscale V/Sc Multilayer for Soft X-ray Water Window Region.

Science.gov (United States)

Huang, Qiushi; Yi, Qiang; Cao, Zhaodong; Qi, Runze; Loch, Rolf A; Jonnard, Philippe; Wu, Meiyi; Giglia, Angelo; Li, Wenbin; Louis, Eric; Bijkerk, Fred; Zhang, Zhong; Wang, Zhanshan

2017-10-10

V/Sc multilayer is experimentally demonstrated for the first time as a high reflectance mirror for the soft X-ray water window region. It primarily works at above the Sc-L edge (λ = 3.11 nm) under near normal incidence while a second peak appears at above the V-L edge (λ = 2.42 nm) under grazing incidence. The V/Sc multilayer fabricated with a d-spacing of 1.59 nm and 30 bilayers has a smaller interface width (σ = 0.27 and 0.32 nm) than the conventional used Cr/Sc (σ = 0.28 and 0.47 nm). For V/Sc multilayer with 30 bilayers, the introduction of B 4 C barrier layers has little improvement on the interface structure. As the number of bilayers increasing to 400, the growth morphology and microstructure of the V/Sc layers evolves with slightly increased crystallization. Nevertheless, the surface roughness remains to be 0.25 nm. A maximum soft X-ray reflectance of 18.4% is measured at λ = 3.129 nm at 9° off-normal incidence using the 400-bilayers V/Sc multilayer. According to the fitted model, an s-polarization reflectance of 5.2% can also be expected at λ = 2.425 nm under 40° incidence. Based on the promising experimental results, further improvement of the reflectance can be achieved by using a more stable deposition system, exploring different interface engineering methods and so on.

Analysis of the archaeal sub-seafloor community at Suiyo Seamount on the Izu-Bonin Arc.

Science.gov (United States)

Hara, Kurt; Kakegawa, Takeshi; Yamashiro, Kan; Maruyama, Akihiko; Ishibashi, Jun-Ichiro; Marumo, Katsumi; Urabe, Tetsuro; Yamagishi, Akihiko

2005-01-01

A sub-surface archaeal community at the Suiyo Seamount in the Western Pacific Ocean was investigated by 16S rRNA gene sequence and whole-cell in situ hybridization analyses. In this study, we drilled and cased holes at the hydrothermal area of the seamount to minimize contamination of the hydrothermal fluid in the sub-seafloor by penetrating seawater. PCR clone analysis of the hydrothermal fluid samples collected from a cased hole indicated the presence of chemolithoautotrophic primary biomass producers of Archaeoglobales and the Methanococcales-related archaeal HTE1 group, both of which can utilize hydrogen as an electron donor. We discuss the implication of the microbial community on the early history of life and on the search for extraterrestrial life. c2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

Biology Reflective Assessment Curriculum

Science.gov (United States)

Bayley, Cheryl Ann

Often students and educators view assessments as an obligation and finality for a unit. In the current climate of high-stakes testing and accountability, the balance of time, resources and emphasis on students' scores related to assessment have been slanted considerably toward the summative side. This tension between assessment for accountability and assessment to inform teaching strains instruction and educators' ability to use that information to design learning opportunities that help students develop deeper conceptual understanding. A substantive body of research indicates that formative and reflective assessment can significantly improve student learning. Biology Reflective Assessment Curriculum (BRAC) examines support provided for high school science students through assessment practices. This investigation incorporates the usage of reflective assessments as a guiding practice for differentiated instruction and student choice. Reflective assessment is a metacognitive strategy that promotes self-monitoring and evaluation. The goals of the curriculum are to promote self-efficacy and conceptual understanding in students learning biology through developing their metacognitive awareness. BRAC was implemented in a high school biology classroom. Data from assessments, metacognitive surveys, self-efficacy surveys, reflective journals, student work, a culminating task and field notes were used to evaluate the effectiveness of the curriculum. The results suggest that students who develop their metacognitive skills developed a deeper conceptual understanding and improved feelings of self-efficacy when they were engaged in a reflective assessment unit embedded with student choice. BRAC is a tool for teachers to use assessments to assist students in becoming metacognitive and to guide student choice in learning opportunities.

Reflecting reflection in supervision

DEFF Research Database (Denmark)

Lystbæk, Christian Tang

associated with reflection and an exploration of alternative conceptions that view reflection within the context of settings which have a more group- and team-based orientation. Drawing on an action research project on health care supervision, the paper questions whether we should reject earlier views...... of reflection, rehabilitate them in order to capture broader connotations or move to new ways of regarding reflection that are more in keeping with not only reflective but also emotive, normative and formative views on supervision. The paper presents a critical perspective on supervision that challenge...... the current reflective paradigm I supervision and relate this to emotive, normative and formative views supervision. The paper is relevant for Nordic educational research into the supervision and guidance...

Hydrothermal Upflow, Serpentinization and Talc Alteration Associated with a High Angle Normal Fault Cutting an Oceanic Detachment, Northern Apennines, Italy

Science.gov (United States)

Alt, J.; Crispini, L.; Gaggero, L.; Shanks, W. C., III; Gulbransen, C.; Lavagnino, G.

2017-12-01

Normal faults cutting oceanic core complexes are observed at the seafloor and through geophysics, and may act as flow pathways for hydrothermal fluids, but we know little about such faults in the subsurface. We present bulk rock geochemistry and stable isotope data for a fault that acted as a hydrothermal upflow zone in a seafloor ultramafic-hosted hydrothermal system in the northern Apennines, Italy. Peridotites were exposed on the seafloor by detachment faulting, intruded by MORB gabbros, and are overlain by MORB lavas and pelagic sediments. North of the village of Reppia are fault shear zones in serpentinite, oriented at a high angle to the detachment surface and extending 300 m below the paleo-seafloor. The paleo-seafloor strikes roughly east-west, dipping 30˚ to the north. At depth the fault zone occurs as an anticlinal form plunging 40˚ to the west. A second fault strikes approximately north-south, with a near vertical dip. The fault rock outcrops as reddish weathered talc + sulfide in 0.1-2 m wide anastomosing bands, with numerous splays. Talc replaces serpentinite in the fault rocks, and the talc rocks are enriched in Si, metals (Fe, Cu, Pb), Light Rare Earth Elements (LREE), have variable Eu anomalies, and have low Mg, Cr and Ni contents. In some cases gabbro dikes are associated with talc-alteration and may have enhanced fluid flow. Sulfide from a fault rock has d34S=5.7‰. The mineralogy and chemistry of the fault rocks indicate that the fault acted as the upflow pathway for high-T black-smoker type fluids. Traverses away from the fault (up to 1 km) and with depth below the seafloor (up to 500 m) reveal variable influences of hydrothermal fluids, but there are no consistent trends with distance. Background serpentinites 500 m beneath the paleoseafloor have LREE depleted trends. Other serpentinites exhibit correlations of LREE with HFSE as the result of melt percolation, but there is significant scatter, and hydrothermal effects include LREE enrichment

Use of pre-pulse in laser spot welding of materials with high optical reflection

Science.gov (United States)

Mys, Ihor; Geiger, Manfred

2003-11-01

Laser micro welding has become a standard manufacturing technique, particularly in industry sectors, such as automotive and aerospace electronics or medical devices, where the requirements for strength, miniaturization and temperature resistance are constantly rising. So far the use of laser micro welding is limited due to the fluctuation of the quality of the welded joints, because the welding results for material with high optical reflection and thermal conductivity, such as copper and copper alloys, depend very strongly on the condition of the material surface. This paper presents investigations on the use of a laser pre-pulse in spot welding of electronic materials with Nd:YAG laser. In order to achieve reproducible joining results two strategies are followed-up. The first one utilizes a reflection-based process control for measuring the reflection during the short pre-pulse. The intensity of the reflected light is used to calculate an appropriated welding pulse power, which corresponds to the measured relative absorption. Adjustment of laser parameters according to the condition of the surface is done in real time before laser main pulse. A second possibility for the stabilization of copper welding is the employment of a short and powerful laser pre-pulse before laser main pulse. This pre-pulse affects the workpiece surface and creates more reproducible absorption conditions for the main pulse, independent from the initial situation on material surface.

The Reflective Foundation

DEFF Research Database (Denmark)

Lunde Jørgensen, Ida

Private foundations and cultural philanthropy by élites is viewed with increasing skepticism in recent years, begging the question of the extent to which foundations reflect on their role vis a vis wider societal norms. Through the prism of the New Carlsberg Foundation, financed by the brewery...... Carlsberg A/S, the paper seeks to elucidate the way in which one culturally significant foundation from Denmark has reflected on - and legitimated - its work and investments at critical moments in the past decades. The paper indicates a foundation with a high degree of reflection on the wider societal...

Reflecting and Polarizing Properties of Conductive Fabrics in Ultra-High Frequency Range

Directory of Open Access Journals (Sweden)

Oleg Kiprijanovič

2015-09-01

Full Text Available The system based on ultra-wide band (UWB signals was employed for qualitative estimation of attenuating, reflecting and polarizing properties of conductive fabrics, capable to prevent local static charge accumulation. Pulsed excitation of triangle monopole antenna of 6.5 cm height by rectangular electric pulses induced radiation of UWB signals with spectral density of power having maximum in ultra-high frequency (UHF range. The same antenna was used for the radiated signal receiving. Filters and amplifiers of different passband were employed to divide UHF range into subranges of 0.3-0.55 GHz, 0.55-1 GHz, 1-2 GHz and 2-4 GHz bands. The free space method, when conductive fabric samples of 50x50 cm2 were placed between transmitting and receiving antennas, was used to imitate a practical application. Received wideband signals corresponding to the defined range were detected by unbiased detectors. The fabrics made of two types of warps, containing different threads with conductive yarns, were investigated. It was estimated attenuation and reflective properties of the fabrics when electric field is collinear or perpendicular to thread direction. In the UHF range it was revealed good reflecting properties of the fabrics containing metallic component in the threads. The system has advantages but not without a certain shortcoming. Adapting it for specific tasks should lead to more effective usage, including yet unused properties of the UWB signals.

Review of an analysis system of `Long-Term Deep Seafloor Observatory off Muroto Peninsula`; Kochiken Murotomisakioki `kaitei jishin sogo kansoku system` data no kaiseki system no shokai

Energy Technology Data Exchange (ETDEWEB)

Tsuru, T; Machiyama, H; Hattori, M; Kaneda, Y [Japan Marine Science and Technology Center, Kanagawa (Japan)

1997-10-22

Introduced is a data analysis system for Long-Term Deep Seafloor Observatory established off Muroto Point by Japan Marine Science and Technology Center (JAMSTEC), from which observatory data collected by seismograph and tsunami-meter are transmitted real time. JAMSTEC Long-Term Deep Seafloor Observatory Project Team has begun constructing an analysis system for disposing of events in the data and for locating the hypocenter. The analysis system is composed of a data converting unit that converts the forwarded data into the Win format; a data storage/time-dependent data integration unit that keeps the data in a hard disk for a specified period of time, performs disposition and analysis of events in the data, and forwards the data after disposition and analysis to a data recording unit; a data recording unit that stores selected data of seismic events in a recording medium; and a real-time monitor/NTP server unit that displays real time the observed seismic waveform data. 2 figs.

Analysis of Properties of Reflectance Reference Targets for Permanent Radiometric Test Sites of High Resolution Airborne Imaging Systems

Directory of Open Access Journals (Sweden)

Eero Ahokas

2010-08-01

Full Text Available Reliable and optimal exploitation of rapidly developing airborne imaging methods requires geometric and radiometric quality assurance of production systems in operational conditions. Permanent test sites are the most promising approach for cost-efficient performance assessment. Optimal construction of permanent radiometric test sites for high resolution airborne imaging systems is an unresolved issue. The objective of this study was to assess the performance of commercially available gravels and painted and unpainted concrete targets for permanent, open-air radiometric test sites under sub-optimal climate conditions in Southern Finland. The reflectance spectrum and reflectance anisotropy and their stability were characterized during the summer of 2009. The management of reflectance anisotropy and stability were shown to be the key issues for better than 5% reflectance accuracy.

Organic-inorganic hybrid optical foils with strong visible reflection, excellent near infrared-shielding ability and high transparency

Science.gov (United States)

Zhou, Yijie; Huang, Aibin; Zhou, Huaijuan; Ji, Shidong; Jin, Ping

2018-03-01

Research on functional flexible films has recently been attracting widespread attention especially with regards to foils, which can be designed artificially on the basis of the practical requirements. In this work, a foil with high visible reflection and a strong near infrared shielding efficiency was prepared by a simple wet chemical method. In the process of making this kind of optical foil, emulsion polymerization was first introduced to synthesize polymer opals, which were further compressed between two pieces of polyethylene terephthalate (PET) foil under polymer melting temperature to obtain a photonic crystal film with a strong reflection in the visible region to block blue rays. The following step was to coat a layer of the inorganic nano paint, which was synthesized by dispersing Cs-doped WO3 (CWO) nanoparticles homogenously into organic resin on the surface of the PET to achieve a high near infrared shielding ability. The final composite foil exhibited unique optical properties such as high visible reflectance (23.9%) to block blue rays, and excellent near infrared shielding efficiency (98.0%), meanwhile it still maintained a high transparency meaning that this foil could potentially be applied in energy-saving window films. To sum up, this study provides new insight into devising flexible hybrid films with novel optical properties, which could be further extended to prepare other optical films for potential use in automobile, architectural and other decorative fields.

Searching for the seafloor signature of the 21 May 2003 Boumerdès earthquake offshore central Algeria

Directory of Open Access Journals (Sweden)

A. Cattaneo

2012-07-01

Full Text Available Shaking by moderate to large earthquakes in the Mediterranean Sea has proved in the past to potentially trigger catastrophic sediment collapse and flow. On 21 May 2003, a magnitude 6.8 earthquake located near Boumerdès (central Algerian coast triggered large turbidity currents responsible for 29 submarine cable breaks at the foot of the continental slope over ~150 km from west to east. Seafloor bathymetry and backscatter imagery show the potential imprints of the 2003 event and of previous events. Large slope scarps resulting from active deformation may locally enhance sediment instabilities, although faults are not directly visible at the seafloor. Erosion is evident at the foot of the margin and along the paths of the numerous canyons and valleys. Cable breaks are located at the outlets of submarine valleys and in areas of turbiditic levee overspilling and demonstrate the multi-source and multi-path character of the 2003 turbiditic event. Rough estimates of turbidity flow velocity are not straightforward because of the multiple breaks along the same cable, but seem compatible with those measured in other submarine cable break studies elsewhere.

While the signature of the turbidity currents is mostly erosional on the continental slope, turbidite beds alternating with hemipelagites accumulate in the distal reaches of sediment dispersal systems. In perspective, more chronological work on distal turbidite successions offshore Algeria offers promising perspectives for paleoseismology reconstructions based on turbidite dating, if synchronous turbidites along independent sedimentary dispersal systems are found to support triggering by major earthquakes. Preliminary results on sediment core PSM-KS23 off Boumerdès typically show a 800-yr interval between turbidites during the Holocene, in accordance with the estimated mean seismic cycle on land, even if at this stage it is not yet possible to prove the earthquake origin of all the turbidites.

Reflectance spectra of subarctic lichens

International Nuclear Information System (INIS)

Petzold, D.E.; Goward, S.N.

1988-01-01

Lichens constitute a major portion of the ground cover of high latitude environments, but little has been reported concerning their in situ solar spectral reflectance properties. Knowledge of these properties is important for the interpretation of remotely sensed observations from high latitude regions, as well as in studies of high latitude ecology and energy balance climatology. The spectral reflectance of common boreal vascular plants is similar to that of vascular plants of the mid latitudes. The dominant lichens, in contrast, display variable reflectance patterns in visible wavelengths. The relative reflectance peak at 0.55 μm, common to green vegetation, is absent or indistinct in spectra of pervasive boreal forest and tundra lichens, despite the presence of chlorophyll in the inner algal cells. Lichens of the dominant genus, Cladina, display strong absorption of ultraviolet energy and short-wavelength blue light relative to their absorption in other visible wavelengths. Since the Cladinae dominate both the surface vegetation in open woodlands of the boreal forest and the low arctic tundra, their unusual spectral reflectance patterns will enable accurate monitoring of the boreal forest-tundra ecotone and detection of its vigor and movement in the future. (author)

Reflectance spectra of subarctic lichens

Science.gov (United States)

Petzold, Donald E.; Goward, Samuel N.

1988-01-01

Lichens constitute a major portion of the ground cover of high latitude environments, but little has been reported concerning their in situ solar spectral reflectance properties. Knowledge of these properties is important for the interpretation of remotely sensed observations from high latitude regions, as well as in studies of high latitude ecology and energy balance climatology. The spectral reflectance of common boreal vascular plants is similar to that of vascular plants of the midlatitudes. The dominant lichens, in contrast, display variable reflectance patterns in visible wavelengths. The relative reflectance peak at 0.55 microns, common to green vegetation, is absent or indistinct in spectra of pervasive boreal forest and tundra lichens, despite the presence of chlorophyll in the inner algal cells. Lichens of the dominant genus, Cladina, display strong absorption of ultraviolet energy and short-wavelength blue light relative to their absorption in other visible wavelengths. Since the Cladinae dominate both the surface vegetation in open woodlands of the boreal forest and the low arctic tundra, their unusual spectral reflectance patterns will enable accurate monitoring of the boreal forest-tundra ecotone and detection of its vigor and movement in the future.

California State Waters Map Series-Offshore of Point Reyes, California

Science.gov (United States)

Watt, Janet T.; Dartnell, Peter; Golden, Nadine E.; Greene, H. Gary; Erdey, Mercedes D.; Cochrane, Guy R.; Johnson, Samuel Y.; Hartwell, Stephen R.; Kvitek, Rikk G.; Manson, Michael W.; Endris, Charles A.; Dieter, Bryan E.; Sliter, Ray W.; Krigsman, Lisa M.; Lowe, Erik; Chinn, John L.; Watt, Janet T.; Cochran, Susan A.

2015-01-01

This publication about the Offshore of Point Reyes map area includes ten map sheets that contain explanatory text, in addition to this descriptive pamphlet and a data catalog of geographic information system (GIS) files. Sheets 1, 2, and 3 combine data from four different sonar surveys to generate comprehensive high-resolution bathymetry and acoustic-backscatter coverage of the map area. These data reveal a range of physiographic features (highlighted in the perspective views on sheet 4) such as the flat, sediment-covered seafloor in Drakes Bay, as well as abundant “scour depressions” on the Bodega Head–Tomales Point shelf (see sheet 9) and local, tectonically controlled bedrock uplifts. To validate geological and biological interpretations of the sonar data shown in sheets 1, 2, and 3, the U.S. Geological Survey towed a camera sled over specific offshore locations, collecting both video and photographic imagery; these “ground-truth” surveying data are summarized on sheet 6. Sheet 5 is a “seafloor character” map, which classifies the seafloor on the basis of depth, slope, rugosity (ruggedness), and backscatter intensity and which is further informed by the ground-truth-survey imagery. Sheet 7 is a map of “potential habitats,” which are delineated on the basis of substrate type, geomorphology, seafloor process, or other attributes that may provide a habitat for a specific species or assemblage of organisms. Sheet 8 compiles representative seismic-reflection profiles from the map area, providing information on the subsurface stratigraphy and structure of the map area. Sheet 9 shows the distribution and thickness of young sediment (deposited over the last about 21,000 years, during the most recent sea-level rise) in both the map area and the larger Salt Point to Drakes Bay region, interpreted on the basis of the seismic-reflection data, and it identifies the Offshore of Point Reyes map area as lying within the Bodega Head–Tomales Point shelf, Point

Specular Reflectivity and Hot-Electron Generation in High-Contrast Relativistic Laser-Plasma Interactions

Energy Technology Data Exchange (ETDEWEB)

Kemp, Gregory Elijah [The Ohio State Univ., Columbus, OH (United States)

2013-01-01

Ultra-intense laser (> 1018 W/cm2) interactions with matter are capable of producing relativistic electrons which have a variety of applications in state-of-the-art scientific and medical research conducted at universities and national laboratories across the world. Control of various aspects of these hot-electron distributions is highly desired to optimize a particular outcome. Hot-electron generation in low-contrast interactions, where significant amounts of under-dense pre-plasma are present, can be plagued by highly non-linear relativistic laser-plasma instabilities and quasi-static magnetic field generation, often resulting in less than desirable and predictable electron source characteristics. High-contrast interactions offer more controlled interactions but often at the cost of overall lower coupling and increased sensitivity to initial target conditions. An experiment studying the differences in hot-electron generation between high and low-contrast pulse interactions with solid density targets was performed on the Titan laser platform at the Jupiter Laser Facility at Lawrence Livermore National Laboratory in Livermore, CA. To date, these hot-electrons generated in the laboratory are not directly observable at the source of the interaction. Instead, indirect studies are performed using state-of-the-art simulations, constrained by the various experimental measurements. These measurements, more-often-than-not, rely on secondary processes generated by the transport of these electrons through the solid density materials which can susceptible to a variety instabilities and target material/geometry effects. Although often neglected in these types of studies, the specularly reflected light can provide invaluable insight as it is directly influenced by the interaction. In this thesis, I address the use of (personally obtained) experimental specular reflectivity measurements to indirectly study hot-electron generation in the context of high-contrast, relativistic

Vertical Cable Seismic Survey for Hydrothermal Deposit

Science.gov (United States)

Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

2012-04-01

The vertical cable seismic is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. This type of survey is generally called VCS (Vertical Cable Seismic). Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. Our first experiment of VCS surveys has been carried out in Lake Biwa, JAPAN in November 2009 for a feasibility study. Prestack depth migration is applied to the 3D VCS data to obtain a high quality 3D depth volume. Based on the results from the feasibility study, we have developed two autonomous recording VCS systems. After we carried out a trial experiment in the actual ocean at a water depth of about 400m and we carried out the second VCS survey at Iheya Knoll with a deep-towed source. In this survey, we could establish the procedures for the deployment/recovery of the system and could examine the locations and the fluctuations of the vertical cables at a water depth of around 1000m. The acquired VCS data clearly shows the reflections from the sub-seafloor. Through the experiment, we could confirm that our VCS system works well even in the severe circumstances around the locations of seafloor hydrothermal deposits. We have, however, also confirmed that the uncertainty in the locations of the source and of the hydrophones could lower the quality of subsurface image. It is, therefore, strongly necessary to develop a total survey system that assures a accurate positioning and a deployment techniques

The Relation between Reflection-Impulsivity and Perceived Competence in Junior High School Children

OpenAIRE

桜井, 茂男

1990-01-01

The purpose of this study was to investigate the relation between perceived competence and reflection-impulsivity in junior high school students. Two scales, i. e. , the Perceived Competence Scale for Children developed by Sakurai (1983) and the Matching Familiar Figures (MFF) test developed by Sugihara (1977) , were administrated to 70 eighth male students and 70 eighth female students. The performance, Impulsivity (I) score, and Efficiency (E) score (see Salkind & Wright, 1977) in MFF test ...

Ultra-broadband and planar sound diffuser with high uniformity of reflected intensity

Science.gov (United States)

Fan, Xu-Dong; Zhu, Yi-Fan; Liang, Bin; Yang, Jing; Yang, Jun; Cheng, Jian-Chun

2017-09-01

Schroeder diffusers, as a classical design of acoustic diffusers proposed over 40 years ago, play key roles in many practical scenarios ranging from architectural acoustics to noise control to particle manipulation. Despite the great success of conventional acoustic diffusers, it is still worth pursuing ideal acoustic diffusers that are essentially expected to produce perfect sound diffuse reflection within the unlimited bandwidth. Here, we propose a different mechanism for designing acoustic diffusers to overcome the basic limits in intensity uniformity and working bandwidth in the previous designs and demonstrate a practical implementation by acoustic metamaterials with dispersionless phase-steering capability. In stark contrast to the existing production of diffuse fields relying on random scattering of sound energy by using a specific mathematical number sequence of periodically distributed unit cells, we directly mold the reflected wavefront into the desired shape by precisely manipulating the local phases of individual subwavelength metastructures. We also benchmark our design via numerical simulation with a commercially available Schroeder diffuser, and the results verify that our proposed diffuser scatters incident acoustic energy into all directions more uniformly within an ultra-broad band regardless of the incident angle. Furthermore, our design enables further improvement of the working bandwidth just by simply downscaling each individual element. With ultra-broadband functionality and high uniformity of reflected intensity, our metamaterial-based production of the diffusive field opens a route to the design and application of acoustic diffusers and may have a significant impact on various fields such as architectural acoustics and medical ultrasound imaging/treatment.

The distribution of trace elements in a range of deep-sea sulphide ore deposits and their impact on seafloor mining

Science.gov (United States)

Fallon, E. K.; Scott, T. B.; Brooker, R. A.

2015-12-01

Acid rock drainage is a natural weathering process that is often exacerbated by mining activities, common in onshore sulphide ore deposits, that can lead to considerable environmental impact. A similar 'weathering process' occurs at seafloor massive sulphide (SMS) ore deposits. In contrast to the onshore situation, the expected consequence in the marine environment is often considered to be oxide formation, negligible metal release and minimal net acid generation due to the high buffering capacity of seawater and low solubility of iron at near neutral pH. However, no dissolution studies exist that emulate the true composition of sulphide ore deposits that either sit passively on the seafloor or are actively mined in this colder, more saline, and alkaline environment. In particular, these deposits will include a variety of minerals, and it is the interaction of these minerals and inclusions in regards to galvanic cells that can subsequently increase the dissolution of metals into the water column. Any heavy metal release that is not balanced by subsequent oxidation and precipitation, has the potential to produce toxicity for benthic ecosystems, bioaccumulation and dispersal through currents. The present work has sought to provide a pilot investigation on the deep sea weathering of sulphide minerals, by identifying the mineral phases, trace elements and potential galvanic couples that may arise in sulphide mineral samples collected from various tectonic settings. Samples have been analysed using EMPA and LA-ICPMS in order to identify the range of trace elements and toxins that may be contributed to the water column, especially heavy metals and environmental toxins (e.g. Fe, Cu, Zn, Pb, Co, Ni, Cd, As, Sb, Sn, Hg). Our observations raise important questions about which ore deposits could have more or less environmental impact during any mining activity. These observations will be used to design oxidative dissolution experiments at deep-sea conditions utilising the

Experimental design for reflection measurements of highly reactive liquid or solid substances with application to liquid sodium

International Nuclear Information System (INIS)

Chan, S.H.; Gossler, A.A.

1980-01-01

This technical report describes the experimental part of a program on thermal radiation properties of reactor materials. A versatile goniometer system with associated electronic components and mechanical instruments has been assembled. It is designed to measure spectral, specular reflectances of highly reactive liquid or solid substances over a spectral range of 0.3 μ to 9 μ and incidence angles of 12 0 to 30 0 off the normal direction. The capability of measuring reflectances of liquid substances clearly distinguishes this experimental design from conventional systems which are applicable only to solid substances. This design has been used to measure the spectral, specular reflectance of liquid sodium and preliminary results obtained are compared with those of solid sodium measured by other investigators

Seafloor morphology of the Eurasia-Nubia (Africa) plate boundary between the Tore-Madeira Rise and the Straits of Gibraltar: a case of coexistent Mesozoic through Present day features of tectonic, oceanographic and sedimentary origin

Science.gov (United States)

Terrinha, Pedro; Duarte, João.; Valadares, Vasco; Batista, Luis; Zitellini, Nevio; Grácia, Eulalia; Lourenço, Nuno; Rosas, Filipe; Roque, Cristina

2010-05-01

The joint use of more than 10.000 km multichannel seismic reflection profiles and 180.000km2 of multibeam swath bathymetry and backscatter allowed for a new vision of the seafloor tectonic and geomorphic processes of the area that encompasses the present day plate boundary between Africa and Eurasia, between the Gibraltar Straits and the Tore-Madeira Rise, in the southern sector of the North Atlantic Ocean. The interpretation of this data allowed for the detailed description of the seafloor morphology (i.e. a morphologic map) and the classification of the morphologic features in what respects the genetic process and age. It can be seen that in the same region coexist morphologic features that result from tectonic processes associated with the Triassic-Cretaceous break-up of Pangea, the Paleogene-Miocene compressive phase, the Miocene through Present subduction under the Gibraltar Arc (Gutscher et al., 2002), the Pliocene-Quaternary wrench tectonics and possible coeval plate boundary (Zitellini et al., 2009), the Present day mud volcanism and propagation of the compressive deformation along the West Continental Margin of Portugal (Terrinha et al., 2009). Interpretation of the seismic profiles together with the bathymetry allows the understanding of endogenous and exogenous processes that creates reliefs associated with active structures (related to the Miocene through Present compressive stress field). Other reliefs generated in Mesozoic times by analogous processes can be as well preserved as these active ones. In what concerns exogenous processes, the analysis of the two datasets (reflection seismics and bathymetry) allowed for the description of morphologic features associated with oceanic currents that interact with the seafloor forming these important features. As is the case of the well known active contourites but also less known features, like giant scours at 4 km water depth that have recently been described, suggesting the interaction of deep currents and

A climatology of visible surface reflectance spectra

International Nuclear Information System (INIS)

Zoogman, Peter; Liu, Xiong; Chance, Kelly; Sun, Qingsong; Schaaf, Crystal; Mahr, Tobias; Wagner, Thomas

2016-01-01

We present a high spectral resolution climatology of visible surface reflectance as a function of wavelength for use in satellite measurements of ozone and other atmospheric species. The Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument is planned to measure backscattered solar radiation in the 290–740 nm range, including the ultraviolet and visible Chappuis ozone bands. Observation in the weak Chappuis band takes advantage of the relative transparency of the atmosphere in the visible to achieve sensitivity to near-surface ozone. However, due to the weakness of the ozone absorption features this measurement is more sensitive to errors in visible surface reflectance, which is highly variable. We utilize reflectance measurements of individual plant, man-made, and other surface types to calculate the primary modes of variability of visible surface reflectance at a high spectral resolution, comparable to that of TEMPO (0.6 nm). Using the Moderate-resolution Imaging Spectroradiometer (MODIS) Bidirection Reflectance Distribution Function (BRDF)/albedo product and our derived primary modes we construct a high spatial resolution climatology of wavelength-dependent surface reflectance over all viewing scenes and geometries. The Global Ozone Monitoring Experiment–2 (GOME-2) Lambertian Equivalent Reflectance (LER) product provides complementary information over water and snow scenes. Preliminary results using this approach in multispectral ultraviolet+visible ozone retrievals from the GOME-2 instrument show significant improvement to the fitting residuals over vegetated scenes. - Highlights: • Our goals was visible surface reflectance for satellite trace gas measurements. • Captured the range of surface reflectance spectra through EOF analysis. • Used satellite surface reflectance products for each given scene to anchor EOFs. • Generated a climatology of time/geometry dependent surface reflectance spectra. • Demonstrated potential to

Size and Carbon Content of Sub-seafloor Microbial Cells at Landsort Deep, Baltic Sea

DEFF Research Database (Denmark)

Braun, Stefan; Morono, Yuki; Littmann, Sten

2016-01-01

determined the volume and the carbon content of microbial cells from a marine sediment drill core retrieved by the Integrated Ocean Drilling Program (IODP), Expedition 347, at Landsort Deep, Baltic Sea. To determine their shape and volume, cells were separated from the sediment matrix by multi-layer density......-specific carbon content was 19–31 fg C cell−1, which is at the lower end of previous estimates that were used for global estimates of microbial biomass. The cell-specific carbon density increased with sediment depth from about 200 to 1000 fg C μm−3, suggesting that cells decrease their water content and grow...... small cell sizes as adaptation to the long-term subsistence at very low energy availability in the deep biosphere. We present for the first time depth-related data on the cell volume and carbon content of sedimentary microbial cells buried down to 60 m below the seafloor. Our data enable estimates...

Seafloor massive sulfide deposits support unique megafaunal assemblages: Implications for seabed mining and conservation.

Science.gov (United States)

Boschen, Rachel E; Rowden, Ashley A; Clark, Malcolm R; Pallentin, Arne; Gardner, Jonathan P A

2016-04-01

Mining of seafloor massive sulfides (SMS) is imminent, but the ecology of assemblages at SMS deposits is poorly known. Proposed conservation strategies include protected areas to preserve biodiversity at risk from mining impacts. Determining site suitability requires biological characterisation of the mine site and protected area(s). Video survey of a proposed mine site and protected area off New Zealand revealed unique megafaunal assemblages at the mine site. Significant relationships were identified between assemblage structure and environmental conditions, including hydrothermal features. Unique assemblages occurred at both active and inactive chimneys and are particularly at risk from mining-related impacts. The occurrence of unique assemblages at the mine site suggests that the proposed protected area is insufficient alone and should instead form part of a network. These results provide support for including hydrothermally active and inactive features within networks of protected areas and emphasise the need for quantitative survey data of proposed sites. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Microbiology of Low Temperature Seafloor Deposits Along a Geochemical Gradient in Lau Basin

Science.gov (United States)

sylvan, J. B.; Sia, T. Y.; Haddad, A.; Briscoe, L. J.; Girguis, P. R.; Edwards, K. J.

2011-12-01

The East Lau Spreading Center (ELSC) and Valu Fa Ridge comprise a ridge segment in the southwest Pacific Ocean where rapid transitions in the underlying mantle lenses manifest themselves by gradients in seafloor rock geochemistry. At the spreading center in the north, basaltic host rock extrudes while the influence of subduction in the south creates mainly basaltic andesite host rock. A contuous gradient between these two end members exists along the spreading center. We studied the geology and microbial diversity of three silicate rock samples and three inactive sulfide chimney samples collected along the ELSC and Valu Fa Ridge by X-ray diffraction, elemental analysis, thin section analysis and construction of bacterial 16S rRNA clone libraries. Here, we discuss the geological and biological differences between the collected rocks. We found that the bacterial community composition changed as the host rock mineralogy and chemistry changed from north to south. Also, the bacterial community composition on the silicates is distinct from those on the inactive chimneys, and the interior conduit of an inactive chimney hosts a very different community from the exterior. Basalt from the northern end of the ELSC had high proportions of Alphaproteobacteria and Bacteroidetes. These proportions decreased on the silicates collected further south. Epsilonproteobacteria were also present on the basalt, decreased further south and were absent on the basaltic andesite. Conversely, basaltic andesite rocks from the southern end had high proportions of Chloroflexi, which decreased further north and were absent on basalt. The exterior of inactive sulfide structures were dominated by lineages of sulfur oxidizing Gammaproteobacteria and Epsilonproteobacteria and were less diverse than those on the silicates. The interior of one chimney was dominated by sulfate-reducing Deltaproteobacteria and was the least diverse of all samples. These results support the Mantle to Microbe hypothesis in

In-situ geophysical measurements in marine sediments: Applications in seafloor acoustics and paleoceanography

Science.gov (United States)

Gorgas, Thomas Joerg

Acoustic in-situ sound speeds and attenuation were measured on the Eel River shelf, CA, with the Acoustic Lance between 5 and 15 kHz to 2.0 meters below seafloor (mbsf). A comparison with laboratory ultrasonic geoacoustic data obtained at 400 kHz on cored sediments showed faster in-situ and ultrasonic sound speeds in coarse-grained deposits in water depths to 60 m than in fine-grained deposits below that contour line. Ultrasonic attenuation was often greater than in-situ values and remained almost constant below 0.4 mbsf in these heterogeneous deposits. In-situ attenuation decreased with depth. These observations partly agree with results from other field studies, and with theoretical models that incorporate intergranular friction and dispersion from viscosity as main controls on acoustic wave propagation in marine sediments. Deviations among in-situ and laboratory acoustic data from the Eel Margin with theoretical studies were linked to scattering effects. Acoustic Lance was also deployed in homogeneous, fine-grained sediments on the inner shelf of SE Korea, where free gas was identified in late-September, but not in mid-September 1999. Free gas was evidenced by an abrupt decrease of in-situ sound speed and by characteristic changes in acoustic waveforms. These results suggest the presence of a gassy sediment layer as shallow as 2 mbsf along the 70 m bathymetry line, and was attributed to a variable abundance of free gas on short-term and/or small-regional scales on the SE Korea shelf. Bulk density variations in marine sediments obtained along the Walvis Ridge/Basin, SW Africa, at Ocean Drilling Program (ODP) Sites 1081 to 1084 were spectral-analyzed to compute high-resolution sedimentation rates (SRs) in both the time- and age domains by correctly identifying Milankovitch cycles (MCs). SRs for the ODP sites yielded age-depth models that often correlate positively with biostratigraphic data and with organic mass accumulation rates (MAR Corg), a proxy for

Preliminary hard and soft bottom seafloor substrate map derived from an supervised classification of bathymetry derived from multispectral World View-2 satellite imagery of Ni'ihau Island, Territory of Main Hawaiian Islands, USA

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Preliminary hard and soft seafloor substrate map derived from a supervised classification from multispectral World View-2 satellite imagery of Ni'ihau Island,...

NOAA TIFF Image - 2m Multibeam Bathymetry, W00217 USVI 2011, Seafloor Characterization of the US Caribbean - Nancy Foster - NF-11-1 (2011), UTM 20N NAD83 (NCEI Accession 0131858)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains a GeoTIFF with 2x2 meter cell size representing the bathymetry of a broad portion of seafloor south of St. Thomas, USVI, derived from data...

NOAA TIFF Image - 2m Multibeam Bathymetry, W00216 USVI 2011, Seafloor Characterization of the US Caribbean - Nancy Foster - NF-11-1 (2011), UTM 20N NAD83 (NCEI Accession 0131858)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains a GeoTIFF with 2x2 meter cell size representing the bathymetry of a sharply sloping swath of the St. John Shelf, a selected portion of seafloor...

NOAA TIFF Image - 8m Multibeam Bathymetry , W00216 USVI 2011 , Seafloor Characterization of the US Caribbean - Nancy Foster - NF-11-1 (2011), UTM 20N NAD83 (NCEI Accession 0131858)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains a GeoTIFF with 8x8 meter cell size representing the bathymetry of a sharply sloping swath of the St. John Shelf, a selected portion of seafloor...

High Performance Paper White- and Full-Color Reflective Displays

National Research Council Canada - National Science Library

Fiske, Thomas

2001-01-01

This report documents work performed by a team led by dpiX LLC to develop fabrication technology for a paper-white, video-rate, full-color reflective display technology based on holographically formed...

Solution-processable MoOx nanocrystals enable highly efficient reflective and semitransparent polymer solar cells

KAUST Repository

Jagadamma, Lethy Krishnan

2016-09-09

Solution-manufacturing of organic solar cells with best-in-class power conversion efficiency (PCE) will require all layers to be solution-coated without compromising solar cell performance. To date, the hole transporting layer (HTL) deposited on top of the organic bulk heterojunction layer in the inverted architecture is most commonly an ultrathin (<10 nm) metal oxide layer prepared by vacuum-deposition. Here, we show that an alcohol-based nanocrystalline MoOx suspension with carefully controlled nanocrystal (NC) size can yield state of the art reflective and semitransparent solar cells. Using NCs smaller than the target HTL thickness (∼10 nm) can yield compact, pinhole-free films which result in highly efficient polymer:fullerene bulk heterojunction (BHJ) solar cells with PCE=9.5%. The solution processed HTL is shown to achieve performance parity with vacuum-evaporated HTLs for several polymer:fullerene combinations and is even shown to work as hole injection layer in polymer light emitting diodes (PLED). We also demonstrate that larger MoOx NCs (30–50 nm) successfully composite MoOx with Ag nanowires (NW) to form a highly conducting, transparent top anode with exceptional contact properties. This yields state-of-the-art semitransparent polymer: fullerene solar cells with PCE of 6.5% and overall transmission >30%. The remarkable performance of reflective and semitransparent OPVs is due to the uncommonly high fill factors achieved using a carefully designed strategy for implementation of MoOx nanocrystals as HTL materials. © 2016 Elsevier Ltd

A Data-Driven Reflectance Model

OpenAIRE

Matusik, Wojciech; Pfister, Hanspeter; Brand, Matt; McMillan, Leonard

2003-01-01

We present a generative model for isotropic bidirectional reflectance distribution functions (BRDFs) based on acquired reflectance data. Instead of using analytical reflectance models, we represent each BRDF as a dense set of measurements. This allows us to interpolate and extrapolate in the space of acquired BRDFs to create new BRDFs. We treat each acquired BRDF as a single high-dimensional vector taken from a space of all possible BRDFs. We apply both linear (subspace) and non-linear (manif...

Low-temperature relative reflectivity measurements of reflective and scintillating foils used in rare event searches

Science.gov (United States)

Langenkämper, A.; Ulrich, A.; Defay, X.; Feilitzsch, F. v.; Lanfranchi, J.-C.; Mondragón, E.; Münster, A.; Oppenheimer, C.; Potzel, W.; Roth, S.; Schönert, S.; Steiger, H.; Trinh Thi, H. H.; Wawoczny, S.; Willers, M.; Zöller, A.

2018-03-01

In this work we investigate the reflectivity of highly reflective multilayer polymer foils used in the CRESST experiment. The CRESST experiment searches directly for dark matter via operating scintillating CaWO4 crystals as targets for elastic dark matter-nucleon scattering. In order to suppress background events, the experiment employs the so-called phonon-light technique which is based on the simultaneous measurement of the heat signal in the main CaWO4 target crystal and of the emitted scintillation light with a separate cryogenic light detector. Both detectors are surrounded by a highly reflective and scintillating multilayer polymer foil to increase the light collection efficiency and to veto surface backgrounds. While this study is motivated by the CRESST experiment, the results are also relevant for other rare event searches using scintillating cryogenic bolometers in the field of the search of dark matter and neutrinoless double beta decay (0 νββ). In this work a dedicated experiment has been set up to determine the relative reflectivity at 300 K and 20 K of three multilayer foils ("VM2000", "VM2002", "Vikuiti") produced by the company 3M. The intensity of a light beam reflected off the foil is measured with a CCD camera. The ratio of the intensities at 300 K and 20 K corresponds to the relative reflectivity change. The measurements performed in this work show no variation of the reflectivity with temperature at a level of ∼1%.

Surface mapping and drilling of extinct seafloor massive sulphide deposits (eSMS) from the TAG Hydrothermal Field, 26oN: A tale of two `Jaspers'

Science.gov (United States)

Stobbs, I. J.; Lusty, P.; Petersen, S.; Murton, B. J.

2017-12-01

Two extinct seafloor massive sulphide (eSMS) deposits within the TAG hydrothermal field, 26oN, mid-Atlantic ridge, were mapped and drilled: Southern Mound and the newly discovered `Rona Mound'. Surface mapping was undertaken by combining high definition video footage and high resolution bathymetry to interpret surface geological and geomorphological features. Drill core was recovered using the BGS RD2 robotic drilling rig. Surface mapping of the mounds revealed a superficial cover of carbonate and iron-oxyhydroxides sediments, observed to directly overly oxide coated sulphide material within fault scarps, which dissect the flanks of both mounds. Drilling at the summits of the mounds revealed similar stratigraphy to the mapping, with the addition of a coherent and dense layer of red-coloured silica-rich `jasper', up to 3m thick, underlying the sediments and overlying unoxidised massive sulphides. The jasper mineralogy is dominated by silica, with minor iron oxides and rare disseminated sulphides. It displays a range of complex textures including filamentous and dendritic iron oxides often coated in silica. Drill core samples show the material to be porous, but relatively impermeable. Strong and positive Eu (REE) anomalies indicates a hydrothermal origin with little evidence of a seawater signature (lack of negative Ce anomaly). Silica precipitation is associated with low temperature hydrothermal activity, chert and jasper materials are locally present within the nearby hydrothermally active TAG mound and are more widespread at low-temperature diffuse hydrothermal sites such as within the MESO field. We interpret the `jasper' layers to be a common product, formed during the waning, low temperature, stage of the hydrothermal cycle which may form an impermeable and resistant `cap' that protects the underlying massive sulphide ore body from oxidation and dissolution. The formation of a `jasper cap' could act automatically to preserve eSMS deposits when hydrothermal

The Reflective Learning Continuum: Reflecting on Reflection

Science.gov (United States)

Peltier, James W.; Hay, Amanda; Drago, William

2005-01-01

The importance of reflection to marketing educators is increasingly recognized. However, there is a lack of empirical research that considers reflection within the context of both the marketing and general business education literature. This article describes the use of an instrument that can be used to measure four identified levels of a…

Highly directive Fabry-Perot leaky-wave nanoantennas based on optical partially reflective surfaces

Energy Technology Data Exchange (ETDEWEB)

Lorente-Crespo, M.; Mateo-Segura, C., E-mail: C.Mateo-Segura@hw.ac.uk [Institute of Sensors, Signals and Systems, Heriot-Watt University, EH14 4AS Edinburgh (United Kingdom)

2015-05-04

Nanoantennas enhance the conversion between highly localized electromagnetic fields and far-field radiation. Here, we investigate the response of a nano-patch partially reflective surface backed with a silver mirror to an optical source embedded at the centre of the structure. Using full wave simulations, we demonstrate a two orders of magnitude increased directivity compared to the isotropic radiator, 50% power confinement to a 13.8° width beam and a ±16 nm bandwidth. Our antenna does not rely on plasmonic phenomena thus reducing non-radiative losses and conserving source coherence.

High School Mathematics Teachers' Levels of Achieving Technology Integration and In-Class Reflections: The Case of Mathematica

Science.gov (United States)

Ardiç, Mehmet Alper; Isleyen, Tevfik

2017-01-01

The purpose of this study is to determine the levels of high school mathematics teachers in achieving mathematics instruction via computer algebra systems and the reflections of these practices in the classroom. Three high school mathematics teachers employed at different types of school participated in the study. In the beginning of this…

Practical research on junior high school mathematics about students' learning processes : using 'reflective sheet' (the Math Journal) et al.

OpenAIRE

吉岡, 睦美; 重松, 敬一

2015-01-01

In this paper, we discuss the case study of mathematics education for Junior High School students' learning processes focusing students' metacognition and knowledge using 'Reflective Sheet' (the Math Journal) et al.. The metacognition is rather than direct action on the environment and the perception that target cognitive function and cognitive recognition of that, and say what happens in the mind. Especially, we use Reflective Sheet which is formed to check students' cognitive and metacognit...

Reflections on having children in the future--interviews with highly educated women and men without children.

Science.gov (United States)

Eriksson, Carola; Larsson, Margareta; Tydén, Tanja

2012-08-01

There is a trend to delay birth of the first child until the age at which female reproductive capacity has started to decrease. The aim of the present study was to explore how highly educated women and men reflected on future parenthood. Twenty-two women and 18 men, who had started their professional career, were subjected to individual qualitative semi-structured interviews with qualitative content analysis guiding the analysis. All informants, except for three women, planned to have children when some important prerequisites were fulfilled. Women and men reflected in much the same way, and prerequisites for parenthood were being of reasonable age and having a partner in the same phase of life. A reasonable age was considered in relation to reproductive capacity, and both women and men expressed awareness of the natural decline in fertility at higher ages. Good living conditions with stable finances were also important. Parenthood was perceived as a challenge and a sacrifice but also as enriching life. Reasons for having children included being part of the future and settling down to build their own family. Many concluded that there would never be a perfect time for having children. Highly educated women and men reflect on various factors when considering family planning. Being of reasonable age and having good living conditions, in particular a sound personal economy, were important. Given their goals, it is not surprising that many postpone parenthood until ages when female reproductive capacity is decreased.

Geology of the continental margin beneath Santa Monica Bay, Southern California, from seismic-reflection data

Science.gov (United States)

Fisher, M.A.; Normark, W.R.; Bohannon, R.G.; Sliter, R.W.; Calvert, A.J.

2003-01-01

We interpret seismic-reflection data, which were collected in Santa Monica Bay using a 70-in3 generator-injector air gun, to show the geologic structure of the continental shelf and slope and of the deep-water, Santa Monica and San Pedro Basins. The goal of this research is to investigate the earthquake hazard posed to urban areas by offshore faults. These data reveal that northwest of the Palos Verdes Peninsula, the Palos Verdes Fault neither offsets the seafloor nor cuts through an undeformed sediment apron that postdates the last sea level rise. Other evidence indicates that this fault extends northwest beneath the shelf in the deep subsurface. However, other major faults in the study area, such as the Dume and San Pedro Basin Faults, were active recently, as indicated by an arched seafloor and offset shallow sediment. Rocks under the lower continental slope are deformed to differing degrees on opposite sides of Santa Monica Canyon. Northwest of this canyon, the continental slope is underlain by a little-deformed sediment apron; the main structures that deform this apron are two lower-slope anticlines that extend toward Point Dume and are cored by faults showing reverse or thrust separation. Southeast of Santa Monica Canyon, lower-slope rocks are deformed by a complex arrangement of strike-slip, normal, and reverse faults. The San Pedro Escarpment rises abruptly along the southeast side of Santa Monica Canyon. Reverse faults and folds underpinning this escarpment steepen progressively southeastward. Locally they form flower structures and cut downward into basement rocks. These faults merge downward with the San Pedro Basin fault zone, which is nearly vertical and strike slip. The escarpment and its attendant structures diverge from this strike-slip fault zone and extend for 60 km along the margin, separating the continental shelf from the deep-water basins. The deep-water Santa Monica Basin has large extent but is filled with only a thin (less than 1.5-km

Bathymetry of the waters surrounding the Elizabeth Islands, Massachusetts

Science.gov (United States)

Pendleton, Elizabeth A.; Andrews, Brian D.; Ackerman, Seth D.; Twichell, Dave

2014-01-01

The Elizabeth Islands in Massachusetts that separate Vineyard Sound from Buzzards Bay are the remnants of a moraine (unconsolidated glacial sediment deposited at an ice sheet margin; Oldale and O’Hara, 1984). The most recent glacial ice retreat in this region occurred between 25,000 and 20,000 years ago, and the subsequent rise in sea level that followed deglaciation caused differences in the seafloor character between Buzzards Bay and Vineyard Sound. The relatively rough seafloor of Vineyard Sound reflects widespread exposure of glacial material. Shoals mark the location of recessional ice contact material, and deep channels illustrate where meltwater drainage incised glacial deposits. Following ice retreat from the Elizabeth Islands, a glacial lake formed across the mouth of Buzzards Bay, when the lake drained, it scoured two deep channels at the southern end of the bay. Sea level rise began to inundate Vineyard Sound and Buzzards Bay about 8,000 years ago and continues to modify the modern seafloor (Robb and Oldale, 1977). Fine-grained marine and estuarine sediments were deposited in the partially protected setting of Buzzards Bay. These deposits, up to 10 meters in thickness, buried the high-relief glacial landscape and created the generally smooth modern seafloor. In contrast, the Vineyard Sound of today experiences strong tidal currents, which largely prevent the deposition of fine-grained material and constantly rework the glacial sand and gravel within shoals. The seafloor of the sound largely reflects the contours of the ancient glaciated landscape that existed before sea level began to rise. The bathymetric data used to create the hillshaded relief image of the seafloor were collected by the U.S. Geological Survey (USGS) in cooperation with the Massachusetts Office of Coastal Zone Management and supplemented with National Oceanic and Atmospheric Administration hydrographic survey data. The map shows the detailed bathymetry of Buzzards Bay and Vineyard

High resolution reflection seismic mapping of shallow coal seams

CSIR Research Space (South Africa)

Mngadi, SB

2013-10-01

Full Text Available the extent of the mine workings. Two 94 m profiles (tied to boreholes) were surveyed using a sledgehammer source. Processing was optimized to image the shallow reflections. The refraction seismic models and stacked time sections were compared and integrated...

Salinity and spectral reflectance of soils

Science.gov (United States)

Szilagyi, A.; Baumgardner, M. F.

1991-01-01

The basic spectral response related to the salt content of soils in the visible and reflective IR wavelengths is analyzed in order to explore remote sensing applications for monitoring processes of the earth system. The bidirectional reflectance factor (BRF) was determined at 10 nm of increments over the 520-2320-nm spectral range. The effect of salts on reflectance was analyzed on the basis of 162 spectral measurements. MSS and TM bands were simulated within the measured spectral region. A strong relationship was found in variations of reflectance and soil characteristics pertaining to salinization and desalinization. Although the individual MSS bands had high R-squared values and 75-79 percent of soil/treatment combinations were separable, there was a large number of soil/treatment combinations not distinguished by any of the four highly correlated MSS bands under consideration.

Theoretical analysis of open aperture reflection Z-scan on materials with high-order optical nonlinearities

International Nuclear Information System (INIS)

Petris, Adrian I.; Vlad, Valentin I.

2010-03-01

We present a theoretical analysis of open aperture reflection Z-scan in nonlinear media with third-, fifth-, and higher-order nonlinearities. A general analytical expression for the normalized reflectance when third-, fifth- and higher-order optical nonlinearities are excited is derived and its consequences on RZ-scan in media with high-order nonlinearities are discussed. We show that by performing RZ-scan experiments at different incident intensities it is possible to put in evidence the excitation of different order nonlinearities in the medium. Their contributions to the overall nonlinear response can be discriminated by using formulas derived by us. A RZ-scan numerical simulation using these formulas and data taken from literature, measured by another method for the third-, fifth-, and seventh-order nonlinear refractive indices of As 2 S 3 chalcogenide glass, is performed. (author)

High precision AlGaAsSb ridge-waveguide etching by in situ reflectance monitored ICP-RIE

Science.gov (United States)

Tran, N. T.; Breivik, Magnus; Patra, S. K.; Fimland, Bjørn-Ove

2014-05-01

GaSb-based semiconductor diode lasers are promising candidates for light sources working in the mid-infrared wavelength region of 2-5 μm. Using edge emitting lasers with ridge-waveguide structure, light emission with good beam quality can be achieved. Fabrication of the ridge waveguide requires precise etch stop control for optimal laser performance. Simulation results are presented that show the effect of increased confinement in the waveguide when the etch depth is well-defined. In situ reflectance monitoring with a 675 nm-wavelength laser was used to determine the etch stop with high accuracy. Based on the simulations of laser reflectance from a proposed sample, the etching process can be controlled to provide an endpoint depth precision within +/- 10 nm.

High-order dynamic modeling and parameter identification of structural discontinuities in Timoshenko beams by using reflection coefficients

Science.gov (United States)

Fan, Qiang; Huang, Zhenyu; Zhang, Bing; Chen, Dayue

2013-02-01

Properties of discontinuities, such as bolt joints and cracks in the waveguide structures, are difficult to evaluate by either analytical or numerical methods due to the complexity and uncertainty of the discontinuities. In this paper, the discontinuity in a Timoshenko beam is modeled with high-order parameters and then these parameters are identified by using reflection coefficients at the discontinuity. The high-order model is composed of several one-order sub-models in series and each sub-model consists of inertia, stiffness and damping components in parallel. The order of the discontinuity model is determined based on the characteristics of the reflection coefficient curve and the accuracy requirement of the dynamic modeling. The model parameters are identified through the least-square fitting iteration method, of which the undetermined model parameters are updated in iteration to fit the dynamic reflection coefficient curve with the wave-based one. By using the spectral super-element method (SSEM), simulation cases, including one-order discontinuities on infinite- and finite-beams and a two-order discontinuity on an infinite beam, were employed to evaluate both the accuracy of the discontinuity model and the effectiveness of the identification method. For practical considerations, effects of measurement noise on the discontinuity parameter identification are investigated by adding different levels of noise to the simulated data. The simulation results were then validated by the corresponding experiments. Both the simulation and experimental results show that (1) the one-order discontinuities can be identified accurately with the maximum errors of 6.8% and 8.7%, respectively; (2) and the high-order discontinuities can be identified with the maximum errors of 15.8% and 16.2%, respectively; and (3) the high-order model can predict the complex discontinuity much more accurately than the one-order discontinuity model.

ON ESTIMATING THE HIGH-ENERGY CUTOFF IN THE X-RAY SPECTRA OF BLACK HOLES VIA REFLECTION SPECTROSCOPY

Energy Technology Data Exchange (ETDEWEB)

García, Javier A.; Steiner, James F.; McClintock, Jeffrey E.; Keck, Mason L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Dauser, Thomas; Wilms, Jörn, E-mail: javier@head.cfa.harvard.edu, E-mail: jem@cfa.harvard.edu, E-mail: jsteiner@head.cfa.harvard.edu, E-mail: keckm@bu.edu, E-mail: thomas.dauser@sternwarte.uni-erlangen.de [Dr. Karl Remeis-Observatory and Erlangen Centre for Astroparticle Physics, Sternwartstr. 7, D-96049 Bamberg (Germany)

2015-08-01

The fundamental parameters describing the coronal spectrum of an accreting black hole are the slope Γ of the power-law continuum and the energy E{sub cut} at which it rolls over. Remarkably, this latter parameter can be accurately measured for values as high as 1 MeV by modeling the spectrum of X-rays reflected from a black hole accretion disk at energies below 100 keV. This is possible because the details in the reflection spectrum, rich in fluorescent lines and other atomic features, are very sensitive to the spectral shape of the hardest coronal radiation illuminating the disk. We show that by fitting simultaneous NuSTAR (3–79 keV) and low-energy (e.g., Suzaku) data with the most recent version of our reflection model relxill one can obtain reasonable constraints on E{sub cut} at energies from tens of keV up to 1 MeV, for a source as faint as 1 mCrab in a 100 ks observation.

High accuracy subwavelength distance measurements: A variable-angle standing-wave total-internal-reflection optical microscope

International Nuclear Information System (INIS)

Haynie, A.; Min, T.-J.; Luan, L.; Mu, W.; Ketterson, J. B.

2009-01-01

We describe an extension of the total-internal-reflection microscopy technique that permits direct in-plane distance measurements with high accuracy (<10 nm) over a wide range of separations. This high position accuracy arises from the creation of a standing evanescent wave and the ability to sweep the nodal positions (intensity minima of the standing wave) in a controlled manner via both the incident angle and the relative phase of the incoming laser beams. Some control over the vertical resolution is available through the ability to scan the incoming angle and with it the evanescent penetration depth.

Deployment of a Long-Term Broadband Seafloor Observatory in Monterey Bay

Science.gov (United States)

McGill, P.; Neuhauser, D.; Stakes, D.; Romanowicz, B.; Ramirez, T.; Uhrhammer, R.

2002-12-01

MOBB (Monterey bay Ocean floor Broad Band project) is a collaborative project between the Monterey Bay Aquarium Research Institute (MBARI) and the Berkeley Seismological Laboratory (BSL). Its goal is to install and operate a permanent seafloor broadband seismic station as a first step towards extending the on-shore broadband seismic network in northern California to the seaside of the North-America/Pacific plate boundary, providing better azimuthal coverage for regional earthquake and structure studies. The successful MOBB deployment took place 40km off shore at a water depth of 1000m during three dives on April 9-11, 2002. The seismometer was buried in a 60-cm deep caisson, which was later back filled with glass beads to stabilize the instrument. New tools, including a high-pressure water-jet excavator, were developed for the ROV Ventana to accomplish these tasks. The ocean-bottom MOBB station currently comprises a three-component seismometer package, a current-meter, and a recording and battery package. Data recovery dives, during which the recording and battery package will be exchanged, are planned every three months for the next three years. A differential pressure gauge (DPG) (Cox et al., 1984) will be deployed as part of the recording package during the next data recovery dive in September 2002. The station is currently recording data autonomously. Eventually, it will be linked to the planned (and recently funded) MARS (Monterey Accelerated Research System; rl {http://www.mbari.org/mars/}) cable and provide real-time, continuous seismic data to be merged with the rest of the northern California real-time seismic system. The data are archived at the NCEDC for on-line availability, as part of the Berkeley Digital Seismic Network (BDSN). This project follows the 1997 MOISE experiment, in which a three-component broadband system was deployed for a period of three months, 40km off shore in Monterey Bay. MOISE was a cooperative program sponsored by MBARI, UC

Association Mapping of Total Carotenoids in Diverse Soybean Genotypes Based on Leaf Extracts and High-Throughput Canopy Spectral Reflectance Measurements.

Directory of Open Access Journals (Sweden)

Arun Prabhu Dhanapal

Full Text Available Carotenoids are organic pigments that are produced predominantly by photosynthetic organisms and provide antioxidant activity to a wide variety of plants, animals, bacteria, and fungi. The carotenoid biosynthetic pathway is highly conserved in plants and occurs mostly in chromoplasts and chloroplasts. Leaf carotenoids play important photoprotective roles and targeted selection for leaf carotenoids may offer avenues to improve abiotic stress tolerance. A collection of 332 soybean [Glycine max (L. Merr.] genotypes was grown in two years and total leaf carotenoid content was determined using three different methods. The first method was based on extraction and spectrophotometric determination of carotenoid content (eCaro in leaf tissue, whereas the other two methods were derived from high-throughput canopy spectral reflectance measurements using wavelet transformed reflectance spectra (tCaro and a spectral reflectance index (iCaro. An association mapping approach was employed using 31,253 single nucleotide polymorphisms (SNPs to identify SNPs associated with total carotenoid content using a mixed linear model based on data from two growing seasons. A total of 28 SNPs showed a significant association with total carotenoid content in at least one of the three approaches. These 28 SNPs likely tagged 14 putative loci for carotenoid content. Six putative loci were identified using eCaro, five loci with tCaro, and nine loci with iCaro. Three of these putative loci were detected by all three carotenoid determination methods. All but four putative loci were located near a known carotenoid-related gene. These results showed that carotenoid markers can be identified in soybean using extract-based as well as by high-throughput canopy spectral reflectance-based approaches, demonstrating the utility of field-based canopy spectral reflectance phenotypes for association mapping.

Challenging Narcissus, or Reflecting on Reflecting.

Science.gov (United States)

Achilles, C. M.

The concept of reflective practice and teaching people to be reflective practitioners is examined. The document begins with a look at professional knowledge according to three prominent professionals in the educational administration field: Schon, Schein, and Achilles. "Reflective" strategies that could be incorporated into courses and…

Estimation of interplate coupling along Nankai trough considering the block motion model based on onland GNSS and seafloor GPS/A observation data using MCMC method

Science.gov (United States)

Kimura, H.; Ito, T.; Tadokoro, K.

2017-12-01

Introduction In southwest Japan, Philippine sea plate is subducting under the overriding plate such as Amurian plate, and mega interplate earthquakes has occurred at about 100 years interval. There is no occurrence of mega interplate earthquakes in southwest Japan, although it has passed about 70 years since the last mega interplate earthquakes: 1944 and 1946 along Nankai trough, meaning that the strain has been accumulated at plate interface. Therefore, it is essential to reveal the interplate coupling more precisely for predicting or understanding the mechanism of next occurring mega interplate earthquake. Recently, seafloor geodetic observation revealed the detailed interplate coupling distribution in expected source region of Nankai trough earthquake (e.g., Yokota et al. [2016]). In this study, we estimated interplate coupling in southwest Japan, considering block motion model and using seafloor geodetic observation data as well as onland GNSS observation data, based on Markov Chain Monte Carlo (MCMC) method. Method Observed crustal deformation is assumed that sum of rigid block motion and elastic deformation due to coupling at block boundaries. We modeled this relationship as a non-linear inverse problem that the unknown parameters are Euler pole of each block and coupling at each subfault, and solved them simultaneously based on MCMC method. Input data we used in this study are 863 onland GNSS observation data and 24 seafloor GPS/A observation data. We made some block division models based on the map of active fault tracing and selected the best model based on Akaike's Information Criterion (AIC): that is consist of 12 blocks. Result We find that the interplate coupling along Nankai trough has heterogeneous spatial distribution, strong at the depth of 0 to 20km at off Tokai region, and 0 to 30km at off Shikoku region. Moreover, we find that observed crustal deformation at off Tokai region is well explained by elastic deformation due to subducting Izu Micro

Embedding reflection and learning into agile software development

DEFF Research Database (Denmark)

Babb, Jeffry; Hoda, Rashina; Nørbjerg, Jacob

2014-01-01

The theoretical underpinnings of agile methods emphasize regular reflection as a means to sustainable development pace and continuous learning, but in practice, high iteration pressure can diminish reflection opportunities. The Reflective Agile Learning Model (REALM) combines insights and results...... from studies of agile development practices in India, New Zealand, and the US with Schön’s theory of reflective practice to embed reflection in everyday agile practices....

Reflections on having children in the future—interviews with highly educated women and men without children

Science.gov (United States)

Eriksson, Carola; Larsson, Margareta

2012-01-01

Background There is a trend to delay birth of the first child until the age at which female reproductive capacity has started to decrease. The aim of the present study was to explore how highly educated women and men reflected on future parenthood. Methods Twenty-two women and 18 men, who had started their professional career, were subjected to individual qualitative semi-structured interviews with qualitative content analysis guiding the analysis. Results All informants, except for three women, planned to have children when some important prerequisites were fulfilled. Women and men reflected in much the same way, and prerequisites for parenthood were being of reasonable age and having a partner in the same phase of life. A reasonable age was considered in relation to reproductive capacity, and both women and men expressed awareness of the natural decline in fertility at higher ages. Good living conditions with stable finances were also important. Parenthood was perceived as a challenge and a sacrifice but also as enriching life. Reasons for having children included being part of the future and settling down to build their own family. Many concluded that there would never be a perfect time for having children. Conclusion Highly educated women and men reflect on various factors when considering family planning. Being of reasonable age and having good living conditions, in particular a sound personal economy, were important. Given their goals, it is not surprising that many postpone parenthood until ages when female reproductive capacity is decreased. PMID:22300332

Hewlett-Packard's Approaches to Full Color Reflective Displays

Science.gov (United States)

Gibson, Gary

2012-02-01

Reflective displays are desirable in applications requiring low power or daylight readability. However, commercial reflective displays are currently either monochrome or capable of only dim color gamuts. Low cost, high-quality color technology would be rapidly adopted in existing reflective display markets and would enable new solutions in areas such as retail pricing and outdoor digital signage. Technical breakthroughs are required to enable bright color gamuts at reasonable cost. Pixel architectures that rely on pure reflection from a single layer of side-by-side primary-color sub-pixels use only a fraction of the display area to reflect incident light of a given color and are, therefore, unacceptably dark. Reflective devices employing stacked color primaries offer the possibility of a somewhat brighter color gamut but can be more complex to manufacture. In this talk, we describe HP's successes in addressing these fundamental challenges and creating both high performance stacked-primary reflective color displays as well as inexpensive single layer prototypes that provide good color. Our stacked displays utilize a combination of careful light management techniques, proprietary high-contrast electro-optic shutters, and highly transparent active-matrix TFT arrays based on transparent metal oxides. They also offer the possibility of relatively low cost manufacturing through roll-to-roll processing on plastic webs. To create even lower cost color displays with acceptable brightness, we have developed means for utilizing photoluminescence to make more efficient use of ambient light in a single layer device. Existing reflective displays create a desired color by reflecting a portion of the incident spectrum while absorbing undesired wavelengths. We have developed methods for converting the otherwise-wasted absorbed light to desired wavelengths via tailored photoluminescent composites. Here we describe a single active layer prototype display that utilizes these materials

High-Efficiency Volume Reflection of an Ultrarelativistic Proton Beam with a Bent Silicon Crystal

CERN Document Server

Scandale, Walter; Carnera, Alberto; Della Mea, Gianantonio; De Salvador, Davide; Milan, Riccardo; Vomiero, Alberto; Baricordi, Stefano; Dalpiaz, Pietro; Fiorini, Massimiliano; Guidi, Vincenzo; Martinelli,Giuliano; Mazzolari, Andrea; Milan, Emiliano; Ambrosi, Giovanni; Azzarello, Philipp; Battiston, Roberto; Bertucci, Bruna; Burger, William J; Ionica, Maria; Zuccon, Paolo; Cavoto, Gianluca; Santacesaria, Roberta; Valente, Paolo; Vallazza, Erik; Afonin, Alexander G; Baranov, Vladimir T; Chesnokov, Yury A; Kotov, Vladilen I; Maisheev, Vladimir A; Yaznin, Igor A; Afansiev, Sergey V; Kovalenko, Alexander D; Taratin, Alexander M; Denisov, Alexander S; Gavrikov, Yury A; Ivanov, Yuri M; Ivochkin, Vladimir G; Kosyanenko, Sergey V; Petrunin, Anatoli A; Skorobogatov, Vyacheslav V; Suvorov, Vsevolod M; Bolognini, Davide; Foggetta,Luca; Hasan, Said; Prest, Michela

2007-01-01

The volume reflection phenomenon was detected while investigating 400 GeV proton interactions with bent silicon crystals in the external beam H8 of the CERN Super Proton Synchrotron. Such a process was observed for a wide interval of crystal orientations relative to the beam axis, and its efficiency exceeds 95%, thereby surpassing any previously observed value. These observations suggest new perspectives for the manipulation of high-energy beams, e.g., for collimation and extraction in new-generation hadron colliders, such as the CERN Large Hadron Collider.

CH4 fluxes across the seafloor at three district gas hydrate fields: Impacts on ocean and atmosphere chemistry

Energy Technology Data Exchange (ETDEWEB)

Kastner, M.; Bartlett, D.; MacDonald, I.; Solomon, E.

2005-07-01

The role of methane hydrate in the global methane budget is poorly documented because relatively little is known about the transport of methane through the seafloor into the ocean and atmosphere, and the extent of en route water-column methanotrophy. Pore fluids and water column samples within and adjacent to methane plumes were analyzed for methane, dissolved inorganic C (DIC), sulfide/sulfate, alkalinity, and major element concentrations, and for delta{sup 13}C-CH4 and DIC, at three distinct gas hydrate environments. The three environments are: Bush Hill (BH) in the northern Gulf of Mexico (GOM), Eel River (ER) offshore Northern California, and North and South Hydrate Ridges (HR), Cascadia, Oregon margin. The methane source at these sites ranges from mostly thermogenic at GOM to primarily biogenic at HR. At these three distinct gas hydrate environments, at all the sites a significant enrichment in {sup 13}C-CH4 along isopycnals away from the methane plumes is observed, indicating extensive aerobic bacterial methane oxidation in the water column, and correspondingly of oxygen consumption. This is principally pronounced in the mostly biogenic methane setting. The delta{sup 13}C-CH4 values range from approx. 12 to -67 , PDB, at the Hydrate Ridges, from approx. 34 to -52 at Eel River, and from approx. 41 to -67 at Bush Hill. The large variation in methane C isotope ranges between the sites suggests that major differences exist in both the rates of aerobic methane oxidation and system openness at the studied locations. Methane fluxes across the sediment/seawater interface were measured, with a flux meter, MOSQUITO (Multiple Orifice Sampler and Quantitative Injection Tracer Observers) only at BH (Solomon et al., 2005). Water column methane concentrations are on average lower at HR than at ER and GOM. Preliminary estimates suggests that aerobic oxidation is nearly complete, consumes most to all of the water column methane at HR, but at the GOM only approx. 80% to a

Polar front associated variation in prokaryotic community structure in Arctic shelf seafloor.

Science.gov (United States)

Nguyen, Tan T; Landfald, Bjarne

2015-01-01

Spatial variations in composition of marine microbial communities and its causes have largely been disclosed in studies comprising rather large environmental and spatial differences. In the present study, we explored if a moderate but temporally permanent climatic division within a contiguous arctic shelf seafloor was traceable in the diversity patterns of its bacterial and archaeal communities. Soft bottom sediment samples were collected at 10 geographical locations, spanning spatial distances of up to 640 km, transecting the oceanic polar front in the Barents Sea. The northern sampling sites were generally colder, less saline, shallower, and showed higher concentrations of freshly sedimented phytopigments compared to the southern study locations. Sampling sites depicted low variation in relative abundances of taxa at class level, with persistent numerical dominance by lineages of Gamma- and Deltaproteobacteria (57-66% of bacterial sequence reads). The Archaea, which constituted 0.7-1.8% of 16S rRNA gene copy numbers in the sediment, were overwhelmingly (85.8%) affiliated with the Thaumarchaeota. Beta-diversity analyses showed the environmental variations throughout the sampling range to have a stronger impact on the structuring of both the bacterial and archaeal communities than spatial effects. While bacterial communities were significantly influenced by the combined effect of several weakly selective environmental differences, including temperature, archaeal communities appeared to be more uniquely structured by the level of freshly sedimented phytopigments.

Searching for reflected light from τ Bootis b with high-resolution ground-based spectroscopy: Approaching the 10-5 contrast barrier

Science.gov (United States)

Hoeijmakers, H. J.; Snellen, I. A. G.; van Terwisga, S. E.

2018-02-01

Context. It is challenging to measure the starlight reflected from exoplanets because of the extreme contrast with their host stars. For hot Jupiters, this contrast is in the range of 10-6 to 10-4, depending on their albedo, radius and orbital distance. Searches for reflected light have been performed since the first hot Jupiters were discovered, but with very limited success because hot Jupiters tend to have low albedo values due to the general absence of reflective cloud decks. Aim. The aim of this study is to search for reflected light from τ Boo b, a hot Jupiter with one of the brightest host stars. Since its discovery in 1997, it has been the subject of several reflected-light searches using high-dispersion spectroscopy. Here we aim to combine these data in to a single meta-analysis. Methods: We analysed more than 2000 archival high-dispersion spectra obtained with the UVES, ESPaDOnS, NARVAL UES and HARPS-N spectrographs during various epochs between 1998 and 2013. Each spectrum was first cleaned of the stellar spectrum and subsequently cross-correlated with a PHOENIX model spectrum. These were then Doppler shifted to the planet rest-frame and co-added in time, weighted according to the expected signal-to-noise of the planet signal. Results: We reach a 3σ upper limit of the planet-to-star contrast of 1.5 × 10-5. Assuming a planet radius of 1.15 RJ, this corresponds to an optical albedo of between 400-700 nm. A low albedo is in line with secondary eclipse and phase curve observations of other hot Jupiters using space-based observatories, as well as theoretical predictions of their reflective properties.

Teaching, Reflecting, and Writing from the Heart: High School Students Learn about and from Preschoolers

Science.gov (United States)

Wolff, Ann Lesser

2012-01-01

Effective teacher educators reflect and upon reflection, make important changes to lessons, units, and instructional strategies. But have they ever considered the importance reflection has for students or what bearing "their" reflections have on them as their teachers? During the first six weeks of the (introductory) Child Development…

2011 NOAA Bathymetric Lidar: U.S. Virgin Islands - St. Thomas, St. John, St. Croix (Salt River Bay, Buck Island)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This data represents a LiDAR (Light Detection & Ranging) gridded bathymetric surface and a gridded relative seafloor reflectivity surface (incorporated into the...

Study at high angular momentum of the reflection asymmetry in the 218 Ra transition nuclei

International Nuclear Information System (INIS)

Aiche, M.

1990-07-01

The investigations concerning the 218 Ra nuclei at high angular momentum are discussed. The aim of the study is to enlarge the knowledge on the octupolar phenomena and to analyse its evolution as a funcion of the angular momentum. The 218 Ra nuclei is obtained from the ( 14 C, 4n) reaction. The gamma angular distribution and the gamma-gamma coincidence were measured by means of the Chateau de Cristal multicounter. The reflection asymmetric mean field theory and the bosons interaction model were applied to analyze the data and obtain the structure at high angular moments. The results show the existence of dipole-octupole correlations in the nuclei [fr

Photoluminescence and reflectivity studies of high energy light ions irradiated polymethyl methacrylate films

Science.gov (United States)

Bharti, Madhu Lata; Singh, Fouran; Ramola, R. C.; Joshi, Veena

2017-11-01

The self-standing films of non-conducting polymethyl methacrylate (PMMA) were irradiated in vacuum using high energy light ions (HELIs) of 50 MeV Lithium (Li+3) and 80 MeV Carbon (C+5) at various ion dose to induce the optical changes in the films. Upon HELI irradiation, films exhibit a significant enhancement in optical reflectivity at the highest dose. Interestingly, the photoluminescence (PL) emission band with green light at (514.5 nm) shows a noticeable increase in the intensity with increasing ion dose for both ions. However, the rate of increase in PL intensity is different for both HELI and can be correlated with the linear energy transfer by these ions in the films. Origin of PL is attributed to the formation of carbon cluster and hydrogenated amorphous carbon in the polymer films. HAC clusters act as PL active centres with optical reflectivity. Most of the harmful radiation like UV are absorbed by the material and is becoming opaque after irradiation and this PL active material are useful in fabrication of optoelectronic devices, UV-filter, back-lit components in liquid crystal display systems, micro-components for integrate optical circuits, diffractive elements, advanced materials and are also applicable to the post irradiation laser treatment by means of ion irradiation.

Selectively reflective transparent sheets

Science.gov (United States)

Waché, Rémi; Florescu, Marian; Sweeney, Stephen J.; Clowes, Steven K.

2015-08-01

We investigate the possibility to selectively reflect certain wavelengths while maintaining the optical properties on other spectral ranges. This is of particular interest for transparent materials, which for specific applications may require high reflectivity at pre-determined frequencies. Although there exist currently techniques such as coatings to produce selective reflection, this work focuses on new approaches for mass production of polyethylene sheets which incorporate either additives or surface patterning for selective reflection between 8 to 13 μ m. Typical additives used to produce a greenhouse effect in plastics include particles such as clays, silica or hydroxide materials. However, the absorption of thermal radiation is less efficient than the decrease of emissivity as it can be compared with the inclusion of Lambertian materials. Photonic band gap engineering by the periodic structuring of metamaterials is known in nature for producing the vivid bright colors in certain organisms via strong wavelength-selective reflection. Research to artificially engineer such structures has mainly focused on wavelengths in the visible and near infrared. However few studies to date have been carried out to investigate the properties of metastructures in the mid infrared range even though the patterning of microstructure is easier to achieve. We present preliminary results on the diffuse reflectivity using FDTD simulations and analyze the technical feasibility of these approaches.

Estimating the composition of gas hydrate using 3D seismic data from Penghu Canyon, offshore Taiwan

Directory of Open Access Journals (Sweden)

Sourav Kumar Sahoo

2018-01-01

Full Text Available Direct measurements of gas composition by drilling at a few hundred meters below seafloor can be costly, and a remote sensing method may be preferable. The hydrate occurrence is seismically shown by a bottom-simulating reflection (BSR which is generally indicative of the base of the hydrate stability zone. With a good temperature profile from the seafloor to the depth of the BSR, a near-correct hydrate phase diagram can be calculated, which can be directly related to the hydrate composition. However, in the areas with high topographic anomalies of seafloor, the temperature profile is usually poorly defined, with scattered data. Here we used a remote method to reduce such scattering. We derived gas composition of hydrate in stability zone and reduced the scattering by considering depth-dependent geothermal conductivity and topographic corrections. Using 3D seismic data at the Penghu canyon, offshore SW Taiwan, we corrected for topographic focusing through 3D numerical thermal modeling. A temperature profile was fitted with a depth-dependent geothermal gradient, considering the increasing thermal conductivity with depth. Using a pore-water salinity of 2%, we constructed a gas hydrate phase model composed of 99% methane and 1% ethane to derive a temperature depth profile consistent with the seafloor temperature from in-situ measurements, and geochemical analyses of the pore fluids. The high methane content suggests predominantly biogenic source. The derived regional geothermal gradient is 40°C km-1. This method can be applied to other comparable marine environment to better constrain the composition of gas hydrate from BSR in a seismic data, in absence of direct sampling.

Total Reflection X-ray Fluorescence Analysis (TXRF) using the high flux SAXS camera

CERN Document Server

Wobrauschek, P; Pepponi, G; Bergmann, A; Glatter, O

2002-01-01

Combining the high photon flux from a rotating anode X-ray tube with an X-ray optical component to focus and monochromatize the X-ray beam is the most promising instrumentation for best detection limits in the modern XRF laboratory. This is realized by using the design of a high flux SAXS camera in combination with a 4 kW high brilliant rotating Cu anode X-ray tube with a graded elliptically bent multilayer and including a new designed module for excitation in total reflection geometry within the beam path. The system can be evacuated thus reducing absorption and scattering of air and removing the argon peak in the spectra. Another novelty is the use of a Peltier cooled drift detector with an energy resolution of 148 eV at 5.9 keV and 5 mm sup 2 area. For Co detection limits of about 300 fg determined by a single element standard have been achieved. Testing a real sample NIST 1643d led to detection limits in the range of 300 ng/l for the medium Z.

Mercury Anomaly in the Okinawa Trough Sediments—An Indicator of Modern Seafloor Hydrothermal Activity

Institute of Scientific and Technical Information of China (English)

赵一阳; 鄢明才

1995-01-01

The Okinawa Trough is located between the shelf-sea area of the East China Sea and the deep-sea area of western Pacific Ocean.More than 60 chemical elements in the sediments from the shelf area of the East China Sea,the Okinawa Trough and western Pacific Ocean were determined by advanced techniques including neutron acti-vation analysis,X-ray fluorescence spectrometry,atomic fluorescence spectrometry and atomic absorption spectrometry.Quantitative comparisons of the element abundances of the sediments were made in terms of the enrichment coefficients(K) of the elements.K>1.5 indicates enrichment (K=1.5-2, weak enrichment;K=2-4,strong enrichment) and K>4,anomalous enrichment.The results show that the Okinawa Trough sediments are characterized by Hg anomaly and the enrichment of such elements as Au,Ag,Se,Te,Sb,Cd,Mn,Mo,etc.Detailed studies show that the excess Hg comes from hydrothermal solutions rather than from the continent,sea water ,marine organisms,cosmic dust or vol-canic rocks.Attributed to modern hydrothermal activities on the sea floor ,Hg anomaly can be used as a geochemical indicator of modern seafloor hydrothermal activity.

A high-density relativistic reflection origin for the soft and hard X-ray excess emission from Mrk 1044

Science.gov (United States)

Mallick, L.; Alston, W. N.; Parker, M. L.; Fabian, A. C.; Pinto, C.; Dewangan, G. C.; Markowitz, A.; Gandhi, P.; Kembhavi, A. K.; Misra, R.

2018-06-01

We present the first results from a detailed spectral-timing analysis of a long (˜130 ks) XMM-Newton observation and quasi-simultaneous NuSTAR and Swift observations of the highly-accreting narrow-line Seyfert 1 galaxy Mrk 1044. The broadband (0.3-50 keV) spectrum reveals the presence of a strong soft X-ray excess emission below ˜1.5 keV, iron Kα emission complex at ˜6 -7 keV and a `Compton hump' at ˜15 -30 keV. We find that the relativistic reflection from a high-density accretion disc with a broken power-law emissivity profile can simultaneously explain the soft X-ray excess, highly ionized broad iron line and the Compton hump. At low frequencies ([2 - 6] × 10-5 Hz), the power-law continuum dominated 1.5-5 keV band lags behind the reflection dominated 0.3-1 keV band, which is explained with a combination of propagation fluctuation and Comptonization processes, while at higher frequencies ([1 - 2] × 10-4 Hz), we detect a soft lag which is interpreted as a signature of X-ray reverberation from the accretion disc. The fractional root-mean-squared (rms) variability of the source decreases with energy and is well described by two variable components: a less variable relativistic disc reflection and a more variable direct coronal emission. Our combined spectral-timing analyses suggest that the observed broadband X-ray variability of Mrk 1044 is mainly driven by variations in the location or geometry of the optically thin, hot corona.

Self-reflection, gender and science achievement

Science.gov (United States)

Shoop, Kathleen A.

Drawing on socio-cognitive learning theory, this study compared achievement scores of 134 male and female high school biology students randomly assigned to groups which either used self-reflection, used self-reflection and received feedback, or did not self-reflect. Following a pretest, the teacher provided self-reflection strategy instruction to students in the two intervention groups and then subsequently provided in-class self-reflection time for these groups. The posttest concluded the unit; the retention measure was five weeks later. A quasi-experimental 3 x 3 x 2 (time x intervention x gender) factorial repeated-measures control group design was used for this study; a repeated measures ANOVA and several one-way ANOVA's were used to answer the research questions. Results from the repeated-measures ANOVA revealed significant results for Time and Time x Intervention, with the reflection group demonstrating significantly lower gains from pretest to posttest than the other two groups. The ANOVA examining differences between those who reflected and those who reflected and received feedback provided significant results with similar results for the difference between the control group and the reflection group. For teachers and students this study provides several areas of practical significance. Primarily, teachers may find lower student achievement if students regularly self-reflect but do not receive feedback for their reflection.

Continuous monitoring of fluid flow rate and contemporaneous biogeochemical fluxes in the sub-seafloor; the Mosquito flux meter

Science.gov (United States)

Culling, D. P.; Solomon, E. A.; Kastner, M.; Berg, R. D.

2013-12-01

Fluid flow through marine sediments and oceanic crust impacts seawater chemistry as well as diagenetic, thermal, seismic, and magmatic processes at plate boundaries, creates ore and gas hydrate deposits at and below seafloor, and establishes and maintains deep microbial ecosystems. However, steady-state fluid flow rates, as well as the temporal and spatial variability of fluid flow and composition are poorly constrained in many marine environments. A new, low-cost instrument deployable by ROV or submersible, named the Mosquito, was recently developed to provide continuous, long-term and campaign style monitoring of fluid flow rate and contemporaneous solute fluxes at multiple depths below the sea floor. The Mosquito consists of a frame that houses several osmotic pumps (Osmo-Samplers [OS]) connected to coils of tubing that terminate with an attachment to long thin titanium (Ti) needles, all of which are mounted to a release plate. The OS's consist of an acrylic housing which contains a brine chamber (BC) and a distilled water chamber (DWC) separated by semi permeable membranes. The osmotic gradient between the chambers drives the flow of distilled water into the BC. The DWC is connected to the Teflon tubing coil and a Ti needle, both of which are also filled with distilled water, thus the OS pulls fluid from the base of the needle through the tubing coil. One central Ti needle is attached to a custom-made tracer injection assembly, filled with a known volume of tracer, which is triggered, injecting a point source in the sediment. On a typical Mosquito, 4 needles are mounted vertically at varying depths with respect to the tracer injection needle, and 4 needles are mounted at equal depth but set at variable horizontal distances away from the tracer injection. Once the Mosquito has been placed on the seafloor, the release plate is manually triggered pushing the Ti needles into the sediment, then the tracer injection assembly is actuated. As the tracer is advected

High Angular Resolution Measurements of the Anisotropy of Reflectance of Sea Ice and Snow

Science.gov (United States)

Goyens, C.; Marty, S.; Leymarie, E.; Antoine, D.; Babin, M.; Bélanger, S.

2018-01-01

We introduce a new method to determine the anisotropy of reflectance of sea ice and snow at spatial scales from 1 m2 to 80 m2 using a multispectral circular fish-eye radiance camera (CE600). The CE600 allows measuring radiance simultaneously in all directions of a hemisphere at a 1° angular resolution. The spectral characteristics of the reflectance and its dependency on illumination conditions obtained from the camera are compared to those obtained with a hyperspectral field spectroradiometer manufactured by Analytical Spectral Device, Inc. (ASD). Results confirm the potential of the CE600, with the suggested measurement setup and data processing, to measure commensurable sea ice and snow hemispherical-directional reflectance factor, HDRF, values. Compared to the ASD, the reflectance anisotropy measured with the CE600 provides much higher resolution in terms of directional reflectance (N = 16,020). The hyperangular resolution allows detecting features that were overlooked using the ASD due to its limited number of measurement angles (N = 25). This data set of HDRF further documents variations in the anisotropy of the reflectance of snow and ice with the geometry of observation and illumination conditions and its spectral and spatial scale dependency. Finally, in order to reproduce the hyperangular CE600 reflectance measurements over the entire 400-900 nm spectral range, a regression-based method is proposed to combine the ASD and CE600 measurements. Results confirm that both instruments may be used in synergy to construct a hyperangular and hyperspectral snow and ice reflectance anisotropy data set.

Wave-equation reflection traveltime inversion

KAUST Repository

Zhang, Sanzong

2011-01-01

The main difficulty with iterative waveform inversion using a gradient optimization method is that it tends to get stuck in local minima associated within the waveform misfit function. This is because the waveform misfit function is highly nonlinear with respect to changes in the velocity model. To reduce this nonlinearity, we present a reflection traveltime tomography method based on the wave equation which enjoys a more quasi-linear relationship between the model and the data. A local crosscorrelation of the windowed downgoing direct wave and the upgoing reflection wave at the image point yields the lag time that maximizes the correlation. This lag time represents the reflection traveltime residual that is back-projected into the earth model to update the velocity in the same way as wave-equation transmission traveltime inversion. No travel-time picking is needed and no high-frequency approximation is assumed. The mathematical derivation and the numerical examples are presented to partly demonstrate its efficiency and robustness. © 2011 Society of Exploration Geophysicists.

Lipid profiles reflecting high and low risk for coronary heart disease : Contribution of apolipoprotein E polymorphism and lifestyle

NARCIS (Netherlands)

Boer, J.M.A.; Feskens, E.J.M.; Schouten, E.G.; Havekes, L.M.; Seidell, J.C.; Kromhout, D.

1998-01-01

To elucidate the role of modifiable factors and the apolipoprotein E polymorphism in explaining lipid profiles reflecting low, average and high risk for coronary heart disease, we selected subjects from a large population-based study. Subjects with low total cholesterol (TC) (< 15th percentile) and

Lipid profiles reflecting high and low risk for coronary heart disease: contribution of apolipoprotein E polymorphism and lifestyle.

NARCIS (Netherlands)

Boer, J.M.A.; Feskens, E.J.M.; Schouten, E.G.; Havekes, L.M.; Seidell, J.C.; Kromhout, D.

1998-01-01

To elucidate the role of modifiable factors and the apolipoprotein E polymorphism in explaining lipid profiles reflecting low, average and high risk for coronary heart disease, we selected subjects from a large population-based study. Subjects with low total cholesterol (TC) (<15th percentile)

X-ray View of Four High-Luminosity Swift-BAT AGN: Unveiling Obscuration and Reflection with Suzaku

Science.gov (United States)

Fiorettil, V.; Angelini, L.; Mushotzky, R. F.; Koss, M.; Malaguti, G.

2013-01-01

Aims. A complete census of obscured Active Galactic Nuclei (AGN) is necessary to reveal the history of the super massive black hole (SMBH) growth and galaxy evolution in the Universe given the complex feedback processes and the fact that much of this growth occurs in an obscured phase. In this context, hard X-ray surveys and dedicated follow-up observations represent a unique tool for selecting highly absorbed AGN and for characterizing the obscuring matter surrounding the SMBH. Here we focus on the absorption and reflection occurring in highly luminous, quasar-like AGN, to study the relation between the geometry of the absorbing matter and the AGN nature (e.g. X-ray, optical, and radio properties), and to help to determine the column density dependency on the AGN luminosity. Methods. The Swift/BAT nine-month survey observed 153 AGN, all with ultra-hard X-ray BAT fluxes in excess of 10(exp -11) erg per square centimeter and an average redshift of 0.03. Among them, four of the most luminous BAT AGN (44.73 less than LogLBAT less than 45.31) were selected as targets of Suzaku follow-up observations: J2246.0+3941 (3C 452), J0407.4+0339 (3C 105), J0318.7+6828, and J0918.5+0425. The column density, scattered/reflected emission, the properties of the Fe K line, and a possible variability are fully analyzed. For the latter, the spectral properties from Chandra, XMM-Newton and Swift/XRT public observations were compared with the present Suzaku analysis, adding an original spectral analysis when non was available from the literature. Results. Of our sample, 3C 452 is the only certain Compton-thick AGN candidate because of i) the high absorption (N(sub H) approximately 4 × 10(exp 23) per square centimeter) and strong Compton reflection; ii) the lack of variability; iii) the "buried" nature, i.e. the low scattering fraction (less than 0.5%) and the extremely low relative [OIII] luminosity. In contrast 3C 105 is not reflection-dominated, despite the comparable column density

Self-Reflection, Insight, and Individual Differences in Various Language Tasks

Science.gov (United States)

Xu, Xu

2011-01-01

This study explored the relationships of self-reflection and insight with individuals' performances on various language tasks. The Self-Reflection and Insight Scale (SRIS; Grant, Franklin, & Langford, 2002) assessed individual differences in three factors: engagement in reflection, need for reflection, and insight. A high need for reflection was…

Seismic reflection imaging, accounting for primary and multiple reflections

Science.gov (United States)

Wapenaar, Kees; van der Neut, Joost; Thorbecke, Jan; Broggini, Filippo; Slob, Evert; Snieder, Roel

2015-04-01

Imaging of seismic reflection data is usually based on the assumption that the seismic response consists of primary reflections only. Multiple reflections, i.e. waves that have reflected more than once, are treated as primaries and are imaged at wrong positions. There are two classes of multiple reflections, which we will call surface-related multiples and internal multiples. Surface-related multiples are those multiples that contain at least one reflection at the earth's surface, whereas internal multiples consist of waves that have reflected only at subsurface interfaces. Surface-related multiples are the strongest, but also relatively easy to deal with because the reflecting boundary (the earth's surface) is known. Internal multiples constitute a much more difficult problem for seismic imaging, because the positions and properties of the reflecting interfaces are not known. We are developing reflection imaging methodology which deals with internal multiples. Starting with the Marchenko equation for 1D inverse scattering problems, we derived 3D Marchenko-type equations, which relate reflection data at the surface to Green's functions between virtual sources anywhere in the subsurface and receivers at the surface. Based on these equations, we derived an iterative scheme by which these Green's functions can be retrieved from the reflection data at the surface. This iterative scheme requires an estimate of the direct wave of the Green's functions in a background medium. Note that this is precisely the same information that is also required by standard reflection imaging schemes. However, unlike in standard imaging, our iterative Marchenko scheme retrieves the multiple reflections of the Green's functions from the reflection data at the surface. For this, no knowledge of the positions and properties of the reflecting interfaces is required. Once the full Green's functions are retrieved, reflection imaging can be carried out by which the primaries and multiples are

Reflective masks for extreme ultraviolet lithography

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Khanh Bao [Univ. of California, Berkeley, CA (United States)

1994-05-01

Extreme ultraviolet lithographic masks are made by patterning multilayer reflective coatings with high normal incidence reflectivity. Masks can be patterned by depositing a patterned absorber layer above the coating or by etching the pattern directly into the coating itself. Electromagnetic simulations showed that absorber-overlayer masks have superior imaging characteristics over etched masks (less sensitive to incident angles and pattern profiles). In an EUVL absorber overlayer mask, defects can occur in the mask substrate, reflective coating, and absorber pattern. Electromagnetic simulations showed that substrate defects cause the most severe image degradation. A printability study of substrate defects for absorber overlayer masks showed that printability of 25 nm high substrate defects are comparable to defects in optical lithography. Simulations also indicated that the manner in which the defects are covered by multilayer reflective coatings can affect printability. Coverage profiles that result in large lateral spreading of defect geometries amplify the printability of the defects by increasing their effective sizes. Coverage profiles of Mo/Si coatings deposited above defects were studied by atomic force microscopy and TEM. Results showed that lateral spread of defect geometry is proportional to height. Undercut at defect also increases the lateral spread. Reductions in defect heights were observed for 0.15 μm wide defect lines. A long-term study of Mo/Si coating reflectivity revealed that Mo/Si coatings with Mo as the top layer suffer significant reductions in reflectivity over time due to oxidation.