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Sample records for norwegian continental shelf

  1. Formation waters of the Norwegian Continental Shelf

    Energy Technology Data Exchange (ETDEWEB)

    McCartney, R. A.; Rein, E.

    2006-03-15

    New and previously published analyses of formation waters for the Norwegian Continental Shelf (NCS) have been evaluated and interpreted to determine the compositional distribution of formation waters in the region and factors controlling their compositions, and also to obtain information on subsurface fluid flow. Formation waters in the region are Na-Cl and Na-Ca-Cl-type waters that display a wide range of salinity (2500-212000 mg/kg Cl). Generally, the concentrations of most dissolved constituents are positively correlated with Cl so that their distribution in formation waters largely reflects the variations shown by salinity. Exceptions are SO4 which is generally low (less than 40 mg/l) regardless of Cl, and HCO3 and in-situ pH which are negatively correlated with Cl. The main factors determining the compositions of the formation waters are mixing of meteoric water (probably late-Jurassic to Eocene), ancient seawater and primary brine together with diagenetic reactions that have affected each of these components individually as well as mixtures of them. Evaluation of the distribution of salinity has helped us identify where vertical and/or lateral migration of brine from the evaporites has occurred. This has in turn provided us with information on the presence of leak-points and vertical mixing, although further investigation of the location of evaporites and basin palaeohydrogeology are required to determine whether regional lateral advection has occurred in the past. The results of this study may benefit oil exploration and production activities in the NCS including constraint of hydrocarbon migration models, economic evaluation of undrilled prospects, scale management and compartmentalisation studies. (Author)

  2. The petroleum resources on the Norwegian continental shelf. 2007

    Energy Technology Data Exchange (ETDEWEB)

    2007-07-01

    The petroleum resources will not last for ever. It is therefore important for Norway to look ahead so as to be prepared for the changes that will come. In this report, the Norwegian Petroleum Directorate presents the current status of the petroleum resources on the Norwegian continental shelf. This is the basis on which the authorities can lay plans for the future. Since no-one can predict the future with certainty, on this occasion the Directorate is presenting four alternative scenarios for the future of Norwegian petroleum activities if the basic scenario proves incorrect. This will enable us to prepare ourselves for changes that may come, and to view the consequences of the various choices we can make. In this report, the Directorate also describes the various plays on the continental shelf, and explains the techniques used and the evaluations made when it estimates the undiscovered resources. This information is important for exploration work, particularly for new companies which need to get acquainted with the geology and the possibilities for finding oil and gas in Norway. Significant volumes remain to be produced and found on the Norwegian continental shelf. Only a third of the total resources have so far been produced, and a quarter of them have still not been discovered. Oil and gas prices are high at the moment, giving the industry and society in general good incentives to produce at a maximum rate. Oil production reached its peak a couple of years ago, but gas production is still increasing. However, the industry is finding less than it produces, which places demands on both it and the authorities. The industry must actively explore the acreage it has been allocated. The Petroleum Directorate believes that substantial resources can still be discovered in areas where production licences have been awarded. At the same time, the industry must gain access to new areas for exploration. The authorities must find an appropriate balance between concern for the

  3. The petroleum resources on the Norwegian Continental Shelf. 2009

    Energy Technology Data Exchange (ETDEWEB)

    2009-07-01

    Exploration activity has reached record-breaking levels in the last couple of years, which has led to many, but small, discoveries. The NPD believes that large discoveries can still be made in areas of the shelf that have not been extensively explored. Content: Challenges on the Norwegian continental shelf; Value creation in fields; 40 years of oil and gas production; Resource management; Still many possibilities; Energy consumption and the environment; Exploration; Access to acreage; Awards of new licenses; Exploration in frontier areas; Exploration history and statistics; Resources and forecasts; Undiscovered resources; Proven recoverable resources; Forecasts; Short-term petroleum production forecast (2009-2013); Investments- and operating costs forecasts; Long-term forecast for the petroleum production; Emissions from the petroleum activity. (AG)

  4. State intervention causing inefficiency: an empirical analysis of the Norwegian Continental Shelf

    International Nuclear Information System (INIS)

    Kashani, Hossein A.

    2005-01-01

    State intervention in the Norwegian Continental Shelf started with the establishment of Statoil as the medium of state ownership over the found petroleum and as a tool to monitor oil companies' procurement behaviour. This paper tests the extent to which the state intervention created inefficiencies in the Norwegian Continental Shelf (NCS) activities, as measured by data envelopment analysis, stochastic frontier analysis, Malmquist Indices, and standard regression analysis. Our results confirm such inefficiencies. Accordingly, the results provide an important insight into NCS production techniques and, more generally, into governments' abilities to influence private sector behaviour through contracts and tendering

  5. Greenhouse gas quotas on the Norwegian continental shelf

    International Nuclear Information System (INIS)

    Torvanger, Asbjoern; Godal, Odd; Kolshus, Hans H.; Aaheim, Asbjoern

    2002-01-01

    This report discusses advantages and disadvantages of voluntary quota obligations in a greenhouse gas emissions trading system at the company level, and advantages and disadvantages associated with various initial allocation mechanisms in a quota system. The analysis is based on the situation for the Norwegian oil industry in an early Norwegian emissions trading system in the period 2005-2007, and on oil companies' participation in international emissions trading under the Kyoto Protocol in the period 2008-2012. The report has been commissioned by the Norwegian Oil Industry Association, and was written in the period March-April 2002. (author)

  6. The potential for satellite and marginal field developments on the Norwegian continental shelf

    International Nuclear Information System (INIS)

    Raustein, O.; Abrahamsen, L.E.; Einang, G.

    1994-01-01

    Norway is faced with decreasing field sizes in hostile waters. On the other hand, approximately 620 billion 1993-NOK have been invested in field installations and transport systems. These installations will have significant available processing and transport capacity in the future, and thus represent a valuable infrastructure. This paper describes the resource situation and the installed infrastructure on the Norwegian Continental Shelf. Then the potential of still maintaining a high activity level in field developments is outlined

  7. The Petroleum resources on the Norwegian Continental Shelf. 2011

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-07-01

    This resource report provides a survey of petroleum resources on the NCS. Content: Resource account; Unconventional oil and gas resources; Future oil and gas production; Challenges for producing fields; Discoveries; Undiscovered resources; Curbing greenhouse gas emissions; Technology and talent; Exploration and new areas; How undiscovered resources are calculated; The NPD's project database; Play analysis; Changes to and reductions in estimated undiscovered resources; Unconventional petroleum resources; Many wells, Increased exploration, Every little helps; Varied discovery success; Sub-basalt in the Norwegian Sea; High exploration costs; Profitable exploration; Unopened areas - mostly in the far north; Resource base; Small discoveries; Location; Development solutions, Profitability of discoveries; Things may take time; Area perspective; Development of production; Remaining reserves and resources in fields; Target for reserve growth; Existing technology; Water and gas injection; Drilling and wells; Infrastructure challenges; New methods and technology; Challenges for pilot projects; Long-term thinking and creativity. (eb)

  8. Production development on the Norwegian continental shelf; KonKraft rapport 2

    Energy Technology Data Exchange (ETDEWEB)

    2008-07-01

    After almost 40 years of virtually uninterrupted growth, total hydrocarbon production on the Norwegian continental shelf (NCS) has reached its highest level ever, with a daily output of 4-4.5 million barrels of oil equivalent per day. It is expected to remain at this level for the next 7 years. After 2015 or thereabouts, however, total oil and gas production is forecast to start declining. Oil production is already falling. Gas output has been increasing, but this is not expected to continue offsetting the drop in liquid production beyond 2015 or thereabouts if no action is taken. Only half the combined oil and gas resources predicted by the Norwegian Petroleum Directorate (NPD) will have been produced in 2015. Remaining recoverable resources, including those expected to be found by further exploration, are currently estimated to be 38-77 billion barrels of oil equivalent (boe). This estimate could be 25-65 billion boe in 2015. Only 40 per cent of the total expected remaining hydrocarbon resources remains to be discovered today, which explains the wide range in the estimates. This huge potential must be managed well to avoid a sharp decline in production and to support a healthy level of long-term investment. The report on production development on the Norwegian continental shelf is published at a time when major changes are taking place both inside and outside the petroleum industry. Several factors make a review of what can be done to address the production decline particularly urgent. Although the current level of activity in the Norwegian petroleum sector is high, assessing the long-term perspectives for the industry is very important. In many cases, the period between the award of licences and the start of production can be 15 years or more. Decisions taken now may have important implications for levels of production and activity in the 2020s. (Author)

  9. Production development on the Norwegian continental shelf; KonKraft rapport 2; Produksjonsutviklingen paa norsk sokkel

    Energy Technology Data Exchange (ETDEWEB)

    2008-07-01

    After almost 40 years of virtually uninterrupted growth, total hydrocarbon production on the Norwegian continental shelf (NCS) has reached its highest level ever, with a daily output of 4-4.5 million barrels of oil equivalent per day. It is expected to remain at this level for the next 7 years. After 2015 or thereabouts, however, total oil and gas production is forecast to start declining. Oil production is already falling. Gas output has been increasing, but this is not expected to continue offsetting the drop in liquid production beyond 2015 or thereabouts if no action is taken. Only half the combined oil and gas resources predicted by the Norwegian Petroleum Directorate (NPD) will have been produced in 2015. Remaining recoverable resources, including those expected to be found by further exploration, are currently estimated to be 38-77 billion barrels of oil equivalent (boe). This estimate could be 25-65 billion boe in 2015. Only 40 per cent of the total expected remaining hydrocarbon resources remains to be discovered today, which explains the wide range in the estimates. This huge potential must be managed well to avoid a sharp decline in production and to support a healthy level of long-term investment. The report on production development on the Norwegian continental shelf is published at a time when major changes are taking place both inside and outside the petroleum industry. Several factors make a review of what can be done to address the production decline particularly urgent. Although the current level of activity in the Norwegian petroleum sector is high, assessing the long-term perspectives for the industry is very important. In many cases, the period between the award of licences and the start of production can be 15 years or more. Decisions taken now may have important implications for levels of production and activity in the 2020s. (Author)

  10. Determination of in-situ rock stresses related to petroleum activities on the Norwegian Continental Shelf

    Energy Technology Data Exchange (ETDEWEB)

    Fejerskov, Morten

    1996-12-31

    In-situ rock stresses have proved to be important for exploration and production of hydrocarbons. This thesis uses various stress determination techniques to characterize the in-situ stress field on the Norwegian Continental Shelf. Leak off tests and borehole breakouts have been used to determine the in-situ stress in deep well bores. Overcoring and earthquake focal mechanisms data have also been compiled and evaluated together with stress information from petroleum wells. A new test procedure is suggested to improve the quality of leak off tests that emphasises the importance of accurate pressure determination, longer test periods and digital data sampling. Four-arm calliper logs are used to identify borehole breakouts on the Tampen Spur and Horda Platform. However, it proved difficult to distinguish borehole breakouts from other drilling processes since the elongations of the borehole consistently appeared in the direction of hole azimuth; drilling-induced key seats are here observed in vertical wells. This behaviour is discussed but not fully understood. This reduces the number of reliable stress data and their quality enormously and even casts some doubt about the quality of previous breakout studies from the North Sea. A highly compressive horizontal stress field seems to be present onshore and offshore Norway. Different stress determination techniques yield very consistent stress orientation, regional and internal variation. A 1. order stress direction is identified, where the maximum horizontal stress direction is rotating from N-S in the Barents Sea to NW-SE in the Norwegian Sea and WNW-ESE in the northern North Sea. At Tampen Spur, a dominant WNW-ESE maximum horizontal stress direction, normal to the major tectonic structures is identified as well as a minimum stress close to the vertical stress, the latter indicating high horizontal stresses. 250 refs., 91 figs., 14 tabs.

  11. Exploration economics in a regulated petroleum province: The case of the Norwegian Continental Shelf

    International Nuclear Information System (INIS)

    Mohn, Klaus; Osmundsen, Petter

    2008-01-01

    Reserve replacement remains a key challenge for the international oil and gas companies. As market-oriented oil and gas provinces are maturing, exploration activity is shifted towards the resource-rich, regulated regimes outside the OECD. Regulated oil and gas provinces remain under-explored also in econometric terms. In this paper, we specify and estimate an econometric model of exploration and appraisal drilling for the highly regulated Norwegian Continental Shelf (NCS) over the period 1965 to 2004. Explanatory variables include the oil price, cumulative discoveries and open exploration acreage. Estimated error-correction models account explicitly for sluggishness and short-term adjustments in exploration drilling. We find robust long-term oil price effects on exploration activity, whereas the short-term response is muted. On the other hand, the temporary influence on exploration drilling from licensing rounds for new exploration acreage is significant, and so are the feedback effects from historical exploration success. At the same time, the longer-term impact of these variables is more moderate. (author)

  12. Discharges and Emissions on the Norwegian Continental Shelf : Oil, chemicals and emissions to air; Utslipp paa norsk kontinentalsokkel 2000. Olje, kjemikalier og utslipp til luft

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-07-01

    The report gives an overview of the discharges of oil and chemicals to sea and emissions to air from the Norwegian Continental Shelf for 2000. This report is based on the operators annual report to the Norwegian Pollution Control Authorities. (author)

  13. Oil spill contingency planning for offshore oil fields - a new concept established for the Norwegian continental shelf

    International Nuclear Information System (INIS)

    Singsaas, I.; Reed, M.; Nygaard, T.; Sundnes, G.Jr.

    1998-01-01

    The development of a new concept for oil spill contingency planning to be used for offshore oil fields on the Norwegian continental shelf was discussed. The factors which are important in developing a good oil spill contingency plan include a good understanding of: (1) the fate, behaviour and weathering of the specific oil, (2) relevant oil spill scenarios, (3) drift and spreading of the oil, and (4) specific requirements for the effectiveness of the chosen response options. The oil spill contingency and response (OSCAR) model was used for quantitative comparison of alternative response options. 21 refs., 2 tabs., 7 figs

  14. Loss of health certificates among offshore petroleum workers on the Norwegian Continental Shelf 2002-2010.

    Science.gov (United States)

    Horneland, Alf Magne; Moen, Bente E; Holte, Kari Anne; Merkus, Suzanne L; Ellingsen, Kjersti Lunde; Carter, Tim; Aas, Randi W; Ulven, Arne Johan

    2011-01-01

    A health certificate is required to work on the offshore petroleum installations of the Norwegian Shelf. Loss of health certificate (loss of licence, LOL) may cause economic problems for the individual worker. A private compensation system (OSO) was established for Norwegian offshore workers in 2002, comprising 8000-11,000 individual members of workers organisations: approximately one third of the population offshore. This study aims at describing the reasons for compensation of offshore workers who have lost their certificates. Of 595 workers who applied for compensation in the period 2002-2010, 38 declined to participate in the study. Of the remaining 557, 507 were granted and 50 were denied compensation. All medical records held by the scheme concerning the 507 compensated applicants were examined. Health data were systematically extracted, analysed, and compared with general population statistics. Musculoskeletal conditions were the most frequent conditions causing LOL for both sexes (42.5%), followed by psychiatric, neurological, and malignant diseases for women, and cardiovascular (19%), neurological, and psychiatric conditions for men. Musculoskeletal disorders were more prevalent than in the general population, and the prevalence of knee problems was particularly high. Among malignant diseases we found a high proportion of brain tumours and renal cancer. The causes are unknown and warrant further investigation in this population. Among women granted compensation, 78% were catering workers, while 50% of the men were process workers, reflecting the gender distribution in these working groups. Musculoskeletal conditions were the most frequent cause of application for LOL compensation for both sexes, followed by psychiatric, neurological, and malignant diseases for women, and cardiovascular, neurological, and psychiatric conditions for men. The cause of the higher incidence of musculoskeletal diseases, brain tumours, and renal cancer found in this study

  15. Radiocarbon and seismic evidence of ice-sheet extent and the last deglaciation on the mid-Norwegian continental shelf

    International Nuclear Information System (INIS)

    Rokoengen, Kaare; Frengstad, Bjoern

    1999-01-01

    Reconstruction of the ice extent and glacier chronology on the continental shelf off mid-Norway has been severely hampered by the lack of dates from the glacial deposits. Seismic interpretation and new accelerator mass spectrometer radiocarbon dates show that the ice sheet extended to the edge of the continental shelf at the last glacial maximum. The two youngest till units near the shelf edge were deposited about 15000 and 13500 BP. The results indicate that the ice sheet partly reached the shelf break as late as 11000 BP followed by a deglaciation of most of the continental shelf in less than 1000 years

  16. The SPARDIG project - Transforming analogue sparker records from the Norwegian continental shelf into SEG-Y format, first results

    Science.gov (United States)

    Schaming, Marc; Rise, Leif; Chand, Shyam; Reidulv, Bøe; Terje Osmundsen, Per; Redfield, Tim

    2017-04-01

    A large number of sparker lines were acquired on the Norwegian continental shelf during the years 1970-1982, by IKU (Sintef Petroleum Research). The responsibility of the analogue seismic database was transferred to NGU in 1998; this included storage of the physical data (original paper rolls and half-scale film copies) and the digital navigation database. The data (from 60°N to 71°30N) were in the early eighties subdivided in 6 data packages, and offered for sale to oil companies as half scale folded paper copies (25 cm width). Navigation applied was mainly Decca Main Chain. The 2014-2016 SPARDIG project (Chand et al., 2016) was supported by NGU, AkerBP (Det Norske), Lundin Norway and the Seabed Project. In the project, IPGS has transformed 374 rolls of analogue sparker lines in 17 different surveys into SEG-Y format. The total length of converted survey lines is 31 261 kilometers. Rolls were scanned at 600 dpi and converted into SEG-Y using the SeisTrans (Caldera software) application (Miles et al., 2007). SeisTrans uses interactive, iterative and repeatable steps in a dedicated graphics window. A first step allows definition of axes and scales, then record time lines (horizontal TWT times and navigation time lines down the record) are picked and removed, and traces are defined. At this step, control tools are available to ensure the quality of the traces. After that, navigation information extracted and interpolated from excel files are added to trace headers. A continuous QC process allows production of SEG-Y files directly readable by interpretation software. The SEG-Y data will be delivered to the Norwegian Discos National Repository (https://portal.diskos.cgg.com/whereoil-data/) but access will be restricted to participants until 1st April 2019. IKU sparker lines have higher resolution than conventional 2D lines, but the penetration is limited. The data sets are complementary to each other. In 2D seismic lines, it is often difficult to delineate units in

  17. An Industrial Cloud: Integrated Operations in Oil and Gas in the Norwegian Continental Shelf

    Science.gov (United States)

    Rong, Chunming

    Cloud computing may provide the long waiting technologies and methodologies for large scale industrial collaboration across disciplines and enterprise boundaries. Industrial cloud is introduced as a new inter-enterprise integration concept in cloud computing. Motivations and advantages are given by a practical exploration of the concept from the perspective of the on-going effort by the Norwegian oil and gas industry to build industry wide information integration and collaboration. ISO15926 is recognized as a standard enabling cross boundaries data integration and processing.

  18. The Myanmar continental shelf

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Rao, P.S.

    reveal a minimum of 18 m thick strata of modern muds (Fig. 2g). At the outer boundary of the Gulf of Myanmar Continental Shelf 8 Martaban (15oN Latitude), brown muds overlie coarse sands indicating that modern deltaic sediments... on the Myeik Bank (Rodolfo, 1969a). Modern sediments on the Ayeyarwady shelf General composition, Texture and Grain-size: The distribution and sediment texture on the Ayeyarwady shelf shows fine-grained sediments comprising silty-clay and clayey...

  19. Outer Continental Shelf Lands Act

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data represents geographic terms used within the Outer Continental Shelf Lands Act (OCSLA or Act). The Act defines the United States outer continental shelf...

  20. Integrated management plan for the North Sea and Skagerrak: Status description for the petroleum industry with emphasis on the Norwegian continental shelf; Helhetlig forvaltningsplan for Nordsjoeen og Skagerrak: Statusbeskrivelse for petroleumsvirksomheten med hovedvekt paa norsk sokkel

    Energy Technology Data Exchange (ETDEWEB)

    2010-06-15

    Status description of the petroleum industry covers mainly the Norwegian continental shelf, but it is also given a brief description of the activity in other offshore areas of the North Sea. It shows a list of producing fields, fields under development, developments in the future, findings that are in the planning phase, and completed fields. It also describes the pipelines and other petroleum-related activities at sea and on shore. (AG)

  1. Polychaete/amphipod ratio as an indicator of environmental impact related to offshore oil and gas production along the Norwegian continental shelf.

    Science.gov (United States)

    Andrade, Hector; Renaud, Paul E

    2011-12-01

    Benthic faunal data is regularly collected worldwide to assess the ecological quality of marine environments. Recently, there has been renewed interest in developing biological indices able to identify environmental status and potential anthropogenic impacts. In this paper we evaluate the performance of a general polychaete/amphipod ratio along the Norwegian continental shelf as an environmental indicator for offshore oil and gas impacts. Two main trends are apparent: first, a contamination gradient is discernible from where production takes place compared to stations 10,000 m away. Second, the quality of the marine environment has improved over time. These results are consistent with monitoring reports employing a combination of uni- and multi-variate statistics. Thus, we consider this ratio as a relatively simple, useful and potentially cost-effective complement to other more demanding assessment techniques. Because of its strong theoretical basis, it may also be useful for detecting ecological change as a result of other activities. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. The Statoil/Hydro fusion in a continental shelf perspective

    International Nuclear Information System (INIS)

    Osmundsen, Petter

    2007-01-01

    The article analysis the consequences of the Statoil/Hydro merger on the development on the Norwegian continental shelf. Various indicators of results of the market power the merger are presented and the effects of reduced competition on the markets are discussed. The advantages of the merger on the activities on the shelf are analyzed. (tk)

  3. Industry comparison through systematic self assessment of the maintenance function of each operation company of the Norwegian continental shelf

    International Nuclear Information System (INIS)

    Nielsen, L.

    2000-01-01

    In this paper The Norwegian Petroleum Directorate (NPD) will describe a method for internal evaluation or self-assessment of the maintenance function of each operating oil company in the Norwegian offshore petroleum industry. Due to the current trends of cost reduction, demanning and downsizing, the industry has started to use RCM and other risk based maintenance techniques. Judged by the experience gained so far in this industry, the successful implementation of RCM and other risk based maintenance optimisation techniques seems to be closely linked with the existence of a efficient and professional maintenance management system. NPD is therefore now developing a guideline for systematic self-assessment of the maintenance function and the maintenance management system. The guideline has been developed based on a method developed by SKI. NPD has in close co-operation with the industry adapted SKI's guideline to fit the problems and challenges of the petroleum industry. It is NPD's intention to highlight different strategic, organisational and administrative issues linked with the introduction of risk based maintenance methods in the guideline. NPD also try to reflect 'best practices' in the industry in the guideline in order to provoke the oil companies to review their own practices in different areas. The results so far from using this method for self-assessment will be presented, and both the advantages and disadvantages of such an approach will be discussed. (author)

  4. Whither the UK Continental Shelf?

    International Nuclear Information System (INIS)

    Kemp, A.G.

    1999-01-01

    The development of the oil and gas fields on the United Kingdom continental shelf has been carried out with remarkable success. However, low oil prices now threaten fresh investment and make it likely that both oil and gas output will start to fall in about 2001. The impact of a number of different price scenarios on further development is assessed. It is concluded that continuing technological improvements and the provision of adequate incentives by government should ensure a long productive future for the province. (UK)

  5. Coordination: southeast continental shelf studies. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Menzel, D.W.

    1981-02-01

    The objectives are to identify important physical, chemical and biological processes which affect the transfer of materials on the southeast continental shelf, determine important parameters which govern observed temporal and spatial varibility on the continental shelf, determine the extent and modes of coupling between events at the shelf break and nearshore, and determine physical, chemical and biological exchange rates on the inner shelf. Progress in meeting these research objectives is presented. (ACR)

  6. Swell propagation across a wide continental shelf

    OpenAIRE

    Hendrickson, Eric J.

    1996-01-01

    The effects of wave refraction and damping on swell propagation across a wide continental shelf were examined with data from a transect of bottom pressure recorders extending from the beach to the shelf break near Duck, North Carolina. The observations generally show weak variations in swell energy across the shelf during benign conditions, in qualitative agreement with predictions of a spectral refraction model. Although the predicted ray trajectories are quite sensitive to the irregular she...

  7. Coordination: Southeast Continental Shelf studies. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Menzel, D.W.

    1981-02-01

    An overview of the Oceanograhic Program of Skidaway Institute of Oceanograhy is presented. Included are the current five year plan for studies of the Southeast Continental Shelf, a summary of research accomplishments, proposed research for 1981-1982, current status of the Savannah Navigational Light Tower, and a list of publications. (ACR)

  8. 75 FR 1076 - Outer Continental Shelf Civil Penalties

    Science.gov (United States)

    2010-01-08

    ... initiate civil penalty proceedings; however, violations that cause injury, death, or environmental damage... DEPARTMENT OF THE INTERIOR Minerals Management Service Outer Continental Shelf Civil Penalties... daily civil penalty assessment. SUMMARY: The Outer Continental Shelf Lands Act requires the MMS to...

  9. Mean Lagrangian drift in continental shelf waves

    Science.gov (United States)

    Drivdal, M.; Weber, J. E. H.

    2012-04-01

    The time- and depth-averaged mean drift induced by barotropic continental shelf waves (CSW's) is studied theoretically for idealized shelf topography by calculating the mean volume fluxes to second order in wave amplitude. The waves suffer weak spatial damping due to bottom friction, which leads to radiation stress forcing of the mean fluxes. In terms of the total wave energy density E¯ over the shelf region, the radiation stress tensor component S¯11 for CSW's is found to be different from that of shallow water surface waves in a non-rotating ocean. For CSW's, the ratio ¯S11/¯E depends strongly on the wave number. The mean Lagrangian flow forced by the radiation stress can be subdivided into a Stokes drift and a mean Eulerian drift current. The magnitude of the latter depends on the ratio between the radiation stress and the bottom stress acting on the mean flow. When the effect of bottom friction acts equally strong on the waves and the mean current, calculations for short CSW's show that the Stokes drift and the friction-dependent wave-induced mean Eulerian current varies approximately in anti-phase over the shelf, and that the latter is numerically the largest. For long CSW's they are approximately in phase. In both cases the mean Lagrangian current, which is responsible for the net particle drift, has its largest numerical value at the coast on the shallow part of the shelf. Enhancing the effect of bottom friction on the Eulerian mean flow, results in a general current speed reduction, as well as a change in spatial structure for long waves. Applying realistic physical parameters for the continental shelf west of Norway, calculations yield along-shelf mean drift velocities for short CSW's that may be important for the transport of biological material, neutral tracers, and underwater plumes of dissolved oil from deep water drilling accidents.

  10. Seabottom backscatter studies in the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Chakraborty, B.; Pathak, D.

    The study is initiated to observe the interaction effects of the sound signal with three different sediment bottoms in the shelf area between Cochin and Mangalore in the western continental shelf of India. An echo signal acquisition system has been...

  11. Seaweed culture and continental shelf protection

    Energy Technology Data Exchange (ETDEWEB)

    Przhemenetskaya, V F

    1985-07-01

    The initial impression that the resources of the oceans were limitless has been replaced by a more rational appreciation that everything has its limits, including the seemingly infinite resources of marine plant life. In addition, experience in California, Australia, China, Japan and Korea has demonstrated that depletion of seaweed resources for commercial utilization has a deleterious effect on the biocenotic status of the continental shelf. In view of this, many countries, such as Japan, China, Korea, the Philippines and the USSR, have embarked on aquaculture programs, in which seaweeds are cultivated on marine plantations. Successful developments in this direction should go a long way to preserving the natural ecologic balance on the continental shelf, and yet provide mankind with the resources of the deep. Many difficulties remain to be resolved before aquaculture programs become fully cost effective, one of which deals with the susceptibility of a monoculture to a given predator or disease. To that end, such programs necessitate the creation of well balanced systems that would support a variety of marine plant and animal life without an adverse effect on the desired crop. 4 references, 6 figures.

  12. State of the soft bottoms of the continental shelf

    International Nuclear Information System (INIS)

    Guzman Alvis, Angela I; Solano, Oscar David

    2002-01-01

    The presented information, it is based on studies carried out on the continental shelf of the Colombian Caribbean, mainly in the Gulf of Morrosquillo and the Magdalena and Guajira departments in the last ten years. A diagnostic is done of the soft bottoms of the Colombian continental shelf

  13. Sediments of the western continental shelf of India - Environmental significance

    Digital Repository Service at National Institute of Oceanography (India)

    Guptha, M.V.S.

    The degree of fragmentation and colour of the skeletal fragments, colouration in benthic foraminifers have been studied in surficial sediment samples collected from forty stations from the continental shelf region between Ratnagiri in the south...

  14. Geochemistry of sediments of the eastern continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Mascarenhas, A.; Paropkari, A.L.; Murty, P.S.N.

    The bulk and partition geochemistry of Al, Fe, Ti, Mn, Zn, and Cu have been investigated in sediments of the eastern continental shelf of India. The results show that (1) the bulk geochemistry varies from one shelf unit to the other, (2) all...

  15. Glacial morphology and depositional sequences of the Antarctic Continental Shelf

    Science.gov (United States)

    ten Brink, Uri S.; Schneider, Christopher

    1995-01-01

    Proposes a simple model for the unusual depositional sequences and morphology of the Antarctic continental shelf. It considers the regional stratal geometry and the reversed morphology to be principally the results of time-integrated effects of glacial erosion and sedimentation related to the location of the ice grounding line. The model offers several guidelines for stratigraphic interpretation of the Antarctic shelf and a Northern Hemisphere shelf, both of which were subject to many glacial advances and retreats. -Authors

  16. Modern sedimentary processes along the Doce river adjacent continental shelf

    Directory of Open Access Journals (Sweden)

    Valéria da Silva Quaresma

    Full Text Available In areas of the continental shelf where sediment supply is greater than the sediment dispersion capacity, an extensive terrigenous deposits and consequently submerged deltas can be formed. The Eastern Brazilian shelf is characterized by the occurrence of river feed deltas in between starving coasts. Herein, modern sedimentary processes acting along the Doce river adjacent continental shelf are investigated. The main objective was to understand the shelf sediment distribution, recognizing distinct sedimentary patterns and the major influence of river sediment discharge in the formation of shelf deposits. The study used 98 surficial samples that were analyzed for grain size, composition and bulk density. Results revealed 3 distinct sectors: south - dominated by mud fraction with a recent deposition from riverine input until 30 m deep and from this depth bioclastic sands dominate; central north - sand mud dominated, been recognized as a bypass zone of resuspended sediment during high energy events; and north - relict sands with high carbonate content. The modern sedimentation processes along the Doce river continental shelf is dominated by distinct sedimentary regimes, showing a strong fluvial influence associated with wave/wind induced sediment dispersion and a carbonate regime along the outer shelf. These regimes seem to be controlled by the distance from the river mouth and bathymetric gradients.

  17. Uncovering the glacial history of the Irish continental shelf (Invited)

    Science.gov (United States)

    Dunlop, P.; Benetti, S.; OCofaigh, C.

    2013-12-01

    In 1999 the Irish Government initiated a €32 million survey of its territorial waters known as the Irish National Seabed Survey (INSS). The INSS is amongst the largest marine mapping programmes ever undertaken anywhere in the world and provides high-resolution multibeam, backscatter and seismic data of the seabed around Ireland. These data have been used to provide the first clear evidence for extensive glaciation of the continental shelf west and northwest of Ireland. Streamlined drumlins on the mid to outer shelf record former offshore-directed ice flow towards the shelf edge and show that the ice sheet was grounded in a zone of confluence where ice flowing onto the shelf from northwest Ireland merged with ice flowing across the Malin Shelf from southwest Scotland. The major glacial features on the shelf are well developed nested arcuate moraine systems that mark the position of the ice sheet margin and confirm that the former British Irish Ice Sheet was grounded as far as the shelf edge around 100 km offshore of west Donegal at the last glacial maximum. Distal to the moraines, on the outermost shelf, prominent zones of iceberg plough marks give way to the Barra/Donegal fan and a well developed system of gullies and canyons which incise the continental slope. Since 2008 several scientific cruises have retrieved cores from the shelf and slope to help build a more detailed understanding of glacial events in this region. This presentation will provide an overview of the glacial history of the Irish shelf and will discuss ongoing research programmes that are building on the initial research findings to produce a better understanding of the nature and timing of ice sheet events in this region.

  18. Areas with special ecological values on the Dutch Continental Shelf

    NARCIS (Netherlands)

    Lindeboom, H.J.; Kessel, J.G.; Berkenbosch, L.

    2005-01-01

    In this report we are submitting proposals for the boundaries of areas on the Dutch Continental Shelf (DCS). In the National Spatial Strategy a conservation regime has been determined for five areas in the North Sea with special ecological values. RIKZ and Alterra have formulated this report in

  19. Clay mineral distribution on the Kerala continental shelf and slope

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.; Nair, R.R.; Hashimi, N.H.

    Seventy-five sediment samples collected from the Kerala continental shelf and slope during the 17th and 71st Cruises of @iRV gaveshani@@ were analysed by X-ray diffraction for clay mineral cntent. The distribution of total clay (< 4~k fraction...

  20. Potential power-generating stations on the Atlantic Continental Shelf

    International Nuclear Information System (INIS)

    Mittl, R.L.

    1975-01-01

    Progress toward the installation of floating power plants, which represent a beneficial use of the continental shelf, is presented. The demonstration of the feasibility of such facilities with existing technology, and the thorough support by safety and environmental reviews, have been made possible by the efforts of engineers and scientists working toward supplying the nation's growing energy needs

  1. Mineralogy of the carbonate sediments - western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, R.R.; Hashimi, N.H.

    An X-ray diffraction study of forty-six sediment samples and three oolitic limestone samples from the western continental shelf of India shows that aragonite is the dominant carbonate mineral (99% maximum), followed by low-magnesium calcite (77...

  2. Geochemistry of sediments of the western Canadian continental shelf

    Science.gov (United States)

    Macdonald, R. W.; Pedersen, T. F.

    1991-08-01

    Few chemical data exist for the sedimentary environment off the Canadian west coast. Here we define the chemical nature of the shelf sediments by examining the important sources of material (natural and anthropogenic) to the region and processes relevant to diagenesis. Slightly more data exist for the continental shelf to the south (Washington) and north (Alaska), however it is clear that the sedimentary environment of these neighbouring shelves differs importantly from the Canadian portion. The British Columbia shelf receives little modern terrigenous detritus due mainly to isolation from terrestrial sediment sources by fiords, inland seas, or bypassing by shelf canyons. The chemical state of the sediments depends on the rate of supply of material, the energy of the depositional or erosional environment and the organic and inorganic composition of the material. These features in concert with bottom water characteristics control the redox state. Although no basins hosting continuous depositional records for the Holocene on the open British Columbia shelf have been identified or studied in a manner described by BUCKLEY ( Continental Shelf Research, 11, 1099-1122), some coastal embayments and fiords provide valuable historical records of post-glacial sedimentation. Such environments will prove to be increasingly useful in future studies of changes in regional climate and in establishing the chronology of natural disasters and anthropogenic impacts. Recommendations are given for a variety of research projects that would help us to understand better both chemical interactions at the seabed and Late Quaternary depositional history.

  3. Radiation stress and mean drift in continental shelf waves

    Science.gov (United States)

    Weber, Jan Erik H.; Drivdal, Magnus

    2012-03-01

    The time- and depth-averaged mean drift induced by barotropic continental shelf waves (CSW's) is studied theoretically for idealized shelf topography by calculating the mean volume fluxes to second order in wave amplitude. The waves suffer weak spatial damping due to bottom friction, which leads to radiation stress forcing of the mean fluxes. In terms of the total wave energy density E̅̅ over the shelf region, the radiation stress tensor component S̅11 for CSW's is found to be different from that of shallow water surface waves in a non-rotating ocean. For CSW's, the ratio S̅11/E̅ depends strongly on the wave number. The mean Lagrangian flow forced by the radiation stress can be subdivided into a Stokes drift and a mean Eulerian drift current. The magnitude of latter depends on ratio between the radiation stress and the bottom stress acting on the mean flow. When the effect of bottom friction acts equally strong on the waves and the mean current, calculations for short CSW's show that the Stokes drift and the friction-dependent wave-induced mean Eulerian current varies approximately in anti-phase over the shelf, and that the latter is numerically the largest. For long CSW's they are approximately in phase. In both cases the mean Lagrangian current, which is responsible for the net particle drift, has its largest numerical value at the coast on the shallow part of the shelf. Enhancing the effect of bottom friction on the Eulerian mean flow, results in a general current speed reduction, as well as a change in spatial structure for long waves. Applying realistic physical parameters for the continental shelf west of Norway, calculations yield along-shelf mean drift velocities for short CSW's that may be important for the transport of biological material, neutral tracers, and underwater plumes of dissolved oil from deepwater drilling accidents.

  4. Seabed geology of the Canadian eastern continental shelf

    Science.gov (United States)

    Piper, David J. W.

    1991-08-01

    The physiography of the continental shelf off eastern Canada is irregular, developed by glacial erosion of a previously fluvially-dominated landscape. Northern shelves are deeper than southern shelves. Most surficial sediments on the shelf are relict or palimpsest. The principal modern source of sediment to the northern shelves is ice rafting and iceberg scour reworking of Quaternary sediments. Southern shelves receive sediment through erosion of Quaternary sediments; only small amounts of fine-grained sediment derived from coastal erosion and rivers escape from the coastal zone. Regional maps of sediment texture, carbonate content and heavy mineralogy consequently show differences between the northern and southern shelves. Large areas of the shelf show little net deposition. On the northern shelves, there is a surface veneer up to 0.5 m thick derived from ice rafting and iceberg turbation of underlying Quaternary sediment, modified by south-flowing currents [ WOODWORTH-LYNASet al. (this issue) Continental Shelf Research, 11, 939-961]. The overall effects of former iceberg turbation may extend to a depth of 10 m sub-bottom. On the southern shelves, bioturbation and perhaps storm-related currents rework exposed Quaternary sediments more slowly. Muds accumulate in deep basins on the shelves at rates of about 0.5 m per 1000 years; this accumulation is probably episodic and related to major storms reworking sediment from the surface sediment veneer in shallower areas of little net deposition. In water depths less than 110 m sand and gravel have formed as a result of reworking in the coastal zone during the post-glacial transgression. Over large areas of Georges Bank, the eastern Scotian Shelf and the Grand Banks of Newfoundland, such sands are mobilized during storms to form a wide suite of bedforms [ AMOS and JUDGE (this issue) Continental Shelf Research, 11, 1037-1068]. Elsewhere, particularly in deeper water, sandy surfaces appear moribund or inactive and large

  5. New approaches to cost reduction on the UK continental shelf

    Energy Technology Data Exchange (ETDEWEB)

    Curtis, M I

    1994-12-31

    The conference paper deals with cost reduction on the UK continental shelf. New approaches on the reduction of field development costs are compared with the cases if traditional approaches had been followed. Field developments where success in aligning the goals and objectives of the contractors and owners which led to projects being delivered on time but more than 20% below budget, are exemplified. The contractors in the alliance received 55% of the savings in addition to their normal profit. The procedure to follow in such cases, is discussed

  6. New approaches to cost reduction on the UK continental shelf

    International Nuclear Information System (INIS)

    Curtis, M.I.

    1994-01-01

    The conference paper deals with cost reduction on the UK continental shelf. New approaches on the reduction of field development costs are compared with the cases if traditional approaches had been followed. Field developments where success in aligning the goals and objectives of the contractors and owners which led to projects being delivered on time but more than 20% below budget, are exemplified. The contractors in the alliance received 55% of the savings in addition to their normal profit. The procedure to follow in such cases, is discussed

  7. Geochemistry of zinc in the sediments of the western continental shelf and slope of India

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, P.S.N.; Paropkari, A.L.; Rao, Ch.M.

    The bulk geochemistry of zinc in the sediments of the western continental shelf and slope of India and also the partition geochemistry of the sediments of the shelf and slope regions between Ratnagiri and Mangalore have been studied. The studies...

  8. Facts 2009 - The Norwegian petroleum sector

    Energy Technology Data Exchange (ETDEWEB)

    2009-07-01

    The publication provides a general overview of information regarding the petroleum activities on the Norwegian continental shelf. Contents: Foreword; The petroleum sector; Norwegian resource management; Government petroleum revenues; Exploration activities; Development and operations; Norwegian gas exports; Decommissioning; Research, technology; Environmental considerations; Petroleum resources; Fields in production; Fields under development; Future developments; Fields where production has ceased; Pipelines and onshore facilities. (AG)

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

    Digital Repository Service at National Institute of Oceanography (India)

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

    are predominantly mixed, semidiurnal in nature. Motion over any continental shelf is governed by the tide-driven oscillatory flow. In this paper, tidal and non-tidal characteristics of the waters of Southwest continental shelf of India are assessed using...

  10. Nutrient Distributions, Transports, and Budgets on the Inner Margin of a River-Dominated Continental Shelf

    Science.gov (United States)

    2013-10-02

    Nutrient distributions, transports, and budgets on the inner margin of a river-dominated continental shelf John C. Lehrter,1 Dong S. Ko,2 Michael C...and D. C. Biggs (1993), The influence of advec- tion on the spatial variability of nutrient concentrations on the Texas- Louisiana continental shelf

  11. Potential alternative energy technologies on the Outer Continental Shelf.

    Energy Technology Data Exchange (ETDEWEB)

    Elcock, D.; Environmental Assessment

    2007-04-20

    This technical memorandum (TM) describes the technology requirements for three alternative energy technologies for which pilot and/or commercial projects on the U.S. Outer Continental Shelf (OCS) are likely to be proposed within the next five to seven years. For each of the alternative technologies--wind, wave, and ocean current--the TM first presents an overview. After each technology-specific overview, it describes the technology requirements for four development phases: site monitoring and testing, construction, operation, and decommissioning. For each phase, the report covers the following topics (where data are available): facility description, electricity generated, ocean area (surface and bottom) occupied, resource requirements, emissions and noise sources, hazardous materials stored or used, transportation requirements, and accident potential. Where appropriate, the TM distinguishes between pilot-scale (or demonstration-scale) facilities and commercial-scale facilities.

  12. Habitat specialization in tropical continental shelf demersal fish assemblages.

    Directory of Open Access Journals (Sweden)

    Ben M Fitzpatrick

    Full Text Available The implications of shallow water impacts such as fishing and climate change on fish assemblages are generally considered in isolation from the distribution and abundance of these fish assemblages in adjacent deeper waters. We investigate the abundance and length of demersal fish assemblages across a section of tropical continental shelf at Ningaloo Reef, Western Australia, to identify fish and fish habitat relationships across steep gradients in depth and in different benthic habitat types. The assemblage composition of demersal fish were assessed from baited remote underwater stereo-video samples (n = 304 collected from 16 depth and habitat combinations. Samples were collected across a depth range poorly represented in the literature from the fringing reef lagoon (1-10 m depth, down the fore reef slope to the reef base (10-30 m depth then across the adjacent continental shelf (30-110 m depth. Multivariate analyses showed that there were distinctive fish assemblages and different sized fish were associated with each habitat/depth category. Species richness, MaxN and diversity declined with depth, while average length and trophic level increased. The assemblage structure, diversity, size and trophic structure of demersal fishes changes from shallow inshore habitats to deeper water habitats. More habitat specialists (unique species per habitat/depth category were associated with the reef slope and reef base than other habitats, but offshore sponge-dominated habitats and inshore coral-dominated reef also supported unique species. This suggests that marine protected areas in shallow coral-dominated reef habitats may not adequately protect those species whose depth distribution extends beyond shallow habitats, or other significant elements of demersal fish biodiversity. The ontogenetic habitat partitioning which is characteristic of many species, suggests that to maintain entire species life histories it is necessary to protect corridors of

  13. Acoustic masking in sediments due to gases on the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Siddiquie, H.N.; Rao, D.G.; Vora, K.H.; Topgi, R.S.

    Surveys carried out on the western continental shelf of India indicate that the inner and middle shelf to a depth of 50-60 m is covered by acoustically transparent clays. On the shelf off Bombay, the clays are thin near the shore where they overlie...

  14. On risk assessment in the petroleum activities on the Norwegian and UK continental shelves

    International Nuclear Information System (INIS)

    Avena, Terje; Pitblado, Robin

    1998-01-01

    This article discusses some key principles and tools of safety management, with focus on risk analyses, risk interpretation, risk acceptance criteria and risk communication, as well as emergency preparedness. The starting point for the discussion is the experience from the activity on the Norwegian and UK continental shelves, and the implementation of new safety regulations in particular

  15. Risk level project. Summary report, Norwegian Shelf, Phase 7; Risikonivaaprosjektet. Sammendragsrapport Norsk Sokkel, fase 7

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2007-04-15

    The project 'developments in risk level - Norwegian shelf', also known as the risk level project, was initiated by the Norwegian Petroleum Directorate in 2000. From 2004 the project has been continued by Petroleum Safety Authority Norway. The project's main objectives are to measure the effect of the health, security and environment (HSE) work in the industry, and contribute to identify the areas critical to HSE, where efforts must be made to prevent unwanted events or accidents. A summary report with results from phase 7 in the project (ml)

  16. Facts 2010 - The Norwegian petroleum sector

    Energy Technology Data Exchange (ETDEWEB)

    2010-07-01

    The publication provides a general overview of information regarding the petroleum activities on the Norwegian continental shelf. Content; Foreword; The petroleum sector - Norway's largest industry; Organisation of Norwegian petroleum activity; Government petroleum revenues; Exploration activities; Development and operations; Norwegian gas exports; Decommissioning; Research, technology and industrial development; Environmental considerations in the Norwegian petroleum sector; Petroleum resources; Fields in production; Fields under development; Future developments; Fields where production has ceased; Pipelines and onshore facilities. (AG)

  17. Facts 2010 - The Norwegian petroleum sector

    Energy Technology Data Exchange (ETDEWEB)

    2010-07-01

    The publication provides a general overview of information regarding the petroleum activities on the Norwegian continental shelf. Content; Foreword; The petroleum sector - Norway's largest industry; Organisation of Norwegian petroleum activity; Government petroleum revenues; Exploration activities; Development and operations; Norwegian gas exports; Decommissioning; Research, technology and industrial development; Environmental considerations in the Norwegian petroleum sector; Petroleum resources; Fields in production; Fields under development; Future developments; Fields where production has ceased; Pipelines and onshore facilities. (AG)

  18. Facts 2011 - The Norwegian petroleum sector

    Energy Technology Data Exchange (ETDEWEB)

    2011-07-15

    The publication provides a general overview of information regarding the petroleum activities on the Norwegian continental shelf. Content; Foreword; The petroleum sector - Norway's largest industry; Organisation of Norwegian petroleum activity; Government petroleum revenues; Exploration activities; Development and operations; Norwegian gas exports; Decommissioning; Research, technology and industrial development; Environmental considerations in the Norwegian petroleum sector; Petroleum resources; Fields in production; Fields under development; Future developments; Fields where production has ceased; Pipelines and onshore facilities. (AG)

  19. Supervised classification of continental shelf sediment off western Donegal, Ireland

    Science.gov (United States)

    Monteys, X.; Craven, K.; McCarron, S. G.

    2017-12-01

    Managing human impacts on marine ecosystems requires natural regions to be identified and mapped over a range of hierarchically nested scales. In recent years (2000-present) the Irish National Seabed Survey (INSS) and Integrated Mapping for the Sustainable Development of Ireland's Marine Resources programme (INFOMAR) (Geological Survey Ireland and Marine Institute collaborations) has provided unprecedented quantities of high quality data on Ireland's offshore territories. The increasing availability of large, detailed digital representations of these environments requires the application of objective and quantitative analyses. This study presents results of a new approach for sea floor sediment mapping based on an integrated analysis of INFOMAR multibeam bathymetric data (including the derivatives of slope and relative position), backscatter data (including derivatives of angular response analysis) and sediment groundtruthing over the continental shelf, west of Donegal. It applies a Geographic-Object-Based Image Analysis software package to provide a supervised classification of the surface sediment. This approach can provide a statistically robust, high resolution classification of the seafloor. Initial results display a differentiation of sediment classes and a reduction in artefacts from previously applied methodologies. These results indicate a methodology that could be used during physical habitat mapping and classification of marine environments.

  20. Facts 2009 - The Norwegian petroleum sector; Fakta 2009 - norsk petroleumsverksemd

    Energy Technology Data Exchange (ETDEWEB)

    2009-07-01

    The publication provides a general overview of information regarding the petroleum activities on the Norwegian continental shelf. Contents: Foreword; The petroleum sector; Norwegian resource management; Government petroleum revenues; Exploration activities; Development and operations; Norwegian gas exports; Decommissioning; Research, technology; Environmental considerations; Petroleum resources; Fields in production; Fields under development; Future developments; Fields where production has ceased; Pipelines and onshore facilities. (AG)

  1. BLM/OCS Southern California Outer Continental Shelf Environmental Baseline Studies

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Data in this file were produced by Science Applications, Inc., prime contractor on the Bureau of Land Management/Outer Continental Shelf - Southern California...

  2. BLM/OCS South Texas Outer Continental Shelf (STOCS) Project Sediment Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The South Texas Outer Continental Shelf Project (STOCS) conducted by the University of Texas and the USGS with funding from BLM/NOAA. The USGS produced geochemical...

  3. Mining of phosphorite resources from the Indian continental shelf will help food production

    Digital Repository Service at National Institute of Oceanography (India)

    Qasim, S.Z.; Nair, R.R.

    of phosphorite deposits would depend on several technical and economic factors Phosphorites occur in water depths upto 200 meters of the western continental shelf of India These are the areas associated with upwelling The relationship between phosphorite deposits...

  4. Regional tectonic trends on the inner continental shelf off Konkan and central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Ramana, M.V.

    Satellite imagery and offshore magnetic data were analysed to correlate regional tectonic elements on the inner continental shelf off Konkan and the adjacent Deccan plateau. Three statistically important lineament trends N-S, WNW-ESE and ENE...

  5. 77 FR 10707 - Safety Zone; NOBLE DISCOVERER, Outer Continental Shelf Drillship, Chukchi and Beaufort Seas, Alaska

    Science.gov (United States)

    2012-02-23

    ... indigenous population; (4) the lack of any established shipping fairways, fueling and supply storage... location of the DRILLSHIP NOBLE DISCOVERER on the Outer Continental Shelf and its distance from both land...

  6. Grain Size Data from the NOAA Outer Continental Shelf Environmental Assessment Program (OCSEAP)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains grain size data from samples acquired under the NOAA Outer Continental Shelf Environmental Assessment Program (OCSEAP) from the Outer...

  7. Origins of Stratal Surfaces in Channel Fills on the New Jersey Continental Shelf

    National Research Council Canada - National Science Library

    Sommerfield, Christopher K

    2006-01-01

    The goal of this project was to advance an understanding of acoustic anomalies created by sub-seafloor paleochannels by investigating the geologic properties of channel-rich strata on the New Jersey continental shelf...

  8. Archive of Geosample Data and Information from the U.S. Extended Continental Shelf (ECS) Project.

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Geological samples collected as part of the U.S. Extended Continental Shelf (ECS) Project are curated by the U.S. Geological Survey, a partner in the ECS Project. To...

  9. Geochemistry of marine sediments of the Brazilian Northeastern continental shelf

    Directory of Open Access Journals (Sweden)

    Fernanda Souza do Nascimento

    2010-01-01

    Full Text Available The marine sediment samples collected from the northeastern Brazilian continental shelf, at water depths between 20 and 80 m, consisted mainly of sands with an almost total absence of gravel and granules. Medium, coarse and very coarse sand grains are mostly composed of halimeda, lithothamnium, rodoliths and bioclastic sands with a carbonate content varying between 77 and 96 %. The chemistry in general shows a decreasing content of Ca (86.1 % >Si (6 % > Cl (3.6 % > Sr (0.8 % > K (0.66 % > S (0.62 % > Al (0.6 % > Na (0.55% > Mg (0.43 % > Fe (0.4 % > P (0.2 % > Br (0.04 % in the samples. There was no correlation between CaCO3 and chemical contents and grain size with depth and bio-components. With the exception of Sr of marine origin, all other elements (P, S, Br, Cl, Fe are of continental origin. The lithothamnium of some offshore samples shows higher CaCO3 content, while Mg and Na are present only in halimedas. Bioclastic sands contain no Br, and silt and clay fractions are rare and characterize samples closer to the coast. These marine bioclastic granulates are of very pure biogenic calcium carbonates and are thus highly to be recommended for economic purposes.Os granulados marinhos, da Plataforma Continental do nordeste brasileiro, coletados de profundidades entre 20 e 80 m, são predominantemente areias cascalhosas constituídas de halimedas, litotames, rodolitos e areias bioclásticas, cujos teores de carbonatos variam de 77 a 96 %. A concentração média geral de elementos químicos na ordem decrescente é Ca (86.1 % > Si (6 % > Cl (3.6 % > Sr (0.8 % > K (0.66 % > S (0.62 % > Al (0.6 % > Na (0.55 % > Mg (0.43 % > Fe (0.4 % > P (0.2 % > Br (0,04 %, independentemente da profundidade e tipo de bio-componente. Com exceção do Sr, que é de origem marinha, os demais elementos (P, S, Br, Cl, Fe são de origem continental. Elementos como Mg e Na foram restritos às halimedas em apenas duas amostras, enquanto Br não foi detectado nas areias

  10. Variability in measured current structure on the southwest continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    DineshKumar, P.K.; Srinivas, K.

    -1 Variability in Measured Current Structure on the Southwest Continental Shelf of India P.K. Dinesh Kumar and K. Srinivas National Institute of Oceanography, Regional Centre P.O.Box 1913, Cochin - 682018,India Email: dineshku@niokochi.org ABSTRACT... WORDS: Direct current measurements, tidal currents, southwest coast of India. INTRODUCTION The circulation pattern of the eastern Arabian Sea over the southwest continental shelf of India (inferred...

  11. Submerged reef systems on the central western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Vora, K.H.; Almeida, F.

    -262 255 Elsevier Science Publishers B.V., Amsterdam -- Printed in the Netherlands Letter Section Submerged Reef Systems on the Central Western Continental Shelf of India K.H. VORA and F. ALMEIDA National Institute of Oceanography, Dona Paula, Goa 403... 004 (India) (Revision accepted October 26, 1989) Abstract Vora, K.H. and Almeida, F., 1990. Submerged reef systems on the central western continental shelf of India. Mar. Geol., 91: 255-262. Echosounding and sidescan sonar data from the western...

  12. Sonograph patterns of the central western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, P.S.

    knolls. A transition zone with tonal variations is present between 40 and 60 m water depth. Ground-truth data sediment and rock distribution maps indicate depositional (inner shelf), nondepositional or erosional (outer shelf) environments and a...

  13. Magnetic surveys of the continental shelf off Visakhapatnam

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, T.C.S.; Murthy, K.S.R.

    shelf. Quantitative estimates made for the anomalies over the inner shelf using the graphical method and by computing the analytical signal suggest the existence of a fault in the nearshore region and a possible zone of heavy mineral concentration off...

  14. Holocene limestones of part of the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, R.R.; Hashimi, N.H.; Guptha, M.V.S.

    , while those on te upper continental slope (130-180 m) are algal bryozoan limestones. The limestones have a radiocarbon age ranging between 9,000 and 11,000 years. Depositional environmental on the continental shelf during the Holocene appears...

  15. Productivity, trophic levels and size spectra of zooplankton in northern Norwegian shelf regions

    Science.gov (United States)

    Zhou, Meng; Tande, Kurt S.; Zhu, Yiwu; Basedow, Sünnje

    2009-10-01

    Many studies have been conducted in northern Norwegian shelf regions to assess distributions and abundances of zooplankton in the last decade using towed Scanfish-conductivity, temperature and depth sensors (CTD)-optical plankton counter (OPC), and plankton nets. Significant progresses have been made in understanding dominant species, life histories and behavior, and in using size-structured data to identify dominant species in a certain size range. Using these Scanfish-CTD-OPC data, the analysis of zooplankton community size structures, compositions and their relationships with water types is made along the shelf region from Lofoten, North Cape to Varangerfjorden. From the relationships between the water types and zooplankton communities, the transports and exchanges of zooplankton communities between the Norwegian Coastal and Norwegian Atlantic Waters in regions near Malangsgrunnen and Nordvestbanken are examined. The biovolume (biomass) spectra are further analyzed for the productivity, trophic levels and seasonality of communities in these regions, indicating a steeper slope of the biovolume spectrum for a community dominated by herbivorous species in spring and a flatter slope for a community dominated by carnivorous-omnivorous species in winter. The comparison with the zooplankton biovolume spectra obtained in areas west of Antarctic Peninsula is made to examine and understand the differences in the zooplankton biovolume spectra, their trophic dynamics and potential human impacts between different regions.

  16. The Asymmetric Continental Shelf Wave in Response to the Synoptic Wind Burst in a Semienclosed Double-Shelf Basin

    Science.gov (United States)

    Qu, Lixin; Lin, Xiaopei; Hetland, Robert D.; Guo, Jingsong

    2018-01-01

    The primary goal of this study is to investigate the asymmetric structure of continental shelf wave in a semienclosed double-shelf basin, such as the Yellow Sea. Supported by in situ observations and realistic numerical simulations, it is found that in the Yellow Sea, the shelf wave response to the synoptic wind forcing does not match the mathematically symmetric solution of classic double-shelf wave theory, but rather exhibits a westward shift. To study the formation mechanism of this asymmetric structure, an idealized model was used and two sets of experiments were conducted. The results confirm that the asymmetric structure is due to the existence of a topographic waveguide connecting both shelves. For a semienclosed basin, such as the Yellow Sea, a connection at the end of the basin eliminates the potential vorticity barrier between the two shelves and hence plays a role as a connecting waveguide for shelf waves. This waveguide enables the shelf wave to propagate from one shelf to the other shelf and produces the asymmetric response in sea level and upwind flow evolutions.

  17. Morphology and sediment dynamics of the northern Catalan continental shelf, northwestern Mediterranean Sea

    Science.gov (United States)

    Durán, Ruth; Canals, Miquel; Sanz, José Luis; Lastras, Galderic; Amblas, David; Micallef, Aaron

    2014-01-01

    The northern Catalan continental shelf, in the northwestern Mediterranean Sea, extends along 200 km from the Cap de Creus submarine canyon to the Llobregat Delta, in the vicinity of the city of Barcelona. In this paper we present the results of a systematic investigation of this area by means of very high-resolution multibeam bathymetry to fully assess its morphological variability. The causative factors and processes determining such variability are subsequently interpreted. The shelf is divided in three segments by two prominent submarine canyons: the northernmost Roses Shelf is separated from the intermediate La Planassa Shelf by the La Fonera Canyon, while the boundary between the La Planassa Shelf and the southernmost Barcelona Shelf is marked by the Blanes Canyon. These two canyons are deeply incised in the continental margin, with their heads located at only 0.8 and 5 km from the shore, respectively. The seafloor character reflects the influence of external controlling factors on the geomorphology and sediment dynamics of the northern continental shelf of Catalonia. These factors are the geological setting, the volume and nature of sediment input, and the type and characteristics of processes leading to sediment redistribution, such as dense shelf water cascading (DSWC) and eastern storms. The interaction of all these factors determines sediment dynamics and allows subdividing the northern Catalan continental shelf into three segments: the erosional-depositional Roses Shelf to the north, the non-depositional La Planassa Shelf in the middle, and the depositional Barcelona Shelf to the south. Erosional features off the Cap de Creus Peninsula and an along-shelf subdued channel in the outer shelf illustrate prevailing sediment dynamics in the Roses segment, which is dominated by erosional processes, local sediment accumulations and the southward bypass of sediment. The rocky character of the seafloor immediately north of the Blanes Canyon head demonstrates that

  18. Norwegian oil and gas policy

    Energy Technology Data Exchange (ETDEWEB)

    Gjerde, B

    1978-04-01

    The Norwegian Minister of Oil and Energy explains the importance of integrating petroleum policy into the broad political picture because of Norway's economic situation. Since oil was found on the continental shelf 13 years ago, changes have been made in projected production levels to reflect the international recession and concerns over unemployment in Norway. Policies are aimed at keeping a constant activity in the petroleum sector through allocation of particular block development that will improve continental shelf mapping and encourage new deepwater exploration and development. He outlines licensing criteria and future exploratory activities. The report covers aspects of safety, transportation, and landing and the impacts of petroleum activities on Norwegian communities.

  19. Facts 2011 - The Norwegian petroleum sector; Fakta 2011 - norsk petroleumsverksemd

    Energy Technology Data Exchange (ETDEWEB)

    2011-07-15

    The publication provides a general overview of information regarding the petroleum activities on the Norwegian continental shelf. Content; Foreword; The petroleum sector - Norway's largest industry; Organisation of Norwegian petroleum activity; Government petroleum revenues; Exploration activities; Development and operations; Norwegian gas exports; Decommissioning; Research, technology and industrial development; Environmental considerations in the Norwegian petroleum sector; Petroleum resources; Fields in production; Fields under development; Future developments; Fields where production has ceased; Pipelines and onshore facilities. (AG)

  20. Facts 2010 - The Norwegian petroleum sector; Fakta 2010 - norsk petroleumsverksemd

    Energy Technology Data Exchange (ETDEWEB)

    2010-07-01

    The publication provides a general overview of information regarding the petroleum activities on the Norwegian continental shelf. Content; Foreword; The petroleum sector - Norway's largest industry; Organisation of Norwegian petroleum activity; Government petroleum revenues; Exploration activities; Development and operations; Norwegian gas exports; Decommissioning; Research, technology and industrial development; Environmental considerations in the Norwegian petroleum sector; Petroleum resources; Fields in production; Fields under development; Future developments; Fields where production has ceased; Pipelines and onshore facilities. (AG)

  1. Neotectonism - An offshore evidence from eastern continental shelf off Visakhapatnam

    Digital Repository Service at National Institute of Oceanography (India)

    Subrahmanyam, A.S.; Venkateswarlu, K.; Murthy, K.S.R.; Rao, M.M.M.; Rao, K.M.; Raju, Y.S.N.

    tremor provide evidence of Neo-tectonic activity in this regio. The epicentral region falls in a shallow marine environment ideal for generating a geophysical database for stable continental region earthquakes....

  2. Topographic features over the continental shelf off Visakhapatnam

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, T.C.S.; Machado, T.; Murthy, K.S.R.

    water depth and the continental shelfedge several interesting topographic features such as Terraces, Karstic structures associated with pinnacles and troughs and smooth dome shaped reef structures are recorded. The nature of these features...

  3. Transport and transfer rates in the waters of the continental shelf and slope: SEEP

    International Nuclear Information System (INIS)

    Biscaye, P.E.; Anderson, R.F.

    1993-01-01

    The overall Shelf Edge Exchange Processes (SEEP) Program, which began in 1980 or 1981, had as its goal the testing of a hypothesis with respect to the fate of particulate matter formed in and introduced into the waters of the continental shelf adjacent to the northern east coast of the US, i.e., the MAB. The original hypothesis was that a large proportion of the particles in general, and of the particulate organic carbon (POC) in particular, was exported from the shelf, across the shelf/slope break and front, into the waters of, and, to some degree, deposited in the sediments of the continental slope. This hypothesis was based on budgets of organic carbon and lead-210 that did not account for a large proportion of those species in the waters or sediments of the shelf, and on a carbon-rich band of sediments centered on the slope at ∼1,000 m water depth. The results of the first SEEP experiment, south of New England and Long Island (SEEP-1) suggested, but did not prove, that there was only a relatively small proportion of the carbon which was exported from the shelf to the slope. The objective of the second experiment -- SEEP-2 -- done under the subject grant, was to tighten the experiment in terms of the kinds of data collected, and to focus it more on the shelf and only the upper slope, where shelf-derived particles were thought to be deposited

  4. Sponge assemblages on the deep Mediterranean continental shelf and slope (Menorca Channel, Western Mediterranean Sea)

    Science.gov (United States)

    Santín, Andreu; Grinyó, Jordi; Ambroso, Stefano; Uriz, Maria J.; Gori, Andrea; Dominguez-Carrió, Carlos; Gili, Josep-Maria

    2018-01-01

    Sponge assemblages on continental shelves and slopes around the world have been known about for centuries. However, due to limitations of the traditional sampling systems, data about individual sponge species rather than assemblages have been reported. This study characterizes sponge assemblages over a wide bathymetric range ( 50-350 m depth) and covering the entire continental shelf and the upper slope of the Menorca Channel, an area soon to be declared a Marine Protected Area (MPA) as part of the Natura 2000 Network. Quantitative analysis of 85 video-transects (a total linear distance of 75 km), together with representative collections to confirm species identifications, allowed us to discriminate six major assemblages. Differences in the assemblages mainly corresponded to differences in substrate type and depth. On the inner continental shelf, a semi-sciaphilous Axinellid assemblage dominated the rocky outcrops. Maërl beds on the inner continental shelf were dominated by Haliclona (Reniera) mediterranea, whereas the horny sponge Aplysina cavernicola and several other haliclonids mostly dominated maërl beds and rocky substrates of the outer shelf. Soft sediments on the shelf break hosted a monospecific Thenea muricata assemblage, whereas rocky substrates of the shelf break were characterized by a mixture of encrusting, columnar and fan-shaped sponges. Finally, the upper slope was dominated by Hamacantha (Vomerula) falcula and the hexactinellid Tretodictyum reiswigi. Overall, sponge diversity showed its highest values above the shelf break, plummeting severely on the upper slope. Despite this diversity decrease, we found very high densities (> 70 ind./m2) of sponges over vast areas of both the shelf break and the upper slope.

  5. Sedimentation on the Valencia Continental Shelf: Preliminary results

    Science.gov (United States)

    Maldonado, Andres; Swift, Donald J. P.; Young, Robert A.; Han, Gregory; Nittrouer, Charles A.; DeMaster, David J.; Rey, Jorge; Palomo, Carlos; Acosta, Juan; Ballester, A.; Castellvi, J.

    1983-10-01

    Preliminary analysis of data collected during the course of a cooperative Spanish-United States investigation of the Valencia Shelf (western Mediterranean) reveals a storm-dominated, mud-accumulating sedimentary regime. Calcareous mud is accumulating seaward of a narrow band of shoreface sand and gravel. On the outer shelf the mud is enriched by a pelagic calcareous component. Preliminary 210Pb data from vertical profiles of box cores yield nominal accumulation rates from 2.6 mm y -1 near the Ebro Delta to 1.3 mm y -1 on the southern portion of the Valencia Shelf. Storm-current winnowing has resulted in the development of a biogenic lag sand over the mid-shelf mud in the northern part of the study area. Piston cores reveal a basal Holocene sand and gravel facies similar to that presently seen on the inner shelf. Upward-fining sequences on the central and outer shelf are inferred to result from the landward shift of lithotopes during the course of the Holocene transgression. These sequences are locally repeated, perhaps as the consequence of brief, local interludes of coastal progradation. Application of a diagnostic circulation model suggests that intense, downwelling coastal flows occur during winter northeastern storms. Storm activity has induced erosional shoreface retreat during the course of the Holocene transgression and has generated by this means the basal coarse facies observed in the piston cores. In the central part of the study area seaward of the Albufera Lagoon, the mud blanket thins to a layer several centimeters thick which is draped over a thickened (10 m) basal sand. The basal sand is molded into northwest trending ridges. The data are not sufficient to determine whether these are overstepped barriers, or submarine sand ridges formed by storm flows during the shoreface retreat process.

  6. Surficial sediments of the continental shelf off Karnataka

    Digital Repository Service at National Institute of Oceanography (India)

    Hashimi, N.H.; Nair, R.R.

    sediments occur betweenthe water depths of 15 to 50m corresponding to a distance of about 40 km from the coast. Beyond 50 m to the shelf edge are calcareous sands. Non-carbonate components of these deep water sands are essentially quartz, many of which...

  7. A Numerical Study of the Plata River Plume Along the Southeastern South American Continental Shelf

    Science.gov (United States)

    2005-01-01

    the effect of ambient shelf currents, level decreased by -0.20 and -0.55 in at the estuary and which would be essential in the determination of the 142...Res. SI 39, realistic wind and tidal forcing. J. Geophys. Res., 101 (submitted). (C2):3435-3455. Piola, A. R. 2002. El impacto del Plata sobre la...discharge on the continental impactos en el Plata y en la regi6n pampeana. Vol. 1. shelf. 1. Modeling the river plume and the inner shelf Assoc. Bonaerense de

  8. Decadal variability on the Northwest European continental shelf

    Science.gov (United States)

    Jones, Sam; Cottier, Finlo; Inall, Mark; Griffiths, Colin

    2018-02-01

    Decadal scale time series of the shelf seas are important for understanding both climate and process studies. Despite numerous investigations of long-term temperature variability in the shelf seas, studies of salinity variability are few. Salt is a more conservative tracer than temperature in shallow seas, and it can reveal changes in local hydrographic conditions as well as transmitted basin-scale changes. Here, new inter-annual salinity time series on the northwest European shelf are developed and a 13 year high resolution salinity record from a coastal mooring in western Scotland is presented and analysed. We find strong temporal variability in coastal salinity on timescales ranging from tidal to inter-annual, with the magnitude of variability greatest during winter months. There is little seasonality and no significant decadal trend in the coastal time series of salinity. We propose 4 hydrographic states to explain salinity variance in the shelf area west of Scotland based on the interaction between a baroclinic coastal current and wind-forced barotropic flow: while wind forcing is important, we find that changes in the buoyancy-driven flow are more likely to influence long-term salinity observations. We calculate that during prevailing westerly wind conditions, surface waters in the Sea of the Hebrides receive a mix of 62% Atlantic origin water to 38% coastal sources. This contrasts with easterly wind conditions, during which the mix is 6% Atlantic to 94% coastal sources on average. This 'switching' between hydrographic states is expected to impact nutrient transport and therefore modify the level of primary productivity on the shelf. This strong local variability in salinity is roughly an order of magnitude greater than changes in the adjacent ocean basin, and we infer from this that Scottish coastal waters are likely to be resilient to decadal changes in ocean climate.

  9. 75 FR 68824 - Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore Maryland-Request...

    Science.gov (United States)

    2010-11-09

    ... No. BOEM-2010-0038] Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore..., Interior. ACTION: RFI in Commercial Wind Energy Leasing Offshore Maryland, and Invitation for Comments from... construction of a wind energy project(s) on the Outer Continental Shelf (OCS) offshore Maryland. The BOEMRE...

  10. 77 FR 52353 - Right-of-Way Grant of Submerged Lands on the Outer Continental Shelf to Support Renewable Energy...

    Science.gov (United States)

    2012-08-29

    ... of Submerged Lands on the Outer Continental Shelf to Support Renewable Energy Development AGENCY... would be used to issue Outer Continental Shelf (OCS) renewable energy right-of-way (ROW) grants in order... renewable energy, but does not constitute a project easement. The ability of an ROW grantee to install such...

  11. 78 FR 47748 - Right-of-Way Grant of Submerged Lands on the Outer Continental Shelf to Support Renewable Energy...

    Science.gov (United States)

    2013-08-06

    ...-Way Grant of Submerged Lands on the Outer Continental Shelf to Support Renewable Energy Development... will use Form 0009 to issue a renewable energy right-of- way (ROW) grant on the Outer Continental Shelf....gov/Renewable-Energy Program/ Regulatory-Information/Index.aspx. DATES: The ROW grant form will be...

  12. 76 FR 48861 - Notice of Issuance of Final Outer Continental Shelf Air Permit for Anadarko Petroleum Corporation

    Science.gov (United States)

    2011-08-09

    ... Continental Shelf Air Permit for Anadarko Petroleum Corporation AGENCY: Environmental Protection Agency (EPA... final Outer Continental Shelf (OCS) air permit for Anadarko Petroleum Corporation (Anadarko). The permit... Petroleum Corporation regarding the project. EPA carefully reviewed each of the comments submitted and...

  13. Continental shelf landscapes of the southeastern United States since the last interglacial

    Science.gov (United States)

    Harris, M. Scott; Sautter, Leslie Reynolds; Johnson, Kacey L.; Luciano, Katherine E.; Sedberry, George R.; Wright, Eric E.; Siuda, Amy N. S.

    2013-12-01

    The wide, sediment-starved continental shelf and modern coastal areas of the southeastern United States retain well-preserved but scattered remnants of a submerged paleolandscape. This paper presents a conceptual model of stratigraphic deposition and landscape formation since the last interglacial on the continental shelf of South Carolina, with portions of North Carolina, Georgia, and Florida (USA). Data for this study include multibeam bathymetry surveys, sidescan sonar mosaics, high-resolution subbottom profiles, and ground-truth surveys from - 250 m to the modern tidewater region. Four bathymetric zones are recognized with eleven landforms and landform indicators. The described zones range in depths from the modern shoreline, across the shelf, and over the shelf edge to - 250 m MSL. Relative sea level curves are presented for the area and discussed in conjunction with cultural and climatic events. The potential for preservation of Paleoamerican sites is high at the shelf edge between - 130 m and - 45 m, with Archaic and later occupations likely in depths of less than - 25 m. Prominent vantage points for Paleoamericans (> 11 kya) would have existed at the shelf edge, and tidewater resources would have been available nearby for a period of almost 6 ka. Rapid transgression rates (> 60 km/ka) after the sea level rose over the shelf edge make preservation of tidewater sites less likely on the outer and middle shelf. Searches for the earliest Paleoamericans should focus on promontories at the edge of the shelf and along future discoveries of paleoincisions on the shelf. Mapping and delineating this paleolandscape and associated unconsolidated sedimentary deposits interspersed with rocky plains and ledges will continue to be a priority to marine archeologists, coastal managers, fishery scientists, and marine spatial planners over the next several decades.

  14. Morphology and stratal geometry of the Antarctic continental shelf: Insights from models

    Science.gov (United States)

    Cooper, Alan K.; Barker, Peter F.; Brancolini, Giuliano

    1997-01-01

    Reconstruction of past ice-sheet fluctuations from the stratigraphy of glaciated continental shelves requires understanding of the relationships among the stratal geometry, glacial and marine sedimentary processes, and ice dynamics. We investigate the formation of the morphology and the broad stratal geometry of topsets on the Antarctic continental shelf with numerical models. Our models assume that the stratal geometry and morphology are principally the results of time-integrated effects of glacial erosion and sedimentation related to the location of the seaward edge of the grounded ice. The location of the grounding line varies with time almost randomly across the shelf. With these simple assumptions, the models can successfully mimic salient features of the morphology and the stratal geometry. The models suggest that the current shelf has gradually evolved to its present geometry by many glacial advances and retreats of the grounding line to different locations across the shelf. The locations of the grounding line do not appear to be linearly correlated with either fluctuations in the 5 l s O record (which presumably represents changes in the global ice volume) or with the global sea-level curve, suggesting that either a more complex relationship exists or local effects dominate. The models suggest that erosion of preglacial sediments is confined to the inner shelf, and erosion decreases and deposition increases toward the shelf edge. Some of the deposited glacial sediments must be derived from continental erosion. The sediments probably undergo extensive transport and reworking obliterating much of the evidence for their original depositional environment. The flexural rigidity and the tectonic subsidence of the underlying lithosphere modify the bathymetry of the shelf, but probably have little effect on the stratal geometry. Our models provide several guidelines for the interpretation of unconformities, the nature of preserved topset deposits, and the

  15. Suspended particulate layers and internal waves over the southern Monterey Bay continental shelf: an important control on shelf mud belts?

    Science.gov (United States)

    Cheriton, Olivia M.; McPhee-Shaw, Erika E.; Shaw, William J.; Stanton, Timothy P.; Bellingham, James G.; Storlazzi, Curt D.

    2014-01-01

    Physical and optical measurements taken over the mud belt on the southern continental shelf of Monterey Bay, California documented the frequent occurrence of suspended particulate matter features, the majority of which were detached from the seafloor, centered 9–33 m above the bed. In fall 2011, an automated profiling mooring and fixed instrumentation, including a thermistor chain and upward-looking acoustic Doppler current profiler, were deployed at 70 m depth for 5 weeks, and from 12 to 16 October a long-range autonomous underwater vehicle performed across-shelf transects. Individual SPM events were uncorrelated with local bed shear stress caused by surface waves and bottom currents. Nearly half of all observed SPM layers occurred during 1 week of the study, 9–16 October 2011, and were advected past the fixed profiling mooring by the onshore phase of semidiurnal internal tide bottom currents. At the start of the 9–16 October period, we observed intense near-bed vertical velocities capable of lifting particulates into the middle of the water column. This “updraft” event appears to have been associated with nonlinear adjustment of high-amplitude internal tides over the mid and outer shelf. These findings suggest that nonlinear internal tidal motions can erode material over the outer shelf and that, once suspended, this SPM can then be transported shoreward to the middle and shallow sections of the mud belt. This represents a fundamental broadening of our understanding of how shelf mud belts may be built up and sustained.

  16. Biodiversity hotspots on the Dutch Continental Shelf: a marine strategy framework directive perspective

    NARCIS (Netherlands)

    Bos, O.G.; Witbaard, R.; Lavaleye, M.S.S.; Moorsel, G.W.N.M.; Teal, L.R.; Hal, van R.; Hammen, van der T.; Hofstede, ter R.; Bemmelen, van R.S.A.; Witte, R.H.; Geelhoed, S.C.V.; Dijkman, E.M.

    2011-01-01

    This report presenst hotspots of biodiversity for benthos, fish, birds, marine mammals and habitats on the Dutch Continental Shelf. These hotspots are based on a spatial application of biodiversity metrics developed in this study for the GES(Good Environmental Status)-descriptor 1 ‘Biological

  17. 77 FR 24734 - Outer Continental Shelf (OCS) Renewable Energy Program Leasing for Marine Hydrokinetic Technology...

    Science.gov (United States)

    2012-04-25

    ... DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management [Docket No. BOEM-2012-0011] Outer Continental Shelf (OCS) Renewable Energy Program Leasing for Marine Hydrokinetic Technology Testing Offshore Florida AGENCY: Bureau of Ocean Energy Management, Interior. ACTION: Notice of the Availability of an...

  18. Wind forcing controls on river plume spreading on a tropical continental shelf

    NARCIS (Netherlands)

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

    2015-01-01

    The Berau Continental Shelf is located close to the Equator in the Indonesian Archipelago, hosting a complex of coral reefs along its oceanic edge. The Berau coral reefs have a very high biodiversity, but the area is under serious risk due to river-derived nutrients and sediments. The region is

  19. Effects of energy-related activities on the Atlantic Continental Shelf

    Energy Technology Data Exchange (ETDEWEB)

    Manowitz, B [ed.

    1975-01-01

    Sixteen papers were presented and are announced separately. Coastal waters, continental shelf geology and aquatic ecosystems are studied for modelling basic data for assessment of possible environmental impacts from offshore energy development. Sediment transport and wave phenomena are modelled for understanding water pollution transport and diffusion. (PCS)

  20. Impacts of Outer Continental Shelf (OCS) development on recreation and tourism. Volume 5. Program logic manual

    Energy Technology Data Exchange (ETDEWEB)

    1987-04-01

    The final report for the project is presented in five volumes. This volume is the Programmer's Manual. It covers: a system overview, attractiveness component of gravity model, trip-distribution component of gravity model, economic-effects model, and the consumer-surplus model. The project sought to determine the impact of Outer Continental Shelf development on recreation and tourism.

  1. 76 FR 20367 - Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Off Delaware...

    Science.gov (United States)

    2011-04-12

    ... No. BOEM-2011-0008] Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Off... determination that no competitive interest exists in acquiring a commercial wind lease in the area offshore... a Request for Interest (RFI) in the Federal Register on April 26, 2010 (75 FR 21653). Bluewater Wind...

  2. 76 FR 14681 - Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore Massachusetts...

    Science.gov (United States)

    2011-03-17

    ... No. BOEM-2010-0063] Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore..., Regulation and Enforcement (BOEMRE), Interior. ACTION: Request for Interest (RFI) in Commercial Wind Energy... (BOEMRE) is reopening the comment period on the RFI in Commercial Wind Energy Leasing Offshore...

  3. 78 FR 36571 - North American Datum of 1983 (NAD 83) Outer Continental Shelf (OCS) Provisional Official...

    Science.gov (United States)

    2013-06-18

    ... DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management [MMAA104000] North American Datum of 1983 (NAD 83) Outer Continental Shelf (OCS) Provisional Official Protraction Diagram (OPDs) AGENCY... OPDs. SUMMARY: Notice is hereby given that effective with this publication two NAD 83-based OCS...

  4. Marine magnetic anomalies over the Direction bank, off Bombay western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    SubbaRaju, L.V.; Subrahmanyam, V.

    Total magnetic intensity data were collected over the Direction Bank, off Bombay on the western continental shelf of India and the isomagnetic anomaly map prepared at a contour interval of 25nT show NNW-SSE trend resemble those of the Dharwarians...

  5. 78 FR 59263 - Outer Continental Shelf Air Regulations Consistency Update for California

    Science.gov (United States)

    2013-09-26

    ..., Nitrogen dioxide, Nitrogen oxides, Outer continental shelf, Ozone, Particulate matter, Permits, Reporting... Solvents (Adopted 10/23/78) Rule 325 Crude Oil Production and Separation (Adopted 07/19/01) Rule 326... (Adopted 04/17/97) Rule 805 Air Quality Impact Analysis and Modeling (Adopted 04/17/97) Rule 808 New Source...

  6. Microbial origin of the phosphorites of the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.; Nair, R.R.

    Phosphatised algal nodules were recovered by dredging from the western continental shelf off Goa at depths ranging from 70 to 150 m. Energy dispersive X-ray analysis indicates that the phosphorus present in the algal nodules is confined to brownish...

  7. Clay mineral distribution in the continental shelf and slope off Saurashtra, West coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.

    Clay mineral distribution in the sediments of the west coast of India indicates that the illite and chlorite-rich sediments, derived from the Indus, occupy the continental shelf of the northern part of the Gulf of Kutch. Montmorillonite derived from...

  8. Recent foraminiferal assemblages from the continental shelf sediments of Madras, Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G.A.P.

    During the 15th cruise of INS Kistna, as part of the International Indian Ocean Expedition, several sub-surface samples were collected, (using LaFond-Dietz snapper), from the continental shelf region of the Bay of Bengal. Samples from two locations...

  9. Atlantic update, July 1986--June 1990: Outer Continental Shelf oil and gas activities

    Energy Technology Data Exchange (ETDEWEB)

    Karpas, R.M.; Gould, G.J.

    1990-10-01

    This report describes outer continental shelf oil and gas activities in the Atlantic Region. This edition of the Atlantic Update includes an overview of the Mid-Atlantic Planning Area and a summary of the Manteo Prospect off-shore North Carolina. 6 figs., 8 tabs.

  10. Transport and transfer rates in the waters of the continental shelf. Annual report

    International Nuclear Information System (INIS)

    Biscaye, P.E.

    1980-09-01

    The goal of govern project is to understand and quantify the processes that the transport and dispersal of energy-related pollutants introduced to the waters of the continental shelf and slope. The report is divided into sections dealing with processes associated with suspended solids; processes associated with sediments sinks for radionuclides and other pollutants; and spreading of water characteristics and species in solution

  11. Seasonal and interannual cross-shelf transport over the Texas and Louisiana continental shelf

    Science.gov (United States)

    Thyng, Kristen M.; Hetland, Robert D.

    2018-05-01

    Numerical drifters are tracked in a hydrodynamic simulation of circulation over the Texas-Louisiana shelf to analyze patterns in cross-shelf transport of materials. While the important forcing mechanisms in the region (wind, river, and deep eddies) and associated flow patterns are known, the resultant material transport is less well understood. The primary metric used in the calculations is the percent of drifters released within a region that cross the 100 m isobath. Results of the analysis indicate that, averaged over the eleven years of the simulation, there are two regions on the shelf - over the Texas shelf during winter, and over the Louisiana shelf in summer - with increased seasonal probability for offshore transport. Among the two other distinct regions, the big bend region in Texas has increased probability for onshore transport, and the Mississippi Delta region has an increase in offshore transport, for both seasons. Some of these regions of offshore transport have marked interannual variability. This interannual variability is correlated to interannual changes in forcing conditions. Winter transport off of the Texas shelf is correlated with winter mean wind direction, with more northerly winds enhancing offshore transport; summer transport off the Louisiana shelf is correlated with Mississippi River discharge.

  12. Flux of energy and essential elements through the continental shelf ecosystem. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Pomeroy, L.R.

    1981-11-30

    There are three distinct but not mutually exclusive areas of research in this contract, studies of intrusions of the west wall of the Gulf Stream onto the outer continental shelf, studies of the flux of materials across nearshore density fronts, and advances in understanding of the planktonic food web of the continental shelf. Studies of frontal events on the outer and inner continental shelf involve distinctive physical and chemical regimes and have proven to require distinctive biological approaches. The studies of the food web run through our work on both of the frontal regimes, but certain aspects have become subjects in their own right. We have developed a simulation model of the flux of energy through the continental shelf food web which we believe to be more realistic than previous ones of its type. We have examined several of the many roles of dissolved organic compounds in sea water which originate either from release by phytoplankton, digestive processes or metabolites of zooplankton, or extracellular digestion of microorganisms. Methods have been developed under this contract to measure both the chelating capacity of naturally occurring organic materials and the copper concentration in the water. It has been possible to characterize the effects, both toxic and stimulatory, of copper on photosynthesis of naturally occurring phytoplankton populations. It is possible to characterize in considerable detail the course of biological events associated with meanders of the Gulf Stream. We are now in a position to explain the limits to biological productivity of the outer continental shelf of the southeastern US and the reasons why that biological production moves through the food web in the characteristic way that it does.

  13. Nutrient regeneration and oxygen demand in Bering Sea continental shelf sediments

    Science.gov (United States)

    Rowe, Gilbert T.; Phoel, William C.

    1992-04-01

    Measurements of seabed oxygen demand and nutrient regeneration were made on continental shelf sediments in the southeast Bering Sea from 1 to 15 June 1981. The mean seabed oxygen demand was relatively modest (267 μM O 2 m -2 h -1), equivalent to a utilization of 60 mg organic carbon m -2 day -1. The seasonal build up of ammonium over the mid-shelf domain was generated at least in part by the bottom biota, as previously suggested ( WHITLEDGEet al., 1986 , Continental Shelf Research, 5, 109-132), but on the outer shelf nitrate replaced ammonium as the dominant inorganic nitrogen compound that was regenerated from the sediments. Comparison of oxygen consumption with the organic matter in sedimenting particulate matter (sampled with sediment traps) could imply that benthic processes were not accounting for the fate of considerable quantities of organic matter. Benthic oxygen demand rates, however, probably lag behind the input of the spring bloom to the bottom, thus extending the remineralization process out over time. Consumption by small microheterotrophs in the water column was also a likely sink, although shelf export and advective transport north were possible as well. Estimated nitrification rates in surface sediments could account for only a small fraction of the abrupt increase in nitrate observed in the water column over the shelf just prior to the spring bloom.

  14. Significance of peat on the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Mascarenhas, A.

    24 and 31 meters. The cores were subsampled depending upon the lithology. A core off Karwar was chosen for geochemical analyses. Calcium carbonate was determined using a 'KarbonatBombe' (Muller and Gastner, 1971). Organic carbon and sulfur were... the present sea level; it is found up to 27 km from the coast. The resulls suggest that peat on the shelf occurs as layers of restricted thickness (2 to 30 em) with a limited lateral distribution and hence appear to be impersistent layers. A strong hydrogen...

  15. Operating costs on Norwegian fields

    International Nuclear Information System (INIS)

    Sunnevaag, K.; Nansve, A.H.

    1992-09-01

    In this report we summarize some of the findings in a project for A/S Norske Shell, where the objective was to find trends in the development of operating expenditures on the Norwegian Continental Shelf if any, and to explain these. We also present a short compilation of articles on the subject. 23 refs., 13 figs

  16. Sound Propagation from the Continental Slope to the Continental Shelf: Remote Sensing Component

    National Research Council Canada - National Science Library

    Kelly, Kathryn

    2000-01-01

    ... along the East Coast of North America. The AVHRR images were used to show the location and orientation of the shelf I/slope front and the altimeter was used to study the fluctuations of the geostrophic currents...

  17. Biological, physical and chemical properties at the Subtropical Shelf Front Zone in the SW Atlantic Continental Shelf

    Science.gov (United States)

    Muelbert, José H.; Acha, Marcelo; Mianzan, Hermes; Guerrero, Raúl; Reta, Raúl; Braga, Elisabete S.; Garcia, Virginia M. T.; Berasategui, Alejandro; Gomez-Erache, Mónica; Ramírez, Fernando

    2008-07-01

    The physical aspects of the Subtropical Shelf Front (STSF) for the Southwest Atlantic Continental Shelf were previously described. However, only scarce data on the biology of the front is available in the literature. The main goal of this paper is to describe the physical, chemical and biological properties of the STSF found in winter 2003 and summer 2004. A cross-section was established at the historically determined location of the STSF. Nine stations were sampled in winter and seven in summer. Each section included a series of conductivity-temperature-depth (CTD) stations where water samples from selected depths were filtered for nutrient determination. Surface samples were taken for chlorophyll a (Chl- a) determination and plankton net tows carried out above and below the pycnocline. Results revealed that winter was marked by an inner-shelf salinity front and that the STSF was located on the mid-shelf. The low salinity waters in the inner-shelf indicated a strong influence of freshwater, with high silicate (72 μM), suspended matter (45 mg l -1), phosphate (2.70 μM) and low nitrate (1.0 μM) levels. Total dissolved nitrogen was relatively high (22.98 μM), probably due to the elevated levels of organic compound contribution close to the continental margin. Surface Chl -a concentration decreased from coastal well-mixed waters, where values up to 8.0 mg m -3 were registered, to offshore waters. Towards the open ocean, high subsurface nutrients values were observed, probably associated to South Atlantic Central Waters (SACW). Zooplankton and ichthyoplankton abundance followed the same trend; three different groups associated to the inner-, mid- and outer-shelf region were identified. During summer, diluted waters extended over the shelf to join the STSF in the upper layer; the concentration of inorganic nutrients decreased in shallow waters; however, high values were observed between 40 and 60 m and in deep offshore waters. Surface Chl -a ranged 0.07-1.5 mg m -3

  18. What kind of oil company do we need? Maturity and industrial structure on the Norwegian Shelf

    International Nuclear Information System (INIS)

    Noreng, Oeystein

    1998-01-01

    After many years with relatively high oil prices and moderately good oil discoveries, there is today an investment pressure on the Shelf. Many current development projects concern smaller discoveries made a long time ago. Thus the present rapid development depletes a capital of discoveries made at an early phase when the Norwegian Shelf was less mature. On this background, this presentation suggests that perhaps Norway, as a mature oil province, may not need the same kind of oil companies that dominated the petroleum activities during the development to maturity. It is experienced internationally that the various phases in the development of an oil province require different competence and thus different companies. Less oil has been found the last years than what has been produced. The command is now to find more oil. The question is how and by what company. Advantages and disadvantages are discussed for four categories of companies: (1) state companies, (2) large multinational, (3) independent, and (4) small newcomers. A section on maturing and the interest of the state as the property owner discusses the processes from large-scale operation to diversity, and maturing and the need for selective competence and low costs. Finally the paper discusses the negotiation policy of the state, political instruments and the company structure and reviews some experience from U.S.A. and UK. 1 table

  19. Radiocarbon dates of sediment cores from inner continental shelf off Taingapatnam, southwest coast of India

    International Nuclear Information System (INIS)

    Nambiar, A.R.; Rajagopalan, G.

    1995-01-01

    Radiocarbon dating of carbonized wood samples from three sediment cores from the inner continental shelf off Taingapatnam, in the southwestern coast of India, indicates ages in the bracket 8400-9400 YBP. These radiometric ages correlate well with the ages of carbonized wood from inner continental shelf off Ponnani, Kerala and Karwar, Karnataka. The occurrence of carbonized wood in widely spread offshore areas probably represents a regional transgressive event in the west coast which resulted in submergence and destruction of coastal mangroves. The rate of sedimentation in the study area varies between 0.12 and 0.37 mm/yr, much lower than those reported from shelf areas north of Mangalore. The slow accumulation of sediments in the southern parts of the western continental shelf of India, as exemplified from the present study, may be due to very poor discharge and low bed load sediments of the west-flowing small rivers of this part of the peninsula and low concentration of suspended particulate matter in them. (author). 24 refs., 2 tabs., 2 figs

  20. Denitrification pathways and rates in the sandy sediments of the Georgia continental shelf, USA

    Directory of Open Access Journals (Sweden)

    Ingall Ellery

    2005-02-01

    Full Text Available Denitrification in continental shelf sediments has been estimated to be a significant sink of oceanic fixed nitrogen (N. The significance and mechanisms of denitrification in organic-poor sands, which comprise 70% of continental shelf sediments, are not well known. Core incubations and isotope tracer techniques were employed to determine processes and rates of denitrification in the coarse-grained, sandy sediments of the Georgia continental shelf. In these sediments, heterotrophic denitrification was the dominant process for fixed N removal. Processes such as coupled nitrification-denitrification, anammox (anaerobic ammonium oxidation, and oxygen-limited autotrophic nitrification-denitrification were not evident over the 24 and 48 h time scale of the incubation experiments. Heterotrophic denitrification processes produce 22.8–34.1 μmole N m-2 d-1 of N2 in these coarse-grained sediments. These denitrification rates are approximately two orders of magnitude lower than rates determined in fine-grained shelf sediments. These lower rates may help reconcile unbalanced marine N budgets which calculate global N losses exceeding N inputs.

  1. Mean hydrography on the continental shelf from 26 repeat glider deployments along Southeastern Australia

    Science.gov (United States)

    Schaeffer, Amandine; Roughan, Moninya; Austin, Tim; Everett, Jason D.; Griffin, David; Hollings, Ben; King, Edward; Mantovanelli, Alessandra; Milburn, Stuart; Pasquer, Benedicte; Pattiaratchi, Charitha; Robertson, Robin; Stanley, Dennis; Suthers, Iain; White, Dana

    2016-08-01

    Since 2008, 26 glider missions have been undertaken along the continental shelf of southeastern Australia. Typically these missions have spanned the continental shelf on the inshore edge of the East Australian Current from 29.5-33.5°S. This comprehensive dataset of over 33,600 CTD profiles from the surface to within 10 m of the bottom in water depths ranging 25-200 m provides new and unprecedented high resolution observations of the properties of the continental shelf waters adjacent to a western boundary current, straddling the region where it separates from the coast. The region is both physically and biologically significant, and is also in a hotspot of ocean warming. We present gridded mean fields for temperature, salinity and density, but also dissolved oxygen and chlorophyll-a fluorescence indicative of phytoplankton biomass. This data will be invaluable for understanding shelf stratification, circulation, biophysical and bio-geochemical interactions, as well as for the validation of high-resolution ocean models or serving as teaching material.

  2. Relict sand waves in the continental shelf of the Gulf of Valencia (Western Mediterranean)

    Science.gov (United States)

    Albarracín, Silvia; Alcántara-Carrió, Javier; Montoya-Montes, Isabel; Fontán-Bouzas, Ángela; Somoza, Luis; Amos, Carl L.; Salgado, Jorge Rey

    2014-10-01

    The presence of fossil or relict bedforms is common in the Quaternary fill of modern continental shelf due to sea level oscillations, tectonic subsidence and migration of associated sedimentary facies. The continental margin of the Gulf of Valencia has been strongly influenced by glacio-eustasy and neotectonics. High-resolution multibeam bathymetry data, seismic reflection profiles and box core samples were collected across the continental shelf of the Gulf of Valencia during the DERIVA cruises carried out in 2010 and 2011. The integrated analysis of this data set and high-resolution mapping of the relict bedforms on the Valencian continental shelf, ranging between 50 and 90 m allowed the study of previously identified system of sand waves located in front of the present-day Albufera de Valencia lagoon. The system is composed of 27 ridges with a NNE-SSW orientation, i.e. oblique to the present shoreline, in which the lateral horns point backwards. These sand waves can reach 10 m in height and 3 km in length resulting in a maximum slope of 6°. According to seismic stratigraphic and relative sea level curve reconstructions, these sand waves were formed during the Younger Dryas (~ 12-10 ky BP). Consequently, they have been classified as Holocene sand waves associated with coastal sedimentary evolution.

  3. Food supply mechanisms for cold-water corals along a continental shelf edge

    Science.gov (United States)

    Thiem, Øyvind; Ravagnan, Elisa; Fosså, Jan Helge; Berntsen, Jarle

    2006-05-01

    In recent years it has been documented that deep-water coral reefs of the species Lophelia pertusa are a major benthic habitat in Norwegian waters. However, basic information about the biology and ecology of this species is still unknown. Lophelia live and thrive under special environmental conditions of which factors such as temperature, water depth, water movement and food supply are important. The present work explores the hypothesis that Lophelia forms reefs in places where the encounter rate of food particles is sufficiently high and stable over long periods of time for continuous growth. This is done by relating the distribution of reefs with the results of numerical ocean modelling. Numerical simulations have been performed with an idealized bottom topography similar to what is found outside parts of the Norwegian coast. In the simulations the model is first forced with an along slope jet and then with an idealized atmospheric low pressure. The model results show that the encounter rates between the particles and the water layer near the seabed are particularly high close to the shelf break. This may indicate that many Lophelia reefs are located along the shelf edges because the supply of food is particularly good in these areas. A sensitivity study of the particle supply in the area close to the seabed for increasing latitude has also been done. This shows that the Ekman transport in the benthic layer tends to create a steady supply of food for benthic organisms near the shelf edge away from the equator.

  4. Architecture and sedimentary processes on the mid-Norwegian continental slope: A 2.7 Myr record from extensive seismic evidence

    Science.gov (United States)

    Montelli, A.; Dowdeswell, J. A.; Ottesen, D.; Johansen, S. E.

    2018-07-01

    Quaternary architectural evolution and sedimentary processes on the mid-Norwegian continental slope are investigated using margin-wide three- and two-dimensional seismic datasets. Of ∼100,000 km3 sediments delivered to the mid-Norwegian shelf and slope over the Quaternary, ∼75,000 km3 comprise the slope succession. The structural high of the Vøring Plateau, characterised by initially low (∼1-2°) slope gradients and reduced accommodation space, exerted a strong control over the long-term architectural evolution of the margin. Slope sediment fluxes were higher on the Vøring Plateau area, increasing up to ∼32 km3 ka-1 during the middle Pleistocene, when fast-flowing ice streams advanced to the palaeo-shelf edge. Resulted in a more rapid slope progradation on the Vøring Plateau, these rates of sediment delivery are high compared to the maximum of ∼7 km3 ka-1 in the adjacent sectors of the slope, characterised by steeper slope (∼3-5°), more available accommodation space and smaller or no palaeo-ice streams on the adjacent shelves. In addition to the broad-scale architectural evolution, identification of more than 300 buried slope landforms provides an unprecedented level of detailed, process-based palaeoenvironmental reconstruction. Channels dominate the Early Pleistocene record (∼2.7-0.8 Ma), during which glacimarine sedimentation on the slope was influenced by dense bottom-water flow and turbidity currents. Morphologic signature of glacigenic debris-flows appear within the Middle-Late Pleistocene (∼0.8-0 Ma) succession. Their abundance increases towards Late Pleistocene, marking a decreasing role for channelized turbidity currents and dense water flows. This broad-scale palaeo-environmental shift coincides with the intensification of Northern Hemispheric glaciations, highlighting first-order climate control on the sedimentary processes in high-latitude continental slopes.

  5. Amazon water lenses and the influence of the North Brazil Current on the continental shelf

    Science.gov (United States)

    Prestes, Yuri O.; Silva, Alex Costa da; Jeandel, Catherine

    2018-05-01

    The exchange processes on the Amazon continental shelf in northern Brazil are subject to complex interactions that involve forcings derived from distinct sources. The Amazon shelf is a unique and highly dynamic environment in which considerable discharge of freshwater enters the Atlantic Ocean, producing extensive Amazon Water Lenses (AWL). In addition to the presence of the AWL, the shelf is influenced by the semidiurnal oscillations of the tides and the strong North Brazil Current (NBC), a boundary current of the western Atlantic. The present study was based primarily on the influence of the freshwater input and the NBC on the shelf and the Amazon Shelf Break (ASB) off the mouth of the Pará River. For this purpose, hydrographic and hydrodynamic data were obtained by moorings of the AMANDES Project (April-July 2008), located on the Amazon shelf and the ASB. Spectral analysis and the continuous wavelet transform were applied to define tidal (high frequency/short period) and subtidal (low frequency/long period) signals. The results indicated that on both the shelf and the break, the semidiurnal tides are responsible for the residual landward transport and are predominantly across-shelf. Low-frequency motions in the synoptic bands and the AWL are related to spatial changes in the velocity field, mainly on the ASB in the along-shelf direction. The flow of the NBC can be interpreted as an along-shelf low-frequency oscillation capable of altering the spatial configuration of the velocity field, although its influence is perceived only in the absence of the AWL.

  6. Continental shelf sediment dynamics in the Anthropocene: A global shift

    Science.gov (United States)

    Oberle, Ferdinand K. J.; Puig, Pere; Martin, Jacobo

    2017-04-01

    Recent technological advances in remote sensing and deep marine sampling have revealed the extent and magnitude of the anthropogenic impacts to the seafloor. In particular, bottom trawling, a fishing technique consisting of dragging a net and fishing gear over the seafloor to capture bottom-dwelling living resources has gained attention due to its destructive effects on the seabed. Trawling gear produces acute impacts on biota and the physical substratum of the seafloor by disrupting the sediment column structure, overturning boulders, resuspending sediments and imprinting deep scars on muddy bottoms. Also, the repetitive passage of trawling gear over the same areas creates long-lasting, cumulative impacts that modify the cohesiveness and texture of sediments. It can be asserted nowadays that due to its recurrence, mobility and wide geographical extent, industrial trawling has become a major force driving seafloor change and affecting not only its physical integrity on short spatial scales but also imprinting measurable modifications to the geomorphology of entire continental margins.

  7. Minimum distribution of subsea ice-bearing permafrost on the US Beaufort Sea continental shelf

    Science.gov (United States)

    Brothers, Laura L.; Hart, Patrick E.; Ruppel, Carolyn D.

    2012-01-01

    Starting in Late Pleistocene time (~19 ka), sea level rise inundated coastal zones worldwide. On some parts of the present-day circum-Arctic continental shelf, this led to flooding and thawing of formerly subaerial permafrost and probable dissociation of associated gas hydrates. Relict permafrost has never been systematically mapped along the 700-km-long U.S. Beaufort Sea continental shelf and is often assumed to extend to ~120 m water depth, the approximate amount of sea level rise since the Late Pleistocene. Here, 5,000 km of multichannel seismic (MCS) data acquired between 1977 and 1992 were examined for high-velocity (>2.3 km s−1) refractions consistent with ice-bearing, coarse-grained sediments. Permafrost refractions were identified along sea ice-bearing permafrost, which does not extend seaward of 30 km offshore or beyond the 20 m isobath.

  8. Adequacy of environmental information for outer continental shelf oil and gas decisions: Georges Bank. Final report

    International Nuclear Information System (INIS)

    1991-01-01

    Georges Bank, a large, shallow marine bank with important fishery resources and possibly important oil and gas resources, lies east of Massachusetts in the territorial waters of both the United States and Canada. The Department of the Interior has planned since 1974 to lease parts of the north Atlantic outer continental shelf (OCS)--including part of Georges Bank--for oil and gas exploration. As a result of public concern about the environmental impacts of oil and gas production on the U.S. OCS, Congress declared a moratorium on drilling on Georges Bank and an area to the southwest. The report--by the NRC's Committee to Review the Outer Continental Shelf Environmental Studies Program and its panels on physical oceanography, ecology, and socioeconomics--reviews the adequacy of information bearing on the potential environmental impacts of OCS oil and gas activities for the Georges Bank sale area

  9. The European water framework directive: A challenge for nearshore, coastal and continental shelf research

    Science.gov (United States)

    Borja, Ángel

    2005-09-01

    The European Water Framework Directive (WFD) establishes a framework for the protection of groundwater, inland surface waters, estuarine waters, and coastal waters. The WFD constitutes a new view of the water resources management in Europe because, for the first time, water management is: (i) based mainly upon biological and ecological elements, with ecosystems being at the centre of the management decisions; (ii) applied to European water bodies, as a whole; and (iii) based upon the whole river basin, including also the adjacent coastal area. Although the marine water bodies affected by the WFD relate to only 19.8% of the whole of the European continental shelf, its application constitutes a challenge and an opportunity in nearshore, coastal and continental shelf research. This contribution highlights some of the main tasks and the research to be undertaken in the coming years, proposing investigations into: typologies; physico-chemical processes; indicator species; reference conditions; integration of the quality assessment; methodologies in determining ecological status, etc.

  10. Transport and transfer rates in the waters of the continental shelf. Annual report

    International Nuclear Information System (INIS)

    Biscaye, P.E.; Broecker, W.S.; Feely, H.W.; Gerard, R.D.

    1976-04-01

    The report is to the Energy Research and Development Administration on accomplishments of the Lamont-Doherty Geological Observatory geochemistry and physical oceanography groups during the 1975-1976 funding period on grant E(11-1)2185. Goals are to obtain detailed, quantitative knowledge of the rates of mixing within coastal waters of the New York Bight and across the continental slope and the exchange of water masses and species transported within them between shelf and Atlantic Ocean waters. The research is aimed at understanding the chemical, physical, and biological processes which control the origin, dispersal, and fate of particulate matter and trace metals, and to ultimately model the impact of energy related pollutants on the continental shelf

  11. Accident statistics for fixed offshore units on the UK Continental Shelf 1980-2001

    International Nuclear Information System (INIS)

    Funnemark, E.; Young, E.

    2003-01-01

    Comprehensive statistics for the accidents and incidents on fixed units engaged in oil and gas exploration/exploitation on the UK continental shelf between 1980 and 2001 have been assembled from other databases. The data includes nature of the incident, type of unit involved, geographical area and time period. The results cover a total of 5,563 events which are described as accidents, hazardous situations or near misses

  12. Gas-charged sediments on the inner continental shelf off western India

    Digital Repository Service at National Institute of Oceanography (India)

    Karisiddaiah, S.M.; Veerayya, M.; Vora, K.H.; Wagle, B.G.

    the enormous reserves of methane hydrates in the Arctic (Nisbet, 1989) and elsewhere. Owens et al. (1991) observed that the northern Arabian Sea is an oceanic region of unusually high methane concentrations and fluxes to the atmo- sphere. In view... The western continental shelf of India between IO°N and 22°N is bordered by the Deccan Traps (volcanic rocks) of Cretaceous age towards the north of Goa, whereas Peninsular gneisses, char- nockites and various schistose formations of Archaean age...

  13. The continental shelf benthic ecosystem: Current status, agents for change and future prospects

    OpenAIRE

    Hall, S.J.

    2002-01-01

    Metadata only record Continental shelf benthic ecosystems play an important role in the economy of many coastal states through the provision of food, non-living resources and through control of climate. Changes in the status of these ecosystems, through either natural or human-induced environmental drivers can be expected to have important economic and social consequences. Agents that could induce change include climate and oceanography, hydrology (river discharge), land-use and waste disp...

  14. Nineteenth-century collapse of a benthic marine ecosystem on the open continental shelf.

    Science.gov (United States)

    Tomašových, Adam; Kidwell, Susan M

    2017-06-14

    The soft-sediment seafloor of the open continental shelf is among the least-known biomes on Earth, despite its high diversity and importance to fisheries and biogeochemical cycling. Abundant dead shells of epifaunal suspension-feeding terebratulid brachiopods ( Laqueus ) and scallops on the now-muddy mainland continental shelf of southern California reveal the recent, previously unsuspected extirpation of an extensive offshore shell-gravel ecosystem, evidently driven by anthropogenic siltation. Living populations of attached epifauna, which formerly existed in a middle- and outer-shelf mosaic with patches of trophically diverse muds, are restricted today to rocky seafloor along the shelf edge and to the sandier shelves of offshore islands. Geological age-dating of 190 dead brachiopod shells shows that (i) no shells have been produced on the mainland shelf within the last 100 years, (ii) their shell production declined steeply during the nineteenth century, and (iii) they had formerly been present continuously for at least 4 kyr. This loss, sufficiently rapid (less than or equal to 100 years) and thorough to represent an ecosystem collapse, coincides with intensification of alluvial-plain land use in the nineteenth century, particularly livestock grazing. Extirpation was complete by the start of twentieth-century urbanization, warming, bottom fishing and scientific surveys. The loss of this filter-feeding fauna and the new spatial homogeneity and dominance of deposit- and detritus-feeders would have altered ecosystem functioning by reducing habitat heterogeneity and seawater filtering. This discovery, attesting to the power of this geological approach to recent ecological transitions, also strongly increases the spatial scope attributable to the negative effects of siltation, and suggests that it has been under-recognized on continental shelves elsewhere as a legacy of coastal land use. © 2017 The Author(s).

  15. Sources of organic carbon in the Portuguese continental shelf sediments during the Holocene period

    International Nuclear Information System (INIS)

    Burdloff, D.; Araujo, M.F.; Jouanneau, J.-M.; Mendes, I.; Monge Soares, A.M.; Dias, J.M.A.

    2008-01-01

    Organic C (OC) and total N (TN) concentrations, and stable isotope ratios (δ 13 C) in muddy deposit sediments of the Northern and Southern Portuguese continental shelf were used to identify sources of fine-sized organic matter ( 13 C ranging, respectively, from 8.5 to 21 and from -22.4 per mille to -27 per mille ). Intense supplies to the Guadiana continental shelf of fine terrigenous particles during the Younger-Dryas Event are closely linked with higher OC/TN values and lower δ 13 C ratios. During the postglacial transgression phase, an increasing contribution of marine supplies (up to 80%) occurred. Higher δ 13 C (up to -22.4 per mille ) values and low OC/TN ratios (down to 8.5) are found as the sea level approaches the current one. The Upper Holocene records emphasize the return to enhanced terrestrial supplies except for the Little Climatic Optimum between the 11th and 15th centuries AD. This climatic event is especially obvious in the three cores as a return to marine production and a decrease in terrestrial sediment supply to the continental shelf. The return to a cooling event, the Little Ice Age, between the 15th and 19th centuries AD, is mirrored by decreased terrigenous supplies in core KSGX 57. Gradually increasing sedimentation in estuaries, as well as formation of coastal dune fields, have been hypothesized on the basis of increasing δ 13 C and decreasing OC, TN and OC/TN values

  16. Temporal coherence of the acoustic field forward propagated through a continental shelf with random internal waves.

    Science.gov (United States)

    Gong, Zheng; Chen, Tianrun; Ratilal, Purnima; Makris, Nicholas C

    2013-11-01

    An analytical model derived from normal mode theory for the accumulated effects of range-dependent multiple forward scattering is applied to estimate the temporal coherence of the acoustic field forward propagated through a continental-shelf waveguide containing random three-dimensional internal waves. The modeled coherence time scale of narrow band low-frequency acoustic field fluctuations after propagating through a continental-shelf waveguide is shown to decay with a power-law of range to the -1/2 beyond roughly 1 km, decrease with increasing internal wave energy, to be consistent with measured acoustic coherence time scales. The model should provide a useful prediction of the acoustic coherence time scale as a function of internal wave energy in continental-shelf environments. The acoustic coherence time scale is an important parameter in remote sensing applications because it determines (i) the time window within which standard coherent processing such as matched filtering may be conducted, and (ii) the number of statistically independent fluctuations in a given measurement period that determines the variance reduction possible by stationary averaging.

  17. Atlantic water variability on the SE Greenland continental shelf and its relationship to SST

    Science.gov (United States)

    Sutherland, D. A.; Straneo, F.; Rosing-Asvid, A.; Stenson, G.; Davidson, F. J.; Hammill, M.

    2012-12-01

    Interaction of warm, Atlantic-origin water (AW) and colder, polar origin water (PW) advecting southward in the East Greenland Current (EGC) influences the heat content of water entering Greenland's outlet glacial fjords. Here we use depth and temperature data derived from deep-diving seals to map out water mass variability across the continental shelf and to augment existing bathymetric products. We find two dominant modes in the vertical temperature structure: a cold mode, with the typical AW/PW layering observed in the EGC, and a warm mode, where AW is present throughout the water column. The prevalence of these modes varies seasonally and spatially across the continental shelf, implying distinct AW pathways. In addition, we find that satellite sea surface temperatures (SST) correlate significantly with temperatures in the upper 50 m (R=0.54), but this correlation decreases with depth (R=0.22 at 200 m), and becomes insignificant below 250 m. Thus, care must be taken in using SST as a proxy for heat content, as AW mainly resides in these deeper layers. Regional map showing the location of all seal tracks originating from Canada and Greenland (stars). Tracks passing inside (red) or outside (blue) the SE Greenland region (black) were subdivided into continental shelf regions (green boxes) near Sermilik Fjord (SF), Cape Farewell (CF) and Kangerdlugssuaq Fjord (KG). GEBCO bathymetry is contoured at 200, 1000, 2000, and 3000 m.

  18. Statistics of Acoustic Pulse Signals Through Nonlinear Internal Waves on the Continental Shelf of the Northeastern South China Sea

    National Research Council Canada - National Science Library

    Reeves, Justin M

    2008-01-01

    ...) was conducted from 13 - 15 April 2005 on the continental shelf in the northeast portion of the South China Sea to study the effects of nonlinear internal waves on the transmission of a 400-Hz signal...

  19. Plankton community respiration, net ecosystem metabolism, and oxygen dynamics on the Louisiana continental shelf: implications for hypoxia

    Science.gov (United States)

    We conducted a multi-year study of the Louisiana continental shelf (LCS) to better understand the linkages between water column metabolism and the formation of hypoxia (dissolved oxygen respiration rates (WR) were measured on 10 cr...

  20. Carbon and oxygen dynamics on the Louisiana continental shelf: role of water column primary production and respiration

    Science.gov (United States)

    We conducted a multi-year study of the Louisiana continental shelf (LCS) to better understand the linkages between water column net metabolism and the formation of hypoxia (dissolved oxygen respiration (R) and primary p...

  1. Impact of Satellite Remote Sensing Data on Simulations of Coastal Circulation and Hypoxia on the Louisiana Continental Shelf

    Science.gov (United States)

    We estimated surface salinity flux and solar penetration from satellite data, and performed model simulations to examine the impact of including the satellite estimates on temperature, salinity, and dissolved oxygen distributions on the Louisiana continental shelf (LCS) near the ...

  2. Spatiotemporal chlorophyll-a dynamics on the Louisiana continental shelf derived from a dual satellite imagery algorithm

    Science.gov (United States)

    A monthly time series of remotely sensed chlorophyll-a (Chlars) over the Louisiana continental shelf (LCS) was developed and examined for its relationship to river discharge, nitrate concentration, total phosphorus concentration, photosynthetically available radiation (PAR), wind...

  3. Physical (Hydrography), chemical (CTD), and biological (Water Quality) processes of the Texas-Louisiana continental shelf, 2013 (NCEI Accession 0162440)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Two sets of CTD data were taken during the 2013 Shelfwide Hypoxia cruise off the Louisiana continental shelf. Hydrographic data were obtained with the LUMCON SeaBird...

  4. Heavy minerals in the sediments on the outer continental shelf between Vengurla and Mangalore on the west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Kidwai, R.M.; Nair, R.R.; Hashimi, N.H.

    Fifty-eight sediment samples from the outer continental shelf between Vengurla and Mangalore were analysed for heavy minerals consist of principally opaques, hornblende, epidote, garnet, sillimanite, hypersthene and zircon, with minor amounts...

  5. Dissolved inorganic nutrients and chlorophyll on the narrow continental shelf of Eastern Brazil

    Directory of Open Access Journals (Sweden)

    Gilmara Fernandes Eça

    2014-03-01

    Full Text Available The eastern Brazilian continental shelf is narrow and subject to the influence of a western boundary current system, presenting lower biological productivity than other regions. In this study, the distribution of water masses, dissolved inorganic nutrients, chlorophyll-a and total suspended solids (TSS on the inner shelf (< 35 m depth, between Itacaré and Canavieiras, eastern Brazil, is presented. Sampling surveys were carried out in March and August 2006 and March 2007. Tropical water (TW prevailed during March 2006 and August 2007 with the lower salinity waters (< 36 found in most samples taken in March 2007, reflecting the influence of continental outflow and rain in coastal waters. Low concentrations of dissolved inorganic nutrients and Chl-a found were typical of TW and results suggested that the inner shelf waters were depleted in dissolved inorganic nitrogen in August 2006 and March 2007, and in phosphate in March 2006, potentially affecting phytoplankton growth. Stratification of the water column was observed due to differences in dissolved nutrient concentrations, chlorophyll-a and TSS when comparing surface and bottom samples, possibly the result of a colder water intrusion and mixing on the bottom shelf and a deep chlorophyll maximum and/or sediment resuspension effect. Despite this stratification, oceanographic processes such as lateral mixing driven by the Brazil Current as well as a northward alongshore drift driven by winds and tides transporting Coastal Water can lead to an enhanced mixing of these waters promoting some heterogeneity in this oligotrophic environment.

  6. Clay sediment accumulation rates on the monsoon-dominated western continental shelf and slope region of India

    Digital Repository Service at National Institute of Oceanography (India)

    Borole, D.V.

    Clay accumulation rates shown in sediment cores from the nearshore to outer continental shelf and slope regions in water depths of 10-1246 m on the western continental margins of India were determined by the 210Pb dating technique. The 210Pb excess...

  7. Geochemical record of Holocene to Recent sedimentation on the Western Indus continental shelf, Arabian Sea

    Science.gov (United States)

    Limmer, David R.; BöNing, Philipp; Giosan, Liviu; Ponton, Camilo; KöHler, Cornelia M.; Cooper, Matthew J.; Tabrez, Ali R.; Clift, Peter D.

    2012-01-01

    We present a multiproxy geochemical analysis of two cores recovered from the Indus Shelf spanning the Early Holocene to Recent (<14 ka). Indus-23 is located close to the modern Indus River, while Indus-10 is positioned ˜100 km further west. The Holocene transgression at Indus-10 was over a surface that was strongly weathered during the last glacial sea level lowstand. Lower Holocene sediments at Indus-10 have higherɛNdvalues compared to those at the river mouth indicating some sediment supply from the Makran coast, either during the deposition or via reworking of older sediments outcropping on the shelf. Sediment transport from Makran occurred during transgressive intervals when sea level crossed the mid shelf. The sediment flux from non-Indus sources to Indus-10 peaked between 11 ka and 8 ka. A hiatus at Indus-23 from 8 ka until 1.3 ka indicates non-deposition or erosion of existing Indus Shelf sequences. HigherɛNdvalues seen on the shelf compared to the delta imply reworking of older delta sediments in building Holocene clinoforms. Chemical Index of Alteration (CIA), Mg/Al and Sr isotopes are all affected by erosion of detrital carbonate, which reduced through the Holocene. K/Al data suggest that silicate weathering peaked ca. 4-6 ka and was higher at Indus-10 compared to Indus-23. Fine-grained sediments that make up the shelf have geochemical signatures that are different from the coarser grained bulk sediments measured in the delta plain. The Indus Shelf data highlight the complexity of reconstructing records of continental erosion and provenance in marine settings.

  8. Variations in organic carbon fluxes from Long Island Sound to the Continental Shelf

    Science.gov (United States)

    Vlahos, P.; Whitney, M. M.

    2017-12-01

    Organic carbon balances for the Long Island Sound estuary over the years 2009-2012 are presented to assess the particulate and dissolved organic carbon contributions of the estuary to the adjacent shelf waters with respect to the Delaware and Chesapeake. Observations were coupled to a hydrodynamic model (ROMS) for both seasonal and annual estimates. During stratified summer periods, LIS was consistently a net exporter of OC to the continental shelf. LIS annual net carbon export however, varied with river flow. The heterotrophic or autotrophic nature of LIS also shifted seasonally and inter-annually. During the mass balance analysis period LIS ranged between net OC import from the continental shelf and heterotrophy in the lowest river flow year (2012) and net export of OC and autotrophy in the highest flow year (2011). Analysis suggests that LIS switches from net OC import to export when the annual river inputs exceed 19 km3 yr-1. Applying these thresholds to the annual river flow record suggests that net import occurred in 15% of the last 20 years and that LIS usually is a net exporter of OC (85%). Annually averaged LIS carbon export values based on river flow conditions over the last 20 yr are estimated at 56 ± 64 x 106 km3 yr-1. Analysis also suggests that LIS shifts from net heterotrophic to net autotrophic when annual river flow exceeds 26 km3 yr-1 (35% of the last 20 yr). Net heterotrophic conditions are most common, representing 65% of the last 20 yr.

  9. Temporal variability of the Circumpolar Deep Water inflow onto the Ross Sea continental shelf

    Science.gov (United States)

    Castagno, Pasquale; Falco, Pierpaolo; Dinniman, Michael S.; Spezie, Giancarlo; Budillon, Giorgio

    2017-02-01

    The intrusion of Circumpolar Deep Water (CDW) is the primary source of heat, salt and nutrients onto Antarctica's continental shelves and plays a major role in the shelf physical and biological processes. Different studies have analyzed the processes responsible for the transport of CDW across the Ross Sea shelf break, but until now, there are no continuous observations that investigate the timing of the intrusions. Also, few works have focused on the effect of the tides that control these intrusions. In the Ross Sea, the CDW intrudes onto the shelf in several locations, but mostly along the troughs. We use hydrographic observations and a mooring placed on the outer shelf in the middle of the Drygalski Trough in order to characterize the spatial and temporal variability of CDW inflow onto the shelf. Our data span from 2004 to the beginning of 2014. In the Drygalski Trough, the CDW enters as a 150 m thick layer between 250 and 400 m, and moves upward towards the south. At the mooring location, about 50 km from the shelf break, two main CDW cores can be observed: one on the east side of the trough spreading along the west slope of Mawson Bank from about 200 m to the bottom and the other one in the central-west side from 200 m to about 350 m depth. A signature of this lighter and relatively warm water is detected by the instruments on the mooring at bottom of the Drygalski Trough. High frequency periodic CDW intrusion at the bottom of the trough is related to the diurnal and spring/neap tidal cycles. At lower frequency, a seasonal variability of the CDW intrusion is noticed. A strong inflow of CDW is observed every year at the end of December, while the CDW inflow is at its seasonal minimum during the beginning of the austral fall. In addition an interannual variability is also evident. A change of the CDW intrusion before and after 2010 is observed.

  10. Nepheloid Layers: Origin and Development In A Narrow Continental Shelf (nw Portugal)

    Science.gov (United States)

    Oliveira, A.; Vitorino, J.; Rodrigues, A.; Jouanneau, J. M.; Weber, O.; Dias, J. A.

    A general hydrographic, nephelometric and sedimentological surveying of the NW Portuguese continental shelf and slope was undertaken, under winter and spring con- ditions in order to elaborate a conceptual model of suspended sediments (nepheloid layer) dynamics. Two major situations were found: 1) Spring/Summer - with northerly winds (upwelling) and low energetic wave regime that favour the deposition of sedi- ments. The northerly winds promote offshore transport in the surface nepheloid layer (SNL) and the establishment of a seasonal thermocline allow the expansion of the SNL to the west. The SNL can reach or even cross the shelf-break (50 km from coastline). Particulate organic carbon (POC) content in this layer highlights the higher contribution of biogenic particles (average concentration of 22%); 2) Winter, with southerly winds (downwelling) and high energetic wave regime that favour mid- shelf sediments resuspension and offshore transport in the bottom nepheloid layer (BNL). In the shelf-break the BNL detached to form intermediate nepheloid layers (INL). The SNL is restricted to the inner shelf. The effect of southerly winds gener- ates shoreward Ekman transport and detains the offshore westward extension of this layer even during high river run-off periods. The POC content indicates a dominance of litogenic particles in suspension (average concentration of 8%). Over the mid- and inner-shelf the dominant resuspension mechanism is associated with surface waves (Vitorino et al., 2002). Estimates based on wave measurements at mid-shelf (86m depth) suggested that, in winter, the wave shear velocity frequently exceeds 1 cm/s, assumed as the critical shear velocity for the resuspension of the fine grained sedi- ments (34m) of the bottom cover. Storm events, such as the one observed in November 1996 easily increase the wave shear velocities over 3 cm/s, leading to the increase of the BNL thickness (20-30m) (Vitorino et al., 2002; Oliveira et al., 2002). Low

  11. Quaternary nanofossils on the Brazilian continental shelf; Nanofosseis calcarios do quaternario da margem continental brasileira

    Energy Technology Data Exchange (ETDEWEB)

    Antunes, Rogerio Loureiro [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES). Gerencia de Bioestratigrafia e Paleoecologia], E-mail: rlantunes@petrobras.com.br

    2007-07-01

    The study of calcareous nanofossils occurring in the deposits on the Brazilian continental margin began in the late 1960s, undertaken solely by PETROBRAS. Instead of presenting an academic outlook, the purpose of these investigations is first to formulate a biostratigraphic framework to apply to oil well samples. The initial result was the first zoning for the Brazilian continental margin, which considered the deposits formed between the Aptian and Miocene series. Since the 1960s to date, many papers have been written either with details of that original zoning or applying nanofossil biostratigraphy to solve stratigraphic problems. Regardless of all the papers and studies undertaken, little attention has been paid to the Quaternary, since these deposits are normally of no interest to petroleum geology stricto sensu, especially in a large part of the Brazilian margin. On the other hand, there are a few articles and some Master's dissertations and PhD theses that were written and/or are in progress in Brazilian universities. On the other hand, elsewhere in the world, Quaternary nanofossils have been thoroughly investigated in terms of biostratigraphy and paleoceanography. It is, therefore, very clear that there is a gap between what is being done elsewhere in the world and what has been done in Brazil. In fact, this gap is not larger simply because of a few researchers in Brazilian universities who are studying this topic. The intention of this paper is to contribute toward a richer study of Quaternary nanofossils. It, therefore, contains illustrations and taxonomic descriptions of many species observed in the younger strata of the Brazilian margin basins. This article not only aspires to portray and disseminate the potential of nanofossils for the marine Quaternary study but is also an invitation to students (under and post-graduates) and university researchers - an invitation to learn a little more about the subject and spend some time studying these real gems

  12. Quaternary nanofossils on the Brazilian continental shelf; Nanofosseis calcarios do quaternario da margem continental brasileira

    Energy Technology Data Exchange (ETDEWEB)

    Antunes, Rogerio Loureiro [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES). Gerencia de Bioestratigrafia e Paleoecologia], E-mail: rlantunes@petrobras.com.br

    2007-07-01

    The study of calcareous nanofossils occurring in the deposits on the Brazilian continental margin began in the late 1960s, undertaken solely by PETROBRAS. Instead of presenting an academic outlook, the purpose of these investigations is first to formulate a biostratigraphic framework to apply to oil well samples. The initial result was the first zoning for the Brazilian continental margin, which considered the deposits formed between the Aptian and Miocene series. Since the 1960s to date, many papers have been written either with details of that original zoning or applying nanofossil biostratigraphy to solve stratigraphic problems. Regardless of all the papers and studies undertaken, little attention has been paid to the Quaternary, since these deposits are normally of no interest to petroleum geology stricto sensu, especially in a large part of the Brazilian margin. On the other hand, there are a few articles and some Master's dissertations and PhD theses that were written and/or are in progress in Brazilian universities. On the other hand, elsewhere in the world, Quaternary nanofossils have been thoroughly investigated in terms of biostratigraphy and paleoceanography. It is, therefore, very clear that there is a gap between what is being done elsewhere in the world and what has been done in Brazil. In fact, this gap is not larger simply because of a few researchers in Brazilian universities who are studying this topic. The intention of this paper is to contribute toward a richer study of Quaternary nanofossils. It, therefore, contains illustrations and taxonomic descriptions of many species observed in the younger strata of the Brazilian margin basins. This article not only aspires to portray and disseminate the potential of nanofossils for the marine Quaternary study but is also an invitation to students (under and post-graduates) and university researchers - an invitation to learn a little more about the subject and spend some time studying these real gems of

  13. Direct observations of American eels migrating across the continental shelf to the Sargasso Sea.

    Science.gov (United States)

    Béguer-Pon, Mélanie; Castonguay, Martin; Shan, Shiliang; Benchetrit, José; Dodson, Julian J

    2015-10-27

    Since inferring spawning areas from larval distributions in the Sargasso Sea a century ago, the oceanic migration of adult American eels has remained a mystery. No adult eel has ever been observed migrating in the open ocean or in the spawning area. Here, we track movements of maturing eels equipped with pop-up satellite archival tags from the Scotian Shelf (Canada) into the open ocean, with one individual migrating 2,400 km to the northern limit of the spawning site in the Sargasso Sea. The reconstructed routes suggest a migration in two phases: one over the continental shelf and along its edge in shallow waters; the second in deeper waters straight south towards the spawning area. This study is the first direct evidence of adult Anguilla migrating to the Sargasso Sea and represents an important step forward in the understanding of routes and migratory cues.

  14. Oil, gas potential in shallow water: Peru`s continental shelf basins

    Energy Technology Data Exchange (ETDEWEB)

    Zuniga-Rivero, F.; Keeling, J.A.; Hay-Roe, H. [BPZ and Associates Inc., Houston, TX (United States)

    1998-11-16

    This third article of a series highlights the three sedimentary basins that underlie the 16 million acres of continental shelf adjacent to a 650-mile stretch of Peruvian coastline. This area lies roughly between the ports of Chiclayo and Pisco. These basins offer a variety of reservoirs, traps, and source-rock potential in water depths of less than 1,000 ft. They are characterized by a thick sequence of Neogene strata, underlain by Paleogene, Mesozoic, and Upper Paleozoic sediments down to as much as 7 sec two-way time on modern seismic records. In some places the sedimentary section may reach an aggregate thickness in excess of 50,000 ft. From north to south these contiguous shelf basins are the Sechura-Salaverry, Huacho, and Pisco basins. All three basins are described.

  15. Distribution of Upper Circumpolar Deep Water on the warming continental shelf of the West Antarctic Peninsula

    Science.gov (United States)

    Couto, Nicole; Martinson, Douglas G.; Kohut, Josh; Schofield, Oscar

    2017-07-01

    We use autonomous underwater vehicles to characterize the spatial distribution of Upper Circumpolar Deep Water (UCDW) on the continental shelf of the West Antarctic Peninsula (WAP) and present the first near-synoptic measurements of mesoscale features (eddies) containing UCDW on the WAP. Thirty-three subsurface eddies with widths on the order of 10 km were detected during four glider deployments. Each eddy contributed an average of 5.8 × 1016 J to the subpycnocline waters, where a cross-shelf heat flux of 1.37 × 1019 J yr-1 is required to balance the diffusive loss of heat to overlying winter water and to the near-coastal waters. Approximately two-thirds of the heat coming onto the shelf diffuses across the pycnocline and one-third diffuses to the coastal waters; long-term warming of the subpycnocline waters is a small residual of this balance. Sixty percent of the profiles that contained UCDW were part of a coherent eddy. Between 20% and 53% of the lateral onshore heat flux to the WAP can be attributed to eddies entering Marguerite Trough, a feature in the southern part of the shelf which is known to be an important conduit for UCDW. A northern trough is identified as additional important location for eddy intrusion.

  16. Diversity and Distribution Patterns of Cetaceans in the Subtropical Southwestern Atlantic Outer Continental Shelf and Slope

    Science.gov (United States)

    Di Tullio, Juliana Couto; Gandra, Tiago B. R.; Zerbini, Alexandre N.; Secchi, Eduardo R.

    2016-01-01

    Temporal and spatial patterns of cetacean diversity and distribution were investigated through eight ship-based surveys carried out during spring and autumn between 2009 and 2014 on the outer continental shelf (~150m) and slope (1500m) off southeastern and southern Brazil (~23°S to ~34°S). The survey area was divided into southeast and south areas according to their oceanographic characteristics. Twenty-one species were observed in 503 sightings. The overall number of species was similar between the two areas, though it was higher in the spring in the south area. Five species were dominant and diversity varied more seasonally than spatially. ANOVA and kernel analyses showed that overall cetacean densities were higher in spring compared to autumn. Physeter macrocephalus, the most frequent species, concentrated throughout the south area at depths over 1000m in both seasons. Despite the overlapped occurrence at a broader scale, small delphinids presented latitudinal and in-offshore gradients as well as seasonal variation in distribution patterns, which could indicate habitat partitioning between some species. Delphinus delphis was only recorded in the south and its density decreased in areas where the presence of Stenella frontalis increased, mainly beyond the 250m isobath. Densities of S. longirostris and S. attenuata increased in lower latitudes and beyond the shelf break. The large delphinids Tursiops truncatus and Globicephala melas formed mixed groups in many occasions and were observed along the study area around depths of 500m. Grampus griseus was twice as frequent in the south area and densities increased in waters deeper than 600m. As expected, densities of both small and large migratory whales were higher during spring, over the continental slope, in the southeast area. The results presented here provided strong evidence on the importance of the outer continental shelf and slope to a diverse community of cetaceans occurring in the subtropical Southwestern

  17. Denudation of the continental shelf between Britain and France at the glacial–interglacial timescale

    Science.gov (United States)

    Mellett, Claire L.; Hodgson, David M.; Plater, Andrew J.; Mauz, Barbara; Selby, Ian; Lang, Andreas

    2013-01-01

    The erosional morphology preserved at the sea bed in the eastern English Channel dominantly records denudation of the continental shelf by fluvial processes over multiple glacial–interglacial sea-level cycles rather than by catastrophic flooding through the Straits of Dover during the mid-Quaternary. Here, through the integration of multibeam bathymetry and shallow sub-bottom 2D seismic reflection profiles calibrated with vibrocore records, the first stratigraphic model of erosion and deposition on the eastern English Channel continental shelf is presented. Published Optical Stimulated Luminescence (OSL) and 14C ages were used to chronometrically constrain the stratigraphy and allow correlation of the continental shelf record with major climatic/sea-level periods. Five major erosion surfaces overlain by discrete sediment packages have been identified. The continental shelf in the eastern English Channel preserves a record of processes operating from Marine Isotope Stage (MIS) 6 to MIS 1. Planar and channelised erosion surfaces were formed by fluvial incision during lowstands or relative sea-level fall. The depth and lateral extent of incision was partly conditioned by underlying geology (rock type and tectonic structure), climatic conditions and changes in water and sediment discharge coupled to ice sheet dynamics and the drainage configuration of major rivers in Northwest Europe. Evidence for major erosion during or prior to MIS 6 is preserved. Fluvial sediments of MIS 2 age were identified within the Northern Palaeovalley, providing insights into the scale of erosion by normal fluvial regimes. Seismic and sedimentary facies indicate that deposition predominantly occurred during transgression when accommodation was created in palaeovalleys to allow discrete sediment bodies to form. Sediment reworking over multiple sea-level cycles (Saalian–Eemian–early Weichselian) by fluvial, coastal and marine processes created a multi-lateral, multi-storey succession of

  18. Denudation of the continental shelf between Britain and France at the glacial-interglacial timescale.

    Science.gov (United States)

    Mellett, Claire L; Hodgson, David M; Plater, Andrew J; Mauz, Barbara; Selby, Ian; Lang, Andreas

    2013-12-01

    The erosional morphology preserved at the sea bed in the eastern English Channel dominantly records denudation of the continental shelf by fluvial processes over multiple glacial-interglacial sea-level cycles rather than by catastrophic flooding through the Straits of Dover during the mid-Quaternary. Here, through the integration of multibeam bathymetry and shallow sub-bottom 2D seismic reflection profiles calibrated with vibrocore records, the first stratigraphic model of erosion and deposition on the eastern English Channel continental shelf is presented. Published Optical Stimulated Luminescence (OSL) and 14 C ages were used to chronometrically constrain the stratigraphy and allow correlation of the continental shelf record with major climatic/sea-level periods. Five major erosion surfaces overlain by discrete sediment packages have been identified. The continental shelf in the eastern English Channel preserves a record of processes operating from Marine Isotope Stage (MIS) 6 to MIS 1. Planar and channelised erosion surfaces were formed by fluvial incision during lowstands or relative sea-level fall. The depth and lateral extent of incision was partly conditioned by underlying geology (rock type and tectonic structure), climatic conditions and changes in water and sediment discharge coupled to ice sheet dynamics and the drainage configuration of major rivers in Northwest Europe. Evidence for major erosion during or prior to MIS 6 is preserved. Fluvial sediments of MIS 2 age were identified within the Northern Palaeovalley, providing insights into the scale of erosion by normal fluvial regimes. Seismic and sedimentary facies indicate that deposition predominantly occurred during transgression when accommodation was created in palaeovalleys to allow discrete sediment bodies to form. Sediment reworking over multiple sea-level cycles (Saalian-Eemian-early Weichselian) by fluvial, coastal and marine processes created a multi-lateral, multi-storey succession of

  19. Composition of the metazooplankton community and structure across the continental shelf off tropical NW Australia

    DEFF Research Database (Denmark)

    Jaspers, Cornelia; Nielsen, Torkel Gissel; Maar, Marie

    This talk focuses on the distribution pattern and grazing impact of different functional metazooplankton groups in a tropical marine ecosystem. We studied the metazooplankton distribution across the continental shelf from eutrophic mangrove areas to the oligotrophic deep blue ocean off NW Australia....... Chlorophyll a concentrations were reduced by factor 10 along the transect including a shift towards small sized primary producers. The metazooplankton biomass followed the same pattern. Even though low in abundance, copepods were most frequent followed by larvaceans, doliolids other thaliacea and chaetognaths...

  20. On the occurrence of caliche pisolites from the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.

    leader for his interest and for valuable suggestions which improved the manuscript. Thanks are due to Mr. V.S. Raja Raman for his assistance. References Aristarain, L.F., 1970. Chemical analysis of caliche profiles from the High Plains, New Mexico... limestones and associated sediments from the western continental shelf of India. Mar. Geol., 95: 17-29. Reeves, C.C., 1970. Origin classification and geologic history of caliche on the southern High plains, Texas and eastern New Mexico. J. Geol., 78: 352...

  1. Biodiversity of a wreck from the Belgian Continental Shelf: monitoring using scientific diving: preliminary results

    OpenAIRE

    Massin, Cl.; Norro, A.; Mallefet, J.

    2002-01-01

    Scientific diving from aboard the r/v Belgica has been employed to carry out a preliminary study of the macrofauna living on a wreck (the Birkenfels) located on the Belgian Continental Shelf (BCS). The study revealed an extremely rich sessile and slow moving fauna (at least 40 species), 3 jellyfish species and 8 fish species. The presence of at least 51 species represents a biodiversity of macrofauna on the wreck that is much higher than that found in nearly all known surrounding soft bottorn...

  2. Very large dune formation along the Ebro outer continental shelf (Western Mediterranean)

    Science.gov (United States)

    Lo Iacono, Claudio; Guillén, Jorge; Puig, Pere; Ribó, Marta; Ballesteros, Maria; Palanques, Albert; Farrán, Marcelli; Acosta, Juan

    2010-05-01

    Large and very large subaqueous dunes have been observed in a number of outer shelf regions around the world, tipically developing on fossil sand bodies and ridges. Dunes observed on outer shelves usually display large dimensions with maximum wavelength reaching up to 500 m and heights up to 20 m. Forcing mechanisms able to induce their formation have been described as strong bottom currents related to tidal variations and water masses flowing under geostrophic conditions, generally controlled and enhanced by local geomorphologic configurations. In this study, such bed features have been recognized, mapped and measured around the Columbretes Islands (Ebro continental shelf - Western Mediterranean) with the aim to reconstruct which are the potential forcing processes that could generate them in relation to the local settings of the area. Swath-bathymetry around the Columbretes Islands was collected using 30 kHz and 180 kHz Multi Beam echo-sounders for a 50-400 m water depth range. Bathymetric data revealed the presence of three main relict sand bodies along the outer shelf, for a 80-116 m depth range, above which asymmetrical, slightly asymmetrical and symmetrical large and very large 2D and 3D subaqueous dunes were observed. Dunes range from 150 to 760 m in wavelength and from tens of cm to 6 m in height. These bedforms are composed of sandy sediments, presumably coming from the degraded relict sand bodies on which they developed, mixed to the fine fractions coming from the recent draping holocenic sediments. The orientation of the dunes is SSW and progressively turns to W directions moving towards the southernmost sector of the area, following the trend of the shelf-edge. Observed dunes display a strong asymmetric profile for those occurring along the shelf-edge (Symmetry Index (SI): 2.6) and lose progressively their asymmetry towards the inner portion of the shelf (SI: 0.5), being 0.6 the minimum SI value to classify the dunes as asymmetric. The subaqueous dunes

  3. The Project for the Extension of the Continental Shelf - the Portuguese experience

    Science.gov (United States)

    Madureira, Pedro; Ribeiro, Luísa P.; Roque, Cristina; Henriques, Guida; Brandão, Filipe; Dias, Frederico; Simões, Maria; Neves, Mariana; Conceição, Patricia; Botelho Leal, Isabel; Emepc, Equipa

    2017-04-01

    Under the United Nations Convention on the Law of the Sea (UNCLOS), the continental shelf is a juridical term used to define a submarine area that extends throughout the natural prolongation of a land territory, where the coastal State exercises sovereign rights for the purpose of exploring it and exploiting its natural resources. Article 76 provides a methodology for determining the outer edge of the continental margin and to delineate the outer limits of the continental shelf. The task of preparing the Portuguese submission to the Commission on the Limits of the Continental Shelf was committed to the Task Group for the Extension of the Continental Shelf (EMEPC), which formally began its activity in January 2005. At that time, the existing national capacity to conduct such a task was very limited in its hydrographic, geological and geophysical components. A great effort has been made by Portugal to overcome these weaknesses and develop a strategy to submit the proposal for the extension of the continental shelf beyond 200 nautical miles on 11th May of 2009. The execution of the project involved the implementation of several complementary strategies including: 1) intensive bathymetric, geophysical and, locally, geological data acquisition; 2) acquisition/development of new stand-alone and ship mounted equipment; 3) interactions with universities and research institutes, with emphasis in R&D initiatives; 4) creation of critical mass in deep-sea research by promoting advanced studies on: International Law, Geophysics, Geology, Hydrography, Biology, amongst others; 5) promotion of the sea as a major national goal, coupled with an outreach strategy. Until now, more than 1050 days of surveying have resulted in a large scale seafloor mapping using two EM120 and one EM710 multibeam echosounders from Kongsberg mounted on two hydrographic vessels. The surveys follow IHO Order 2 Standard (SP44, 5th Edition) and cover an area over 2.6 million km2. A multichannel reflection

  4. Seismic data processing for domestic seismic survey over the continental shelf of Korea using the Geobit

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Jin Yong [Korea Inst. of Geology Mining and Materials, Taejon (Korea, Republic of)

    1995-12-01

    The `Geobit`, a new seismic data processing software introduced by the Korea Institute of Geology, Mining and Materials recently, is the token of the achievement for the development of technology in the oil exploration over the Korean continental shelf. In comparison with the foreign seismic data processing systems previously used in Korea, the Geobit system has some advanced facilities; it provides an interactive mode which makes the seismic processing easier and has the user-friendly programs which allow the construction of a job control file simpler. Most of all, the Geobit can be run with many computer hardware systems, from PC to supercomputer. The current version of the Geobit can take care of the two-dimensional multi-channel seismic data and is open to the public for an education tool and a research purpose. To demonstrate the ability of the Geobit, a multi-channel field data acquired in the domestic continental shelf over the Yellow Sea in 1970 has been selected and processed with standard seismic data processing techniques. In this report, the Geobit job files and the corresponding results for the construction of a stack are provided. (author). 8 refs., 14 figs., 1 tab.

  5. Impact of the oil price and fiscal facilities on offshore mining at the Dutch Continental Shelf

    International Nuclear Information System (INIS)

    Cate, Arie ten; Mulder, Machiel

    2007-01-01

    The surge in the oil price has raised questions about the magnitude of global reserves of oil. According to some analysts, the current high oil prices indicate a looming decline in the global production of oil. Others believe, however, that the increased level of the oil price encourages exploration and production activities, bringing the oil price to a lower equilibrium level in the near future. In this paper, we assess the impact of the unit profit (depending on the oil price) as well as fiscal facilities on the level of exploration and development drillings in the Dutch Continental Shelf. We conducted an econometric analysis of exploration and development drillings in the Dutch Continental Shelf over the period 1981-2003. Except a few fiscal changes, the regulatory framework for offshore activities in the Netherlands, the so-called 'small fields policy' was unchanged in this period. We find that the expected unit profit based on a moving average of the oil price significantly explains the level of both exploration and development drillings. In addition, the analysis suggests that fiscal facilities have only a temporary effect on exploration activities but are more important for development activities. We conclude that the oil price is a major economic incentive for activities of the mining industry

  6. Detection of introduced sessile species on the near shore continental shelf in southern Brazil

    Directory of Open Access Journals (Sweden)

    Janaína de Araújo Bumbeer

    2012-04-01

    Full Text Available Invasion by marine species, often considered a grave threat to marine ecosystems, occurs throughout the world as a consequence of many anthropogenic activities. In coastal Paraná, many factors including shipping, aquaculture and the use of artificial substrates provide suitable environments for the establishment and rapid spread of introduced marine species. To better understand this process, the encrusting community was studied on polyethylene plates (n = 120, 10 x 10 cm that were placed seasonally at fixed locations on the inner continental shelf to detect non-native species. Of the 62 taxa found, 40 were identified to species, 14 of which were native, 9 introduced and 17 cryptogenic. We found a new introduction while most introduced species were previously reported at a nearby estuary with an international port. Possible complementary explanations for these detections are 1 estuaries influence ecological processes on the inner continental shelf, 2 the study area is near the route of cargo and other ships entering the port, 3 other local vectors, such as hulls of fishing and recreational boats, and artificial reefs link the estuary to the offshore areas. Thus, not only are estuaries invaded by exotic species, but also non-indigenous marine species may be present in the open sea where they are likely to colonize artificial substrates.

  7. Plankton community respiration, net ecosystem metabolism, and oxygen dynamics on the Louisiana continental shelf: Implications for hypoxia

    Science.gov (United States)

    Murrell, Michael C.; Stanley, Roman S.; Lehrter, John C.; Hagy, James D.

    2013-01-01

    We conducted a multi-year study of the Louisiana continental shelf (LCS) to better understand the linkages between water column metabolism and the formation of hypoxia (dissolved oxygen Continental Shelf Research, 29: 1861-1872) to estimate net water column metabolism. There was consistent evidence of net heterotrophy, particularly in western transects, and in deeper waters (>40 m depth), indicating a net organic carbon deficit on the LCS. We offer a simple scale argument to suggest that riverine and inshore coastal waters may be significant sources of organic carbon to account for this deficit. This study provided unprecedented, continental shelf scale coverage of heterotrophic metabolism, which is useful for constraining models of oxygen, carbon, and nutrient dynamics along the LCS.

  8. Submarine glacial landforms on the Bay of Fundy–northern Gulf of Maine continental shelf

    Science.gov (United States)

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

    2016-01-01

    The Bay of Fundy–northern Gulf of Maine region surrounds the southern part of Nova Scotia, encompassing, from west to east, the Bay of Fundy, Grand Manan Basin, German Bank, Browns Bank, Northeast Channel and northeastern Georges Bank (Fig. 1a, b). During the last glacial maximum (c. 24–20 14C ka BP), the SE margin of the Laurentide Ice Sheet (LIS) occupied the study area, the rest of the Gulf of Maine and the continental Scotian Shelf off Atlantic Canada (see Dyke et al. 2002, fig. 1; Shaw et al. 2006, fig. 8; Hundert & Piper 2008, fig. 16). Early mapping of the glaciated region on the Scotian Shelf using side-scan sonar imagery and seismic-reflection profiles revealed topographic features interpreted to be recessional moraines indicative of retreat of the LIS (King et al. 1972; King 1996). Subsequently, multibeam sonar seafloor mapping of local-scale glacial landforms on the inner Scotian Shelf off Halifax, Nova Scotia (Fig. 1b) provided further information on the dynamics of the advance and retreat of the ice sheet (Loncarevic et al.1994). Interpretation of seismic-reflection profiles across Georges Bank revealed that the surficial sediment is a veneer of glacial debris transported to Georges Bank by the LIS during the late Pleistocene from continental areas to the north (Shepard et al. 1934; Knott & Hoskins 1968; Schlee 1973; Twichell et al. 1987; Fader et al. 1988). Recent high-resolution multibeam sonar surveys of German Bank and the Bay of Fundy mapped a complex of ice-advance and ice-retreat features attributed to the activity of the LIS (Todd et al. 2007; Todd & Shaw 2012).

  9. Changes in the diet composition of transitory fishes in coastal systems, estuary and continental shelf

    Directory of Open Access Journals (Sweden)

    Chaves Paulo T. C.

    2003-01-01

    Full Text Available The feeding habits of five species of teleosts in the southern coast of Brazil were analyzed comparatively between estuary and continental shelf. The displacement between the two sites caused expressive qualitative alterations, the proportion of different items varying from 50% in the diet of Micropogonias furnieri to 89% in Isopisthus parvipinnis. In the group of species, 57% of the items were exclusive to one of the environments and, within the three most common items in the estuary - fish, Polychaeta and plants, only the former was also among the most common items in the shelf. In spite of these differences, the high spectrum of items in both environments and the nature of the item that was most consumed in each one, indicate that there was a certain similarity of patterns between estuary and shelf: Chloroscombrus chrysurus had a carnivorous diet, with a predominance of copepods; M. furnieri and Menticirrhus americanus showed a tendency towards an omnivorous diet; and Cynoscion leiarchus and I. parvipinnis showed a tendency towards ichthyophagy.

  10. 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.

  11. Biocenoses of benthic foraminifera of the Aveiro Continental Shelf (Portugal: influence of the upwelling events and other shelf processes

    Directory of Open Access Journals (Sweden)

    Maria Virgínia Alves Martins

    2017-03-01

    Full Text Available This work aims to compare the dimensions and composition of benthic foraminiferal biocenoses (living specimens during two summer sampling events. Forty-four sediment samples were collected on the Aveiro Continental Shelf (Center of Portugal (latitude of 40º30'N-40º50'N, longitude of 8º46'W-9º20'W for granulometry, total organic matter (TOM and living foraminiferal analyses. The sediment samples were collected during summers of 1994 and 1995, on stations located along transects (east-west direction and between the bathymetries of 10-200 m. During the sampling campaigns, measurements of salinity, temperature and density data were recorded in the water column. The results showed that the living assemblages were mainly found in stations located between 20-80 m depth. The abundance of living foraminifera was generally reduced at depths <20 m in the so-called “coastal deposits”, where the sediments are frequently remobilized and transported by the littoral drift. Living benthic foraminiferal densities were also reduced in stations at 80-200 m depth, despite the high sedimentary TOM contents. Results obtained in this work indicate that, in this marine setting, the most determinant factors for the dimension and composition of living foraminifera are not the sediments’ granulometry and organic matter content. In fact, the coastal dynamics, sediment stability, availability of quality food, among other factors, such as the bottom salinity oscillations and their combination, should better explain the abundance of living foraminifera and the biocenoses composition.

  12. Polycyclic aromatic hydrocarbon concentrations across the Florida Panhandle continental shelf and slope after the BP MC 252 well failure

    International Nuclear Information System (INIS)

    Snyder, Richard A.; Ederington-Hagy, Melissa; Hileman, Fredrick; Moss, Joseph A.; Amick, Lauren; Carruth, Rebecca; Head, Marie; Marks, Joel; Tominack, Sarah; Jeffrey, Wade H.

    2014-01-01

    Graphical abstract: The R/V Bellows, Florida Institute of Oceanography (FIO), with faculty and students from the University of West Florida (UWF), sampling mats of oil floating over the continental shelf south of Pensacola Florida during the BP MC 252 well failure. PAH concentrations in sediments on the shelf declined over time after the well was capped with a half life of ∼200 days. - Highlights: • PAHs concentrations were highest in slope sediments near the failed well site. • PAH concentrations in the shelf sediments were highest during the oil spill. • PAHs concentrations declined over time since the spill. - Abstract: The Florida Panhandle continental shelf environment was exposed to oil from the BP oil well failure in the Gulf of Mexico during 2010. Floating mats of oil were documented by satellite, but the distribution of dissolved components of the oil in this region was unknown. Shipek® grab samples of sediments were taken during repeated cruises between June 2010 and June 2012 to test for selected polycyclic aromatic hydrocarbons (PAHs) as indicators of this contamination. Sediments were collected as composite samples, extracted using standard techniques, and PAHs were quantified by GC/MS-SIM. PAHs in samples from the continental slope in May 2011 were highest near to the failed well site and were reduced in samples taken one year later. PAHs from continental shelf sediments during the spill (June 2010) ranged from 10 to 165 ng g −1 . Subsequent cruises yielded variable and reduced amounts of PAHs across the shelf. The data suggest that PAHs were distributed widely across the shelf, and their subsequent loss to background levels suggests these compounds were of oil spill origin. PAH half-life estimates by regression were 70–122 days for slope and 201 days for shelf stations

  13. Gas hydrates:estimation of the gas potential, from reflection seismic data in the continental shelf of Uruguay

    International Nuclear Information System (INIS)

    De Santa Ana, H.; Ucha, N.; Gutierrez, L.; Veroslavsky, G.

    2004-01-01

    The uruguayan continental shelf shows geophysical indicators of gas hydrates in the Oriental del Plata, Pelotas and Punta del Este basin. The aim of this work is to present the potential presence of gas at the continental shelf in Uruguay and to evaluate the possibility of exploration of unconventional hydrocarbon plays. Analysis of the seismic surface based on regional and stratgigraphic information that proceeded from previous hydrocarbon exploration in the area have been used to estimatge resources of gas hydrates. Gas hydrates accumulation was mapped using characteristic reflectors and amplitude anomalies of seismic lines (BSR). Its quantity was estimated on this basis in about 86 TCF.

  14. Considerations about the recommendations of the Commission on the Limits of the Continental Shelf on the Amazon fan

    Directory of Open Access Journals (Sweden)

    Rodrigo Fernandes More

    2014-01-01

    Full Text Available In 2004, Brazil submitted to the Commission on the Limits of the Continental Shelf (CLCS a Submission for the outer limit of the Brazilian continental shelf for its extension beyond the limits of 200 nautical miles. In 2007, the CLCS presented its recommendations, however it did not recommend four areas proposed by Brazil, the Amazon Fan among them. The objective of this study is to present the main legal and technical aspects of the controversy about the Amazon Fan, in order to evaluate some alternatives for a future submission, new or revised.

  15. The NSW Steam Trawl Fishery on the South-East Continental Shelf of Australia, 1915-1961

    DEFF Research Database (Denmark)

    Jacobsen, A. Lif Lund

    2014-01-01

    How was modern fishing methods, in the form of steam trawling, introduced in Australia? And what were the consequences for the fish stocks found on the South-East Continental Shelf? Through historical catch records and archival resources, the history of the NSW Steam Trawl Industry from 1915...... that flathead biomass on the South-East Continental shelf was permanently reduced. The study furthermore reveals how the trawl industry was influenced by government policy, market conditions, war and fishing effort with little understanding of the marine resources which they relied on....

  16. Arctic continental shelf morphology related to sea-ice zonation, Beaufort Sea, Alaska

    Science.gov (United States)

    Reimnitz, E.; Toimil, L.; Barnes, P.

    1978-01-01

    Landsat-1 and NOAA satellite imagery for the winter 1972-1973, and a variety of ice and sea-floor data were used to study sea-ice zonation and dynamics and their relation to bottom morphology and geology on the Beaufort Sea continental shelf of arctic Alaska. In early winter the location of the boundary between undeformed fast ice and westward-drifting pack ice of the Pacific Gyre is controlled by major coastal promontories. Pronounced linear pressure- and shear-ridges, as well as hummock fields, form along this boundary and are stabilized by grounding, generally between the 10- and 20-m isobaths. Slippage along this boundary occurs intermittently at or seaward of the grounded ridges, forming new grounded ridges in a widening zone, the stamukhi zone, which by late winter extends out to the 40-m isobath. Between intermittent events along the stamukhi zone, pack-ice drift and slippage is continuous along the shelf edge, at average rates of 3-10 km/day. Whether slippage occurs along the stamukhi zone or along the shelf edge, it is restricted to a zone several hundred meters wide, and ice seaward of the slip face moves at uniform rates without discernible drag effects. A causal relationship is seen between the spatial distribution of major ice-ridge systems and offshore shoals downdrift of major coastal promontories. The shoals appear to have migrated shoreward under the influence of ice up to 400 m in the last 25 years. The sea floor seaward of these shoals within the stamukhi zone shows high ice-gouge density, large incision depths, and a high degree of disruption of internal sedimentary structures. The concentration of large ice ridges and our sea floor data in the stamukhi zone indicate that much of the available marine energy is expended here, while the inner shelf and coast, where the relatively undeformed fast ice grows, are sheltered. There is evidence that anomalies in the overall arctic shelf profile are related to sea-ice zonation, ice dynamics, and bottom

  17. Data Management Supporting the U.S. Extended Continental Shelf Project

    Science.gov (United States)

    Lim, E.; Henderson, J. F.; Warnken, R.; McLean, S. J.; Varner, J. D.; Mcquinn, E.; LaRocque, J.

    2013-12-01

    The U.S. Extended Continental Shelf (ECS) Project is a multi-agency collaboration led by the U.S. Department of State whose mission is to establish the full extent of the continental shelf of the United States consistent with international law. Since 2003, the U.S. has been actively collecting bathymetric, seismic, and other geophysical data and geologic samples required to delineate its outer limits in accordance with Article 76 of the UN Convention on the Law of the Sea. In 2007, the U.S. ECS Task Force designated the National Geophysical Data Center (NGDC) to serve as both the Data Management lead and the Data Archive and Integration Center for the U.S. ECS Project. NGDC, one of three National Oceanic and Atmospheric Administration (NOAA) Offices active in the ECS Project, has the primary responsibility to provide a common infrastructure and a means to integrate the data supporting, and products resulting from ECS analysis. One of the key challenges in the ECS project is the requirement to track the provenance of data and derived products. Final ECS analyses may result in hundreds of points that define a new maritime boundary that is our extended continental shelf. These points will be developed in a rigorous process of analysis encompassing potentially thousands of raw datasets and derived products. NGDC has spent the past two years planning, designing, and partially implementing the Information Management System (IMS), a highly functional, interactive software system that serves as the master database for the ECS Project. The purpose of this geospatial database is to archive, access, and manage the primary data, derivative data and products, associated metadata, information and decisions that will form the U.S. submission. The IMS enables team members to manage ECS data in a consistent way while maintaining institutional memory and the rationale behind decisions. The IMS contains two major components: First, a catalog that acts as the interface to the IMS by

  18. Geophysical and sampling data from the inner continental shelf: Duxbury to Hull, Massachusetts

    Science.gov (United States)

    Barnhardt, Walter A.; Ackerman, Seth D.; Andrews, Brian D.; Baldwin, Wayne E.

    2010-01-01

    The U.S. Geological Survey (USGS) and the Massachusetts Office of Coastal Zone Management (CZM) have cooperated to map approximately 200 km² of the Massachusetts inner continental shelf between Duxbury and Hull. This report contains geophysical and geological data collected by the USGS on three cruises between 2006 and 2007. These USGS data are supplemented with a National Oceanic and Atmospheric Administration (NOAA) hydrographic survey conducted in 2003 to update navigation charts. The geophysical data include (1) swath bathymetry from interferometric sonar and multibeam echosounders, (2) acoustic backscatter from sidescan sonar and multibeam echosounders, and (3) subsurface stratigraphy and structure from seismic-reflection profilers. The geological data include sediment samples, seafloor photographs, and bottom videos. These spatial data support research on the influence sea-level change and sediment supply have on coastal evolution, and on efforts to understand the type, distribution, and quality of subtidal marine habitats in the Massachusetts coastal ocean.

  19. Regulation and efficiency: an empirical analysis of the United Kingdom continental shelf petroleum industry

    International Nuclear Information System (INIS)

    Kashani, H.A.

    2005-01-01

    The petroleum industry of the United Kingdom Continental Shelf (UKCS) has been subject to various degrees of regulation. Self-sufficiency, security of supply and developing offshore supply industry triggered government regulations that were seen as interventionary and protectionist. This paper tests the extent to which regulations targeting involvement of British offshore supply industry in the UKCS activity created inefficiencies. Data envelopment analysis (DEA), stochastic frontier analysis (SFA), Malmquist Indices, and standard regression analysis are used to measure the amount and address the source of inefficiencies. We will show that such inefficiencies could not be ruled out. The results provide an important insight into the UKCS production techniques and, more generally, into governments' abilities to influence private sector behaviour through contracts and tendering

  20. Sources, extent and history of methane seepage on the continental shelf off northern Norway

    Science.gov (United States)

    Sauer, Simone; Lepland, Aivo; Chand, Shyam; Schubert, Carsten J.; Eichinger, Florian; Knies, Jochen

    2014-05-01

    Active natural hydrocarbon gas seepage was recently discovered in the Hola area on the continental shelf off Vesterålen, northern Norway. We conducted acoustic and geochemical investigations to assess the modern and past extent, source and pathways of the gas seepage . Water column echosounder surveys showed bubble plumes up to several tens of metres above the seafloor. Analyses of dissolved methane in the water column indicated slightly elevated concentrations (50 nM) close to the seafloor. To identify fluxes and origin of methane in the sediments we analysed sediment pore water chemistry, the isotopic composition of methane and of dissolved inorganic carbon (d13CCH4, d2HCH4, d13CDIC) in three closely spaced (

  1. Delimitation of the continental shelf and exclusive economic Zone the Sea Border between Romania and Ukraine

    Directory of Open Access Journals (Sweden)

    Mihai Mereuţă

    2011-07-01

    Full Text Available Decision I.C.J. from The Hague, since 3rd February 2009, in the case of “Romania vs. Ukraine - the maritime delimitation in the Black Sea”, has an important role in bilateral relations and regional plans of the riparian states and thus also eliminating a potential factor of instability at the sea border between the two countries and in the Black Sea. Drawing a line of demarcation equitable maritime economic zone and continental shelf between the two countries was an example of dispute settlement in the wider Black Sea area. Snake Island was not considered relevant in substantiating the court decision, because the I.C.J. has not declared it a rock, giving it a length of 12 nautical miles territorial sea and has not ruled on the nature of this formation, in accordance with the provisions of art. 121 of the Montego Bay Convention of 1982.

  2. Impacts of Outer Continental Shelf (OCS) development on recreation and tourism. Volume 3. Detailed methodology

    Energy Technology Data Exchange (ETDEWEB)

    1987-04-01

    The final report for the project is presented in five volumes. This volume, Detailed Methodology Review, presents a discussion of the methods considered and used to estimate the impacts of Outer Continental Shelf (OCS) oil and gas development on coastal recreation in California. The purpose is to provide the Minerals Management Service with data and methods to improve their ability to analyze the socio-economic impacts of OCS development. Chapter II provides a review of previous attempts to evaluate the effects of OCS development and of oil spills on coastal recreation. The review also discusses the strengths and weaknesses of different approaches and presents the rationale for the methodology selection made. Chapter III presents a detailed discussion of the methods actually used in the study. The volume contains the bibliography for the entire study.

  3. Impacts of Outer Continental Shelf (OCS) development on recreation and tourism. Volume 1. Executive summary

    Energy Technology Data Exchange (ETDEWEB)

    1987-04-01

    The study was intended to provide the Mineral Management Service (MMS) with an analytical tool to evaluate possible economic impacts from Outer Continental Shelf (OCS) development. In particular, the study was designed to provide MMS staff who work on lease sale Energy Impact Statements with an objective technique for estimating the impacts to coastal communities from events that might occur as a result of lease sales: oil spills, onshore construction, and construction of platforms offshore. The project had several specific objectives: (1) provide profiles of 1982 socio-economic conditions in coastal communities, including an analysis of the relative importance of the tourist industry in each coastal county; (2) develop a methodology for determining the effects of OCS development on coastal recreation; and recommend mitigation measure that may reduce the negative effect of OCS development on coastal recreation using gravity and economic effects models.

  4. Environmental studies results: 1973-1992. Atlantic Outer Continental Shelf. Final report

    International Nuclear Information System (INIS)

    Wilson, J.M.

    1992-01-01

    The Outer Continental Shelf (OCS) Environmental Studies Program was initiated in 1973 under the Bureau of Land Management by the Secretary of the Interior. The Purpose of the program was to conduct studies needed to predict, assess and manage impacts on the human, marine and coastal environments of the OCS and nearshore areas that may be affected by oil and gas activities. The narrative summary updates the version printed in 1986, which covered studies managed by the MMS in the Atlantic OCS region between 1973 and 1985. Descriptions of the study results are divided into the following categories: baseline studies and environmental inventories, biology/ecology, drill site monitoring, endangered species, geology/chemistry, oil spill studies, physical oceanography/meteorology, and social and economic studies. Results of each major type of study are subdivided into North Atlantic, Mid-Atlantic, South Atlantic, and multiregional studies in chronological sequence

  5. Pollution by petroleum hydrocarbons in sediments from continental shelf of Tabasco State, Mexico

    International Nuclear Information System (INIS)

    Botello, A.V.; Gonzalez, C.; Diaz, G.

    1991-01-01

    The Wider Caribbean is potentially one of the largest oil producing areas in the world. Major petroleum production areas include Louisiana and Texas, USA; the Bay of Campeche, Mexico; Lake Maracaibo, Venezuela; and Gulf of Paria, Trinidad; all of which are classified as production accident high-risk zones. About 5 million of barrels are transported every day in the Caribbean, thus generating an intense tanker traffic. It has been estimated that oil discharges from tank washings within the Wider Caribbean could be as high as 7 million barrels/year. For all those reasons petroleum pollution is considered as the major environmental problem in the Wider Caribbean area and increasing day to day due to the use of petroleum as the main energy source. On the other hand, the continental shelf of Tabasco state actually represents one of the most productive areas for crude oil in the Gulf of Mexico. Sediments were collected from this area and analyzed for hydrocarbons

  6. Sea level anomaly on the Patagonian continental shelf: Trends, annual patterns and geostrophic flows

    Science.gov (United States)

    Saraceno, M.; Piola, A. R.; Strub, P. T.

    2016-01-01

    Abstract We study the annual patterns and linear trend of satellite sea level anomaly (SLA) over the southwest South Atlantic continental shelf (SWACS) between 54ºS and 36ºS. Results show that south of 42°S the thermal steric effect explains nearly 100% of the annual amplitude of the SLA, while north of 42°S it explains less than 60%. This difference is due to the halosteric contribution. The annual wind variability plays a minor role over the whole continental shelf. The temporal linear trend in SLA ranges between 1 and 5 mm/yr (95% confidence level). The largest linear trends are found north of 39°S, at 42°S and at 50°S. We propose that in the northern region the large positive linear trends are associated with local changes in the density field caused by advective effects in response to a southward displacement of the South Atlantic High. The causes of the relative large SLA trends in two southern coastal regions are discussed as a function meridional wind stress and river discharge. Finally, we combined the annual cycle of SLA with the mean dynamic topography to estimate the absolute geostrophic velocities. This approach provides the first comprehensive description of the seasonal component of SWACS circulation based on satellite observations. The general circulation of the SWACS is northeastward with stronger/weaker geostrophic currents in austral summer/winter. At all latitudes, geostrophic velocities are larger (up to 20 cm/s) close to the shelf‐break and decrease toward the coast. This spatio‐temporal pattern is more intense north of 45°S. PMID:27840784

  7. Increased marine production of N sub(2)O due to intensifying anoxia on the Indian continental shelf

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W; Jayakumar, D.A.; Narvekar, P.V.; Naik, H.; Sarma, V.V.S.S; DeSouza, W; Joseph, S; George, M.D.

    . The intensification of one of the largest low-oxygen zones in the ocean, which develops naturally over the western Indian continental shelf during late summer and autumn is reported here. The highest accumulations yet observed of hydrogen sulphide (H sub(2)S...

  8. 76 FR 30956 - Outer Continental Shelf, Alaska OCS Region, Chukchi Sea Planning Area, Oil and Gas Lease Sale 193

    Science.gov (United States)

    2011-05-27

    ... Point Hope et al., v. Salazar, No. 1:08-cv-00004-RRB (D. Alaska)]. The sale was conducted in February... Continental Shelf, Alaska OCS Region, Chukchi Sea Planning Area, Oil and Gas Lease Sale 193 AGENCY: Bureau of...: BOEMRE announces the availability of a Revised Draft SEIS, OCS Oil and Gas Lease Sale 193, Chukchi Sea...

  9. Geochronology of sediments in the Cananeia-Iguape estuary and in southern continental shelf of Sao Paulo State, Brazil

    International Nuclear Information System (INIS)

    Saito, R.T.; Figueira, R.C.L.; Cunha, I.I.L.; Tessler, M.G.

    2001-01-01

    Instrumental analysis methods for 210 Pb, 226 Ra and 137 Cs by gamma-spectrometry in sediments, as well as the sedimentation rates in cores collected from Brazilian coastal region are presented. Sampling locations have covered the Cananeia-Iguape estuary and the continental shelf of southern Sao Paulo State. Values for 210 Pb ranged from 122.5 to 14.3 Bq x kg -1 for estuarine sediments and from 195.5 to 23.6 Bq x kg -1 at the continental shelf. For 226 Ra the values obtained in sediments varied from 15.2 to 2.3 Bq x kg -1 in the estuary and from 30.1 to 16.1 Bq x kg -1 at the continental shelf. Sedimentation rates are variable, ranging from 0.53 to 0.98 cm x y -1 in estuary sediments and from 0.18 to 0.40 cm x y -1 at the continental shelf. (author)

  10. The NSW Steam Trawl Fishery on the South-East Continental Shelf of Australia, 1915–1961

    DEFF Research Database (Denmark)

    Lund Jacobsen, A. Lif

    2014-01-01

    How was modern fishing methods, in the form of steam trawling, introduced in Australia? And what were the consequences for the fish stocks found on the South-East Continental Shelf? Through historical catch records and archival resources, the history of the NSW Steam Trawl Industry from 1915...

  11. 77 FR 40081 - Gulf of Mexico, Outer Continental Shelf (OCS), Western Planning Area (WPA) and Central Planning...

    Science.gov (United States)

    2012-07-06

    ... DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Gulf of Mexico, Outer Continental Shelf (OCS), Western Planning Area (WPA) and Central Planning Area (CPA), Oil and Gas Lease Sales for 2012-2017 AGENCY: Bureau of Ocean Energy Management (BOEM), Interior. ACTION: Notice of availability...

  12. Gravity anomalies over a segment of Pratap ridge and adjoining shelf margin basin, western continental margin of India

    Digital Repository Service at National Institute of Oceanography (India)

    Subrahmanyam, V.; Rao, D.G.; Ramprasad, T.; KameshRaju, K.A.; Rao, M.G.

    Bathymetric and gravity data totalling 2000 line km on the continental margin off Goa and Mulki, west of India have been studied. The free-air gravity anomalies vary between -60 to 25 mgals with prominent NNW-SSE trends in the outer shelf region...

  13. Impacts of Outer Continental Shelf (OCS) development on recreation and tourism. Volume 4. User's manual

    Energy Technology Data Exchange (ETDEWEB)

    1987-04-01

    The final report for the project is presented in five volumes. The project sought to determine the impact of Outer Continental Shelf development on recreation and tourism in California. This volume is the User's Guide. It includes the following topics: Introduction and Summary Guide; Input Data Files; Gravity Model Programs; Economic Effects Model Programs; Consumer Surplus Model Programs; References; and Appendices.

  14. 78 FR 8190 - Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore North Carolina...

    Science.gov (United States)

    2013-02-05

    ...] Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore North Carolina--Call for... Commercial Leasing for Wind Power Offshore North Carolina (Call), published on December 13, 2012 (77 FR 7204). DATES: BOEM must receive your nomination describing your interest in obtaining a commercial wind lease...

  15. 76 FR 4716 - Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Off Delaware, Notice of...

    Science.gov (United States)

    2011-01-26

    ... No. BOEM-2010-0075] Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Off... commercial wind development on the OCS off Delaware and requests submission of indications of competitive... received two nominations of proposed lease areas: One from Bluewater Wind Delaware LLC (Bluewater) and...

  16. 75 FR 21653 - Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore Delaware-Request...

    Science.gov (United States)

    2010-04-26

    ... Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore Delaware--Request for Interest (RFI... proposal. In June 2008, Bluewater Wind Delaware LLC announced that it signed a 25-year power purchase agreement with Delmarva Power to sell up to 200 megawatts (MW) of power to the utility from an offshore wind...

  17. 77 FR 47877 - Potential Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore Maine...

    Science.gov (United States)

    2012-08-10

    ... Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore Maine; Request for Interest... Request for a Commercial OCS Wind Lease, Request for Interest, and Request for Public Comment SUMMARY: The... (Statoil NA) to acquire an OCS wind lease; (2) solicit public input regarding the proposal, its potential...

  18. 75 FR 63345 - Oil and Gas and Sulphur Operations in the Outer Continental Shelf-Increased Safety Measures for...

    Science.gov (United States)

    2010-10-14

    ... the Outer Continental Shelf in light of the Deepwater Horizon event on April 20, 2010, and resulting...) develop this report as a result of the Deepwater Horizon event on April 20, 2010. This event, which... investigations into the Deepwater Horizon event, that certain equipment, systems, and improved practices are...

  19. 76 FR 38294 - Oil and Gas and Sulphur Operations in the Outer Continental Shelf-Civil Penalties

    Science.gov (United States)

    2011-06-30

    ... affect in a material way the economy, productivity, competition, jobs, the environment, public health or... DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement 30 CFR... Outer Continental Shelf--Civil Penalties AGENCY: Bureau of Ocean Energy Management, Regulation and...

  20. 76 FR 50245 - Gulf of Mexico (GOM), Outer Continental Shelf (OCS), Western Planning Area (WPA), Oil and Gas...

    Science.gov (United States)

    2011-08-12

    ... (BOEMRE), Interior. ACTION: Notice of Availability (NOA) of a Final Supplemental Environmental Impact... sale's incremental contribution to the cumulative impacts on environmental and socioeconomic resources... Mexico (GOM), Outer Continental Shelf (OCS), Western Planning Area (WPA), Oil and Gas Lease Sale for the...

  1. 75 FR 17156 - Gulf of Mexico, Outer Continental Shelf, Western Planning Area, Oil and Gas Lease Sale 215 (2010...

    Science.gov (United States)

    2010-04-05

    ... environmental assessment (EA) for proposed Gulf of Mexico Outer Continental Shelf (OCS) oil and gas Lease Sale... Environmental Impact Statement; Volumes I and II (Multisale EIS, OCS EIS/EA MMS 2007-018) and in the Gulf of...; Western Planning Area Sales 210, 215, and 218--Final Supplemental Environmental Impact Statement...

  2. Flux of energy and essential elements through the continental shelf ecosystem. Progress report, May 31, 1980-May 31, 1981

    Energy Technology Data Exchange (ETDEWEB)

    Pomeroy, L R

    1981-02-01

    There are three distinct areas of research reported, studies of intrusions of the west wall of the Gulf Stream onto the outer continental shelf, studies of the flux of materials across near-shore density fronts, and advances in the understanding of the planktonic food web of the continental shelf. Studies of frontal events on the outer and inner continental shelf involve distinctive physical and chemical regimes and have proven to required distinctive biological approaches. A simulation model of the flux of energy through the continental shelf food web was developed. It represents realistically both details of the energy transfers within the plankton community and the termanal production of fishes. It was discovered that the fecal ribbons of pelagic tunicates break up into flocculent material visually and chemically identical with the flocculent organic aggregates present in sea water. Subsequent experimental work with tunicate fecal matter indicates that some of the naturally occurring aggregates are indeed fecal. This makes it possible to understand and quantify for the first time the production and fate of that population of seston. An examination was made of several of the many roles of dissolved organic compounds in sea water which originate either from release by phytoplankton, digestive processes or metabolites of zooplankton, or extracellular digestion of microorganisms.

  3. Physical (Hydrography), chemical (CTD), and biological (Water Quality) processes of the Texas-Louisiana continental shelf, 2012 (NCEI Accession 0162101)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Two sets of CTD data were taken during the 2012 surveys of the Louisiana continental shelf—Transect C off Terrebonne Bay and Transect F off Atchafalaya Bay and the...

  4. Clay mineral distribution in the continental shelf sediments from Krishna to Ganges river mouth, east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.

    Ninety six sediment samples (less than 2 mu m fractions) of the eastern continental shelf of India between Ganges in the north and Krishna in the south have been studiEd. by X-ray diffraction. On the basis of nature and abundance of different clay...

  5. 75 FR 19880 - Safety Zone; BW PIONEER at Walker Ridge 249, Outer Continental Shelf FPSO, Gulf of Mexico

    Science.gov (United States)

    2010-04-16

    ... BW PIONEER, a Floating Production, Storage and Offloading (FPSO) system, at Walker Ridge 249 in the Outer Continental Shelf. The purpose of the safety zone is to protect the FPSO from vessels operating... reduces the threat of allisions, oil spills, and releases of natural gas, and thereby protects the safety...

  6. Particulate and dissolved spectral absorption on the continental shelf of the southeastern United States

    Science.gov (United States)

    Nelson, James R.; Guarda, Sonia

    1995-05-01

    Visible absorption spectra of particulate and dissolved materials were characterized on the continental shelf off the southeastern United States (the South Atlantic Bight), emphasizing cross-shelf and seasonal variability. A coastal front separates turbid coastal waters from clearer midshelf waters. Spatial and seasonal patterns were evident in absorption coefficients for phytoplankton, detritus, and colored dissolved organic matter (CDOM); spectral shape parameters for CDOM and detritus; and phytoplankton chlorophyll-specific absorption. The magnitude of CDOM absorption reflected seasonal differences in freshwater discharge and the salinity of the midshelf waters. In the spring of 1993 (high discharge), CDOM absorption at 443 nm was >10 times that of total particulate absorption between 12 and 50 km offshore (0.28-0.69 m-1 versus 0.027-0.062 m-1) and up to 10 times the CDOM absorption measured in the previous summer (low discharge). Phytoplankton chlorophyll-specific absorption in the blue increased with distance from shore (from shift in phytoplankton species composition (from predominantly diatoms inshore to a cyanobacteria-dominated assemblage midshelf in summer), pigment packaging, and higher carotenoid:chlorophyll with distance from shore.

  7. Dating recent sediments from the subaqueous Yangtze Delta and adjacent continental shelf, China

    Directory of Open Access Journals (Sweden)

    Zhang-Hua Wang

    2014-04-01

    Full Text Available In this study we analyzed sediment lithology, fallout of 210Pb and 137Cs, and spheroidal carbonaceous particles (SCPs for two short cores, YZE and CX38, obtained by gravity corer from the Yangtze River mouth offshore and adjacent continental shelf, to compare geochronological methods on the recent sediments of this area. Lithology and grain size changes in YZE suggested the re-discharging of the North Channel of the Yangtze River mouth by flood events during 1949–1954 and associated accretion in the offshore area. This event was validated by a remarkable zone of declination in both 137Cs and 210Pb activities and the absolute ages derived from the 137Cs and SCPs. In contrast, 210Pb results show obvious disturbance of grain size by sediment mixing and cannot be interpreted above 100 cm. In CX38, absolute ages for the early- and mid-1950s were derived by the 137Cs and the SCP profile respectively, which occurred in a reasonable sequence. The excess 210Pb distribution shows exponentially decreasing activities with depth, and the mean sedimentation rate agrees roughly with the one inferred from the SCP profile. We suggest that the limitation of the 210Pb method needs consideration while the SCP profile has the potential to provide a useful and independent dating method for recent Yangtze offshore and adjacent shelf sediments.

  8. Transport and transfer rates in the waters of the Continental Shelf. Annual report

    International Nuclear Information System (INIS)

    Biscaye, P.E.

    1978-07-01

    The present contract year has been one of transition from an emphasis on field work and sample gathering to the predominance of sample and data analysis and the formulation of testable hypotheses concerning specific processes in the New York Bight. We have begun to understand the seasonal transition in the role of phytoplankton vs. grazing zooplankton in forming the particles on which some reactive pollutants are removed. Using natural radioactive tracers we have estimated the removal rates of reactive metals from the surface waters and these range over an order of magnitude from most rapid nearshore to least rapid over the upper continental slope. Once removed nearshore, however, these tracers, and the pollutants for which they proxy, do not remain permanently in the sediments but appear to be remobilized (probably by oxidation) during the winter and are reintroduced into the water column. Work on transport and mixing processes of pollutants which are or behave like those in solution has continued along several fronts. Hydrographic data on the structure of the water column continues to give a description of the system that is crucial to understanding geochemical and biological processes which affect pollutants. Hydrographic characterization of water masses from the data sets of cruises has resulted in hypotheses concerning the renewal of shelf water by direct exchange between shelf and upper slope water

  9. Sedimentology and geochemistry of surface sediments, outer continental shelf, southern Bering Sea

    Science.gov (United States)

    Gardner, J.V.; Dean, W.E.; Vallier, T.L.

    1980-01-01

    Present-day sediment dynamics, combined with lowerings of sea level during the Pleistocene, have created a mixture of sediments on the outer continental shelf of the southern Bering Sea that was derived from the Alaskan Mainland, the Aleutian Islands, and the Pribilof ridge. Concentrations of finer-grained, higher-organic sediments in the region of the St. George basin have further modified regional distribution patterns of sediment composition. Q-mode factor analysis of 58 variables related to sediment size and composition - including content of major, minor, and trace elements, heavy and light minerals, and clay minerals - reveals three dominant associations of sediment: 1. (1) The most significant contribution, forming a coarse-grained sediment scattered over most of the shelf consists of felsic sediment derived from the generally quartz-rich rocks of the Alaskan mainland. This sediment contains relatively high concentrations of Si, Ba, Rb, quartz, garnet, epidote, metamorphic rock fragments, potassium feldspar, and illite. 2. (2) The next most important group, superimposed on the felsic group consists of andesitic sediment derived from the Aleutian Islands. This more mafic sediment contains relatively high concentrations of Na, Ca, Ti, Sr, V, Mn, Cu, Fe, Al, Co, Zn, Y, Yb, Ga, volcanic rock fragments, glass, clinopyroxene, smectite, and vermiculite. 3. (3) A local group of basaltic sediment, derived from rocks of the Pribilof Islands, is a subgroup of the Aleutian andesite group. Accumulation of fine-grained sediment in St. George basin has created a sediment group containing relatively high concentrations of C, S, U, Li, B, Zr, Ga, Hg, silt, and clay. Sediment of the Aleutian andesite group exhibits a strong gradient, or "plume", with concentrations decreasing away from Unimak Pass and toward St. George basin. The absence of present-day currents sufficient to move even clay-size material as well as the presence of Bering submarine canyon between the Aleutian

  10. Fossil ostracodes of continental shelf cores at IODP Site U1354 (Expedition 317)

    Science.gov (United States)

    Kusunoki, S.; Ohi, T.; Kawagata, S.; Ishida, K.; Shipboard Scientific Party, E.

    2010-12-01

    Integrated Ocean Drilling Program (IODP) Expedition 317 was devoted to understanding the relative importance of global sea level (eustasy) versus local tectonic and sedimentary processes in controlling continental margin sedimentary cycles. The expedition recovered sediments from the Eocene to recent period, with a particular focus on the sequence stratigraphy of the late Miocene to recent, when global sea level change was dominated by glacioeustasy. Drilling in the Canterbury Basin, on the eastern margin of the South Island of New Zealand took advantage of high rates of Neogene sediment supply, which preserved a high-frequency (0.1-0.5 m.y.) record of depositional cyclicity. Ostracodes are crustaceans that widely inhabit marine, brackish, and non-marine environments. Shallow marine species have more restricted habitat and respond sensitively to environmental changes. Therefore they are a useful tool for high-resolution analyses of paleoenvironmental changes. We study samples older than ~1.0 Ma from Site U1354, which is in an intermediate position within the three shelf sites transect of Expedition 317. Quaternary to early Pliocene (~4.5 Ma) sediments were cored in this site with best core recovery (81%) among the shelf sites. The period from the Pliocene to Pleistocene is known for distinct paleoclimatic changes, from the intensive warming at around 3.5 Ma, to the cooling stage starting from 2.75 Ma. We expect that high-resolution analyses of fossil ostracode assemblages reveal detailed sea level and paleoceanographic changes on the continental shelf of the Canterbury Basin caused by global climate changes. Samples were examined at 1.5 m depth intervals. Samples of ~20 cc were freeze-dried and washed through a 63 µm opening sieve. The residues were dried and then divided into aliquot parts containing around 200 specimens using a sample splitter. All individual ostracodes were picked from residues coarser than 125 µm. Valves and carapaces were counted as one

  11. Contribution to atmospheric methane by natural seepages on the Bulgarian continental shelf

    Energy Technology Data Exchange (ETDEWEB)

    Dimitrov, L. [Bulgarian Academy of Science, Varna (Bulgaria). Inst. of Oceanology

    2002-07-01

    This paper provides an estimation of the atmospheric methane flux from Bulgarian Black Sea continental shelf. Potential gas source rocks include Holocene gas-charged sediments, Quaternary peats and sapropels, and deep-lying Palaeocene and Neogene clays, Cretaceous coals, and other sediments of late Jurassic to early Cretaceous age. These cover almost the whole continental shelf and slope and, together with irregularly developed seal rocks and widespread active and conducting faults, provide good conditions for upward gas migration. A total of 5 100 line kilometers of shallow seismic (boomer) and echo-sounder records acquired during the Institute of Oceanology's regional surveys, and several detailed side-scan sonar lines, have been reviewed for water column targets. Four hundred and eighty-two targets were assigned as gas seepage plumes. It is estimated that a total of 19,735 individual seeps exists on the open shelf. The number of seeps in coastal waters was estimated to be 6020; this is based on available public-domain data, specific research, and results of a specially made questionnaire which was distributed to a range of 'seamen'. More than 150 measurements of the seabed flux rates were made in the 'Golden sands' and 'Zelenka' seepage areas between 1976 and 1991. Indirect estimations of flux rates from video and photo materials, and a review of published data have also been undertaken. Based on these data, three types of seepages were identified as the most representative of Bulgarian coastal waters. These have flux rates of 0.4, 1.8, and 3.51/min. The contribution to atmospheric methane is calculated by multiplying the flux rates with the number of seepages, and entering corrections for methane concentration and the survival of gas bubbles as they ascend through seawater of the corresponding water depth. The estimation indicates that between 45,100,000 (0.03 Tg) and 210,650,000 m{sup 3} (0. 15 Tg) methane yr{sup -1} come

  12. OESbathy version 1.0: a method for reconstructing ocean bathymetry with generalized continental shelf-slope-rise structures

    Science.gov (United States)

    Goswami, A.; Olson, P. L.; Hinnov, L. A.; Gnanadesikan, A.

    2015-09-01

    We present a method for reconstructing global ocean bathymetry that combines a standard plate cooling model for the oceanic lithosphere based on the age of the oceanic crust, global oceanic sediment thicknesses, plus generalized shelf-slope-rise structures calibrated at modern active and passive continental margins. Our motivation is to develop a methodology for reconstructing ocean bathymetry in the geologic past that includes heterogeneous continental margins in addition to abyssal ocean floor. First, the plate cooling model is applied to maps of ocean crustal age to calculate depth to basement. To the depth to basement we add an isostatically adjusted, multicomponent sediment layer constrained by sediment thickness in the modern oceans and marginal seas. A three-parameter continental shelf-slope-rise structure completes the bathymetry reconstruction, extending from the ocean crust to the coastlines. Parameters of the shelf-slope-rise structures at active and passive margins are determined from modern ocean bathymetry at locations where a complete history of seafloor spreading is preserved. This includes the coastal regions of the North, South, and central Atlantic, the Southern Ocean between Australia and Antarctica, and the Pacific Ocean off the west coast of South America. The final products are global maps at 0.1° × 0.1° resolution of depth to basement, ocean bathymetry with an isostatically adjusted multicomponent sediment layer, and ocean bathymetry with reconstructed continental shelf-slope-rise structures. Our reconstructed bathymetry agrees with the measured ETOPO1 bathymetry at most passive margins, including the east coast of North America, north coast of the Arabian Sea, and northeast and southeast coasts of South America. There is disagreement at margins with anomalous continental shelf-slope-rise structures, such as around the Arctic Ocean, the Falkland Islands, and Indonesia.

  13. The Impact of Internal Wave Seasonality on the Continental Shelf Energy Budget

    Science.gov (United States)

    Wihsgott, Juliane U.; Sharples, Jonathan; Hopkins, Joanne; Palmer, Matthew R.; Mattias Green, J. A.

    2017-04-01

    Heating-stirring models are widely used to simulate the timing and strength of stratification in continental shelf environments. Such models are based on bulk potential energy (PE) budgets: the loss of PE due to thermal stratification is balanced by wind and tidal mixing. The model often fails to accurately predict the observed vertical structure, as it only considers forces acting on the surface and bottom boundary of the water column. This highlights the need for additional internal energy sources to close this budget, and produce an accurate seasonal cycle of stratification. We present new results that test the impact of boundary layer and internal wave forcing on stratification and vertical density structure in continental shelves. A new series of continuous measurements of full water depth vertical structure, dynamics and meteorological data spanning 17 months (March'14-July'15) provide unprecedented coverage over a full seasonal cycle at a station 120 km north-east from the continental shelf break. We observe a highly variable but energetic internal wave field from the onset of stratification that suggests a continuous supply of internal PE. The heating-stirring model reproduces bulk characteristics of the seasonal cycle. While it accurately predicts the timing of the onset in spring and peak stratification in late summer there is a persistent 20 J m-3 positive offset between the model and observations throughout this period. By including a source of internal energy in the model we improve the prediction for the strength of stratification and the vertical distribution of heat. Yet a constant source of PE seems to result in a seasonal discrepancy resulting in too little mixing during strong stratification and too much mixing during transient periods. The discrepancy seen in the model is consistent with the seasonality observed in the internal wave field. We will establish the role that changing stratification (N2) exerts on the internal wave field and vice

  14. Trophic Ecology and Movement Patters of Tiger Sharks (Galeocerdo Cuvier) off the Western North Atlantic Coastal and Continental Shelf Waters

    Science.gov (United States)

    Sancho, G.; Edman, R.; Frazier, B.; Bubley, W.

    2016-02-01

    Understanding the trophic dynamics and habitat utilization of apex predators is central to inferring their influence on different marine landscapes and to help design effective management plans for these animals. Tiger sharks (Galeocerdo cuvier) are abundant in shelf and offshore Gulf Stream waters of the western North Atlantic Ocean, and based on movements from individuals captured in Florida and Bahamas, seem to avoid coastal and shelf waters off South Carolina and Georgia. This contradicts reports of tiger sharks regularly being caught nearshore by anglers in these states, indicating that separate sub-populations may exist in the western North Atlantic. In the present study we captured Tiger Sharks in coastal waters off South Carolina in 2014 and 2015 in order to describe their movement patterns through acoustic and satellite tagging, and trophic dynamics through stable isotope analyses. Movement data show that these tiger sharks repeatedly visit particular inshore areas and mainly travel over the continental shelf, but rarely venture offshore beyond the continental shelf edge. Ongoing C and N stable isotope analyses of muscle, blood and skin tissues from adult and juvenile tiger sharks, as well as from potential prey species and primary producers, will help determine if their diets are based on inshore, shelf or offshore based food webs. Tiger sharks exploiting nearshore environments and shelf waters have much higher probabilities of interacting with humans than individuals occupying far offshore Gulf Stream habitats.

  15. Facts 2000. Norwegian petroleum activities; Fakta 2000. Norsk petroleumsvirksomhet

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    The petroleum resources discovered on the Norwegian Continental Shelf amounts to about 9,6 billion Sm{sup 3} oil equivalents, 76 percent in the North Sea, 20 percent in the Norwegian Sea and 4 percent in the Barents Sea. The present publication gives a summary of the resources, the exploration, the field development, the production of oil and gas, and the revenue from petroleum sale for the year 1999.

  16. Topographic registers of paleo-valleys on the southeastern Brazilian continental shelf

    Directory of Open Access Journals (Sweden)

    Luis Américo Conti

    2009-06-01

    Full Text Available The evolution of paleo-incised-valleys in the São Paulo State region of the southeastern Brazilian continental shelf is presented in this study in relation to the post Last Glacial Maximum (LGM sea-level rises based on the submarine topography modeled by a detailed Digital Elevation Model and evidences noted in high resolution seismic profiles. The hypothesis that has guided this study is that the set of paleo-valley characteristics (i.e. the fluvial parameters of modern coastal drainage systems, the topographical shape and dimensions of the valleys and of the subsurface channels may indicate aspects of the relation between the influence of the fluvial and the eustatic variation regime in geomorphological-stratigraphic registers. Models described in the literature sustain the view that faster marine transgressions tend to increase erosion in estuaries, which may explain the lack of registers of paleo-drainage both in topography and the sub-surface in areas with wider shelves. On the other hand, on narrower shelves, with a higher slope angle, the transgression process can preserve, or even enhance, the incised valley registers during shoreface retreat. In the area studied, we observed that the dimensions and form of the continental shelf varies from the northern to the southern part of the area, affecting aspects of the geomorphological registers of the submerged incised valleys.Este trabalho apresenta aspectos da relação entre a evolução da paleo-drenagem e evolução do nível do mar pós Último Máximo Glacial (UMG para a região da plataforma continental do Estado de São Paulo. Para tal, foram analisados modelos topográficos de detalhe da região de Plataforma Continental a partir de Modelos Digitais de Terreno além de dados de subsuperfície obtidos a partir de linhas sísmicas de alta resolução. A hipótese que guiou este trabalho é de que o conjunto de características relativas aos paleo-vales (i.e. sua relação com a rede de

  17. Petroleum Characterisation and Reservoir Dynamics - The Froey Field and the Rind Discovery, Norwegian Continental Shelf

    Energy Technology Data Exchange (ETDEWEB)

    Bhullar, Abid G.

    1999-07-01

    The objective of this thesis is to apply the fundamental principles of petroleum geochemistry integrated with petroleum/reservoir engineering and geological concepts to the dynamics and characterisation of petroleum reservoirs. The study is based on 600 core samples and 9 DST oils from 11 wells in the Froey Field and the Rind Discovery. The work is presented in five papers. Paper 1 is a detailed characterisation of the reservoirs using a petroleum geochemical approach. Paper 2 describes the application of a single reservoir geochemical screening technique to exploration, appraisal and production geology and reservoir/petroleum engineering. Paper 3 compares the Iatroscan TLC-FID screening technique and the extraction efficiency of micro-extraction used in this work with the well-established Rock-Eval geochemical screening method and with the Soxtec extraction method. Paper 4 refines the migration and filling models of Paper 1, and Paper 5 presents a comparison of models of petroleum generation, migration and accumulation based on geochemical data with 1D burial history, a ''pseudo well'' based on actual well data and regional seismic analysis representing the hydrocarbon generative basin conditions.

  18. OESbathy version 1.0: a method for reconstructing ocean bathymetry with realistic continental shelf-slope-rise structures

    Science.gov (United States)

    Goswami, A.; Olson, P. L.; Hinnov, L. A.; Gnanadesikan, A.

    2015-04-01

    We present a method for reconstructing global ocean bathymetry that uses a plate cooling model for the oceanic lithosphere, the age distribution of the oceanic crust, global oceanic sediment thicknesses, plus shelf-slope-rise structures calibrated at modern active and passive continental margins. Our motivation is to reconstruct realistic ocean bathymetry based on parameterized relationships of present-day variables that can be applied to global oceans in the geologic past, and to isolate locations where anomalous processes such as mantle convection may affect bathymetry. Parameters of the plate cooling model are combined with ocean crustal age to calculate depth-to-basement. To the depth-to-basement we add an isostatically adjusted, multicomponent sediment layer, constrained by sediment thickness in the modern oceans and marginal seas. A continental shelf-slope-rise structure completes the bathymetry reconstruction, extending from the ocean crust to the coastlines. Shelf-slope-rise structures at active and passive margins are parameterized using modern ocean bathymetry at locations where a complete history of seafloor spreading is preserved. This includes the coastal regions of the North, South, and Central Atlantic Ocean, the Southern Ocean between Australia and Antarctica, and the Pacific Ocean off the west coast of South America. The final products are global maps at 0.1° × 0.1° resolution of depth-to-basement, ocean bathymetry with an isostatically adjusted, multicomponent sediment layer, and ocean bathymetry with reconstructed continental shelf-slope-rise structures. Our reconstructed bathymetry agrees with the measured ETOPO1 bathymetry at most passive margins, including the east coast of North America, north coast of the Arabian Sea, and northeast and southeast coasts of South America. There is disagreement at margins with anomalous continental shelf-slope-rise structures, such as around the Arctic Ocean, the Falkland Islands, and Indonesia.

  19. Polycyclic aromatic hydrocarbons (PAHs) in continental shelf sediment of China: Implications for anthropogenic influences on coastal marine environment

    International Nuclear Information System (INIS)

    Liu Liangying; Wang Jizhong; Wei Gaoling; Guan Yufeng; Zeng, Eddy Y.

    2012-01-01

    Sediments collected from the continental shelf of China, embracing Yellow Sea, inner shelf of the East China Sea (ECS), and the South China Sea (SCS), were analyzed for polycyclic aromatic hydrocarbons (PAHs). The concentrations of anthropogenic PAHs (Σ 18 PAH) were 27–224 ng/g dry weight, with an average of 82 ng/g. Sedimentary PAHs in the continental shelf off China were mainly derived from mixed residues of biomass, coal, and petroleum combustion. Fluvial transport and atmospheric deposition mainly accounted for sediment PAHs in the ECS inner shelf and Yellow Sea (and the SCS), respectively. Furthermore, statistically higher levels of Σ 18 PAH (28–224 ng/g; mean 110 ng/g) in the Yellow Sea sediment than in the SCS sediment (28–109 ng/g; mean 58 ng/g) were probably resulted from higher PAH emissions from coke industry and domestic coal combustion in North China than in South China. - Highlights: ► Coal and biomass combustion was the main origin of PAHs in coastal marine sediment of China. ► Fluvial transport was the main mode for transporting PAHs to the East China Sea inner shelf. ► Atmospheric deposition largely accounted for sediment PAHs in Yellow Sea and the South China Sea. ► Regional energy use pattern in China was responsible for the spatial distribution of PAHs in coastal marine sediment. - Sources, compositions and spatial distributions of PAHs in continental shelf sediments off China are analyzed to estimate anthropogenic influences.

  20. Storm-induced inner-continental shelf circulation and sediment transport: Long Bay, South Carolina

    Science.gov (United States)

    Warner, John C.; Armstrong, Brandy N.; Sylvester, Charlene S.; Voulgaris, George; Nelson, Tim; Schwab, William C.; Denny, Jane F.

    2012-01-01

    -pressure systems drove a net sediment flux southwestward. Analysis of a 12-year data record from a local buoy shows an average of 41 cold fronts, 32 warm fronts, and 26 low-pressure systems per year. The culmination of these events would yield a cumulative net inner-continental shelf transport to the south–west, a trend that is further verified by sediment textural analysis and bedform morphology on the inner-continental shelf.

  1. Outer Continental Shelf Stratigraphic Development and Sand Resource Potential: Integration of New and Legacy Geologic Datasets

    Science.gov (United States)

    Hughes, M.; Harris, S.; Luciano, K. E.; Alexander, C. R., Jr.

    2017-12-01

    Following the impact of Hurricane Sandy on the U.S. Atlantic coast in 2012 the Bureau of Ocean Energy Management (BOEM), in cooperation with state partners, instituted several regional offshore resource studies for the near outer continental shelf (OCS) on the US East Coast. This study focuses on a portion of this region, offshore of South Carolina and Georgia, with a primary goal of identifying beach renourishment sands and wind-tower placement locations, and creating a conceptual model of the evolution of the shelf in these areas. New and previously collected data are being used to identify sediment distribution patterns, paleolandscapes, sand resources for beach renourishment projects, and feasible locations for offshore wind installations. New chirp subbottom profiler data ( 1000 km), sidescan sonar data ( 7900km2), magnetometer data ( 1700 km), and multibeam bathymetry data ( 430km2) have been processed and interpreted at the University of Charleston using SonarWiz7, QPS-Qimera and QPS-Fledermaus software suites. Areas of focus for the Atlantic Sand Assessment Program (ASAP) data collection along the SC and GA coast are located within the 3 to 8 nautical mile (nm) OCS offshore of (North to South) Little River, Cape Romain, Folly Beach, Hilton Head, Wassaw, Ossabaw, Jekyll, St. Simons, and Cumberland islands. Ravinement, pre-Holocene, and other seismic surfaces, along with internal geometries, were mapped in these distinctly different tidal and wave regimes. Holocene sediment thickness gradually increases to the south with several sediment wedges in excess of 40 meters thickness. Where mapped, subsurface paleochannels/valleys were identified and analyzed for their orientation and complexity, as well as their size and distribution. These paleochannels are more numerous and increasingly complex in the southern survey areas. The channels are possibly related to transgressive channeling, Pleistocene low-stand river channeling, and braided stream formation during

  2. Mercury in sediments from shelf and continental slope at Campos Basin near Rio de Janeiro, Brazil

    Science.gov (United States)

    Araujo, Beatriz; Hintelmann, Holger; Dimock, Brian; Gomes de Almeida, Marcelo; Falcão, Ana Paula; de Rezende, Carlos Eduardo

    2016-04-01

    Mercury (Hg) is a global pollutant due to its ability to undergo long-range transport from source regions to remote parts of the world, and its ubiquitous presence in aquatic ecosystems. The Hg isotope ratios could be an effective tool for tracing the sources and process of Hg in the environment. This study aimed to establish the distribution of mercury in surface sediments of three transects (25- 3000m water depth) in continental shelf and slope in Campos Basin-RJ-Brazil, using the Hg isotopes to understand the geochemical processes relating to Hg cycling that occur in a subtropical coastal environment. The study area was divided into three transects: A (located to the south and close to a upwelling area), D (located opposite the mouth of the Paraiba do Sul River) and I (located north near the top of Vitória-ES). Sampling isobaths were 25, 50, 75, 100, 150, 400, 700, 1000, 1300, 1900, 2500 and 3000m. The Total Hg, MMHg and Hg stable isotopes were determined based on EPA Method 1631, EPA method 1630 and Foucher and Hintelmann (2006), respectively. The silt/clay ranged from 0.05 to 95%, and the organic carbon (OC) from 0.07 to 1.43 % for all transects. THg and MMHg concentrations in the shelf were 11.9 ± 7.2 (1.7- 22.2) ng.g-1 and 0.15 ± 0.12 (0.02 - 0.40) ng.g-1; in the slope 30.3 ± 9.2 (11.6 - 51.6) ng.g-1 and 0.13 ± 0.06 (0.03 -0.29) ng.g-1 , respectively. The δ202Hg and Δ199Hg varied from -0.32 to -1.85 ‰ (-0.79 ± 0.44‰) and -0.41 to 0.09 ‰ (-0.03 ± 0.12 ‰) for all transects, respectively. The delta values between both regions are significantly different, the shelf region showed δ202Hg from -0.59 to -2.19 ‰ (mean: -1.52 ±0.65) and Δ199Hg from - 0.53 to 0.08 ‰ (mean: -0.27 ±0.55) and the slope region were observed δ202Hg values from -0.32 to -1.82 ‰ (mean: -0.73 ±0.39 ‰ n=18) and gΔ199Hg from -0.23 to 0.09‰ (mean: -0.02 ±0.08‰ n=5). The slope appears to be enriched with heavier isotopes compared to the shelf, however, in the

  3. Distribution of hydrocarbon-utilizing microorganisms and hydrocarbon biodegradation potentials in Alaskan continental shelf areas

    International Nuclear Information System (INIS)

    Roubal, G.; Atlas, R.M.

    1978-01-01

    Hydrocarbon-utilizing microogranisms were enumerated from Alaskan continental shelf areas by using plate counts and a new most-probable-number procedure based on mineralization of 14 C-labeled hydrocarbons. Hydrocarbon utilizers were ubiquitously distributed, with no significant overall concentration differences between sampling regions or between surface water and sediment samples. There were, however, significant seasonal differences in numbers of hydrocarbon utilizers. Distribution of hydrocarbon utilizers within Cook Inlet was positively correlated with occurrence of hydrocarbons in the environment. Hydrocarbon biodegradation potentials were measured by using 14 C-radiolabeled hydrocarbon-spiked crude oil. There was no significant correlation between numbers of hydrocarbon utilizers and hydrocarbon biodegradation potentials. The biodegradation potentials showed large seasonal variations in the Beaufort Sea, probably due to seasonal depletion of available nutrients. Non-nutrient-limited biodegradation potentials followed the order hexadecane > naphthalene >> pristane > benzanthracene. In Cook Inlet, biodegradation potentials for hexadecane and naphthalene were dependent on availability of inorganic nutrients. Biodegradation potentials for pristane and benzanthracene were restricted, probably by resistance to attack by available enzymes in the indigenous population

  4. Downscaling an Eddy-Resolving Global Model for the Continental Shelf off South Eastern Australia

    Science.gov (United States)

    Roughan, M.; Baird, M.; MacDonald, H.; Oke, P.

    2008-12-01

    The Australian Bluelink collaboration between CSIRO, the Bureau of Meteorology and the Royal Australian Navy has made available to the research community the output of BODAS (Bluelink ocean data assimilation system), an ensemble optimal interpolation reanalysis system with ~10 km resolution around Australia. Within the Bluelink project, BODAS fields are assimilated into a dynamic ocean model of the same resolution to produce BRAN (BlueLink ReANalysis, a hindcast of water properties around Australia from 1992 to 2004). In this study, BODAS hydrographic fields are assimilated into a ~ 3 km resolution Princeton Ocean Model (POM) configuration of the coastal ocean off SE Australia. Experiments were undertaken to establish the optimal strength and duration of the assimilation of BODAS fields into the 3 km resolution POM configuration for the purpose of producing hindcasts of ocean state. It is shown that the resultant downscaling of Bluelink products is better able to reproduce coastal features, particularly velocities and hydrography over the continental shelf off south eastern Australia. The BODAS-POM modelling system is used to provide a high-resolution simulation of the East Australian Current over the period 1992 to 2004. One of the applications that we will present is an investigation of the seasonal and inter-annual variability in the dispersion of passive particles in the East Australian Current. The practical outcome is an estimate of the connectivity of estuaries along the coast of southeast Australia, which is relevant for the dispersion of marine pests.

  5. 137Cs inventory in sedimentary columns from continental shelf of Sao Paulo state

    International Nuclear Information System (INIS)

    Figueira, Rubens C.L.; Cordero, Luisa M.; Mahiques, Michel M. de; Tessler, Moyses G.

    2009-01-01

    137 Cs is an artificial radioactive isotope produced by 235 U fission. This radionuclide has a high fission yield and a half-life of 30 years. It has been detected in the environment since 1945 and its principal contamination source has been nuclear tests in the atmosphere. There are other sources of 137 Cs contamination in the environment, such as: release from nuclear and reprocessing plants, radioactive dumping and nuclear accidents (Chernobyl, for example). This paper presents an inventory of 137 Cs on the Continental Shelf of Sao Paulo State, a region located between Cabo de Santa Marta Grande (Santa Catarina state) and Cabo Frio (Rio de Janeiro state). In this area, 9 cores were collected by the Instituto Oceanografico da Universidade de Sao Paulo (Sao Paulo University Institute of Oceanography). The cores were sliced at every 2 cm; sub-samples were lyophilized, grinded and stored in plastic containers. 137 Cs was determined by 661 keV photopeak using a gamma spectrometry detector (Ge hyperpure). The analysis was performed by efficiency and background in different counting times. 137 Cs concentration activities varied from 0.3 to 3.6 Bq kg -1 with a mean value of 1.2±0.6 Bq kg -1 . The inventory of 137 Cs in this area was 13±7 Bq m-2. Values obtained are in agreement with the Southern Hemisphere, a region contaminated by atmospheric fallout due to past nuclear explosions. (author)

  6. Adequacy of environmental information for outer continental shelf oil and gas decisions: Florida and California

    International Nuclear Information System (INIS)

    1989-01-01

    The environmental impacts of oil and gas production on the U.S. outer continental shelf (OCS) have been studied and debated for many years. The issues derive from the complexity of coastal and offshore marine processes and ecosystems, human socio-economic systems, and interactions with OCS oil and gas development activities. On Feb. 9, 1989, President Bush announced his decision to postpone leasing for OCS areas off southwestern Florida (sale 116, part 2), northern California (sale 91), and southern California (sale 95). At the same time, the President created a cabinet-level task force to review the environmental concerns for these three OCS areas, and he also requested independent advice from the National Research Council (NRC). The NRC was asked to assess the adequacy of the available scientific and technical information on estimated hydrocarbon resources and potential environmental effects for the three specified areas. The report, by the OCS Committee and its three panels dealing with ecology, physical oceanography, and socioeconomics, reviews the adequacy of information bearing upon the potential environmental impacts of OCS oil and gas activities for the three sale areas

  7. Recent Advances in Bathymetric Surveying of Continental Shelf Regions Using Autonomous Vehicles

    Science.gov (United States)

    Holland, K. T.; Calantoni, J.; Slocum, D.

    2016-02-01

    Obtaining bathymetric observations within the continental shelf in areas closer to the shore is often time consuming and dangerous, especially when uncharted shoals and rocks present safety concerns to survey ships and launches. However, surveys in these regions are critically important to numerical simulation of oceanographic processes, as bathymetry serves as the bottom boundary condition in operational forecasting models. We will present recent progress in bathymetric surveying using both traditional vessels retrofitted for autonomous operations and relatively inexpensive, small team deployable, Autonomous Underwater Vehicles (AUV). Both systems include either high-resolution multibeam echo sounders or interferometric sidescan sonar sensors with integrated inertial navigation system capabilities consistent with present commercial-grade survey operations. The advantages and limitations of these two configurations employing both unmanned and autonomous strategies are compared using results from several recent survey operations. We will demonstrate how sensor data collected from unmanned platforms can augment or even replace traditional data collection technologies. Oceanographic observations (e.g., sound speed, temperature and currents) collected simultaneously with bathymetry using autonomous technologies provide additional opportunities for advanced data assimilation in numerical forecasts. Discussion focuses on our vision for unmanned and autonomous systems working in conjunction with manned or in-situ systems to optimally and simultaneously collect data in environmentally hostile or difficult to reach areas.

  8. Direct impacts of outer continental shelf activities on wetland loss in the central Gulf of Mexico

    International Nuclear Information System (INIS)

    Baumann, R.H.; Turner, R.E.

    1990-01-01

    The direct impacts of outer continental shelf (OCS) development on recent wetland loss in the northern Gulf of Mexico were quantified using aerial imagery, field surveys, and literature review. The total direct impacts accounted for an estimated 25.6 percent of total net wetland loss within the Louisiana portion of the study area from 1955/56 to 1978. Of the total direct impacts of 73,905 ha, OCS-related activities accounted for 11,589-13,631 ha of the wetland loss during the same time interval. Although this is a substantial areal loss, it represents only 4.0-4.7 percent of the total Louisiana wetland loss from 1955/56 to 1978, and 15.7-18.4 percent of direct impacts. Direct impacts from OCS pipelines averages 2.49 ha/km, lower than published guidelines, and totaled 12,012 ha. Lowest impacts are for backfilled pipelines in the Chenier Plain of western Louisiana and for small young pipeline canals does not appear to be an important factor for total new wetland loss in the coastal zone because few pipelines are open to navigation and, for the examples found, the impact width was not significantly different than for open pipelines closed to navigation. Navigation channels account for a minimum of 16,902 ha of habitat change. Direct impacts per unit length of navigation channel average 20 times greater than pipelines

  9. A longitudinal study of fallow dynamics in the UK Continental Shelf (UKCS)

    International Nuclear Information System (INIS)

    Kemp, Alexander G.; Kasim, Sola A.

    2007-01-01

    This paper identifies the causes of and solutions to the problems posed by the fallow assets' phenomenon in the UK Continental Shelf (UKCS). Using data available in the public domain, including the Fifth Fallow Release, the province's assets were grouped into two broad cross-sections of fallow and non-fallow assets, with further sub-divisions. The dependent variable of interest was the median fallow duration of the assets. Fallow duration was measured in two ways, namely those relating to censored and uncensored data. An empirical panel econometric model was formulated, estimated and simulated to establish the principal causal factors and the effective remedial policy measures. The model estimation results provide evidence that the interactive effects of the key influencing variables are stronger than their individual effects. Thus, the combined effects of reserves and distance from infrastructure have a greater weight on the fallow spell than their individual effects. Several policy simulation runs established that, contrary to some theoretical propositions (a) stronger rather than weaker government intervention, on occasion, is preferable, and (b) price is not a central determinant of investment timing

  10. {sup 137}Cs inventory in sedimentary columns from continental shelf of Sao Paulo state

    Energy Technology Data Exchange (ETDEWEB)

    Figueira, Rubens C.L.; Cordero, Luisa M.; Mahiques, Michel M. de; Tessler, Moyses G., E-mail: rfigueira@usp.b [Universidade de Sao Paulo (USP), SP (Brazil). Inst. Oceanografico. Dept. de Oceanografia Fisica, Quimica e Geologica; Cruz, Jacson L.S. [Universidade Cruzeiro do Sul, Sao Paulo, SP (Brazil)

    2009-07-01

    {sup 137}Cs is an artificial radioactive isotope produced by {sup 235}U fission. This radionuclide has a high fission yield and a half-life of 30 years. It has been detected in the environment since 1945 and its principal contamination source has been nuclear tests in the atmosphere. There are other sources of {sup 137}Cs contamination in the environment, such as: release from nuclear and reprocessing plants, radioactive dumping and nuclear accidents (Chernobyl, for example). This paper presents an inventory of {sup 137}Cs on the Continental Shelf of Sao Paulo State, a region located between Cabo de Santa Marta Grande (Santa Catarina state) and Cabo Frio (Rio de Janeiro state). In this area, 9 cores were collected by the Instituto Oceanografico da Universidade de Sao Paulo (Sao Paulo University Institute of Oceanography). The cores were sliced at every 2 cm; sub-samples were lyophilized, grinded and stored in plastic containers. {sup 137}Cs was determined by 661 keV photopeak using a gamma spectrometry detector (Ge hyperpure). The analysis was performed by efficiency and background in different counting times. {sup 137}Cs concentration activities varied from 0.3 to 3.6 Bq kg{sup -1} with a mean value of 1.2+-0.6 Bq kg{sup -1}. The inventory of {sup 137}Cs in this area was 13+-7 Bq m-2. Values obtained are in agreement with the Southern Hemisphere, a region contaminated by atmospheric fallout due to past nuclear explosions. (author)

  11. A preliminary assessment of geologic framework and sediment thickness studies relevant to prospective US submission on extended continental shelf

    Science.gov (United States)

    Hutchinson, Deborah R.; Childs, Jonathan R.; Hammar-Klose, Erika; Dadisman, Shawn; Edgar, N. Terrence; Barth, Ginger A.

    2004-01-01

    Under the provisions of Articles 76 and 77 of the United Nations Convention on the Law of the Sea (UNCLOS), coastal States have sovereign rights over the continental shelf territory beyond 200-nautical mile (nm) from the baseline from which the territorial sea is measured if certain conditions are met regarding the geologic and physiographic character of the legal continental shelf as defined in those articles. These claims to an extended continental shelf must be supported by relevant bathymetric, geophysical and geological data according to guidelines established by the Commission on the Limits of the Continental Shelf (CLCS, 1999). In anticipation of the United States becoming party to UNCLOS, Congress in 2001 directed the Joint Hydrographic Center/Center for Coastal and Ocean Mapping at the University of New Hampshire to conduct a study to evaluate data relevant to establishing the outer limit of the juridical continental shelf beyond 200 nm and to recommend what additional data might be needed to substantiate such an outer limit (Mayer and others, 2002). The resulting report produced an impressive and sophisticated GIS database of data sources. Because of the short time allowed to complete the report, all seismic reflection data were classified together; the authors therefore recommended that USGS perform additional analysis on seismic and related data holdings. The results of this additional analysis are the substance of this report, including the status of geologic framework, sediment isopach research, and resource potential in the eight regions1 identified by Mayer and others (2002) where analysis of seismic data might be crucial for establishing an outer limit . Seismic reflection and refraction data are essential in determining sediment thickness, one of the criteria used in establishing the outer limits of the juridical continental shelf. Accordingly, the initial task has been to inventory public-domain seismic data sources, primarily those regionally

  12. Oil-spill risk analysis: Gulf of Mexico (Proposed Lease Sales 131/135/137) Outer Continental Shelf. Final report

    International Nuclear Information System (INIS)

    Hannon, L.J.; LaBelle, R.P.; Lear, E.M.

    1991-09-01

    The Federal Government has proposed to offer Outer Continental Shelf lands in the Gulf of Mexico for oil and gas leasing. Because oil spills may occur from activities associated with offshore oil production, the Minerals Management Service conducts a formal risk assessment. In evaluating the significance of accidental oil spills, it is important to remember that the occurrence of such spills is fundamentally probabilistic. The effects of oil spills that could occur during oil and gas production must be considered. The report summarizes results of an oil spill risk analysis conducted for the proposed Gulf of Mexico Outer Continental Shelf Lease Sales 131/135/137. The objective of this analysis was to estimate relative risks associated with oil and gas production for the proposed lease sales

  13. Net Heterotrophy in the Amazon Continental Shelf Changes Rapidly to a Sink of CO2 in the Outer Amazon Plume

    Directory of Open Access Journals (Sweden)

    Nathalie Lefèvre

    2017-09-01

    Full Text Available The Amazon continental shelf and adjacent oceanic area were sampled for inorganic and organic carbon parameters in order to improve data coverage and understanding of carbon cycling dynamics within this important region. Seasonal coverage of the Amazon plume on the French Guiana continental shelf further north, was provided by CO2 monitoring using a merchant ship sailing from France to French Guiana (2006–2016. Salinity ranged from 1 to 36 (transects in April 2013, and May 2014. At salinity below 10, strong outgassing was observed with fugacity of CO2 (fCO2 over 2,000 μatm. This region displayed net heterotrophy, fueled by organic matter with terrestrial origin, as shown by δ13C and δ15N values of suspended particles. A δ13C cross shelf average of −31% was measured during May 2014, contrasting with oceanic values in excess of −20%. The reactivity of this terrestrial material resulted in the local production of dissolved inorganic and organic carbon as well as fluorescent humic compounds. Further offshore, the dilution of freshwater by ocean waters created a sink for CO2, enhanced by biological activity. The strongest CO2 drawdowns, associated with high chlorophyll a concentrations, were observed on the French Guiana continental shelf in the outer Amazon plume, with fCO2 values below 150 μatm. Here, a CO2 sink was present almost throughout the year, with a seasonal maximum of −9.2 mmol CO2 m−2d−1 observed in June 2015. However, both the CO2 and salinity distributions could vary significantly within a few days, confirming the presence of many eddies in this region. The Amazon continental shelf hence behaved as a transition zone between an inshore source of CO2 to the atmosphere and an offshore sink. Some marine phytoplankton production was detected but occurred mainly close to the French Guiana shelf. A mean net CO2 outgassing of 44 ± 43.6 mmol m−2d−1 was estimated for the area. Quantifying the CO2 flux for the entire Amazon

  14. OESbathy version 1.0: a method for reconstructing ocean bathymetry with realistic continental shelf-slope-rise structures

    OpenAIRE

    A. Goswami; P. L. Olson; L. A. Hinnov; A. Gnanadesikan

    2015-01-01

    We present a method for reconstructing global ocean bathymetry that uses a plate cooling model for the oceanic lithosphere, the age distribution of the oceanic crust, global oceanic sediment thicknesses, plus shelf-slope-rise structures calibrated at modern active and passive continental margins. Our motivation is to reconstruct realistic ocean bathymetry based on parameterized relationships of present-day variables that can be applied to global oceans in th...

  15. Delineating the relationship between chromophoric dissolved organic matter (CDOM) variability and biogeochemical parameters in a shallow continental shelf

    OpenAIRE

    Sourav Das; Sugata Hazra; Aneesh A. Lotlikar; Isha Das; Sandip Giri; Abhra Chanda; Anirban Akhand; Sourav Maity; T. Srinivasa Kumar

    2016-01-01

    Absorption coefficient of chromophoric dissolved organic matter (CDOM) at 440 nm [aCDOM (440)], sea surface salinity (SSS), total suspended matter (TSM) and chlorophyll-a (chl-a) were measured during October, 2014 to March, 2015 in the shallow continental shelf waters of the Hugli Estuary, adjacent to West Bengal coast, India. The primary objective of the study was to characterize the relationship between aCDOM (440) and the above mentioned biogeochemical parameters. Upon analyzing the result...

  16. Impact of Satellite Remote Sensing Data on Simulations of Coastal Circulation and Hypoxia on the Louisiana Continental Shelf

    OpenAIRE

    Dong S. Ko; Richard W. Gould; Bradley Penta; John C. Lehrter

    2016-01-01

    We estimated surface salinity flux and solar penetration from satellite data, and performed model simulations to examine the impact of including the satellite estimates on temperature, salinity, and dissolved oxygen distributions on the Louisiana continental shelf (LCS) near the annual hypoxic zone. Rainfall data from the Tropical Rainfall Measurement Mission (TRMM) were used for the salinity flux, and the diffuse attenuation coefficient (Kd) from Moderate Resolution Imaging Spectroradiometer...

  17. Microalgae of the continental shelf off Paraná State, southeastern Brazil: a review of studies

    Directory of Open Access Journals (Sweden)

    Frederico P. Brandini

    1996-01-01

    Full Text Available The paper reviews the taxonomic and ecological works on marine microalgae (phytoplankton and microphytobenthos off Paraná State, Southeastern Brazil. Various studies refer to the taxonomy of benthic diatoms. Few descriptive field works in coastal and adjacent shelf waters contribute to the understanding of phytoplankton dynamics in coastal and shelf areas. Patterns of geographic distribution and changes in the phytoplankton community are described in relation to water masses and seasonal variations in the hydrographic regime. During summertime, when warm oligotrophic waters predominate over the shelf, the phytoplankton is nummerically dominated by small phytotlagellates, dinotlagellates, coccolithophorids and filaments of cyanobacteria. During wintertime, the abundance of micro-size diatoms over the shclf increase due to the dominance of cold nutrient-rich waters from the South Atlantic Central Water and wind-driven vertical circulation. The phytoplankton community off Paraná State may be classified into two categorics: the diatom-dominated coastal assemblage, mainly controlled by nutrient inputs from land drainage and ressuspension of bottom sediments, and the tlagellate-dominated shelf assemblage, more affectcd by the seasonality of local hydrographic regime.O trabalho é uma revisão dos estudos taxonômicos e ecológicos das microalgas (planctônicas e bentônicas realizados no Estado do Paraná. A maioria dos trabalhos sobre microfitobentos são de caráter taxonômico e, basicamente, referem-se à diatomáceas bênticas sobre macroalgas ou fundos lodosos e consolidados. Poucos trabalhos contribuiram para o estudo da dinâmica espaço-temporal do fitoplâncton em áreas costeiras e de plataforma. São descritos os padrões de distribuição geográfica e as mudanças sazonais na comunidade fitoplanctônica em relação ao regime hidrográfico. No verão, quando águas quentes oligotróficas predominam na superfície, o fitoplâncton

  18. Bacteria, carbon dioxide and methane measurements in the Cariaco Basin on the continental shelf of Venezuela, April 2001 - January 2002 (NODC Accession 0001078)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Bacteria, carbon dioxide and methane measurements were collected using bottle casts in the Cariaco Basin on the continental shelf of Venezuela from 30 April 2001 to...

  19. Distribution and sources of organic carbon, nitrogen and their isotopic signatures in sediments from the Ayeyarwady (Irrawaddy) continental shelf, northern Andaman Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Gaye, B.; Shirodkar, P.V.; Rao, P.S.; Chivas, A.R.; Wheeler, D.; Thwin, S.

    Total organic carbon (TOC), total nitrogen (TN) and their delta sup(13) C and delta sup (15) N values were determined from 110 sediment samples from the Ayeyarwady (Irrawaddy) continental shelf, northern Andaman Sea to decipher the concentration...

  20. Use of Geological, Geophysical and Geomorphological Information as support for the harmonization of the legal limits of the continental shelf between Brazil and Uruguay

    International Nuclear Information System (INIS)

    Torres, L.; Villena, H.

    2010-01-01

    The United Nations Convention of the Law of the Sea (UNCLOS) establishes the juridical and legal frameworks which the Coastal States (C S) establish their respective outer limit of the continental shelf in which will exercise sovereignty rights under the resources in the on the seabed and seabed subsurface. The base to reach the delineation of continental shelf outer limit is ruled by the application the criteria which take into consideration mainly data and pieces of information from Geology, Geophysics and Geomorphology employed both lonely or conjunction. In the current presentation were employed both data carried out by Brazilian Continental Shelf Project (Laplace) and data from public domain. As the underwater features do not follow political limits, the goal of this proposal work is to present the integration of both data and pieces of information from geological, geophysical and geomorphologic characteristics in order to reach the harmonization of the Brazil and Uruguay continental shelf outer limit nearby their Maritime Lateral Boundary

  1. Atlantic Offshore Seabird Dataset Catalog, Atlantic Coast and Outer Continental Shelf, from 1938-01-01 to 2013-12-31 (NODC Accession 0115356)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Several bureaus within the Department of Interior compiled available information from seabird observation datasets from the Atlantic Outer Continental Shelf into a...

  2. Polycyclic aromatic hydrocarbons (PAHs) in continental shelf sediment of China: implications for anthropogenic influences on coastal marine environment.

    Science.gov (United States)

    Liu, Liang-Ying; Wang, Ji-Zhong; Wei, Gao-Ling; Guan, Yu-Feng; Zeng, Eddy Y

    2012-08-01

    Sediments collected from the continental shelf of China, embracing Yellow Sea, inner shelf of the East China Sea (ECS), and the South China Sea (SCS), were analyzed for polycyclic aromatic hydrocarbons (PAHs). The concentrations of anthropogenic PAHs (Σ(18)PAH) were 27-224 ng/g dry weight, with an average of 82 ng/g. Sedimentary PAHs in the continental shelf off China were mainly derived from mixed residues of biomass, coal, and petroleum combustion. Fluvial transport and atmospheric deposition mainly accounted for sediment PAHs in the ECS inner shelf and Yellow Sea (and the SCS), respectively. Furthermore, statistically higher levels of Σ(18)PAH (28-224 ng/g; mean 110 ng/g) in the Yellow Sea sediment than in the SCS sediment (28-109 ng/g; mean 58 ng/g) were probably resulted from higher PAH emissions from coke industry and domestic coal combustion in North China than in South China. Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. Seasonal Dynamics of Dissolved Organic Carbon Under Complex Circulation Schemes on a Large Continental Shelf: The Northern South China Sea

    Science.gov (United States)

    Meng, Feifei; Dai, Minhan; Cao, Zhimian; Wu, Kai; Zhao, Xiaozheng; Li, Xiaolin; Chen, Junhui; Gan, Jianping

    2017-12-01

    We examined the distribution and seasonality of dissolved organic carbon (DOC) based on a large data set collected from the northern South China Sea (NSCS) shelf under complex circulation schemes influenced by river plume, coastal upwelling, and downwelling. The highest surface values of ˜117 μmol L-1 were observed nearshore in summer suggesting high DOC supplies from the river inputs, whereas the lowest surface values of ˜62 μmol L-1 were on the outer shelf in winter due to entrainment of DOC-poor subsurface water under strengthened vertical mixing. While the summer coastal upwelling brought lower DOC from offshore depth to the nearshore surface, the winter coastal downwelling delivered higher surface DOC to the midshelf deep waters from the inner shelf fueled by the China Coastal Current (CCC) transporting relatively high DOC from the East China Sea to the NSCS. The intensified winter downwelling generated a cross-shelf DOC transport of 3.1 × 1012 g C over a large shelf area, which induced a significant depression of the NSCS DOC inventory in winter relative to in autumn. In addition to the variable physical controls, net biological production of DOC was semiquantified in both the river plume (2.8 ± 3.0 μmol L-1) and coastal upwelling (3.1 ± 1.3 μmol L-1) in summer. We demonstrated that the NSCS shelf had various origins of DOC including riverine inputs, inter-shelf transport and in situ production. Via cross-shelf transport, the accumulated DOC would be exported to and stored in the deep ocean, suggesting that continental shelves are a potentially effective carbon sink.

  4. Oil-spill risk analysis: Central and western Gulf of Mexico Outer Continental Shelf, Lease Sales 139 and 141. Final report

    International Nuclear Information System (INIS)

    Johnson, W.R.; Lear, E.M.

    1992-02-01

    The Federal Government has proposed to offer Outer Continental Shelf lands in the Gulf of Mexico for oil and gas leasing. Because oil spills may occur from activities associated with offshore oil production, the Minerals Management Service conducts a formal risk assessment. The effects of oil spills that could occur during oil and gas production must be considered. The report summarizes results of an oil spill risk analysis conducted for the proposed Gulf of Mexico Outer Continental Shelf Lease Sales 139 and 141

  5. Aeromagnetic and gravity investigations of the Coastal Area and Continental Shelf of Liberia, West Africa, and their relation to continental drift

    Science.gov (United States)

    Behrendt, John C.; Wotorson, Cletus S.

    1970-01-01

    An aeromagnetic survey has shown the existence of several basins in which magnetic basement depths are greater than 5 km on the continental shelf off Liberia. Magnetic diabase of 176 to 192 m.y. (Jurassic) in age intruding the Paleozoic (?) rocks and overlain by younger rocks onshore requires the distinction between “magnetic basement” and “basement.” Several lines of evidence suggest that the Paleozoic(?) rocks are less than 1 km thick; this implies that the diabase does not introduce a large error in depth-to-basement estimates. The dikes or their extrusive equivalents are traceable, on the basis of the magnetic data, beneath the younger sedimentary rock in the basins to the edge of the continental slope. The magnetic data also delineate a second zone of diabase dikes 90 km inland, parallel to the coast, which cross the entire country. The intrusion of the younger dikes probably coincides with rifting at the beginning of the separation of Africa and South America, and the associated magnetic anomaly zones appear to be parallel with and continuous into the anomaly bands in the Atlantic. A major northeast-trending break in the magnetic fabric intersects the coast near 9° W. and is associated with Eburnean age rocks (about 2000 m.y.) to the southeast as contrasted with Liberian-age rocks (about 2700 m.y.) to the northwest. Change in magnetic fabric direction inland from northeast to northwest in the coastal area allows recognition of a boundary between the Liberian-age rocks inland and Pan-African-age (about 550 m.y.) rocks in the coastal area northwest of about 9° 20'W. Sets of north-northwest-and west-northwest—trending faults of 1 to 2 km vertical displacement cut the Cretaceous sedimentary rocks onshore and can be traced into the offshore basins. Vertical displacements of several kilometers in the magnetic basement underlying the continental shelf suggest a pattern of block faulting all along the coast and continental shelf. Negative Bouguer

  6. Assemblages of fish larvae and mesozooplankton across the continental shelf and shelf slope of the Andaman Sea (NE Indian Ocean)

    DEFF Research Database (Denmark)

    Munk, Peter; Bjørnsen, Peter Koefoed; Boonruang, P.

    2004-01-01

    on the sampling of fish larvae and mesozooplankton. Surveys were carried out during 2 monsoon periods in March and August 1996, using 3 cross-bathymetric transects extending to the deeper part of the shelf slope of the Andaman Sea. Station distances were either 5 or 10 n miles apart, and at each station a series...... with a hydrographic front generated where the pycnocline meets the sea-bottom. An internal wave of pronounced amplitude interacts with the shelf slope at ca. 300 m bottom depth, and findings indicated another zone of enhanced abundance in this area. Analysis of the relative abundances of fish larvae within families...

  7. A century of oceanographic and fisheries exploration on the continental shelf off Argentina

    Science.gov (United States)

    Angelescu, V.; Sánchez, R. P.

    1995-03-01

    A detailed analysis is presented of the main contributions, both local and international, to the fields of oceanography and fishery sciences resulting from exploratory cruises carried out on the continental shelf off Argentina over the last 100 years. The end of the 19th century is chosen as a starting point for this analysis as it marks the beginning of active marine research by Argentinian scientists and an accumulation of information on Antarctic and Subantarctic organisms in foreign journals. Mention is also made of previous contributions derived from the classic expeditions and global circumnavigational voyages during the 18th and 19th centuries. Although the aims of those were not always strictly oceanographic, they rendered significant information to this field of knowledge. In the early years, references arose mainly from the particular geographic situation of the Argentinian shelf, a necessary passage in the navigation routes to the Pacific Ocean, and later on the way to Antarctica. Sources of information are divided into four categories: (a) foreign scientific projects in the area; (b) investigation by Argentinian scientists and research vessels; (c) joint projects between Argentinian and foreign institutions; and (d) contributions from sources other than oceanographic cruises (commercial navigation, maritime weather reports, satellite images, etc.). The analysis includes an updated and classified bibliographical list of the main contributions to the fields of oceanography and fishery sciences derived from those sources, published either in international or local journals or appearing as technical and internal reports. The motivations, objectives and main achievements of foreign surveys and programmes in the area and their impact on local scientific progress are discussed. The early sixties mark a turning point in the evolution of international research in the area. The creation of biological stations along the Argentinian coast, and the support given to

  8. Hurricane Sandy's Fingerprint: Ripple Bedforms at an Inner Continental Shelf Sorted Bedform Field Site

    Science.gov (United States)

    DuVal, C.; Trembanis, A. C.; Beaudoin, J. D.; Schmidt, V. E.; Mayer, L. A.

    2013-12-01

    The hydrodynamics and seabed morphodynamics on the inner continental shelf and near shore environments have increasing relevance with continued development of near shore structures, offshore energy technologies and artificial reef construction. Characterizing the stresses on and response of the seabed near and around seabed objects will inform best practices for structural design, seabed mine and unexploded ordnance detection, and archaeological and benthic habitat studies. As part of an ONR funded project, Delaware's Redbird Reef is being studied for object scour and sorted bedform morphodynamics (Trembanis et al., in press). Central to this study are the effects of large storm events, such as Hurricane Sandy, which have had significant impact on the seafloor. Previous studies of inner shelf bedform dynamics have typically focused on near bed currents and bed stressors (e.g. Trembanis et al., 2004), sorted bedforms (e.g. Green et al., 2004) and object scour (e.g. Quinn, 2006; Trembanis et al., 2007; Mayer et al., 2007), but our understanding of the direct effects of objects and object scour on bedform morphodynamics is still incomplete. With prominent sorted bedform ripple fields, the Delaware Redbird artificial reef site, composed of 997 former New York City subway cars, as well as various military vehicles, tugboats, barges and ballasted tires, has made an ideal study location (Raineault et al., 2013 and 2011). Acoustic mapping of the Redbird reef three days prior to Sandy and two days after the following nor'easter, captured the extensive effects of the storms to the site, while acoustic Doppler current profilers characterized both the waves and bottom currents generated by the storm events. Results of the post-Sandy survey support the theory of sorted bedform evolution proposed by Murray and Thieler (2004). Acoustic imagery analysis indicates a highly energized and mobile bed during the storms, leading to self-organization of bedforms and creation of large

  9. Environmental characterization of the continental shelf of the Gulf of Tehuantepec, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Tapia-Garcia, M; Garcia-Abad, M.C [Departamento de Hidrobiologia, Universidad Autonoma Metropolitana-Iztapalapa, (Mexico); Carranza-Edwards, A; Vazquez-Gutierrez, F [Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de Mexico, Mexico D.F. (Mexico)

    2007-10-15

    This study analyzes data and information of the physical and chemical characteristics of water, and type of sediments of the continental shelf of the Gulf of Tehuantepec, Mexico. The changes of salinity, temperature, and dissolved oxygen fluctuate according to the wet and dry seasons (in the last one, prevails the Tehuantepecanos winds). The stations samples of salinity, temperature, pH, and type of sediments were classified by cluster and factor analysis. The results suggest that the Gulf of Tehuantepec has two subsystems. The Oaxaqueno subsystem extends south-southeast from Salina Cruz to the Tonala inlet. This subsystem is characterized by upwelling periods, which leads to low temperatures, low dissolved oxygen and high nutrient concentration, as well as sandy sediments and insignificant river discharges when low temperature, low dissolved oxygen and high nutrient concentration are typical, and by sandy sediments and insignificant river discharges. The second, the Chiapaneco subsystem, is located between the Tonala inlet and the Suchiate River, with strong influence of coastal lagoons and river discharges. The bottom is characterized by sandy and muddy-sand sediments. This subsystem is not affected by either Tehuantepecanos winds or upwelling. Both subsystems and their characteristics probably determine the patterns of distribution of the biotic resources. [Spanish] Se analizan datos e informacion de las caracteristicas fisico-quimicas del agua y tipo de sedimentos de la plataforma continental del Golfo de Tehuantepec, Mexico. Los cambios de salinidad, temperatura y oxigeno disuelto varian de acuerdo con las estaciones de lluvias y sequia (en esta ultima prevalecen fuertes vientos denominados Tehuantepecanos). Las estaciones de muestreo fueron agrupadas (utilizando salinidad, temperatura, pH y tipo de sedimentos) con analisis por conglomerados y analisis de factores. Los resultados indican que el Golfo de Tehuantepec tiene dos subsistemas. El subsistema

  10. Biology of Chirocentrodon bleekerianus (Poey, 1867 (Clupeiformes: Pristigasteridae in a continental shelf region of southern Brazil

    Directory of Open Access Journals (Sweden)

    Carlos Eduardo Corrêa

    2005-05-01

    Full Text Available This study provides information on the biology of C. bleekerianus from Paraná State coast, Brazil, assembling data about its abundance, size structure, diet and reproduction. Monthly collections were accomplished in 1999 and 2000 in the internal continental shelf, with trawl net. The catch-per-unit-effort did not vary significantly among the seasons. In the summer, the individuals were larger, followed by autumn, spring and winter. C. bleekerianus was predominantly planktivorous and the most frequent items in its diet were copepods followed by diatomaceous algae. Seasonal variation in the frequency values of the gonad maturation stages, gonadossomatic index and gonadal condition factor indicated that the reproductive period encompassed spring and summer. The mean total length at first maturity of females was estimated to be 76 mm.Este trabalho fornece dados sobre a biologia de C. bleekerianus do litoral do Estado do Paraná, reunindo dados sobre sua abundância, estrutura em tamanho, dieta e reprodução. Coletas mensais foram realizadas em 1999 e 2000 na plataforma continental interna, com rede de arrasto de fundo com portas. A captura por unidade de esforço não variou significativamente entre as estações do ano. No verão os indivíduos eram maiores, seguido do outono, primavera e inverno. C. bleekerianus é predominantemente planctívora, sendo copépodos seguidos de algas diatomáceas os itens alimentares mais freqüentes em sua dieta. As variações sazonais de valores da freqüência de estádios de maturação gonadal, do índice gonadossomático e do fator de condição gonadal indicam que o período reprodutivo compreende primavera e verão. O comprimento total médio de primeira maturação das fêmeas é estimado em 76 mm.

  11. On the accumulation of organic matter on the southeastern Brazilian continental shelf: a case study based on a sediment core from the shelf off Rio de Janeiro

    Directory of Open Access Journals (Sweden)

    Renato da Silva Carreira

    2012-03-01

    Full Text Available Sterol and fatty acid biomarkers and isotopic composition (δ13C and δ15N of bulk organic matter (OM were quantified in a sediment core to characterize the accumulation of autochthonous OM in an area on the continental shelf adjacent to Rio de Janeiro State. In the sediment surface (0-1 cm the concentration of total sterols and fatty acids was at least one order of magnitude higher than that measured deeper down in the core and was dominated by labile and planktonic-derived biomarker compounds. These results suggest, as is confirmed by multivariate statistical analysis, the occurrence of an event of enhanced primary production in the water column and efficient export of particles to the bottom. Similar conditions have been observed at Cabo Frio, located 150 km to the north of our study site, during an upwelling event, suggesting that such events may exert a regional influence on primary production on the south-eastern Brazilian continental shelf. Beyond the signatures from this event, the presence of biomarker compounds from vascular plants suggests the additional influence of an outflow from Guanabara Bay at the study site. These results point to the need for further investigation of the relative influence of physical forcings and continental inputs on the biogeochemical processes on the section of the continental shelf considered in the present study.Marcadores moleculares na classe de lipídios (esterois, ácidos graxos e hidrocarbonetos e a composição isotópica (δ13C e δ15N da matéria orgânica bruta foram quantificados em amostras de um testemunho de sedimento para caracterizar o histórico recente de sedimentação da matéria orgânica na plataforma continental adjacente à Baía de Guanabara, no Estado do Rio de Janeiro. Na superfície do sedimento (0-1 cm, a concentração total de esterois e ácidos graxos foi cerca de uma ordem de grandeza maior do que observado nas camadas mais profundas do sedimento, com predominância de lip

  12. Spatially Resolving Ocean Color and Sediment Dispersion in River Plumes, Coastal Systems, and Continental Shelf Waters

    Science.gov (United States)

    Aurin, Dirk Alexander; Mannino, Antonio; Franz, Bryan

    2013-01-01

    Satellite remote sensing of ocean color in dynamic coastal, inland, and nearshorewaters is impeded by high variability in optical constituents, demands specialized atmospheric correction, and is limited by instrument sensitivity. To accurately detect dispersion of bio-optical properties, remote sensors require ample signal-to-noise ratio (SNR) to sense small variations in ocean color without saturating over bright pixels, an atmospheric correction that can accommodate significantwater-leaving radiance in the near infrared (NIR), and spatial and temporal resolution that coincides with the scales of variability in the environment. Several current and historic space-borne sensors have met these requirements with success in the open ocean, but are not optimized for highly red-reflective and heterogeneous waters such as those found near river outflows or in the presence of sediment resuspension. Here we apply analytical approaches for determining optimal spatial resolution, dominant spatial scales of variability ("patches"), and proportions of patch variability that can be resolved from four river plumes around the world between 2008 and 2011. An offshore region in the Sargasso Sea is analyzed for comparison. A method is presented for processing Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua and Terra imagery including cloud detection, stray lightmasking, faulty detector avoidance, and dynamic aerosol correction using short-wave- and near-infrared wavebands in extremely turbid regions which pose distinct optical and technical challenges. Results showthat a pixel size of approx. 520 mor smaller is generally required to resolve spatial heterogeneity in ocean color and total suspended materials in river plumes. Optimal pixel size increases with distance from shore to approx. 630 m in nearshore regions, approx 750 m on the continental shelf, and approx. 1350 m in the open ocean. Greater than 90% of the optical variability within plume regions is resolvable with

  13. Living macromolluscs from a paleo-reef region on the northeastern Venezuelan continental shelf

    Science.gov (United States)

    Buitrago, Joaquín; Capelo, Juan; Gutiérrez, Javier; Rada, Martín; Hernández, Ricardo; Grune, Sylvia

    2006-02-01

    Drowned reefs, fossil reefs or paleo-reefs, are important ecologically as areas of high biodiversity, foraging, shelter environment, and as areas supporting the spawning aggregations of economically important reef fish species. This is particularly significant when the structures are situated in a wide soft-bottom continental shelf. The presence of limestone structures, fossil reefs and pinnacles dating from circa 8 to 9 ka, to the north of the Paria Peninsula in north-eastern Venezuela, has been known to local fishermen for decades. Using echograms obtained during acoustic fisheries evaluations and the scarce previously available information, an improved location map of hard-bottom structures was made. Benthic samples to study macromolluscs were taken at depths between 54 and 93 m using an unmodified 2-m beam trawl. Four trawl samples were located over fossil reef areas while another four were situated in soft-bottom valleys between limestone structures. Fossil reefs in the area showed a highly patchy distribution. A total of 91 species from 43 Bivalvia, Gastropoda and Scaphopoda families were found, Gastropoda being the dominant class with 49 species. Paleo-reef-covered areas showed higher species richness and only 21% of the species found were common to both substrates. Gastropods Tonna maculosa and Polystira albida were the most abundant species and occurred in both substrate types. Bivalve life habits, a mixture of organism-substrate relationships, shell fixation, mobility and feeding type, differed significantly according to bottom type. Six species are recorded for the first time for eastern Venezuelan waters. Bottom heterogeneity plays an important role in marine ecosystems, providing shelter to fish populations and may be significant as breeding and nursery areas. Its presence in a region with biogeographical interest, situated in the confluence of three major provinces and with oceanographic conditions varying seasonally from upwelling dominated to

  14. Environmental drivers of epibenthic megafauna on a deep temperate continental shelf: A multiscale approach

    Science.gov (United States)

    Lacharité, Myriam; Metaxas, Anna

    2018-03-01

    Evaluating the role of abiotic factors in influencing the distribution of deep-water (>75-100 m depth) epibenthic megafaunal communities at mid-to-high latitudes is needed to estimate effects of environmental change, and support marine spatial planning since these factors can be effectively mapped. Given the disparity in scales at which these factors operate, incorporating multiple spatial and temporal scales is necessary. In this study, we determined the relative importance of 3 groups of environmental drivers at different scales (sediment, geomorphology, and oceanography) on epibenthic megafauna on a deep temperate continental shelf in the eastern Gulf of Maine (northwest Atlantic). Twenty benthic photographic transects (range: 611-1021 m; total length surveyed: 18,902 m; 996 images; average of 50 ± 16 images per transect) were performed in July and August 2009 to assess the abundance, composition and diversity of these communities. Surficial geology was assessed using seafloor imagery processed with a novel approach based on computer vision. A bathymetric terrain model (horizontal resolution: 100 m) was used to derive bathymetric variability in the vicinity of transects (1.5, 5 km). Oceanography at the seafloor (temperature, salinity, current speed, current direction) over 10 years (1999-2008) was determined using empirical (World Ocean Database 2013) and modelled data (Finite-Volume Community Ocean Model; 45 vertical layers; horizontal resolution: 1.7-9.5 km). The relative influence of environmental drivers differed between community traits. Abundance was enhanced primarily by swift current speeds, while higher diversity was observed in coarser and more heterogeneous substrates. In both cases, the role of geomorphological features was secondary to these drivers. Environmental variables were poor predictors of change in community composition at the scale of the eastern Gulf of Maine. This study demonstrated the need for explicitly incorporating scales into

  15. Norwegian Petroleum Activity 97. Fact Sheet

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    This report is the official governmental review of the offshore operations on the Norwegian Continental Shelf in 1996. It covers the following topics: (1) Summary, (2) Historical overview, (3) State organization of petroleum activities, (4) The economic impact of Norwegian oil and gas, (5) State revenues, (6) Mainland activities, (7) Petroleum resources, (8) Production, (9) Marketing situation for petroleum products, (10) Environmental aspects, (11) The legal and license framework, (12) Licensing rounds, (13) Exploration, (14) Fields in production, (15) Fields under development, (16) Discoveries with development plan under consideration, (17) Transportation systems, (18) License interests, (19) Company interests, (20) White papers, (21) Useful postal addresses. 24 figs., 16 tabs.

  16. Fact sheet. Norwegian petroleum activity 1995

    International Nuclear Information System (INIS)

    Harv, M.R.

    1995-02-01

    This report on the Norwegian petroleum activity in 1994 is published by the Royal Ministry of Industry and Energy. Production to the end of 1994 totaled 1.63 billion scm oe. At 31 Dec 1994, total reserves on the Norwegian continental shelf comprised 1.34 billion scm oe of oil, 1.35 billion scm oe of gas and 0.1 billion scm oe of NGLs. The net increment in oil and gas during 1994 was about 115 million scm oe. Twenty-seven exploration wells, including 22 wildcats and five appraisal wells, were completed or temporarily abandoned on the Norwegian continental shelf in 1994. Governmental approval was given for developing the second phase of the Ekofisk field, the Vigdis and Snorre Lunde oil fields, and two smaller formations on the Veslefrikk field. Investment in petroleum operations totaled about NOK 50 billion. Norwegian oil and gas production came to about 180 million scm oe. At present levels of output, Norway's petroleum resources are sufficient to support production of oil for 20 years and of gas for 115 years. The estimated value of Norwegian petroleum exports in 1994 is NOK 114 billion, representing about 34% of the country's total export earnings. State revenues from taxes and royalties on petroleum operations came to about NOK 23.7 billion, or eight per cent of total government revenues. 24 figs., 13 tabs

  17. Bathymetry and acoustic backscatter of the mid and outer continental shelf, head of De Soto Canyon, northeastern Gulf of Mexico

    Science.gov (United States)

    Gardner, James V.; Hughes-Clarke, John E.; Meyer, Larry A.

    2002-01-01

    The mid to outer continental shelf off Mississippi-Alabama and off northwest Florida were the focus of US Geological Survey (USGS) multibeam echosounder (MBES) mapping cruises in 2000 and 2001, respectively. These areas were mapped to investigate the extent of "deep-water reefs" first suggested by Ludwick and Walton (1957). The reefs off Mississippi and Alabama were initially described in water depths of 60 to 120 m (Ludwick and Walton, 1957) but the 2000 mapping found reef and hardgrounds to be much more extensive than previously thought (Gardner et al., 2001). The persistent trend of reef-like features along the outer shelf of Mississippi-Alabama suggested the trend might continue along the northwest Florida mid and outer shelf so a MBES-mapping effort was mounted in 2001 to test this suggestion. It is critical to determine the accurate location, geomorphology, and types of the ridges and reefs that occur in this region to understand the Quaternary history of the area and to assess their importance as benthic habitats for fisheries. The 2001 survey found a series of shelf-depth platforms with ridges (possibly reefs) constructed on their surfaces (Gardner et al., 2002). The area known as the "head of De Soto Canyon" is the large unmapped region between the 2000 and 2001 mapped areas. The head of De Soto Canyon is an outer shelf zone with a relatively steep western wall and a much gentler eastern wall. It was unknown prior to this cruise whether the reefs of the Mississippi-Alabama shelf continue eastward into the head of De Soto Canyon and connect with the ridges and reefs mapped on the northwest Florida outer shelf. The existence of carbonate-cemented latest Quaternary to Holocene sandstones along the western wall of the head of De Soto Canyon (Shipp and Hopkins, 1978; Benson et al., 1997; W.W. Schroeder, personnel comm., 2002) is of interest because of the potential benthic habitats they may represent. Precisely georeferenced high-resolution mapping of

  18. Seasonal evolution of the nutrient pattern on Biscay Bay continental shelf over the years 1999-2000

    Directory of Open Access Journals (Sweden)

    Sophie Loyer

    2006-03-01

    Full Text Available The French Atlantic shelf is subjected to strong anthropic influences (urban, industrial and agricultural discharges of two main rivers (Loire and Gironde. The extension and consequences of these continental loadings for the nutrient and chlorophyll distribution have never been studied before on the Bay of Biscay continental shelf as a whole. We present the first synoptic view of the nutrient distribution and evolution on the French Atlantic shelf. Nutrient concentrations of the surface layer were studied during four cruises in April, June, September 1999 and March 2000. Until June, the freshwater inputs induce a nitrate gradient from river mouths to offshore waters in the vicinity of the 100 m isobath. The Redfield’s ratio study highlights the nitrate excess in river loadings. The early spring situation is characterised by high N:P ratios in front of the two estuaries and by a potential Si-limitation in the northern part. Nitrate removal continues in spite of the P-limitation and the increase in silicate concentrations during summer supposes high regeneration processes. At the end of summer, the water column is thermally stratified and the surface mixed layer is totally depleted in nitrate.

  19. P-wave velocity models of continental shelf of East Siberian Sea using the Laplace-domain full waveform inversion

    Science.gov (United States)

    Kang, S. G.; Hong, J. K.; Jin, Y. K.; Jang, U.; Niessen, F.; Baranov, B.

    2017-12-01

    2016 IBRV ARAON Arctic Cruise Leg-2, Expedition ARA07C was a multidisciplinary undertaking carried out in the East Siberian Sea (ESS) from August 25 to September 10, 2016. The program was conducted as a collaboration between the Korea Polar Research Institute (KOPRI), P.P. Shirshov Institute of Oceanology (IORAS), and Alfred Wegener Institute (AWI). During this expedition, the multi-channel seismic (MCS) data were acquired on the continental shelf and the upper slope of the ESS, totaling 3 lines with 660 line-kilometers. The continental shelf of ESS is one of the widest shelf seas in the world and it is believed to cover the largest area of sub-sea permafrost in the Arctic. According to the present knowledge of the glacial history of the western Arctic Ocean, it is likely that during the LGM with a sea level approximately 120 m below present, the entire shelf area of the ESS was exposed to very cold air temperatures so that thick permafrost should have formed. Indeed, in water depths shallower than 80 m, sub-bottom profiles in the ESS recorded from the shelf edge to a latitude of 74°30' N in 60 m water depth exhibited acoustic facies, suggesting that at least relicts of submarine permafrost are present. In order to identify the existence and/or non-existence of subsea permafrost in our study area, we analyze the MCS data using the Laplace domain full waveform inversion (FWI). In case of the Canadian continental shelf of the Beaufort Sea, subsea permafrost has high seismic velocity values (over 2.6 km/sec) and strong refraction events were found in the MCS shotgathers. However, in the EES our proposed P-wave velocity models derived from FWI have neither found high velocity structures (over 2.6 km/sec) nor indicate strong refraction events by subsea permafrost. Instead, in 300 m depth below sea floor higher P-wave velocity structures (1.8 2.2 km/s) than normal subsea sediment layers were found, which are interpreted as cemented strata by glaciation activities.

  20. Assessment of the U.S. outer continental shelf environmental studies program. 1. Physical oceanography. Final report

    International Nuclear Information System (INIS)

    1990-01-01

    Federal responsibility for oil and gas development on the U.S. outer continental shelf (OCS) resides with the Minerals Management Service (MMS) of the U.S. Department of the Interior (DOI). The DOI's Environmental Studies Program (ESP) is the program through which MMS conducts environmental studies on the OCS and collects information to prepare environmental impact statements (EISs). It appeared to MMS in 1986 that the time was ripe to assess the status of the present program and to explore the needs for future studies. MMS requested an evaluation of the adequacy and applicability of ESP studies, a review of the general state of knowledge in the appropriate disciplines, and recommendations for future studies. Three panels were established, one of which, the Physical Oceanography Panel, investigated the physical oceanographic aspects of the ESP, the subject of the report, which is the first of three in a series. In reviewing the ESP's physical oceanography program, the panel evaluated the quality and relevance of studies carried out in waters under federal control, which extend from the limits of state jurisdictions (3-12 miles offshore) and include the central and outer continental shelf waters and the continental slope

  1. The usefulness of resource analysis in national economic planning. Examples from the Norwegian Shelf

    International Nuclear Information System (INIS)

    Kalheim, J.E.; Brekke, H.

    1996-01-01

    Petroleum resources have an important influence on the economic life in Norway. To the official authorities it is therefore essential to have good and detailed knowledge of these resources. Questions like 'what are the total resources', 'how much of the resources have been produced' and 'how much is expected to remain' should be answered. A classification system and an updated resource account is therefore required. Even though there is currently a well defined classification system and a resource account which is annually updated, estimates of discovered resources are associated with considerable uncertainty for some fields and discoveries. The uncertainties are not only connected to the mapping of field sizes but also to the possible potential for improved recovery, particularly in the light of new or sophisticated recovery methods. During the last two years the Norwegian Petroleum Directorate (NPD) has paid considerable attention to the potential for improved oil recovery. This is because of the time-critical aspects in the producing fields. The assessment of undiscovered resources also includes large uncertainties. However, regardless of the uncertainties such assessments are important for long term national planning. Decisions concerning opening of new areas for future exploration will have a considerable impact on the future level of the petroleum activities. To national authorities it is therefore important to have an understanding of what economic potential the undiscovered resources may represent. To resource analysts it will be important to know how the results from the geological assessments are uses in the economic calculations. Different resource assessments of a single play model are compared, and a comparison between different prospect evaluations of one single prospect are also presented. This approach is used to focus on the most critical uncertainty factors. 8 refs

  2. A numerical study of the Plata River plume along the southeastern South American continental shelf

    Directory of Open Access Journals (Sweden)

    Felipe M. Pimenta

    2005-12-01

    Full Text Available The Rio de la Plata, one of the largest rivers on Earth, discharges into the ocean waters from basin that covers a large area of South America. Its plume extends along northern Argentina, Uruguay, and southern Brazil shelves strongly influencing the ecosystems. In spite of this, little is known about the mechanisms that control it. Here we report results of simulations with POM carried out to investigate the roles of wind and river discharge in Plata plume dynamics. Different outflows were explored, including an average climatological value and magnitudes representative of La Niña and El Niño. Forcing the model with river discharge the average plume speed was directly related to the outflow intensity. The Plata northward extension varied from 850 to 1550 km and for average discharge a band of low salinity waters formed from the estuary up to 30ºN of South Brazilian Shelf. Upwelling and downwelling winds were applied after 130 days. The distribution of low salinity waters over the shelf was more sensitive to the wind direction than to the river outflow variability. Downwelling winds were very capable of advecting the low salinity signal downshelf. Upwelling winds were efficient in eroding the plume, which was basically detached from the coast by Ekman drift. Abnormal plume intrusions toward low latitudes may be a result of the original plume position coupled with events of persistent strong downwelling favorable winds.O Rio da Prata, um dos maiores rios da Terra, descarrega no oceano águas de uma bacia de drenagem que cobre uma ampla área da América do Sul. Sua pluma extende-se ao longo do norte da Argentina, Uruguay e sul do Brasil influenciando amplamente os ecossistemas costeiros. A despeito disso, pouco se sabe a respeito dos mecanismos que a controlam. Relatamos aqui simulações conduzidas com o modelo POM na investigação do papel dos ventos e da descarga fluvial na dinâmica da pluma do Prata. Descargas com valores médios climatol

  3. Exposure of coastal ecosystems to river plume spreading across a near-equatorial continental shelf

    Science.gov (United States)

    Tarya, A.; Hoitink, A. J. F.; Vegt, M. Van der; van Katwijk, M. M.; Hoeksema, B. W.; Bouma, T. J.; Lamers, L. P. M.; Christianen, M. J. A.

    2018-02-01

    The Berau Continental Shelf (BCS) in East Kalimantan, Indonesia, harbours various tropical marine ecosystems, including mangroves, seagrass meadows and coral reefs. These ecosystem are located partly within reach of the Berau River plume, which may affect ecosystem health through exposure to land-derived sediments, nutrients and pollutants carried by the plume. This study aims (1) to assess the exposure risk of the BCS coastal ecosystems to river plume water, measured as exposure time to three different salinity levels, (2) to identify the relationships between these salinity levels and the abundance and diversity of coral and seagrass ecosystems, and (3) to determine a suitable indicator for the impacts of salinity on coral reef and seagrass health. We analysed hydrodynamic models, classified salinity levels, and quantified the correlations between the salinity model parameters and ecological metrics for the BCS systems. An Empirical Orthogonal Functions (EOF) analysis revealed three modes of river plume dispersal patterns, which strongly reflect monsoon seasonality. The first mode, explaining 39% of the variability, was associated with the southward movement of the plume due to northerly winds, while the second and third modes (explaining 29% and 26% of the variability, respectively) were associated with the northeastward migration of the plume related to southwesterly and southerly winds. Exposure to low salinity showed higher correlations with biological indicators than mean salinity, indicating that low salinity is a more suitable indicator for coastal ecosystem health. Significant correlations (R2) were found between exposure time to low salinity (days with salinity values below 25 PSU) with coral cover, coral species richness, seagrass cover, the number of seagrass species, seagrass leaf phosphorus, nitrogen, C:N ratio and iron content. By comparing the correlation coefficients and the slopes of the regression lines, our study suggests that coral reefs are

  4. 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

  5. Petroleum resources assessment on the continental shelf basin of the south sea

    Energy Technology Data Exchange (ETDEWEB)

    Cheong, Tae Jin; Kwak, Young Hun; Oh, Jae Ho; Bong, Pil Youn; Son, Jin Dam; Lee, Ho Young; Ryu, Byung Jae; Son, Byoung Kook; Hwang, In Geul; Kwon, Young In; Lee, Young Ju; Kim, Hak Ju; Park, Kwan Soon; Park, Keun Pil; Sunwoo, Don [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)

    1996-12-01

    On the basis of diverse microfossils such as foraminifers, ostracods, micromulluscs, fossil spores and pollen and calcareous nannofossils derived from 14 drill holes, the sediments are divided into two part, the upper marine part and the lower nonmarine one. Marine part is subdivided into 4 foraminiferal zones and 3 nannofossil zones of Plio-Pleistocene age. In the lower part ranging from Oligocene to Late Miocene 4 palynomoph assemblages are established, which reflect climatic changes fluctuating between subtropical and cool temperate. Some fine sediments occurring in the South Sea continental shelf are rich in organic matter to be hydrocarbon source rock. The organic matter is mainly compared to type 3. However, lower part of the Geobuk-1 and Okdom-1 shows more oil prone geochemical characteristics than other wells. The kerosene is mixture type 1 and type 3 organic matter. The main oil generation zone located between 2,500 m and 3,000 m and gas generation zone from 3,500 m to 4,000 m approximately. Hydrocarbon accumulation could be expected in the trap formed in the period earlier than 10 Ma. as the hydrocarbon started to be expelled at 10 Ma. according to the modeling. Approximately 13,000 Line-km of multichannel seismic data integrated with 14 wells and gravity and magnetic data were analyzed to investigate the structural and stratigraphic evolution of southern part of offshore Korea. The northeast-southwest trending Taiwan-Sinzi Uplift Belt separates the area into two regions with different tectonic features, northwestern and southwestern regions. Tectonics of the rifting phase in both regions have been established on the basis of structural and stratigraphic analyses of depositional sequences and their seismic expressions. In the northwestern region, the large rifting activity appears to be occurred during Oligocene and pre-Oligocene, while in the southeastern region it occurred from late Miocene to early Pliocene. The potential hydrocarbon traps associated

  6. Seabed fluid expulsion along the upper slope and outer shelf of the U.S. Atlantic continental margin

    Science.gov (United States)

    Brothers, D.S.; Ruppel, C.; Kluesner, J.W.; ten Brink, Uri S.; Chaytor, J.D.; Hill, J.C.; Andrews, B.D.; Flores, C.

    2014-01-01

    Identifying the spatial distribution of seabed fluid expulsion features is crucial for understanding the substrate plumbing system of any continental margin. A 1100 km stretch of the U.S. Atlantic margin contains more than 5000 pockmarks at water depths of 120 m (shelf edge) to 700 m (upper slope), mostly updip of the contemporary gas hydrate stability zone (GHSZ). Advanced attribute analyses of high-resolution multichannel seismic reflection data reveal gas-charged sediment and probable fluid chimneys beneath pockmark fields. A series of enhanced reflectors, inferred to represent hydrate-bearing sediments, occur within the GHSZ. Differential sediment loading at the shelf edge and warming-induced gas hydrate dissociation along the upper slope are the proposed mechanisms that led to transient changes in substrate pore fluid overpressure, vertical fluid/gas migration, and pockmark formation.

  7. Distribution and dispersal of clay minerals on the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, R.R.; Hashimi, N.H.; Rao, V.P

    off the Gulf of Kutch; (2) the montmorillonite-rich zone off the Gulf of Cambay; (3) a transition zone on the central parts of the shelf; and (4) a relatively montmorillonite poor-gibbsite province on the southwestern part of the shelf. Source...

  8. Geomorphic characterization of four shelf-sourced submarine canyons along the U.S. Mid-Atlantic continental margin

    Science.gov (United States)

    Obelcz, Jeffrey; Brothers, Daniel S.; Chaytor, Jason D.; ten Brink, Uri S.; Ross, Steve W.; Brooke, Sandra

    2013-01-01

    Shelf-sourced submarine canyons are common features of continental margins and are fundamental to deep-sea sedimentary systems. Despite their geomorphic and geologic significance, relatively few passive margin shelf-breaching canyons worldwide have been mapped using modern geophysical methods. Between 2007 and 2012 a series of geophysical surveys was conducted across four major canyons of the US Mid-Atlantic margin: Wilmington, Baltimore, Washington, and Norfolk canyons. More than 5700 km2 of high-resolution multibeam bathymetry and 890 line-km of sub-bottom CHIRP profiles were collected along the outer shelf and uppermost slope (depths of 80-1200 m). The data allowed us to compare and contrast the fine-scale morphology of each canyon system. The canyons have marked differences in the morphology and orientation of canyon heads, steepness and density of sidewall gullies, and the character of the continental shelf surrounding canyon rims. Down-canyon axial profiles for Washington, Baltimore and Wilmington canyons have linear shapes, and each canyon thalweg exhibits morphological evidence for recent, relatively small-scale sediment transport. For example, Washington Canyon displays extremely steep wall gradients and contains ~100 m wide, 5–10 m deep, v-shaped incisions down the canyon axis, suggesting modern or recent sediment transport. In contrast, the convex axial thalweg profile, the absence of thalweg incision, and evidence for sediment infilling at the canyon head, suggest that depositional processes strongly influence Norfolk Canyon during the current sea-level high-stand. The north walls of Wilmington, Washington and Norfolk canyons are steeper than the south walls due to differential erosion, though the underlying cause for this asymmetry is not clear. Furthermore, we speculate that most of the geomorphic features observed within the canyons (e.g., terraces, tributary canyons, gullies, and hanging valleys) were formed during the Pleistocene, and show only

  9. A new era for the offshore oil and gas industry on the UKCS [United Kingdom Continental Shelf

    International Nuclear Information System (INIS)

    Pickering, H.

    1998-01-01

    This paper explores the development of the offshore oil and gas industry on the United Kingdom Continental Shelf (UKCS) and particularly the role played by science and technology in that development. An historical perspective is taken in the first instance to place recent developments in context, before exploring the role of science and technology in the 1990s. Three areas of key importance form the basis of the discussion: the maintenance of production from the traditional provinces, the development of new provinces and the mitigation of environmental impacts. The paper demonstrates the crucial role that science and technology plays in each of these areas. (author)

  10. Gulf of Mexico Outer Continental Shelf daily oil and gas production rate projections from 1999 through 2003

    International Nuclear Information System (INIS)

    Melancon, J.M.; Baud, R.D.

    1999-02-01

    This paper provides daily oil and gas production rate projections for the Gulf of Mexico (GOM) Outer Continental Shelf (OCS) for the years 1999 through 2003. These projections represent daily oil and gas production estimates at calendar year end. In this report, daily oil production rates include both oil and condensate production, and daily gas production rates include both associated and nonassociated gas production. In addition to providing daily oil and gas production rate projections, the authors have included one figure and one table pertaining to leasing history and one table concerning exploration and development plan approvals

  11. Gulf of Mexico outer continental shelf daily oil and gas production rare projections from 1998 through 2002

    International Nuclear Information System (INIS)

    Melancon, J.M.; Roby, D.S.

    1998-02-01

    This paper provides daily oil and gas production rate projections for the Gulf of Mexico (GOM) Outer Continental Shelf (OCS) for the years 1998 through 2002. These projections represent daily oil and gas production estimates at calendar year end. In this report, daily oil production rates include both oil and condensate production, and daily gas production rates include both associated and nonassociated gas production. In addition to providing daily oil and gas production rate projections, the authors have included one figure and one table pertaining to leasing history and one table concerning exploration and development plan approvals

  12. Well construction team approach creates a new future for one company's operations on the Dutch Continental Shelf

    International Nuclear Information System (INIS)

    Stringer, R.B.; Bakker, T.W.; Mejnertsen, T.

    1994-01-01

    Rising costs and low energy prices were inhibiting the development of marginal fields on the Dutch Continental Shelf, resulting in a major reduction in drilling activity. This triggered a change from traditional operating and contracting strategies to a Well Construction Team approach based on partnering agreements with the principal drilling and service contractors. The change has resulted in major cost reductions coupled to improved well quality that are justifying the re-evaluation of previously sub-economic development prospects. This paper describes the strategies employed and presents the results achieved during the first year of the partnership

  13. Methane Metabolizing Microbial Communities in the Cold Seep Areas in the Northern Continental Shelf of South China Sea

    Science.gov (United States)

    Wang, F.; Liang, Q.

    2016-12-01

    Marine sediment contains large amount of methane, estimated approximately 500-2500 gigatonnes of dissolved and hydrated methane carbon stored therein, mainly in continental margins. In localized specific areas named cold seeps, hydrocarbon (mainly methane) containing fluids rise to the seafloor, and support oases of ecosystem composed of various microorganisms and faunal assemblages. South China Sea (SCS) is surrounded by passive continental margins in the west and north and convergent margins in the south and east. Thick organic-rich sediments have accumulated in the SCS since the late Mesozoic, which are continuing sources to form gas hydrates in the sediments of SCS. Here, Microbial ecosystems, particularly those involved in methane transformations were investigated in the cold seep areas (Qiongdongnan, Shenhu, and Dongsha) in the northern continental shelf of SCS. Multiple interdisciplinary analytic tools such as stable isotope probing, geochemical analysis, and molecular ecology, were applied for a comprehensive understanding of the microbe mediated methane transformation in this project. A variety of sediments cores have been collected, the geochemical profiles and the associated microbial distribution along the sediment cores were recorded. The major microbial groups involved in the methane transformation in these sediment cores were revealed, known methane producing and oxidizing archaea including Methanosarcinales, anaerobic methane oxidizing groups ANME-1, ANME-2 and their niche preference in the SCS sediments were found. In-depth comparative analysis revealed the presence of SCS-specific archaeal subtypes which probably reflected the evolution and adaptation of these methane metabolizing microbes to the SCS environmental conditions. Our work represents the first comprehensive analysis of the methane metabolizing microbial communities in the cold seep areas along the northern continental shelf of South China Sea, would provide new insight into the

  14. Investigation of the shelf break and continental slope in the Western part of the Black Sea using acoustic methods

    Science.gov (United States)

    Dutu, F.; Ion, G.; Jugaru Tiron, L.

    2009-04-01

    The Black Sea is a large marginal sea surrounded by a system of Alpine orogenic chains, including the Balkanides-Pontides, Caucasus, Crimea and North Dobrogea located to the south, northeast, north and northwest, respectively (Dinu et al., 2005). The north-western part of the Black Sea is the main depocentre for sediment supply from Central Europe via the Danube River, but also from Eastern Europe through the Ukrainian rivers Dniepr, Dniestr and Southern Bug (Popescu et al., 2004). The shelfbreak is located at water depths of 120-140 m southward of the Danube Canyon, and up to 170 m northward of the canyon possibly due to recent faulting which is very common in this area. The continental slope is dissected by numerous canyons, each of which is fed by several tributaries. The Danube Canyon (also known as Viteaz Canyon) is a large shelf-indenting canyon located in the north-western Black Sea and connected to the youngest channel-levee system of the Danube Fan (Popescu et al., 2004). The acoustic methods are a useful way for investigate the shelf break and the continental slope giving us information about landslides on the continental slope, the topography of the investigated area, the sedimentary zones affected by instability and to quantify the geometry of the underwater landslides. The measurements made on the continental slope from north-western part of the Black Sea gave us the possibility to make a digital terrain model. After processing the data the model offer information about the main access ways of the sediments through gravitational slide on the submarines canyons, with forming of turbidity currents, debris flows and also other transport/transformation phenomena of the sediments on the continental slope like submarine landslides and submarine collapse. References Dinu, C., Wong, H.K., Tambrea, D., Matenco, L., 2005. Stratigraphic and structural characteristics of the Romanian Black Sea shelf. Tectonophysics 410, 417-435. Popescu, I., Lericolais, G., Panin

  15. 3D thermal modelling within the Lofoten-Vesterålen segment of the Mid-Norwegian continental margin

    Science.gov (United States)

    Maystrenko, Yuriy P.; Gernigon, Laurent; Gradmann, Sofie; Olesen, Odleiv

    2017-04-01

    A lithosphere-scale 3D structural model has been constructed based on the available structural data to reveal a deep structure of the Lofoten-Vesterålen segment and the northern part of the Vøring segment of the Mid-Norwegian continental margin. The constructed model covers the Vestfjorden, Ribban and Røst basins, the northern parts of the Vøring Basin and the Trøndelag Platform. The model also extends from the Fennoscandian Shield to the north-eastern part of the North Atlantic Ocean. The initial 3D structural model has been refined using a 3D gravity modelling over the whole study area. The final gravity-consistent model has been used as a structural base for a further 3D thermal modelling, which has been made by use of commercial software package COMSOL Multiphysics. As an upper thermal boundary condition, time-dependent temperature at the Earth's surface and sea bottom has been set, considering palaeoclimatic changes due to the last two Europe-scale glaciations (the Saalian and Weichselian glacial periods). The lithosphere-asthenosphere boundary has been used as a lower thermal boundary which corresponds to the 1300 °C isotherm. In addition to the above-mentioned paleoclimatic scenario, the effects of late Cenozoic erosion onshore and sedimentation offshore have been taken into account during the 3D thermal modelling. Results of this thermal modelling indicate that the continent is generally colder than the basin areas within the upper part of the 3D model. In particular, considering the transient perturbations in the near-surface thermal regime, as a result of the post-Paleogene erosion and sedimentation, helps us to understand additional details of subsurface temperature distribution within the study area. The thermal effects of the simultaneous erosion over the mainland and deposition within the basin areas indicate that a positive thermal anomaly should exist onshore, whereas the negative one must occur in the offshore part. These two thermal

  16. Sources, Fate and Distribution of Organic Matter on the Western Adriatic Continental Shelf, Italy

    International Nuclear Information System (INIS)

    Tesi, Tommaso; Miserocchi, Stefano; Langone, Leonardo; Boni, Laurita; Guerrini, Franca

    2006-01-01

    In the framework of the EUROSTRATAFORM projects, a multidisciplinary research was focused on processes that involve transport and deposition of riverine material in the Adriatic Sea. The aim of our contribution was to increase a more complete understanding of organic matter deposition on the Adriatic shelf, also taking into account the role of Apennine rivers beyond the Po influence. In order to characterize origin, fate and variability of sedimentary organic carbon we utilized elemental and stable carbon isotope data in surficial sediments along shallow cross-shelf transects on the western Adriatic shelf

  17. Observations on the scattering layers over the continental shelf off Konkan coast (India)

    Digital Repository Service at National Institute of Oceanography (India)

    RamaRaju, V.S.

    The echograms obtained by R.V. "varuna" using asdic during the September, 1963 cruise are analysed. Scattering layers observed over the shelf area, off Ratnagiri, are examined and studied in relation to the thermocline layer present. Comparison...

  18. EBSSED database-Surficial sediments of the eastern Bering Sea continental shelf

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — In order to facilitate descriptions of groundfish habitat over a large portion of the EBS shelf, the NMFS/AFSC has assembled a single comprehensive database of the...

  19. Geomorphology and surficial geology of the western continental shelf and slope of India: A review

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.; Wagle, B.G.

    Coastal geology and geomorphology of the area and nearshore currents played a significant role in the distribution of placer minerals off Kerala and Maharashtra. Transport and sedeimentation of fine-grained materials at places on the shelf...

  20. The Deposition and Accumulation of Microplastics in Marine Sediments and Bottom Water from the Irish Continental Shelf.

    Science.gov (United States)

    Martin, Jake; Lusher, Amy; Thompson, Richard C; Morley, Audrey

    2017-09-07

    Microplastics are widely dispersed throughout the marine environment. An understanding of the distribution and accumulation of this form of pollution is crucial for gauging environmental risk. Presented here is the first record of plastic contamination, in the 5 mm-250 μm size range, of Irish continental shelf sediments. Sixty-two microplastics were recovered from 10 of 11 stations using box cores. 97% of recovered microplastics were found to reside shallower than 2.5 cm sediment depth, with the area of highest microplastic concentration being the water-sediment interface and top 0.5 cm of sediments (66%). Microplastics were not found deeper than 3.5 ± 0.5 cm. These findings demonstrate that microplastic contamination is ubiquitous within superficial sediments and bottom water along the western Irish continental shelf. Results highlight that cores need to be at least 4-5 cm deep to quantify the standing stock of microplastics within marine sediments. All recovered microplastics were classified as secondary microplastics as they appear to be remnants of larger items; fibres being the principal form of microplastic pollution (85%), followed by broken fragments (15%). The range of polymer types, colours and physical forms recovered suggests a variety of sources. Further research is needed to understand the mechanisms influencing microplastic transport, deposition, resuspension and subsequent interactions with biota.

  1. Trophic model of the outer continental shelf and upper slope demersal community of the southeastern Brazilian Bight

    Directory of Open Access Journals (Sweden)

    Marcela C. Nascimento

    2012-10-01

    Full Text Available It is increasingly recognized that demersal communities are important for the functioning of continental shelf and slope ecosystems around the world, including tropical regions. Demersal communities are most prominent in areas of high detritus production and transport, and they link benthic and pelagic biological communities. To understand the structure and role of the demersal community on the southeastern Brazilian Bight, we constructed a trophodynamic model with 37 functional groups to represent the demersal community of the outer continental shelf and upper slope of this area, using the Ecopath with Ecosim 6 (EwE approach and software. The model indicates high production and biomass of detritus and benthic invertebrates, and strong linkages of these components to demersal and pelagic sub-webs. The level of omnivory indexes in this ecosystem was high, forming a highly connected trophic web reminiscent of tropical land areas. Although high levels of ascendency may indicate resistance and resilience to disturbance, recent and present fisheries trends are probably degrading the biological community and related ecosystem services.

  2. Observed tidal currents on the continental shelf off the east coast of India

    Science.gov (United States)

    Jithin, A. K.; Unnikrishnan, A. S.; Fernando, V.; Subeesh, M. P.; Fernandes, R.; Khalap, S.; Narayan, S.; Agarvadekar, Y.; Gaonkar, M.; Tari, P.; Kankonkar, A.; Vernekar, S.

    2017-06-01

    In the present study, we analysed 9-month long data from Acoustic Doppler Current Profilers (ADCP) deployed on the shelf off the east coast of India to study the characteristics of tidal currents in the region. The ADCPs were deployed at about 100-150 m depths off Cuddalore (CD, 12.0°N), Ramayapatnam (RM, 15.0°N), Kakinada (KN, 16.3°N) and South of Gopalpur (SG, 18.6°N). Tidal currents in the region are mainly semidiurnal in nature and dominant constituent is M2. Semimajor axes of barotropic tidal ellipses of M2 is about 1.9 cms-1 in the southernmost ADCP location (off CD) and it is about 4.0 cms-1 in the northernmost ADCP location (off SG), which indicate a northward increase of tidal currents. Baroclinic spectra show high energy at tidal frequencies, which suggests the presence of internal tides on the shelf, particularly in the semidiurnal band. Semidiurnal internal tides of about 8-15 cms-1 are observed at different locations and the magnitude is relatively large on the shelf off SG in the northern part of the shelf, which is primarily due to large barotropic forcing on the north. The semidiurnal internal tides are found to be intensified at the bottom, particularly on the shelf off SG and RM. The computed ratio of slope of internal wave characteristics (c) and topographic slope (γ) indicates that large near-critical regions present surrounding the ADCP locations off SG and RM could be the possible reason of bottom intensification at these two locations. EOF analysis shows that observed semidiurnal internal tides are dominated by the first baroclinic mode, where it accounts for about 70-80% of semidiurnal internal tide variability on the shelf off SG and CD, whereas the contribution of the first mode is relatively small (43-50%) on the shelf off KN and RM. Enhanced small-scale vertical shear is observed at the ADCP locations associated with multimode structure of semidiurnal internal tides. Semidiurnal internal tides show a spring-neap variability on the

  3. Exploring the Eastern United States Continental Shelf with the NOAA Cooperative Institute for Ocean Exploration, Research, and Technology

    Science.gov (United States)

    Glickson, D.; Pomponi, S. A.

    2016-02-01

    The Cooperative Institute for Ocean Exploration, Research, and Technology (CIOERT) serves NOAA priorities in three theme areas: exploring the eastern U.S. continental shelf, improving the understanding of coral and sponge ecosystems, and developing advanced underwater technologies. CIOERT focuses on the exploration and research of ecosystems and habitats along frontier regions of the eastern U.S. continental shelf that are of economic, scientific, or cultural importance or of natural hazards concern. One particular focus is supporting ocean exploration and research through the use of advanced underwater technologies and techniques in order to improve the understanding of vulnerable deep and shallow coral and sponge ecosystems. CIOERT expands the scope and efficiency of exploration and research by developing, testing, and applying new and/or innovative uses of existing technologies to ocean exploration and research activities. In addition, CIOERT is dedicated to expanding ocean literacy and building NOAA's technical and scientific workforce through hands-on, at-sea experiences. A recent CIOERT cruise characterized Gulf of Mexico mesophotic and deepwater reef ecosystems off the west Florida shelf, targeting northern Pulley Ridge. This project created and ground-truthed new sonar maps made with an autonomous underwater vehicle; conducted video and photographic transects of benthic habitat and fish using a remotely operated vehicle; and examined the connectivity of fauna from shallow to deep reef ecosystems. CIOERT was established in 2009 by FAU-Harbor Branch Oceanographic Institute, with University of North Carolina, Wilmington, SRI International, and the University of Miami. The primary NOAA partner is the Office of Oceanic and Atmospheric Research's Office of Ocean Exploration and Research.

  4. Carbon mineralization and carbonate preservation in modern cold-water coral reef sediments on the Norwegian shelf

    Directory of Open Access Journals (Sweden)

    L. M. Wehrmann

    2009-04-01

    Full Text Available Cold-water coral ecosystems are considered hot-spots of biodiversity and biomass production and may be a regionally important contributor to carbonate production. The impact of these ecosystems on biogeochemical processes and carbonate preservation in associated sediments were studied at Røst Reef and Traenadjupet Reef, two modern (post-glacial cold-water coral reefs on the Mid-Norwegian shelf. Sulfate and iron reduction as well as carbonate dissolution and precipitation were investigated by combining pore-water geochemical profiles, steady state modeling, as well as solid phase analyses and sulfate reduction rate measurements on gravity cores of up to 3.25 m length. Low extents of sulfate depletion and dissolved inorganic carbon (DIC production, combined with sulfate reduction rates not exceeding 3 nmol S cm−3 d−1, suggested that overall anaerobic carbon mineralization in the sediments was low. These data showed that the coral fragment-bearing siliciclastic sediments were effectively decoupled from the productive pelagic ecosystem by the complex reef surface framework. Organic matter being mineralized by sulfate reduction was calculated to consist of 57% carbon bound in CH2O groups and 43% carbon in -CH2- groups. Methane concentrations were below 1 μM, and failed to support the hypothesis of a linkage between the distribution of cold-water coral reefs and the presence of hydrocarbon seepage. Reductive iron oxide dissolution linked to microbial sulfate reduction buffered the pore-water carbonate system and inhibited acid-driven coral skeleton dissolution. A large pool of reactive iron was available leading to the formation of iron sulfide minerals. Constant pore-water Ca2+, Mg2+ and Sr2+ concentrations in most cores and decreasing Ca2+ and Sr2+ concentrations with depth in core 23–18 GC indicated diagenetic carbonate precipitation. This was

  5. Seismic reflection and vibracoring studies of the continental shelf offshore central and western Long Island, New York

    Science.gov (United States)

    Kelly, W.M.; Albanese, J.R.; Coch, N.K.; Harsch, A.A.

    1999-01-01

    The ridge-and-swale topography on the continental shelf south of Fire Island, New York, is characterized by northeast-trending linear shoals that are shore attached and shore oblique on the inner shelf and isolated and shore parallel on the middle shelf. High-resolution seismic reflection profiles show that the ridges and swales occur independent of, and are not controlled by, the presence of internal structures (for example, filled tidal inlet channels, paleobarrier strata) or underlying structure (for example, high-relief Cretaceous unconformity). Grab samples of surficial sediments on the shelf south of Fire Island average 98% sand. Locally, benthic fauna increase silt and clay content through fecal pellet production or increase the content of gravel-size material by contribution of their fragmented shell remains. Surficial sand on the ridges is unimodal at 0.33 mm (medium sand, about 50 mesh), and surficial sand in troughs is bimodal at 0.33 mm and 0.15 mm (fine sand, about 100 mesh). In addition to seismic studies, 26 vibracores were recovered from the continental shelf in state and federal waters from south of Rockaway and Long Beaches, Long Island, New York. Stratigraphic and sedimentological data gleaned from these cores were used to outline the geologic framework in the study area. A variety of sedimentary features were noted in the cores, including burrow-mottled sections of sand in a finer silty-sand, rhythmic lamination of sand and silty-sand that reflect cyclic changes in sediment transport, layers of shell hash and shells that probably represent tempestites, and changes from dark color to light color in the sediments that probably represent changes in the oxidation-reduction conditions in the area with time. The stratigraphic units identified are an upper, generally oxidized, nearshore facies, an underlying fine- to medium-sand and silty-clay unit considered to be an estuarine facies, and a lower, coarse-grained deeply oxidized, cross-laminated pre

  6. Organic matter distribution in the continental shelf sediments, off Kochi, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Reddy, N.P.C.

    (average 3.8%) than those towards Azhikode (average 1.97%). The sand predominant offshore relict sediments contain very low organic matter values (average 0.71%). The high organic matter content in the inner shelf is mainly controlled by the fine texture...

  7. Phosphatised limestones and associated sediments from the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.; Natarajan, R.; Parthiban, G.; Mascarenhas, A.

    Quaternary carbonate sediments: Rao, Ch.M., Paropkari~ A.L., Mascarenhas, A. and Murty, carbonate sediments and reefs, Yucatan shelf, Mexico. Am. P.S.N., 1987. Distribution of phosphorus and phosphatisa- Assoc. Pet. Geol. Mem., 11: 1-128. tion along...

  8. Improving modeling of tides on the continental shelf off the west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Testut, L.; Unnikrishnan, A.S.

    : modern insights from FES2004.Ocean Dynamics, 56, 394-415. Lyard, F.;Roblou, L., and Birol,F., 2009.Precise error budget for the altimeter-derived tidal constantsin shelf and coastal seas.Ocean Surface Topography Science Team (OSTST), (Seattle...

  9. Holocene submarine terraces on the western continental shelf of India; implications for sea-level changes

    Digital Repository Service at National Institute of Oceanography (India)

    Wagle, B.G.; Vora, K.H.; Karisiddaiah, S.M.; Veerayya, M.; Almeida, F.

    and the shelf break, being more common between 11~' and 20~'N. The terraces are prominent between water depths of 50 and 115 m and occur at six distinct levels: (1) 55-60 m, (2) 65-70 m, (3) 75-80 m, (4) 85-90 m, (5) 95-100 m and (6) 110-115 m...

  10. Geoarchaeological response to landscape changes of the Greek continental shelf since the Last Glacial Maximum

    Science.gov (United States)

    Kapsimalis, Vasilios; Pavlopoulos, Kosmas; Panagiotopoulos, Ioannis

    2010-05-01

    An overview of geological, sedimentological, palaeoclimatic, archaeological and mythological data is presented in order to detect the geomorphological changes of the Aegean and Ionian shelves during the last sea-level transgression, and comprehend the consequent prehistoric human adaptations. The irregular rise of sea level since the Last Glacial Maximum forced the Palaeolithic human to abandon its settlements located near the old (lower) coastlines and to move landward in new positions. Commonly, the coastline movement was very slow causing no significant impact on human activities; however in some cases, the transgression was very prompt causing human migration towards highlands. In some very gentle-dipped and wide regions, e.g. the North Aegean plateau, the sea-level rise caused a rapid coastline retreat (in some extreme case as fast as 10 m/yr) and inundation of an extended surface area. However, at the same time, in the steep parts of the Greek shelf, e.g. the Kyparissiakos Gulf and Crete, the coastline advanced landwards with a slow motion (commonly, a few cm/yr) covering small areas. In addition, coastal regions with particular geomorphologic characteristics, e.g. coastal paleo-lakes protected by a sill (gulfs of Corinth, Amvrakikos, Pagasitikos Evvoikos, Saronikos), were deluged by the sea during different periods and under different intensity, depending on the elevation of the sill and the manner of its overflow. Although the presence of Palaeolithic human in the Greek mainland has been confirmed by several archaeological excavations, there is no certain evidence for human settlement in the deep parts of Greek shelf. However, many archaeologists have suggested that some of Palaeolithic people lived on the shelf, when the sea level was lower than its present position. Nevertheless, some potential Palaeolithic migration routes can be indicated taking into account (a) the palaeogeographic reconstruction of Greek shelf over the Last Quaternary; (b

  11. Deep structure of the Mid-Norwegian continental margin (the Vøring and Møre basins) according to 3-D density and magnetic modelling

    Science.gov (United States)

    Maystrenko, Yuriy Petrovich; Gernigon, Laurent; Nasuti, Aziz; Olesen, Odleiv

    2018-03-01

    A lithosphere-scale 3-D density/magnetic structural model of the Møre and Vøring segments of the Mid-Norwegian continental margin and the adjacent areas of the Norwegian mainland has been constructed by using both published, publically available data sets and confidential data, validated by the 3-D density and magnetic modelling. The obtained Moho topography clearly correlates with the major tectonic units of the study area where a deep Moho corresponds to the base of the Precambrian continental crust and the shallower one is located in close proximity to the younger oceanic lithospheric domain. The 3-D density modelling agrees with previous studies which indicate the presence of a high-density/high-velocity lower-crustal layer beneath the Mid-Norwegian continental margin. The broad Jan Mayen Corridor gravity low is partially related to the decreasing density of the sedimentary layers within the Jan Mayen Corridor and also has to be considered in relation to a possible low-density composition- and/or temperature-related zone in the lithospheric mantle. According to the results of the 3-D magnetic modelling, the absence of a strong magnetic anomaly over the Utgard High indicates that the uplifted crystalline rocks are not so magnetic there, supporting a suggestion that the entire crystalline crust has a low magnetization beneath the greater part of the Vøring Basin and the northern part of the Møre Basin. On the contrary, the crystalline crust is much more magnetic beneath the Trøndelag Platform, the southern part of the Møre Basin and within the mainland, reaching a culmination at the Frøya High where the most intensive magnetic anomaly is observed within the study area.

  12. Cruise report; RV Coastal Surveyor Cruise C1-99; multibeam mapping of the Long Beach, California continental shelf; April 12 through May 19, 1999

    Science.gov (United States)

    Gardner, James V.; Hughes-Clarke, John E.; Mayer, Larry A.

    1999-01-01

    The greater Los Angeles area of California is home to more than 10 million people. This large population puts increased pressure on the adjacent offshore continental shelf and margin with activities such as ocean disposal for dredged spoils, explosive disposal, waste-water outfall, and commercial fishing. The increased utilization of the shelf and margin in this area has generated accelerated multi-disciplinary research efforts in all aspects of the environment of the coastal zone. Prior to 1996 there were no highly accurate base maps of the continental shelf and slope upon which the research activities could be located and monitored. In 1996, the United States Geological Survey (USGS) Pacific Seafloor Mapping Project began to address this problem by mapping the Santa Monica shelf and margin (Fig. 1) using a state-of-the-art, high-resolution multibeam sonar system (Gardner, et al., 1996; 1999). Additional seafloor mapping in 1998 provided coverage of the continental margin from south of Newport to the proximal San Pedro Basin northwest of Palos Verdes Peninsula (Gardner, et al., 1998) (Fig. 1). The mapping of the seafloor in the greater Los Angeles continental shelf and margin was completed with a 30-day mapping of the Long Beach shelf in April and May 1999, the subject of this report. The objective of Cruise C-1-99-SC was to completely map the broad continental shelf from the eastern end of the Palos Verdes Peninsula to the narrow shelf south of Newport Beach, from the break in slope at about 120-m isobath to the inner shelf at about the 10-m isobath. Mapping the Long Beach shelf was jointly funded by the U.S. Geological Survey and the County of Orange (CA) Sanitation District and was conducted under a Cooperative Agreement with the Ocean Mapping Group from the University of New Brunswick (OMG/UNB). The OMG/UNB contracted with C&C Technologies, Inc. of Lafayette, LA for use of the RV Coastal Surveyor and the latest evolution of high-resolution multibeam sonars, a

  13. Managing the visual effects of outer continental shelf and other petroleum-related coastal development

    Science.gov (United States)

    Philip A. Marcus; Ethan T. Smith

    1979-01-01

    Five petroleum-related facilities often sited in the coastal zone during development of Outer Continental oil and gas can change the visual appearance of coastal areas. These facilities are service bases, platform fabrication yards, marine terminals and associated storage facilities, oil and gas processing facilities, and liquified natural gas terminals. Examples of...

  14. Continental shelf drowned landscapes: Submerged geomorphological and sedimentary record of the youngest cycles

    NARCIS (Netherlands)

    Cohen, K.M.; Lobo, F.J.

    2013-01-01

    Continental shelves today find themselves largely submerged as a consequence of the sea-level rise in the last 20,000 years, the time since the Last Glacial Maximum (LGM), the period of maximum ice mass and minimum ocean volume within the Last Glacial Cycle. Their geomorphology, however, is far from

  15. Run-off and sedimentation processes over the continental shelf along the European-Siberian Tundra coast

    Energy Technology Data Exchange (ETDEWEB)

    Josefsson, D. [Univ. of Lund (Sweden)

    2001-04-01

    The contribution of anthropogenic radionuclides from the European sources to the arctic seas have decreased in the first half of the 1990's. This is reflected in the measured activities in the different arctic seas which all show lower concentrations compared to earlier measurements. The influence from the Chernobyl accident were about one third of the total surface activity of {sup 137}CS at the Eurasian continental shelf in 1994 and between 10-30% in the central Arctic Ocean in 1996. The obtained results give no indication of any large extra sources for anthropogenic activity besides the well known fallout from atmospheric nuclear bombs test, discharges from European reprocessing plants and the Chernobyl accident releases. However smaller or local contributions from e.g. the dumped nuclear material in the Kara Sea and releases by the Siberian river from Russian nuclear facilities are not possible to exclude in this investigation.

  16. Dose assessment for public by packages shipping radioactive materials hypothetically sunk on the continental shelf. Annex 3

    International Nuclear Information System (INIS)

    Tsumune, Daisuke; Suzuki, Hiroshi; Saegusa, Toshiari; Watabe, Naohito; Asano, Hiroyuki; Maruyama, Koki; Kinehara, Yoshiki

    2001-01-01

    Radioactive materials such as spent fuel (SF), PuO 2 powder, high level wastes (HLW) and fresh mixed oxide (MOX) fuel have been transported by sea between Europe and Japan. Dose assessments for public have been performed in the past when the packages shipping radioactive materials were hypothetically sunk on the continental shelf. These studies employed various conditions and methods in their assessments and the results were not always the same. In this study, the dose assessment for these packages was performed under the same conditions and by the same methods. The effective dose equivalents of radiation exposure to the public for all materials become smaller than the previous evaluations due to more realistic assumption in this study. These evaluated results are far less than the effective dose equivalent limit (1 mSv year -1 ) by the ICRP recommendation. (author)

  17. Terrigenous material supply to the Peruvian central continental shelf (Pisco, 14° S) during the last 1000 years: paleoclimatic implications

    Science.gov (United States)

    Briceño-Zuluaga, Francisco Javier; Sifeddine, Abdelfettah; Caquineau, Sandrine; Cardich, Jorge; Salvatteci, Renato; Gutierrez, Dimitri; Ortlieb, Luc; Velazco, Federico; Boucher, Hugues; Machado, Carine

    2016-03-01

    In the eastern Pacific, lithogenic input to the ocean responds to variations in the atmospheric and oceanic system and their teleconnections over different timescales. Atmospheric (e.g., wind fields), hydrological (e.g., fresh water plumes) and oceanic (e.g., currents) conditions determine the transport mode and the amount of lithogenic material transported from the continent to the continental shelf. Here, we present the grain size distribution of a composite record of two laminated sediment cores retrieved from the Peruvian continental shelf that record the last ˜ 1000 years at a sub-decadal to centennial time-series resolution. We propose novel grain size indicators of wind intensity and fluvial input that allow reconstructing the oceanic-atmospheric variability modulated by sub-decadal to centennial changes in climatic conditions. Four grain size modes were identified. Two are linked to aeolian inputs (M3: ˜ 54; M4: ˜ 91 µm on average), the third is interpreted as a marker of sediment discharge (M2: ˜ 10 µm on average), and the last is without an associated origin (M1: ˜ 3 µm). The coarsest components (M3 and M4) dominated during the Medieval Climate Anomaly (MCA) and the Current Warm Period (CWP) periods, suggesting that aeolian transport increased as a consequence of surface wind stress intensification. In contrast, M2 displays an opposite behavior, exhibiting an increase in fluvial terrigenous input during the Little Ice Age (LIA) in response to more humid conditions associated with El Niño-like conditions. Comparison with other South American paleoclimate records indicates that the observed changes are driven by interactions between meridional displacement of the Intertropical Convergence Zone (ITCZ), the South Pacific Subtropical High (SPSH) and Walker circulation at decadal and centennial timescales.

  18. Terrigeneous material supply to the Peruvian central continental shelf (Pisco 14° S) during the last 1100 yr: paleoclimatic implications

    Science.gov (United States)

    Briceño Zuluaga, F.; Sifeddine, A.; Caquineau, S.; Cardich, J.; Salvatteci, R.; Gutierrez, D.; Ortlieb, L.; Velazco, F.; Boucher, H.; Machado, C.

    2015-07-01

    In the Eastern Pacific, lithogenic input to the ocean is a response of the atmospheric and ocean system variability and their teleconnections over different timescales. Atmospheric (e.g., wind fields, precipitation), hydrological (e.g., fresh water plumes) and oceanic (e.g., currents) conditions determine the transport mode and the amount of lithogenic material transported from the continent to the continental shelf. Here, we present the grain size distribution of a composite record of two laminated sediment cores retrieved in the Peruvian continental shelf, covering the last ~1100 yr at sub-decadal to centennial time-series resolution. We then discuss the paleo-environmental significance and the climatic mechanisms involved. Four grain size modes were identified. Two are linked to aeolian inputs (M3: 53.0 μm and M4: 90.8 μm on average), the third is interpreted as a marker of sediment discharge (M2: 9.4 μm on average), and the last is without an associated origin (M1: ~3 μm). The coarsest components (M3 and M4) dominated during the Medieval Climate Anomaly (MCA) and Current Warm Period (CWP) periods, suggesting that aeolian transport increased as consequence of wind stress intensification. In contrast, M2 displays an opposite behavior, exhibiting an increase in fluvial terrigenous input during the Little Ice Age (LIA), in response to more humid conditions. Comparison with other South American paleoclimate records indicates that the observed changes are driven by interactions between meridional displacement of the Intertropical convergence zone (ITCZ) and of the South Pacific Sub-tropical High (SPSH) at decadal and centennial time scales.

  19. Surveying the Alentejo continental shelf for minerals and Quaternary environmental changes: preliminary results of the MINEPLAT project survey

    Science.gov (United States)

    Noiva, João; Ribeiro, Carlos; Terrinha, Pedro; Brito, Pedro; Neres, Marta

    2017-04-01

    The tectonic uplift of South Portugal in the last 5 Million years (My) was firstly identified on the basis of morphologic criteria by Mariano Feio (1952, "The evolution of the relief of Baixo Alentejo and Algarve", transl.). However, the assessment of continental vertical movements off Portugal and its relation with tectonics was only initiated in the 1990-ies. This work was carried out in the framework of FP6 and FP7 in the domains of Natural Hazards funded by the European Community. The swath bathymetry cartography of the southwest part of the Iberian Peninsula resulted from the effort of European and national projects, of 19 oceanographic surveys, a total of 200 ship time days executed from 2000 to 2006, involving 14 research institutions from 7 European countries. As a result of this effort together with acquisition and interpretation of thousands of km of seismic reflection profiles, the Pliocene-Quaternary uplift of the Alentejo continental margin (SW Portugal) is now widely accepted by the scientific community. This uplift has not been yet quantified but it is possible that can have contributed to erosion and deposition of metallic ores as placers in the continental shelf. This argues in favor of the potential existence of placers in the continental shelf and the need for the detailed investigation that will allow determination of ideal location for placers deposition in the past Pliocene-Quaternary (5 My). The source for metals can arguably be associated to the Iberian Pyrite Belt ores hosted in the Alentejo Paleozoic formations and to the hyper-alkaline intrusions of Sines and Monchique of Late Cretaceous age. Artificial renourishment of beaches with offshore sand has not been assessed for the Alentejo littoral, despite that the coast located to the south of the Sines segment shows high susceptibility to erosion. This has been observed on a regular basis as the beaches are frequently devoid of sand, thus jeopardizing their touristic potential. The detailed

  20. Genesis of apatite in the phosphatized limestones of the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.; Lamboy, M.

    ) and this siliciclastic flux appear to have transported episodically to the shelf for short duration at about 8300 yr B.P. This flux at places is enriched with iron (Table 1). Iron oxides have strong adsorption capacity for phosphate ions (Nriagu, 1976....C. Burnett and S.R. Riggs (Editors), Neogene to Modern Phosphorites. Phosphate Deposits of the World, 3. Cam- bridge University Press, Cambridge. Cayeux, L., 1939. Existence de nombreuses batteries dans les phosphates sedimentaires de tout age...

  1. Dispersal of the Pearl River plume over continental shelf in summer

    Science.gov (United States)

    Chen, Zhaoyun; Gong, Wenping; Cai, Huayang; Chen, Yunzhen; Zhang, Heng

    2017-07-01

    Satellite images of turbidity were used to study the climatological, monthly, and typical snapshot distributions of the Pearl River plume over the shelf in summer from 2003 to 2016. These images show that the plume spreads offshore over the eastern shelf and is trapped near the coast over the western shelf. Eastward extension of the plume retreats from June to August. Monthly spatial variations of the plume are characterized by eastward spreading, westward spreading, or both. Time series of monthly plume area was quantified by applying the K-mean clustering method to identify the turbid plume water. Decomposition of the 14-year monthly turbidity data by the empirical orthogonal function (EOF) analysis isolated the 1st mode in both the eastward and westward spreading pattern as the time series closely related to the Pearl River discharge, and the 2nd mode with out-of-phase turbidity anomalies over the eastern and western shelves that is associated with the prevailing wind direction. Eight typical plume types were detected from the satellite snapshots. They are characterized by coastal jet, eastward offshore spreading, westward spreading, bidirectional spreading, bulge, isolated patch, offshore branch, and offshore filaments, respectively. Their possible mechanisms are discussed.

  2. EMAP/NOAA 2003 SURVEY OF ECOLOGICAL CONDITIONS OF THE WESTERN U.S. CONTINENTAL SHELF, INCLUDING GULF OF FARALLONES NATIONAL MARINE SANCTUARY

    Science.gov (United States)

    In June of 2003 a partnership between EPA, NOAA, and the western coastal states conducted a joint survey of ecological condition of aquatic resources along the U.S. western continental shelf (30-120 m), using multiple indicators of ecological condition. The study is an element o...

  3. Hydrocarbon production forecast for committed assets in the shallow water Outer Continental Shelf of the Gulf of Mexico

    International Nuclear Information System (INIS)

    Kaiser, Mark J.

    2009-01-01

    In 2007, the federal waters of the Gulf of Mexico averaged daily production of 1.3 million barrels of oil and 7.6 billion cubic feet of natural gas. The majority of oil is produced from deepwater fields in water depth greater than 1000 ft, while most gas production is extracted from the shelf. The Outer Continental Shelf is a mature province with over 3800 fixed structures and 6500 producing wells connected into an integrated pipeline network more than 30,000 miles in length. The purpose of this paper is to develop a methodology to forecast oil and gas production in the shallow water Gulf of Mexico. Structures are categorized according to age and production characteristics, and forecast procedures for each asset class are described and illustrated. The methodology is implemented using the inventory of committed assets circa December 2006. The expected amount of hydrocarbon production arising from the inventory of committed assets under stable reservoir and investment conditions is estimated to be 1056 MMbbl oil and 13.3 Tcf gas valued between $85 and 150 billion. The results of generalized regression models are presented with a discussion of the limitations of analysis. (author)

  4. U, Th, K content, heat production and thermal conductivity of Sao Paulo, Brazil continental shelf sediments: a reconnaissance work

    International Nuclear Information System (INIS)

    Pereira, E.B.; Hamza, V.M.; Furtado, V.V.; Adams, J.A.S.

    1985-01-01

    A reconnaissance of the natural potassium, uranium and thorium content, the radiogenic heat production and the thermal conductivity of 80 bottom surface sediment samples collected from the Brazilian continental shelf off Sao Paulo was made. The average equivalent contents of these radio-elements in an estuarine ambient were 1.21%, 1.75 ppm and 4.29 ppm respectively, and 1.20%, 1.21 ppm and 4.05 ppm, respectively, in the shelf samples. The largest radioelement contents were associated with the more fine-grained sediments. The 234 U to 238 U isotopic ratios varied from 0.60 to 1.75 with an average of 1.11, indicating that the sources for the uranium in these sediments are both terrigenous and from the sea water. An average radiogenic heat production of 0.63 (+ - 0.04) μW.m -3 was calculated from the experimental concentration data. Data for the thermal conductivity measurements ranged from 0.83 to 2.51 μW.m -1 . 0 C -1 , with an average of 1.81 μW.m -1 . 0 C -1 . (Author) [pt

  5. Late Neogene foraminifera from the northern Namibian continental shelf and the transition to the Benguela Upwelling System

    Science.gov (United States)

    Bergh, Eugene W.; Compton, John S.; Frenzel, Peter

    2018-05-01

    Middle Miocene to Plio-Pleistocene foraminifera provide insights into the palaeoenvironment on the northern Namibian continental shelf located at the far northern end of the present-day Benguela Upwelling System (BUS). Biostratigraphy and Strontium Isotope Stratigraphy (SIS) of the recovered basal olive-green mud unit indicate an age of 16 to 14 Ma. A sharp, erosional contact separates the basal mud from the overlying Plio-Pleistocene gravelly pelletal phosphorite sands. Grain size data, P/B ratios and benthic diversity indices indicate a change between the middle Miocene and overlying Plio-Pleistocene palaeoenvironments linked to the timing and conditions associated with the initiation of the BUS. The different lithological units and microfossil assemblages in the olive-green mud unit and the overlying pelletal phosphorite units support the late Miocene initiation of the BUS and the northwards migration of the Angola-Benguela Front. Planktic foraminifera indicate a shift from warmer surface water conditions to cooler conditions during the initiation of the BUS. Benthic palaeobathymetric ranges and P/B ratios are consistent with outer shelf water depths suggesting a deeper palaeoenvironment during the Mid-Miocene Climatic Optimum (MMCO) than today. Benthic foraminifera in the middle Miocene are dominated by large (>1 mm) taxa and adapted to oligotrophic environments before the initiation of the BUS. The benthic assemblage composition indicates that bottom water conditions changed to eutrophic conditions during the Plio-Pleistocene under intensified upwelling conditions.

  6. Impact of Satellite Remote Sensing Data on Simulations of Coastal Circulation and Hypoxia on the Louisiana Continental Shelf

    Directory of Open Access Journals (Sweden)

    Dong S. Ko

    2016-05-01

    Full Text Available We estimated surface salinity flux and solar penetration from satellite data, and performed model simulations to examine the impact of including the satellite estimates on temperature, salinity, and dissolved oxygen distributions on the Louisiana continental shelf (LCS near the annual hypoxic zone. Rainfall data from the Tropical Rainfall Measurement Mission (TRMM were used for the salinity flux, and the diffuse attenuation coefficient (Kd from Moderate Resolution Imaging Spectroradiometer (MODIS were used for solar penetration. Improvements in the model results in comparison with in situ observations occurred when the two types of satellite data were included. Without inclusion of the satellite-derived surface salinity flux, realistic monthly variability in the model salinity fields was observed, but important inter-annual variability was missed. Without inclusion of the satellite-derived light attenuation, model bottom water temperatures were too high nearshore due to excessive penetration of solar irradiance. In general, these salinity and temperature errors led to model stratification that was too weak, and the model failed to capture observed spatial and temporal variability in water-column vertical stratification. Inclusion of the satellite data improved temperature and salinity predictions and the vertical stratification was strengthened, which improved prediction of bottom-water dissolved oxygen. The model-predicted area of bottom-water hypoxia on the Louisiana shelf, an important management metric, was substantially improved in comparison to observed hypoxic area by including the satellite data.

  7. Geologic Setting and Preservation of a Late Pleistocene Bald Cypress Forest Discovered on the Northern Gulf of Mexico Continental Shelf

    Science.gov (United States)

    Gonzalez Rodriguez, S. M.; Bentley, S. J.; DeLong, K. L.; Xu, K.; Harley, G. L.; Reese, C. A.; Obelcz, J.

    2016-02-01

    Following landfall of Hurricane Ivan in 2004, a previously buried bald cypress forest (Taxodium distichum) was discovered on the continental shelf seafloor, offshore of Orange Beach, Alabama, USA, in 20 m of water. The forest is preserved as stumps in life position with little evidence of decay and large pieces of trunks, roots, and branches. Analysis shows the forest is older than can be dated with conventional C-14 methods. Comparison of Pleistocene sea level curves with the study area depth suggests that the forest developed and was likely buried during marine isotope stage 3 or 4, or perhaps older stages. Condition of sampled wood suggests that the forest was buried and preserved in anoxic sediments for millennia, prior to recent exhumation. To better understand the puzzling geological conditions that could allow forest preservation during sea level fall and shelf exposure spanning >30,000 years, submersible vibracores (to 6 m length) and geophysical data (swath bathymetry, sidescan, and chirp subbottom) were collected in August 2015. Cores are being analyzed using a Geotek Multi Sensor Core Logger, granulometric and sediment composition analyses, and a wide range of paleoenvironmental observations. This presentation focuses on the geological setting and mode of forest preservation. Preliminary analysis of sediment types and stratigraphy in cores shows that the local stratigraphy is broadly consistent with previous regional shelf-stratigraphic studies, consisting of (top to bottom) a surface layer of Holocene transgressive sands (to 3 m thick) unconformably overlying Pleistocene terrestrial and coastal deposits. However, the Pleistocene lithofacies (fluvial, backswamp, or possibly delta plain muds) differ considerably in both depositional environment and degree of environmental preservation compared to previous studies. Ongoing analysis will focus on elucidating the succession of events that allows preservation of this unique Pleistocene sedimentary archive.

  8. Characteristics of storms driving wave-induced seafloor mobility on the U.S. East Coast continental shelf

    Science.gov (United States)

    Dalyander, P. Soupy; Butman, Bradford

    2015-01-01

    This study investigates the relationship between spatial and temporal patterns of wave-driven sediment mobility events on the U.S. East Coast continental shelf and the characteristics of the storms responsible for them. Mobility events, defined as seafloor wave stress exceedance of the critical stress of 0.35 mm diameter sand (0.2160 Pa) for 12 or more hours, were identified from surface wave observations at National Data Buoy Center buoys in the Middle Atlantic Bight (MAB) and South Atlantic Bight (SAB) over the period of 1997-2007. In water depths ranging from 36-48 m, there were 4-9 mobility events/year of 1-2 days duration. Integrated wave stress during events (IWAVES) was used as a combined metric of wave-driven mobility intensity and duration. In the MAB, over 67% of IWAVES was caused by extratropical storms, while in the SAB, greater than 66% of IWAVES was caused by tropical storms. On average, mobility events were caused by waves generated by storms located 800+ km away. Far-field hurricanes generated swell 2-4 days before the waves caused mobility on the shelf. Throughout most of the SAB, mobility events were driven by storms to the south, east, and west. In the MAB and near Cape Hatteras, winds from more northerly storms and low-pressure extratropical systems in the mid-western U.S. also drove mobility events. Waves generated by storms off the SAB generated mobility events along the entire U.S. East Coast shelf north to Cape Cod, while Cape Hatteras shielded the SAB area from swell originating to the north offshore of the MAB.

  9. Observed tidal currents on the continental shelf off the west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Subeesh, M.P.; Unnikrishnan, A.S.; Fernando, V.; Agarwadekar, Y.; Khalap, S.T.; Satelkar, N.P.; Shenoi, S.S.C.

    tidal currents have been widely studied around the world ocean particularly on the continental shelves and slopes (for example, Huthnance, 1989; Holloway et al., 2001; Xu et al., 2011b, 2013). The astronomical forcing mainly leads to the generation... directions. Internal tides have temporal scales from inertial to local Brunt-Väisälä frequency (f < σ < N), where σ is the internal wave frequency and f and N are inertial and buoyancy frequencies respectively. The direct astronomical forcing...

  10. Stratigraphic Reconstruction of a Late Pleistocene Cypress Forest Discovered on the Northern Gulf of Mexico Continental Shelf

    Science.gov (United States)

    Gonzalez Rodriguez, S. M.; Bentley, S. J.; Obelcz, J.; Truong, J. T.; DeLong, K. L.; Xu, K.; Harley, G. L.; Reese, C. A.; Caporaso, A.; Shen, Z.

    2017-12-01

    A previously buried bald cypress forest (Taxodium distichum) was discovered on the continental shelf, offshore of Orange Beach, Alabama, USA, in 20 m water depth. The forest was possibly exhumed by Hurricane Ivan in 2004, and is now exposed as stumps in life position in a trough located in the northern Gulf of Mexico continental shelf seafloor. We are investigating the local stratigraphy, paleo-landscape, and mode of forest preservation of this unique site. In August 2015 and July 2016, submersible vibracores (18 in total) were collected. Core analysis included: bulk density and imaging via Geotek multi sensor core logger, sediment grain size, structure, and organic content via loss-on-ignition. Selected samples have been dated using 14C and optically stimulated luminescence (OSL) methods. Multibeam and CHIRP subbottom bathymetry provide context for litho- and chrono-stratigraphy of the site. Integration of core lithostratigraphy and modern shelf bathymetry reveal Holocene transgressive sands blanketing diverse sedimentary facies that are truncated by the late Pleistocene-early Holocene ravinement. Deposits below the ravinement surface include interbedded sand and mud (exact age unknown, but possibly pertaining to a shallow marine environment), overlying a floodplain/swamp facies of woody debris, peat, and mud (provisionally dated by 14C to 41-45 ka). These units grade laterally into paleosols that appear to be 10-15 ka older, based on recently obtained preliminary OSL dates. Occurrence of paleosols and swamp deposits of broadly similar age and elevation suggests that the ancient landscape possessed topographic relief that allowed wetland and upland habitats to develop in close proximity. These new OSL dates enhance our initial hypothesis that floodplain aggradation in the area was a key factor that might have allowed forest preservation. The timing of temporary sea level rises (SLR) ca. 40 and 60 ka. with our 14C and preliminary OSL dates, suggests that floodplain

  11. Observations and a model of undertow over the inner continental shelf

    Science.gov (United States)

    Lentz, Steven J.; Fewings, Melanie; Howd, Peter; Fredericks, Janet; Hathaway, Kent

    2008-01-01

    Onshore volume transport (Stokes drift) due to surface gravity waves propagating toward the beach can result in a compensating Eulerian offshore flow in the surf zone referred to as undertow. Observed offshore flows indicate that wave-driven undertow extends well offshore of the surf zone, over the inner shelves of Martha’s Vineyard, Massachusetts, and North Carolina. Theoretical estimates of the wave-driven offshore transport from linear wave theory and observed wave characteristics account for 50% or more of the observed offshore transport variance in water depths between 5 and 12 m, and reproduce the observed dependence on wave height and water depth.During weak winds, wave-driven cross-shelf velocity profiles over the inner shelf have maximum offshore flow (1–6 cm s−1) and vertical shear near the surface and weak flow and shear in the lower half of the water column. The observed offshore flow profiles do not resemble the parabolic profiles with maximum flow at middepth observed within the surf zone. Instead, the vertical structure is similar to the Stokes drift velocity profile but with the opposite direction. This vertical structure is consistent with a dynamical balance between the Coriolis force associated with the offshore flow and an along-shelf “Hasselmann wave stress” due to the influence of the earth’s rotation on surface gravity waves. The close agreement between the observed and modeled profiles provides compelling evidence for the importance of the Hasselmann wave stress in forcing oceanic flows. Summer profiles are more vertically sheared than either winter profiles or model profiles, for reasons that remain unclear.

  12. On the flow, thermal field and winds along the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Antony, M.K.; Shenoi, S.S.C.

    drift will be in phase with the density field or in geostrophic balance. The instrusion of the Bay of 438 M.K. ANTONY and S. S. C. SHENOI Bengal water (less dense than the Arabian Sea water) into the Arabian Sea along the shelf/slope region (SARMA et... flows during May and November are in geostrophic balance or not. For this purpose we used the thermal wind equation Or_-g Op (1) Oz f Ox and substituted the observed values for the average shear (Ov/Oz) and cross-shore density gradient (Op...

  13. Emergence of burrowing urchins from California continental shelf sediments-A response to alongshore current reversals?

    Science.gov (United States)

    Nichols, F.H.; Cacchione, D.A.; Drake, D.E.; Thompson, J.K.

    1989-01-01

    Two sequences of bottom photographs taken every two or four hours for two months during the Coastal Ocean Dynamics Experiment (CODE) off the Russian River, California, reveal the dynamic nature of interations between the water column, the sediments, and benthic organisms in the mid-shelf silt deposit. Time-lapse photographs taken between late spring and early summer in 1981 and 1982 show that the subsurface-dwelling urchin Brisaster latifrons (one of the largest invertebrates found in shelf-depth fine sediment off the U.S. Pacific coast) occasionally emerged from the sediment, plowed the sediment surface during the course of a few hours to several days, then buried themselves again. Frame-by-frame study of the film sequences shows that the urchins typically emerged following relaxation of coastal upwelling, periods characterized by current direction reversals and increases in bottom water turbidity. Among the possible causes of the emergence of urchins and the consequent bioturbation of the upper few cm of sediment, a response to an enhanced food supply seems most plausible. Circumstantial evidence suggests the possibility that phytoplankton sedimentation during periods of upwelling relaxation could provide a new source of food at the sediment surface. ?? 1989.

  14. Tectonic structure of the Tuscany-Latium Continental Shelf (Tyrrhenian Sea)

    Energy Technology Data Exchange (ETDEWEB)

    Bartole, R.

    1988-08-01

    An old regional seismic multicoverage reflection survey (Zone E) provides useful information on the shallow structure of the southern Tuscany-northern Latium shelf located between Elba Island and Anzio. Three main seismic units have been recognized on the grid, directly tied to the Matilde-1 offshore drilling and correlated to onshore wells and outcrops. The upper unit, characterized by continuous and generally undisturbed reflectors, is constituted by the postorogenic sedimentary cover of late Neogene-Quaternary age. This sequence unconformably lies on an intermediate unit or, when absent, a basal one. These two units, characterized by good-to-poor seismic response, are constituted by the tectonized geologic units of the Northern and Central Apennines. The intermediate unit corresponds to the Ligurids and Sicilids allochthonous complexes, while the basal unit may be attributable to the Tuscan nappe and/or the Tuscan autochthon in the shelf sector north of the Tiber River mouth, and the Umbro-Sabina units south of the same mouth. The widespread distribution and consistent thickness of the allochthonous cover (up to 1,000 msec two-way traveltime) lying over a structured substratum might be of some interest in hydrocarbon prospecting.

  15. The assemblage composition and structure of swimming crabs (Portunoidea) in continental shelf waters of southeastern Brazil

    Science.gov (United States)

    Andrade, L. S.; Frameschi, I. F.; Costa, R. C.; Castilho, A. L.; Fransozo, A.

    2015-02-01

    Three regions along the Brazilian coast characterized by the occurrence of contrasting natural phenomena, such as upwellings and continental input, were surveyed to determine the composition and structure of the assemblage of swimming crabs. Twelve monthly collections were undertaken (July 2010 to June 2011) in Macaé, Rio de Janeiro (MAC); Ubatuba, São Paulo (UBA); and São Francisco do Sul, Santa Catarina (SFS). The lowest values ​​of the phi sediment grain size measure, bottom temperature and the highest values of organic matter and salinity were measured in MAC. In all, 10,686 individuals were collected, belonging to six species of Portunoidea: Arenaeus cribrarius, Callinectes danae, Callinectes ornatus, Callinectes sapidus, Achelous spinicarpus and Achelous spinimanus. A Multiple Response Permutation Procedure (MRPP) test indicated that the species composition differed significantly among the sampling sites, showing substantial heterogeneity in the composition and abundance of species among regions. The results suggest that C. danae was more abundant in waters with lower salinity and lower organic matter content. In contrast, A. spinimanus is positively correlated with these factors, showing a greater abundance under the opposite conditions. Callinectes ornatus appeared not to show strong selectivity for particular habitat characteristics. We conclude from these findings that areas affected by different phenomena produce changes in the composition and abundance of the assemblage of Portunoidea. Although the strength of eutrophication differs between UBA and MAC, the substantial continental inflow affecting SFS favors the development of species that complete their life cycle in the estuary.

  16. Speciation of phosphorus in the continental shelf sediments in the Eastern Arabian Sea

    Science.gov (United States)

    Acharya, Shiba Shankar; Panigrahi, Mruganka Kumar; Kurian, John; Gupta, Anil Kumar; Tripathy, Subhasish

    2016-03-01

    The distributions of various forms of phosphorus (P) and their relation with sediment geochemistry in two core sediments near Karwar and Mangalore offshore have been studied through the modified SEDEX procedure (Ruttenberg et al., 2009) and bulk chemical analysis. The present study provides the first quantitative analysis of complete phosphorus speciation in the core sediments of the Eastern Arabian shelf. The chemical index of alteration (CIA), chemical Index of Weathering (CIW) and Al-Ti-Zr ternary diagram suggest low to moderate source area weathering of granodioritic to tonalitic source rock composition, despite the intense orographic rainfall in the source area. Due to the presence of same source rock and identical oxic depositional environment, the studied sediments show the same range of variation of total phosphorus (24 to 83 μmol/g) with a down-depth depleting trend. Organic bound P and detrital P are the two major chemical forms followed by iron-bound P, exchangeable/loosely bound P and authigenic P. The authigenic P content in the sediments near Mangalore coast varies linearly with calcium (r=0.88) unlike that of Karwar coast. The different reactive-phosphorus pools exhibit identical depleting trend with depth. This indicates that the phosphorus released from the organic matter and Fe bound fractions are prevented from precipitating as authigenic phosphates in the deeper parts of the sediment column. The low concentration of total P, dominance of detrital non-reactive fraction of P and inhibition of formation of authigenic phosphate result in the absence of active phosphatization in the Eastern Arabian Shelf in the studied region. High sedimentation rate (35-58 cm/kyr) and absence of winnowing effect appear to be the dominant factor controlling the P-speciation in the studied sediments.

  17. Spatial distribution of Munida intermedia and M. sarsi (crustacea: Anomura) on the Galician continental shelf (NW Spain): Application of geostatistical analysis

    Science.gov (United States)

    Freire, J.; González-Gurriarán, E.; Olaso, I.

    1992-12-01

    Geostatistical methodology was used to analyse spatial structure and distribution of the epibenthic crustaceans Munida intermedia and M. sarsi within sets of data which had been collected during three survey cruises carried out on the Galician continental shelf (1983 and 1984). This study investigates the feasibility of using geostatistics for data collected according to traditional methods and of enhancing such methodology. The experimental variograms were calculated (pooled variance minus spatial covariance between samples taken one pair at a time vs. distance) and fitted to a 'spherical' model. The spatial structure model was used to estimate the abundance and distribution of the populations studied using the technique of kriging. The species display spatial structures, which are well marked during high density periods and in some areas (especially northern shelf). Geostatistical analysis allows identification of the density gradients in space as well as the patch grain along the continental shelf of 16-25 km diameter for M. intermedia and 12-20 km for M. sarsi. Patches of both species have a consistent location throughout the different cruises. As in other geographical areas, M. intermedia and M. sarsi usually appear at depths ranging from 200 to 500 m, with the highest densities in the continental shelf area located between Fisterra and Estaca de Bares. Althouh sampling was not originally designed specifically for geostatistics, this assay provides a measurement of spatial covariance, and shows variograms with variable structure depending on population density and geographical area. These ideas are useful in improving the design of future sampling cruises.

  18. Seismic evidence for the preservation of several stacked Pleistocene coastal barrier/lagoon systems on the Gulf of Valencia continental shelf (western Mediterranean)

    Science.gov (United States)

    Albarracín, Silvia; Alcántara-Carrió, Javier; Barranco, Andrés; Sánchez García, María José; Fontán Bouzas, Ángela; Rey Salgado, Jorge

    2013-04-01

    The focus of this study is the analysis of coastal sand barriers and associated coastal lagoons on the inner continental shelf of the Gulf of Valencia (western Mediterranean), based on two W-E seismic profiles recorded seaward of the Albufera de Valencia coastal lagoon. Seismic facies identified include a number of coastal sand barriers with landward lagoons draped by contemporary continental shelf deposits. The barrier systems have been grouped into two sedimentary systems tracts, the older one corresponding to a prograding/aggrading highstand systems tract involving at least four paleo-coastal sand barrier/lagoon systems, followed landward by a transgressive systems tract comprising three such systems. All the systems have been allocated a Tyrrhenian age, the formation of individual barrier systems having been associated with successive sea-level stillstands, and their present-day position being explained by the very high regional subsidence rate. In summary, this study demonstrates that the Quaternary stratigraphic record of the Gulf of Valencia inner continental shelf is composed of littoral sand facies, in particular coastal sand barrier and lagoon deposits. These findings are in agreement with corresponding observations on other continental shelves of the western Mediterranean, showing that the formation of coastal sand barriers was a characteristic feature of this region during the Quaternary.

  19. Change in morphology and modern sediment thickness on the inner continental shelf offshore of Fire Island, New York between 2011 and 2014: Analysis of hurricane impact

    Science.gov (United States)

    Schwab, William C.; Baldwin, Wayne E.; Warner, John C.; List, Jeffrey; Denny, Jane F.; Liste Munoz, Maria; Safak, Ilgar

    2017-01-01

    Seafloor mapping investigations conducted on the lower shoreface and inner continental shelf offshore of Fire Island, New York in 2011 and 2014, the period encompassing the impacts of Hurricanes Irene and Sandy, provide an unprecedented perspective regarding regional inner continental shelf sediment dynamics during large storm events. Analyses of these studies demonstrate that storm-induced erosion and sediment transport occurred throughout the study area in water depths up to 30 m. Acoustic backscatter patterns were observed to move from ~1 m to 450 m with a mean of 20 m and movement tended to decrease with increasing water depth. These patterns indicate that both of the primary inner continental shelf sedimentary features in the study area, linear sorted bedforms offshore of eastern Fire Island and shoreface-attached sand ridges offshore of central and western Fire island, migrated alongshore to the southwest. The migration of the sorted bedforms represents the modification of an active ravinement surface and is thought to have liberated a significant volume of sediment. Comparison of isopach maps of sediment thickness show that the volume of modern sediment composing the lower shoreface and shoreface-attached sand ridges decreased by ~2.8 × 106 m3 across the ~73 km2 of common seafloor mapped in both surveys. However, a similar analysis for the relatively calmer 15-yr period prior to 2011 revealed significant accretion. This allows speculation that the shoreface-attached sand ridges are maintained over decadal timescales via sediment supplied through erosion of Pleistocene outwash and lower Holocene transgressive channel-fill deposits exposed on the inner continental shelf, but that the sand ridges also periodically erode and move to the southwest during large storm events. Analyses show that significant storminduced erosion and sediment transport occurs far seaward of the 5 to 9 m depth of closure assumed for Fire Island, where it is thought that an onshore

  20. Flux, Budget and Sources of Black Carbon (BC) in the Continental Shelf of the Bohai and Yellow Seas, China

    Science.gov (United States)

    Fang, Y.; Chen, Y.; Tian, C.

    2015-12-01

    Black carbon (BC) derived from incomplete combustion of fossil fuels and biomass has received increasing attention due to their potential importance in a wide range of biogeochemical processes. China has been generally considered as the world's largest BC emitter. Due to a combination of the prevailing East Asia monsoon and large amounts of riverine outflow, BC released from China can be transported to the adjacent continental shelf seas, the Bohai Sea (BS) and Yellow Sea (YS). Based on measurements of BC in 191 surface sediments, 36 riverine water, and 2 seawater samples, as well as the reported BC data set of the aerosol samples in the Bohai Rim, the concentration, flux, and budget of BC in the BS and YS were investigated. The spatial distribution of the BC concentration in surface sediments was largely influenced by the regional hydrodynamic conditions, with high values mainly occurring in the central mud areas. The BC burial flux in the BS and YS ranged from 4 to 1100 μg/cm2/yr, and averaged 166 ± 200 μg/cm2/yr. The area-integrated sedimentary BC sink flux in the entire BS and YS was ~325 Gg/yr. The BC budget calculated in the BS showed that atmospheric deposition and riverine discharge played comparable importance in delivering BC to the BS, and sequestration to bottom sediments was the major BC output pattern, accounting for ~88% of the total input BC. Besides, we attempted to apportion the BC sources in the BS and YS surface sediments using PAHs (organic molecular proxies cogenerated with BC) and BC as an input data to the Positive Matrix Factorization (PMF) receptor model. Results showed that ~83% of the sediment BC was attributed to the combustion of fossil fuels, and the remaining ~17% was from biomass burning. Due to the differences in their production mechanisms and therefore physicochemical properties, the above distinction and quantification would help us better understand their different environmental behaviors in the complex continental shelf

  1. Spatial changes in fatty acids signatures of the great scallop Pecten maximus across the Bay of Biscay continental shelf

    Science.gov (United States)

    Nerot, Caroline; Meziane, Tarik; Schaal, Gauthier; Grall, Jacques; Lorrain, Anne; Paulet, Yves-Marie; Kraffe, Edouard

    2015-10-01

    The spatial variability of food resources along continental margins can strongly influence the physiology and ecology of benthic bivalves. We explored the variability of food sources of the great scallop Pecten maximus, by determining their fatty acid (FA) composition along an inshore-offshore gradient in the Bay of Biscay (from 15 to 190 m depth). The FA composition of the digestive gland showed strong differences between shallow and deep-water habitats. This trend was mainly driven by their content in diatom-characteristic fatty acids, which are abundant near the coast. Scallops collected from the middle of the continental shelf were characterized by higher contents of flagellate markers than scallops from shallow habitats. This could be related to a permanent vertical stratification in the water column, which reduced vertical mixing of waters, thereby enhancing organic matter recycling through the microbial loop. In the deeper water station (190 m), FA compositions were close to the compositions found in scallops from shallow areas, which suggest that scallops could have access to the same resources (i.e. diatoms). Muscle FA composition was more indicative of the physiological state of scallops over this depth range, revealing contrasting reproductive strategies among the two coastal sites and metabolic or physiological adaptation at greater depth (e.g. structural and functional adjustments of membrane composition). This study therefore revealed contrasted patterns between shallow and deeper habitats for both P. maximus muscle and digestive gland tissues. This emphasizes the variability in the diet of this species along its distribution range, and stresses the importance of analyzing different tissues for their FA composition in order to better understand their physiology and ecology.

  2. Number One Reef: An overstepped segmented lagoon complex on the KwaZulu-Natal continental shelf

    Directory of Open Access Journals (Sweden)

    Godfrey Vella

    2012-07-01

    Full Text Available This study of the bathymetry of the mid-shelf of the Durban Bight, KwaZulu-Natal revealed a series of previously undocumented seafloor features. These features were mapped using a high-resolution multibeam bathymetric echosounder and a detailed map of the seafloor topography was produced. We recognised several features that closely resemble features of contemporary segmented lagoon and lake systems: semicircular seafloor depressions, arcuate ridges, cuspate spits and prograding submerged barriers. Based on the striking similarity in morphology to Kosi Bay – a segmented lagoon system from the sandy northern KwaZulu-Natal coastal plain – a similar evolutionary model is proposed. This model is of an incised valley formed following a sea level lowering to the Last Glacial Maximum at about 18 000 BP. Thereafter, continued transgressive infilling occurred to a point where an extensive lagoon and back-barrier system was established. At this point, sea levels remained static, causing the net segmentation of the system and the slow closure of the tidal basins or circular depressions. This type of seafloor topography is rarely preserved and is the result of fortuitous cementation after deposition and the later removal of sediment that would ordinarily bury such features.

  3. Temporal-Spectral Characterization and Classification of Marine Mammal Vocalizations and Diesel-Electric Ships Radiated Sound over Continental Shelf Scale Regions with Coherent Hydrophone Array Measurements

    Science.gov (United States)

    Huang, Wei

    approach is calibrated by application to known ships present in the Gulf of Maine and in the Norwegian Sea from their underwater sounds received using a coherent hydrophone array. The vocalization behavior of humpback whales was monitored over vast areas of the Gulf of Maine using the POAWRS technique over multiple diel cycles in Fall 2006. The humpback vocalizations, received at a rate of roughly 1800+/-1100 calls per day, comprised of both song and non-song. The song vocalizations, composed of highly structured and repeatable set of phrases, are characterized by inter-pulse intervals of 3.5 +/- 1.8 s. Songs were detected throughout the diel cycle, occuring roughly 40% during the day and 60% during the night. The humpback non-song vocalizations, dominated by shorter duration (≤3 s) downsweep and bow-shaped moans, as well as a small fraction of longer duration (˜5 s) cries, have significantly larger mean and more variable inter-pulse intervals of 14.2 +/- 11 s. The non-song vocalizations were detected at night with negligible detections during the day, implying they probably function as nighttime communication signals. The humpback song and non-song vocalizations are separately localized using the moving array triangulation and array invariant techniques. The humpback song and non-song moan calls are both consistently localized to a dense area on northeastern Georges Bank and a less dense region extended from Franklin Basin to the Great South Channel. Humpback cries occur exclusively on northeastern Georges Bank and during nights with coincident dense Atlantic herring shoaling populations, implying the cries are feeding-related. Sperm whales in the New England continental shelf and slope were passively localized and classified from their vocalizations received using a single low-frequency (<2500 Hz) densely-sampled horizontal coherent hydrophone array deployed in Spring 2013 in Gulf of Maine. Whale bearings were estimated using time-domain beamforming that provided high

  4. Continental Influence versus marine transition in Rio de la Plata zone - internal continental shelf of the South Atlantic - a multi proxy study

    International Nuclear Information System (INIS)

    Burone, L.; Franco-Fraguas, P.; Garcia-Rodriguez, F.; Venturini, N.; Brugnoli, E.; Muniz, P.; Ortega, L.; Marin, Y.; Mahiques, M.; Nagaic, R.; Bicegoc, M.; Figueiras, R.; Salaroli, A.

    2012-01-01

    The terrigenous proxies contribution, the organic matter origin, the productivity, the hydrodynamic and the biological records were used to determine the imrprint of the continental influence along the Rio de la Plata and the Continental Atlantic

  5. Bacterial diversity in the bottom boundary layer of the inner continental shelf of Oregon, USA

    KAUST Repository

    Bertagnolli, AD

    2011-06-21

    There have been few studies of the bacterial community within the bottom boundary layer (BBL) the turbulent region of the water column above the benthos in shallow seas. Typically, the BBL has large amounts of particulate organic matter suspended by turbulence, and it is often the first region of the water column to become hypoxic when oxygen declines. Communities at the surface (5 m) and in the BBL (1 to 10 m above the sea floor) were compared by terminal restriction fragment length polymorphism (T-RFLP) analysis and sequencing of the 16S rRNA gene. Multivariate statistical methods (hierarchical clustering, non-metric multidimensional scaling, and analysis of similarity (ANOSIM)) indicated that the microbial community of the BBL is distinct from the surface community. ANOSIM supported the distinction between surface and BBLs (R values 0.427 and 0.463, based on analysis with restriction enzymes BsuR1 and Hin6I, respectively, p < 0.1%). Six terminal restriction fragments showed an increase in abundance with depth. Cloning, screening and sequencing identified these as a novel environmental clade (Eastern North Pacific Chromatiales (ENPC) clade), the ARTIC96BD-19 clade of Gammaproteobacteria, the 6N14 and Agg8 clades of the phylum Planctomycetes, the OM60/NOR5 clade of Gammaproteobacteria, and uncultivated members of the Roseobacter clade in the MB11C09 and ULA23 subgroups. To the best of our knowledge, this analysis is the first to focus on the unique composition of microbial communities of the BBL in shallow, inner-shelf regions off the coast of Oregon, USA, and the first to report that an uncharacterized clade of Chromatiales is indigenous in this habitat.

  6. Bacterial diversity in the bottom boundary layer of the inner continental shelf of Oregon, USA

    KAUST Repository

    Bertagnolli, AD; Treusch, AH; Mason, OU; Stingl, Ulrich; Vergin, KL; Chan, F; Beszteri, B; Giovannoni, SJ

    2011-01-01

    There have been few studies of the bacterial community within the bottom boundary layer (BBL) the turbulent region of the water column above the benthos in shallow seas. Typically, the BBL has large amounts of particulate organic matter suspended by turbulence, and it is often the first region of the water column to become hypoxic when oxygen declines. Communities at the surface (5 m) and in the BBL (1 to 10 m above the sea floor) were compared by terminal restriction fragment length polymorphism (T-RFLP) analysis and sequencing of the 16S rRNA gene. Multivariate statistical methods (hierarchical clustering, non-metric multidimensional scaling, and analysis of similarity (ANOSIM)) indicated that the microbial community of the BBL is distinct from the surface community. ANOSIM supported the distinction between surface and BBLs (R values 0.427 and 0.463, based on analysis with restriction enzymes BsuR1 and Hin6I, respectively, p < 0.1%). Six terminal restriction fragments showed an increase in abundance with depth. Cloning, screening and sequencing identified these as a novel environmental clade (Eastern North Pacific Chromatiales (ENPC) clade), the ARTIC96BD-19 clade of Gammaproteobacteria, the 6N14 and Agg8 clades of the phylum Planctomycetes, the OM60/NOR5 clade of Gammaproteobacteria, and uncultivated members of the Roseobacter clade in the MB11C09 and ULA23 subgroups. To the best of our knowledge, this analysis is the first to focus on the unique composition of microbial communities of the BBL in shallow, inner-shelf regions off the coast of Oregon, USA, and the first to report that an uncharacterized clade of Chromatiales is indigenous in this habitat.

  7. Spatial and temporal changes in benthic communities of the Galician continental shelf after the Prestige oil spill

    International Nuclear Information System (INIS)

    Serrano, Alberto . E-mail aserrano@st.ieo.es; Sanchez, Francisco; Preciado, Izaskun; Parra, Santiago; Frutos, Inmaculada

    2006-01-01

    Two years after the Prestige oil spill (POS) an assessment of the effects on benthic fauna was carried out using the data obtained in five multidisciplinary surveys. Otter trawl, beam trawl, suprabenthic sled and box corer were used to study the main benthic compartments, along eight transects perpendicular to the coastline. Beam trawl was also employed to quantify the amount of tar aggregates on the continental shelf. No significant correlations between tar aggregates and species richness, biomass and diversity of benthic communities were found. This result was corroborated when the role of depth, season, latitude and sediment characteristics was examined by canonical ordination, in which POS-related variables had low influence on spatial distribution patterns. Depth and sediment grain diameter profoundly influence epibenthic communities. Sediment organic content is a third key variable for the infaunal, suprabenthic and lower-sized epibenthic communities, but not for the larger epibenthic communities. Nevertheless, a decrease in the densities of several epibenthic indicators was detected the first year after spill, followed by a noteworthy recovery in 2004. Non-macroscopic toxicity and some oceanographic agents are suggested as possible causes of these shifts

  8. Modeling the role and impact of alien species and fisheries on the Israeli marine continental shelf ecosystem

    Science.gov (United States)

    Corrales, X.; Ofir, E.; Coll, M.; Goren, M.; Edelist, D.; Heymans, J. J.; Gal, G.

    2017-06-01

    The ecosystems of the Israeli Mediterranean coast have undergone significant changes in recent decades mainly due to species invasions and fishing. In order to characterize the structure and functioning of the marine continental shelf of the Israeli Mediterranean coast and assess temporal changes, we developed a food web model representing two time periods: 1990-1994 and 2008-2012. The 1990-1994 and 2008-2012 food web models were composed of 39 and 41 functional groups, respectively. Functional groups ranged from primary producers to top predators, and included six and eight alien functional groups, respectively, encompassing several crustacean and fish species. Input data included local surveys and fishery statistics, published data on stomach content analyses, and the application of empirical equations to estimate consumption and production rates. Results of the competitive interactions between alien and native species and changes in trophic flows between food web components highlight the increasing impact of alien species over time. Fishing had noticeable impacts in both time periods and played an important role in the ecosystem. Despite different productivity rates and other environmental differences, the Israeli marine ecosystem shared common structural and functional traits with other Mediterranean marine ecosystems. This is the first attempt to study the ecosystem of the Levant region using mass-balance models and to integrate such a large amount of alien species into food web analyses.

  9. Well construction team approach creates a new future for one company's operations on the Dutch Continental Shelf

    International Nuclear Information System (INIS)

    Bakker, T.W.; Stringer, R.B.

    1995-01-01

    Rising costs and low energy prices were inhibiting the development of marginal fields on the Dutch Continental Shelf, resulting in a reduction in drilling activity and a loss of business opportunities. Independent benchmark surveys and critical analysis of total well costs showed the potential for major cost reductions that could turn many of the smaller offshore gas finds into economic development prospects. This triggered a change from traditional operating and contracting strategies to a partnering approach with the principal drilling and service contractors and the institution of a well-construction team (WCT). The WCT proved so successful, with an average well cost reduction of 21% in the first year, that a similar organization has been set up for all the land drilling and workover operations. This paper describes the strategies used and presents a comparison between the traditional performance and the results from the first year of operating as a WCT. The comparison includes the results of an independent benchmark study of 20 North Sea operating companies

  10. Development and production prospects for oil and gas from the UK continental shelf after the Gulf crisis: a financial simulation

    International Nuclear Information System (INIS)

    Kemp, A.G.; Rose, David; Dandie, Russell

    1991-01-01

    A large computerized financial model has been developed to simulate the future exploitation of oil and gas in the UK north sea. Primary inputs into the model include all the publicity available information on currently producing fields relating to their historic and expected production rates, investment, operating and abandonment costs. Information has also been gathered on all new discoveries which have not yet been developed and estimates made of the timing of their development, the commencement of production and costs. Three oil price scenarios base, low and high, have been used in the analysis which extends to the year 2015. The results are presented for two major regions, the central and northern waters and the Southern Gas Basin, including the Irish Sea. Very large numbers of discovered but undeveloped oil and gas fields exist in the UK continental shelf substantial numbers of which could be developed in the event of a very modest real growth in oil and gas prices. The considerable sensitivity of development to movements in oil prices is brought out by the analysis of the three scenarios. (UK)

  11. Megabenthic assemblages in the continental shelf edge and upper slope of the Menorca Channel, Western Mediterranean Sea

    Science.gov (United States)

    Grinyó, Jordi; Gori, Andrea; Greenacre, Michael; Requena, Susana; Canepa, Antonio; Lo Iacono, Claudio; Ambroso, Stefano; Purroy, Ariadna; Gili, Josep-Maria

    2018-03-01

    Highly diverse megabenthic assemblages dominated by passive and active suspension feeders have been recently reported in shelf edge environments of the Mediterranean Sea. Due to their frequent association with species of commercial interest, these assemblages have been heavily impacted by fishing. The vulnerability and low resilience of these assemblages, composed mainly by long-living and slow-growing species, have motivated the implementation of management measures such as the restriction of bottom trawling, and the establishment of large protected areas embracing these environments. The Menorca Channel is one of such areas recently included in the European Union Natura 2000 network. Quantitative analysis of video transects recorded at 95-360 m depth by manned submersible and remotely operated vehicles were used to characterize megabenthic assemblages and to assess their geographical and bathymetric distribution. Six different assemblages were identified, mainly segregated by substrate type and depth. Hard substrates hosted coral gardens and sponge grounds, whereas soft sediments were mainly characterized by large extensions of the crinoid Leptometra phalangium and the brachiopod Gryphus vitreus. The good preservation of most of the observed assemblages is probably related to a low bottom trawling pressure, which mainly concentrates deeper on the adjacent continental slope. Because of their biological and ecological value, management and conservation measures need to be established to preserve these benthic assemblages.

  12. Spatial and temporal changes in benthic communities of the Galician continental shelf after the Prestige oil spill

    Energy Technology Data Exchange (ETDEWEB)

    Serrano, Alberto [Instituto Espanol de Oceanografia, P.O. Box 240, 39080 Santander (Spain)]. E-mail aserrano@st.ieo.es; Sanchez, Francisco [Instituto Espanol de Oceanografia, P.O. Box 240, 39080 Santander (Spain); Preciado, Izaskun [Instituto Espanol de Oceanografia, P.O. Box 240, 39080 Santander (Spain); Parra, Santiago [Instituto Espanol de Oceanografia, P.O. Box 130, 15080 La Coruna (Spain); Frutos, Inmaculada [Instituto Espanol de Oceanografia, P.O. Box 130, 15080 La Coruna (Spain)

    2006-07-01

    Two years after the Prestige oil spill (POS) an assessment of the effects on benthic fauna was carried out using the data obtained in five multidisciplinary surveys. Otter trawl, beam trawl, suprabenthic sled and box corer were used to study the main benthic compartments, along eight transects perpendicular to the coastline. Beam trawl was also employed to quantify the amount of tar aggregates on the continental shelf. No significant correlations between tar aggregates and species richness, biomass and diversity of benthic communities were found. This result was corroborated when the role of depth, season, latitude and sediment characteristics was examined by canonical ordination, in which POS-related variables had low influence on spatial distribution patterns. Depth and sediment grain diameter profoundly influence epibenthic communities. Sediment organic content is a third key variable for the infaunal, suprabenthic and lower-sized epibenthic communities, but not for the larger epibenthic communities. Nevertheless, a decrease in the densities of several epibenthic indicators was detected the first year after spill, followed by a noteworthy recovery in 2004. Non-macroscopic toxicity and some oceanographic agents are suggested as possible causes of these shifts.

  13. Facts 2000. The Norwegian Petroleum Sector

    International Nuclear Information System (INIS)

    2000-02-01

    Petroleum production on the Norwegian continental shelf (NCS) in the North Sea, the Norwegian Sea and the Barents Sea totalled 2.7 bn scm oil equivalents (oe) up to 1998. Per December 1999, remaining reserves totalled 1.5 bn scm of oil, 1.2 bn scm oe gas and 0.2 bn scm oe of NGL/condensate. Twenty-eight exploration wells were completed or temporarily abandoned on the NCS in 1999. By 31 December 1999, 967 exploration wells had been completed or temporarily abandoned off Norway. Discoveries totalled 45-60 mill scm of oil and 45-70 bn scm of gas. Governmental approval was given in 1999 for the Tune, Borg and Sygna developments. Investment in exploration, field development and pipeline transport totalled about NOK 67 bn in 1998. Oil and gas production in 1999 was roughly on the par with 1998, while NGL/condensate sales rose by 19 per cent. The Balder, Gullfaks South, Jotun, Oseberg East, Visund and Aasgard projects came on stream during 1999. It is estimated that, with the present production rate, Norway's remaining discovered oil resources will last for 17 years, and gas, 93 years. The estimated value of Norwegian petroleum export in 1999 was NOK 168 bn, which is about 36% of the country's total earnings from foreign sales. Published by the Norwegian Ministry of Petroleum and Energy, the book is a major source of information on the Norwegian offshore petroleum activities

  14. Facts 2000. The Norwegian Petroleum Sector

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-02-01

    Petroleum production on the Norwegian continental shelf (NCS) in the North Sea, the Norwegian Sea and the Barents Sea totalled 2.7 bn scm oil equivalents (oe) up to 1998. Per December 1999, remaining reserves totalled 1.5 bn scm of oil, 1.2 bn scm oe gas and 0.2 bn scm oe of NGL/condensate. Twenty-eight exploration wells were completed or temporarily abandoned on the NCS in 1999. By 31 December 1999, 967 exploration wells had been completed or temporarily abandoned off Norway. Discoveries totalled 45-60 mill scm of oil and 45-70 bn scm of gas. Governmental approval was given in 1999 for the Tune, Borg and Sygna developments. Investment in exploration, field development and pipeline transport totalled about NOK 67 bn in 1998. Oil and gas production in 1999 was roughly on the par with 1998, while NGL/condensate sales rose by 19 per cent. The Balder, Gullfaks South, Jotun, Oseberg East, Visund and Aasgard projects came on stream during 1999. It is estimated that, with the present production rate, Norway's remaining discovered oil resources will last for 17 years, and gas, 93 years. The estimated value of Norwegian petroleum export in 1999 was NOK 168 bn, which is about 36% of the country's total earnings from foreign sales. Published by the Norwegian Ministry of Petroleum and Energy, the book is a major source of information on the Norwegian offshore petroleum activities.

  15. Facts 2000. The Norwegian Petroleum Sector

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-02-01

    Petroleum production on the Norwegian continental shelf (NCS) in the North Sea, the Norwegian Sea and the Barents Sea totalled 2.7 bn scm oil equivalents (oe) up to 1998. Per December 1999, remaining reserves totalled 1.5 bn scm of oil, 1.2 bn scm oe gas and 0.2 bn scm oe of NGL/condensate. Twenty-eight exploration wells were completed or temporarily abandoned on the NCS in 1999. By 31 December 1999, 967 exploration wells had been completed or temporarily abandoned off Norway. Discoveries totalled 45-60 mill scm of oil and 45-70 bn scm of gas. Governmental approval was given in 1999 for the Tune, Borg and Sygna developments. Investment in exploration, field development and pipeline transport totalled about NOK 67 bn in 1998. Oil and gas production in 1999 was roughly on the par with 1998, while NGL/condensate sales rose by 19 per cent. The Balder, Gullfaks South, Jotun, Oseberg East, Visund and Aasgard projects came on stream during 1999. It is estimated that, with the present production rate, Norway's remaining discovered oil resources will last for 17 years, and gas, 93 years. The estimated value of Norwegian petroleum export in 1999 was NOK 168 bn, which is about 36% of the country's total earnings from foreign sales. Published by the Norwegian Ministry of Petroleum and Energy, the book is a major source of information on the Norwegian offshore petroleum activities.

  16. Combined use of Nassarius reticulatus imposex and statolith age determination for tracking temporal evolution of TBT pollution in the NW Portuguese continental shelf.

    Science.gov (United States)

    Barroso, Carlos M; Rato, Milene; Veríssimo, Alfredo; Sousa, Ana; Santos, José António; Coelho, Sónia; Gaspar, Miguel B; Maia, Francisco; Galante-Oliveira, Susana

    2011-11-01

    Spatial and temporal trends of tributyltin (TBT) pollution on the northern continental shelf of Portugal (5-34 m depth) were assessed using Nassarius reticulatus as a bioindicator. Imposex levels were determined in 2006 and 2010, and integrated with age readings from statoliths for a better chronological analysis of the data. Females affected with imposex were detected in 84% of the sites surveyed in 2006, with levels higher than the Ecological Quality Objective (EcoQO) set by the OSPAR Commission for N. reticulatus (VDSI TBT water contamination in 2010 may in fact be lower than that extrapolated from the imposex levels. We conclude that the legislation was indeed very effective in reducing TBT pollution in the NW Portuguese continental shelf, not only in terms of the magnitude but also in terms of fast field repercussion.

  17. Late-Pleistocene evolution of the continental shelf of central Israel, a case study from Hadera

    Science.gov (United States)

    Shtienberg, Gilad; Dix, Justin; Waldmann, Nicolas; Makovsky, Yizhaq; Golan, Arik; Sivan, Dorit

    2016-05-01

    Sea-level fluctuations are a dominant mechanism that control coastal environmental changes through time. This is especially the case for the successive regressions and transgressions over the last interglacial cycle, which have shaped the deposition, preservation and erosion patterns of unconsolidated sediments currently submerged on continental shelves. The current study focuses on creating an integrated marine and terrestrial geophysical and litho-stratigraphic framework of the coastal zone of Hadera, north-central Israel. This research presents a case study, investigating the changing sedimentological units in the study area. Analysis suggest these represent various coastal environments and were deposited during times of lower than present sea level and during the later stages of the Holocene transgression. A multi-disciplinary approach was applied by compiling existing elevation raster grids, bathymetric charts, one hundred lithological borehole data-sets, and a 110 km-long sub-bottom geophysical survey. Based on seismic stratigraphic analysis, observed geometries, and reflective appearances, six bounding surfaces and seven seismic units were identified and characterized. These seismic units have been correlated with the available borehole data to produce a chronologically constrained lithostratigraphy for the area. This approach allowed us to propose a relationship between the lithological units and sea-level change and thus enable the reconstruction of Hadera coastal evolution over the last 100 ka. This reconstruction suggests that the stratigraphy is dominated by lowstand aeolian and fluvial terrestrial environments, subsequently transgressed during the Holocene. The results of this study provide a valuable framework for future national strategic shallow-water infrastructure construction and also for the possible locations of past human settlements in relation to coastal evolution through time.

  18. Arctic Ocean outflow and glacier-ocean interactions modify water over the Wandel Sea shelf (northeastern Greenland)

    DEFF Research Database (Denmark)

    Dmitrenko, Igor A.; Kirillov, Sergey A.; Rudels, Bert

    2017-01-01

    The first-ever conductivity-temperature-depth (CTD) observations on the Wandel Sea shelf in northeastern Greenland were collected in April-May 2015. They were complemented by CTDs taken along the continental slope during the Norwegian FRAM 2014-2015 drift. The CTD profiles are used to reveal...

  19. Oil-Spill Analysis: Gulf of Mexico Outer Continental Shelf (OCS) Lease Sales, Eastern Planning Area, 2003-2007 and Gulfwide OCS Program, 2003-2042

    Science.gov (United States)

    2002-09-01

    The Federal Government plans to offer U.S. Outer Continental Shelf (OCS) lands in the Eastern Planning Area of the Gulf of Mexico (GOM) for oil and gas leasing. This report summarizes results of that analysis, the objective of which was to estimate the risk of oil-spill contact to sensitive offshore and onshore environmental resources and socioeconomic features from oil spills accidentally occurring from the OCS activities.

  20. The U.S. continental shelf beyond 200 nautical miles. Legal questions arising from non-accession to the UN Convention on the Law of the Sea

    OpenAIRE

    Longtain, Shay

    2015-01-01

    The elaborate legal framework contained in Part VI of the 1982 United Nations Convention on the Law of the Sea (LOSC) resembles both codification and progressive development of the law of the sea as it relates to the continental shelf. As a non-party to the Convention, the United States is only bound to those provisions which now reflect customary rules of international law or have otherwise created rights or obligations for third states. This thesis identifies several distinct components o...

  1. Community structure and ecological function of deep-water sponge grounds in the Traenadypet MPA—Northern Norwegian continental shelf

    Science.gov (United States)

    Kutti, Tina; Bannister, Raymond John; Fosså, Jan Helge

    2013-10-01

    Sponges within the 300 km2 Trænadypet coral MPA (Marine Protected Area) were mapped using photographic techniques. Three types of sponge communities were identified. The eastern side of the central circular depression was dominated by fan-shaped Phakellia ventilabrum sponges and further characterized by Mycale lingua and Oceanapia spp. sponges. Phakellia ventilabrum abundance (0.34 ind m-2) was positively correlated with the number of drop stones found. The western side of the depression was dominated by Geodia barretti, G. macandrewii and G. atlantica with an estimated average abundance of 0.40 ind m-2 and a biomass of 2.4 kg WW m-2. A third type of sponge community was found on both sides of the depression (in between the small scattered cold-water coral reefs constituting the MPA), which was characterized by Mycale lingua (0.20 ind m-2) and Oceanapia spp. (0.10 ind m-2), and which supported a high average Geodiidea biomass (1.6 kg WW m-2). The two last communities were both of the boreal ostur type and seemed to form continuous belts along the 2 km transects surveyed only interrupted by a few 15-30 m long empty patches. Within the MPA the average overall biomass of Geodiidea sponges was 1.8 kg WW m-2 and the overall sponge abundance was 1 ind m-2. Water pumping rates and respiration of Geodia barretti were measured, equating to 3000 l kg-1 DW day-1 and 1.5 μmol O2 g-1 DW h-1, respectively. Up-scaling this to the MPA as a whole suggests that the population of G. barretti alone could filter approximately 250 million m3 of water and consume 60 t of carbon daily. This demonstrates the important ecological function of sponges as nutrient vectors and points out the MPA as an ecologically significant area that should be carefully managed and monitored.

  2. Variability of the geothermal gradient across two differently aged magma-rich continental rifted margins of the Atlantic Ocean: the Southwest African and the Norwegian margins

    Directory of Open Access Journals (Sweden)

    E. Gholamrezaie

    2018-02-01

    Full Text Available The aim of this study is to investigate the shallow thermal field differences for two differently aged passive continental margins by analyzing regional variations in geothermal gradient and exploring the controlling factors for these variations. Hence, we analyzed two previously published 3-D conductive and lithospheric-scale thermal models of the Southwest African and the Norwegian passive margins. These 3-D models differentiate various sedimentary, crustal, and mantle units and integrate different geophysical data such as seismic observations and the gravity field. We extracted the temperature–depth distributions in 1 km intervals down to 6 km below the upper thermal boundary condition. The geothermal gradient was then calculated for these intervals between the upper thermal boundary condition and the respective depth levels (1, 2, 3, 4, 5, and 6 km below the upper thermal boundary condition. According to our results, the geothermal gradient decreases with increasing depth and shows varying lateral trends and values for these two different margins. We compare the 3-D geological structural models and the geothermal gradient variations for both thermal models and show how radiogenic heat production, sediment insulating effect, and thermal lithosphere–asthenosphere boundary (LAB depth influence the shallow thermal field pattern. The results indicate an ongoing process of oceanic mantle cooling at the young Norwegian margin compared with the old SW African passive margin that seems to be thermally equilibrated in the present day.

  3. Variability of the geothermal gradient across two differently aged magma-rich continental rifted margins of the Atlantic Ocean: the Southwest African and the Norwegian margins

    Science.gov (United States)

    Gholamrezaie, Ershad; Scheck-Wenderoth, Magdalena; Sippel, Judith; Strecker, Manfred R.

    2018-02-01

    The aim of this study is to investigate the shallow thermal field differences for two differently aged passive continental margins by analyzing regional variations in geothermal gradient and exploring the controlling factors for these variations. Hence, we analyzed two previously published 3-D conductive and lithospheric-scale thermal models of the Southwest African and the Norwegian passive margins. These 3-D models differentiate various sedimentary, crustal, and mantle units and integrate different geophysical data such as seismic observations and the gravity field. We extracted the temperature-depth distributions in 1 km intervals down to 6 km below the upper thermal boundary condition. The geothermal gradient was then calculated for these intervals between the upper thermal boundary condition and the respective depth levels (1, 2, 3, 4, 5, and 6 km below the upper thermal boundary condition). According to our results, the geothermal gradient decreases with increasing depth and shows varying lateral trends and values for these two different margins. We compare the 3-D geological structural models and the geothermal gradient variations for both thermal models and show how radiogenic heat production, sediment insulating effect, and thermal lithosphere-asthenosphere boundary (LAB) depth influence the shallow thermal field pattern. The results indicate an ongoing process of oceanic mantle cooling at the young Norwegian margin compared with the old SW African passive margin that seems to be thermally equilibrated in the present day.

  4. Late-Pleistocene evolution of the East Mediterranean shallow continental shelf of north-central Israel

    Science.gov (United States)

    Shtienberg, Gilad; Dix, Justin; Waldmann, Nicolas; Makovsky, Yizhaq; Bookman, Revital; Roskin, Joel; Bialik, Or; Golan, Arik; Sivan, Dorit

    2016-04-01

    Sea-level fluctuations are a dominant and dynamic mechanism that control coastal environmental through time. This is especially the case for the successive regressions and transgressions over the last interglacial cycle, which have shaped the deposition, preservation and erosion patterns of unconsolidated sediments currently submerged on continental shelves. The current study focuses on an integrated high-resolution marine and terrestrial litho-stratigraphic and geophysical framework of the north-central Mediterranean coastal zone of Israel. The interpretation enabled the reconstruction of the coastal evolution over the last ˜130 ka. A multi-disciplinary approach was applied by compiling existing elevation raster grids, bathymetric charts, detailed lithological borehole data-sets, a dense 110 km long sub-bottom geophysical survey and seven continuous boreholes sediment records. Based on seismic stratigraphic analysis, observed geometries, and reflective appearances, six bounding surfaces and seven seismic units were identified and characterized. Meanwhile, the chronostratigraphy of the terrestrial side was constructed through integration of magnetic susceptibility, sedimentological and geochemical analysis with 17 new OSL ages. The seismic units were correlated with the available terrestrial borehole data and then associated to the retrieved terrestrial chronostratigraphy to produce a 4D reconstruction model of the paleo-landscape. The entire unconsolidated sequence overlies a calcareous aeolianite (locally named Kurkar unit) dated from ˜131 - ˜104 ka, which represents the top of the last interglacial cycle dune sediments. The lower unconsolidated unit consists of a red silty loam dated to ˜71 ka. This Red-Paleosol unit is overlaid by a dark brown clayey silty loam This Brown-Paleosol unit dates to ˜58 - ˜36 ka and is overlaid by a dark silty clay wetland deposit dated to ˜21 - ˜10 ka. The wetland unit is topped by a quartz sand dated to ˜6.6 - 0.1 ka

  5. Heavy metals transfer through the Inner Continental Shelf to the open ocean data as part of the International Decade of Ocean Exploration (IDOE) submitted October, 1972 (NODC Accession 7300575)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Heavy metals transfer through the Inner Continental Shelf to the open ocean data were collected by the Skidway Institute of Oceanography (SKIO). Data were collected...

  6. Bacteria, carbon dioxide, and methane data from bottle casts in the Cariaco Basin on the continental shelf of Venezuela from the HERMANO GINES from 2001-04-30 to 2001-05-01 (NODC Accession 0000737)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Bacteria, carbon dioxide, and methane data were collected from bottle casts from the HERMANO GINES in the Cariaco Basin on the continental shelf of Venezuela. Data...

  7. Bacteria, carbon dioxide, and methane data from bottle casts in the Cariaco Basin on the continental shelf of Venezuela from the HERMANO GINES from 2000-05-03 to 2000-10-31 (NODC Accession 0000732)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Bacteria, carbon dioxide, and methane data were collected employing bottle casts from the Hermano Gines in the Cariaco Basin on the continental shelf of Venezuela....

  8. Lithology, monsoon and sea-surface current control on provenance, dispersal and deposition of sediments over the Andaman continental shelf

    Digital Repository Service at National Institute of Oceanography (India)

    Damodararao, K.; Singh, S.K.; Rai, V.K.; Ramaswamy, V.; Rao, P.S.

    , constrain their transport pathways and assess the factors influencing the erosion in the catchment and their dispersal and deposition over the Andaman Shelf region. Major elemental compositions of the shelf sediments suggest mafic lithology...

  9. Surficial sediment character of the New York-New Jersey offshore continental shelf region: a GIS compilation

    Science.gov (United States)

    Williams, S. Jeffress; Arsenault, Matthew A.; Poppe, Lawrence J.; Reid, Jane A.; Reid, Jamey M.; Jenkins, Chris J.

    2007-01-01

    Broad continental shelf regions such as the New York Bight are the product of a complex geologic history and dynamic oceanographic processes, dominated by the Holocene marine transgression (>100 m sea-level rise) following the end of the last Pleistocene ice advance ~ 20,000 years ago. The area of the U.S. Exclusive Economic Zone (U.S. EEZ) territory, extending 200 nautical miles seaward from the coast, is larger than the continental U.S. and contains submerged landforms that provide a variety of natural functions and societal benefits, such as: critical habitats for fisheries, ship navigation and homeland security, and engineering activities (i.e. oil and gas platforms, pipeline and cable routes, potential wind-energy-generation sites). Some parts of the continental margins, particularly inner-continental shelf regions, also contain unconsolidated hard-mineral deposits such as sand and gravel that are regarded as potential aggregate resources to meet or augment needs not met by onshore deposits (Williams, 1992). The present distribution of surficial sediment off the northeastern United States is shaped from the deposits left by the last glaciation and reflects the cumulative effects of sediment erosion, transport, sorting, and deposition by storm and tidal processes during the Holocene rise in sea level. As a result, the sediments on the sea floor represent both an historical record of former conditions and a guide to possible future sedimentary environments. The U.S. Geological Survey (USGS) through the Coastal and Marine Geology Program, in cooperation with the University of Colorado and other partners, has compiled extant sediment character and textural data as well as other geologic information on the sea floor from all regions around the U.S. into the usSEABED data system (Reid and others, 2005; Buczkowski and others, 2006; Reid and others, 2006). The usSEABED system, which contains information on sediment grain size and lithology for more than 340

  10. Speciation and spatial distribution of solid-phase iron in surface sediments of the East China Sea continental shelf

    International Nuclear Information System (INIS)

    Zhu, Mao-Xu; Hao, Xiao-Chen; Shi, Xiao-Ning; Yang, Gui-Peng; Li, Tie

    2012-01-01

    Speciation and reactivity characterization of solid-phase Fe in marine sediments are of significance to understanding its heterogeneous mineralogy and crystallinity, the diagenetic cycling of Fe and its regulating roles on many other elements in sediments. In this study, a combination of sequential and single-step extractions was used for the determination of seven Fe pools in surface sediments of the East China Sea (ECS) continental shelf: (1) carbonate associated Fe (Fe(II) carb ) plus acid volatile sulfide-Fe (Fe(II) AVS ), (2) easily reducible amorphous/poorly crystalline Fe oxides (Fe ox1 ), (3) reducible crystalline Fe oxides (Fe ox2 ), (4) magnetite (Fe mag ), (5) poorly reactive sheet silicate Fe (Fe PRS ), (6) pyrite-Fe (Fe py ), and (7) unreactive silicate Fe (Fe U ). Total Fe (Fe T ) in the sediments is largely determined by terrestrial aluminosilicate particles as indicated by a great similarity of the Fe T with that of the Yangtze River and global riverine particulates. The size of Fe PRS is found to be the largest pool, followed by Fe U , Fe ox2 , Fe mag , Fe(II) AVS+carb , Fe ox1 and Fe py . The large Fe PRS may result from neoformation of Fe-rich clay minerals via reverse weathering and subsequent ageing. The small sizes of Fe(II) AVS+carb and Fe py pools is believed to be the result of low SO 4 reduction due to generally low labile organic matter together with the oxic/suboxic, dynamic environments of the surface sediments. The occurrence of Fe ox1 , Fe ox2 and Fe PRS in the sediments is closely associated with the clay fraction as indicated by a high spatial correlation between the former and the latter. Highly reactive Fe(Fe HR ) in the sediments is comparable to that in global marine sediments, but apparently lower than in the Yangtze River and global riverine particulates due probably to sequestration in the Yangtze Estuary. The ratios of Fe HR /Fe T , Fe PR /Fe T and Fe U /Fe T in the ECS surface sediments consistently show more similarity to

  11. Algorithm Development and Validation of CDOM Properties for Estuarine and Continental Shelf Waters Along the Northeastern U.S. Coast

    Science.gov (United States)

    Mannino, Antonio; Novak, Michael G.; Hooker, Stanford B.; Hyde, Kimberly; Aurin, Dick

    2014-01-01

    An extensive set of field measurements have been collected throughout the continental margin of the northeastern U.S. from 2004 to 2011 to develop and validate ocean color satellite algorithms for the retrieval of the absorption coefficient of chromophoric dissolved organic matter (aCDOM) and CDOM spectral slopes for the 275:295 nm and 300:600 nm spectral range (S275:295 and S300:600). Remote sensing reflectance (Rrs) measurements computed from in-water radiometry profiles along with aCDOM() data are applied to develop several types of algorithms for the SeaWiFS and MODIS-Aqua ocean color satellite sensors, which involve least squares linear regression of aCDOM() with (1) Rrs band ratios, (2) quasi-analytical algorithm-based (QAA based) products of total absorption coefficients, (3) multiple Rrs bands within a multiple linear regression (MLR) analysis, and (4) diffuse attenuation coefficient (Kd). The relative error (mean absolute percent difference; MAPD) for the MLR retrievals of aCDOM(275), aCDOM(355), aCDOM(380), aCDOM(412) and aCDOM(443) for our study region range from 20.4-23.9 for MODIS-Aqua and 27.3-30 for SeaWiFS. Because of the narrower range of CDOM spectral slope values, the MAPD for the MLR S275:295 and QAA-based S300:600 algorithms are much lower ranging from 9.9 and 8.3 for SeaWiFS, respectively, and 8.7 and 6.3 for MODIS, respectively. Seasonal and spatial MODIS-Aqua and SeaWiFS distributions of aCDOM, S275:295 and S300:600 processed with these algorithms are consistent with field measurements and the processes that impact CDOM levels along the continental shelf of the northeastern U.S. Several satellite data processing factors correlate with higher uncertainty in satellite retrievals of aCDOM, S275:295 and S300:600 within the coastal ocean, including solar zenith angle, sensor viewing angle, and atmospheric products applied for atmospheric corrections. Algorithms that include ultraviolet Rrs bands provide a better fit to field measurements than

  12. Preliminary Facies Reconstruction of a Late Pleistocene Cypress Forest Discovered on the Northern Gulf of Mexico Continental Shelf

    Science.gov (United States)

    Gonzalez Rodriguez, S. M.; Bentley, S. J.; DeLong, K. L.; Xu, K.; Caporaso, A.; Obelcz, J. B.; Harley, G. L.; Reese, C. A.; Truong, J. T.

    2016-12-01

    We are investigating the origin and preservation of an ancient bald cypress forest (Taxodium distichum) discovered on the continental shelf seafloor, offshore of Gulf Shores, Alabama, USA, in 20 m water depth. The forest was likely buried in the late Pleistocene, possibly exhumed by Hurricane Ivan in 2004, and is now exposed as stumps in life position with little evidence of decay before recent marine exposure. Radiocarbon analyses show that the forest age is near (and in some cases beyond) the limits of 14C dating, at least 41-45 ky BP. In August 2015 and July 2016, submersible vibracores (up to 5 m in length) were collected. Ongoing core analyses include: organic content (loss on ignition), granulometry, and core logging using a Geotek Multi Sensor Core Logger to generate imagery, bulk density, and x-ray fluorescence data. To bolster 14C analyses, cores collected in 2016 are presently being dated using optically stimulated luminescence. Local stratigraphy consists of a surface facies of Holocene transgressive sands, underlain by possible estuarine sediments of interbedded sand and mud (potentially Holocene or Pleistocene), overlying a swamp or delta plain facies (likely Pleistocene) containing woody debris and mud. Deeper woody facies are thought to include the soil horizons of the ancient cypress forest. Cores collected in 2016 revealed a Pleistocene paleosol beneath Holocene sands in a nearby trough. Elevation differences between swamp and paleosol horizons will be evaluated from bathymetric and subbottom data, to help characterize the preserved ancient landscape. Initial interpretation based on close proximity of Pleistocene swamp and oxidized paleosol sediments, and regional geomorphic gradients suggest that this relatively diverse assemblage of facies developed up to tens of km from the glacial-age coastline, and relatively rapid burial prevented erosion by coastal processes during the Holocene transgression thus preserving the tree stumps and wood debris.

  13. Productivity and linkages of the food web of the southern region of the western Antarctic Peninsula continental shelf

    Science.gov (United States)

    Ballerini, Tosca; Hofmann, Eileen E.; Ainley, David G.; Daly, Kendra L.; Marrari, Marina; Ribic, Christine A.; Smith, Walker O.; Steele, John H.

    2014-01-01

    The productivity and linkages in the food web of the southern region of the west Antarctic Peninsula continental shelf were investigated using a multi-trophic level mass balance model. Data collected during the Southern Ocean Global Ocean Ecosystem Dynamics field program were combined with data from the literature on the abundance and diet composition of zooplankton, fish, seabirds and marine mammals to calculate energy flows in the food web and to infer the overall food web structure at the annual level. Sensitivity analyses investigated the effects of variability in growth and biomass of Antarctic krill (Euphausia superba) and in the biomass of Antarctic krill predators on the structure and energy fluxes in the food web. Scenario simulations provided insights into the potential responses of the food web to a reduced contribution of large phytoplankton (diatom) production to total primary production, and to reduced consumption of primary production by Antarctic krill and mesozooplankton coincident with increased consumption by microzooplankton and salps. Model-derived estimates of primary production were 187–207 g C m−2 y−1, which are consistent with observed values (47–351 g C m−2 y−1). Simulations showed that Antarctic krill provide the majority of energy needed to sustain seabird and marine mammal production, thereby exerting a bottom-up control on higher trophic level predators. Energy transfer to top predators via mesozooplanton was a less efficient pathway, and salps were a production loss pathway because little of the primary production they consumed was passed to higher trophic levels. Increased predominance of small phytoplankton (nanoflagellates and cryptophytes) reduced the production of Antarctic krill and of its predators, including seabirds and seals.

  14. Productivity and linkages of the food web of the southern region of the western Antarctic Peninsula continental shelf

    Science.gov (United States)

    Ballerini, Tosca; Hofmann, Eileen E.; Ainley, David G.; Daly, Kendra; Marrari, Marina; Ribic, Christine A.; Smith, Walker O.; Steele, John H.

    2014-03-01

    The productivity and linkages in the food web of the southern region of the west Antarctic Peninsula continental shelf were investigated using a multi-trophic level mass balance model. Data collected during the Southern Ocean Global Ocean Ecosystem Dynamics field program were combined with data from the literature on the abundance and diet composition of zooplankton, fish, seabirds and marine mammals to calculate energy flows in the food web and to infer the overall food web structure at the annual level. Sensitivity analyses investigated the effects of variability in growth and biomass of Antarctic krill (Euphausia superba) and in the biomass of Antarctic krill predators on the structure and energy fluxes in the food web. Scenario simulations provided insights into the potential responses of the food web to a reduced contribution of large phytoplankton (diatom) production to total primary production, and to reduced consumption of primary production by Antarctic krill and mesozooplankton coincident with increased consumption by microzooplankton and salps. Model-derived estimates of primary production were 187-207 g C m-2 y-1, which are consistent with observed values (47-351 g C m-2 y-1). Simulations showed that Antarctic krill provide the majority of energy needed to sustain seabird and marine mammal production, thereby exerting a bottom-up control on higher trophic level predators. Energy transfer to top predators via mesozooplanton was a less efficient pathway, and salps were a production loss pathway because little of the primary production they consumed was passed to higher trophic levels. Increased predominance of small phytoplankton (nanoflagellates and cryptophytes) reduced the production of Antarctic krill and of its predators, including seabirds and seals.

  15. 1300 km long late Pleistocene-Holocene shelf edge barrier reef system along the western continental shelf of India: Occurrence and significance

    Digital Repository Service at National Institute of Oceanography (India)

    Vora, K.H.; Wagle, B.G.; Veerayya, M.; Almeida, F.; Karisiddaiah, S.M.

    . It is surmised that coral/algal reef growth commenced with the advent of the Holocene trangression and favorable antecedent topography, and continued until early Holocene. Subsequently, rapid sea level rise drowned the reefs. The shelf edge reefs, therefore...

  16. The FOODBANCS project: Introduction and sinking fluxes of organic carbon, chlorophyll- a and phytodetritus on the western Antarctic Peninsula continental shelf

    Science.gov (United States)

    Smith, Craig R.; Mincks, Sarah; DeMaster, David J.

    2008-11-01

    The impact of the highly seasonal Antarctic primary production cycle on shelf benthic ecosystems remains poorly evaluated. Here we describe a times-series research project on the West Antarctic Peninsula (WAP) shelf designed to evaluate the seafloor deposition, and subsequent ecological and biogeochemical impacts, of the summer phytoplankton bloom along a transect crossing the Antarctic shelf near Anvers Island. During this project, entitled Food for Benthos on the Antarctic Continental Shelf (FOODBANCS), we deployed replicate sediment traps 150-170 m above the seafloor (total water-column depth of 590 m) on the central shelf from December 1999 to March 2001, recovering trap samples every 3-4 months. In addition, we used a seafloor time-lapse camera system, as well as video surveys conducted at 3-4 months intervals, to monitor the presence and accumulation of phytodetritus at the sediment-water interface. The fluxes of particulate organic carbon and chlorophyll- a into sediment traps (binned over 3-4 month intervals) showed patterns consistent with seasonal variability, with average summer fluxes during the first year exceeding winter fluxes by a factor of ˜2-3. However, inter-annual variability in summer fluxes was even greater than seasonal variability, with 4-10-fold differences in the flux of organic carbon and chlorophyll- a between the summer seasons of 1999-2000 and 2000-2001. Phytodetrital accumulation at the shelf floor also exhibited intense inter-annual variability, with no visible phytodetritus from essentially December 1999 to November 2000, followed by pulsed accumulation of 1-2 cm of phytodetritus over a ˜30,000 km 2 shelf area by March 2001. Comparisons with other studies suggest that the levels of inter-annual variability we observed are typical of the Antarctic shelf over decadal time scales. We conclude that fluxes of particulate organic carbon, chlorophyll- a and phytodetritus to WAP-shelf sediments vary intensely on seasonal to inter

  17. Movement and effects of spilled oil over the outer continental shelf; inadequacy of existent data for the Baltimore Canyon Trough area

    Science.gov (United States)

    Knebel, Harley J.

    1974-01-01

    A deductive approach to the problem of determining the movement and effects of spilled oil over the Outer Continental Shelf requires that the potential paths of oil be determined first, in order that critical subareas may be defined for later studies. The paths of spilled oil, in turn, depend primarily on the temporal and spatial variability of four factors: the thermohaline structure of the waters, the circulation of the water, the winds, and the distribution of suspended matter. A review of the existent data concerning these factors for the Baltimore Canyon Trough area (a relatively well studied segment of the Continental Shelf) reveals that the movement and dispersal of potential oil spills cannot be reliably predicted. Variations in the thermohaline structure of waters and in the distribution of suspended matter are adequately known; the uncertainty is due to insufficient wind and storm statistics and to the lack of quantitative understanding of the relationship between the nontidal drift and its basic driving mechanisms. Similar inadequacies should be anticipated for other potentially leasable areas of the shelf because an understanding of the movement of spilled oil has not been the underlying aim of most previous studies.

  18. Radionuclides in produced water from Norwegian oil and gas installations - concentrations and bioavailability

    International Nuclear Information System (INIS)

    Eriksen, D.Oe.; Sidhu, R.; Stralberg, E.; Iden, K.I.; Hylland, K.; Ruus, A.; Roeyset, O.; Berntssen, M.H.G.; Rye, H.

    2006-01-01

    Substantial amounts of produced water, containing elevated levels of radionuclides (mainly 226 Ra and 228 Ra) are discharged to the sea as a result of oil and gas production on the Norwegian Continental Shelf. So far no study has assessed the potential radiological effects on marine biota in connection with radionuclide discharges to the North Sea. The main objective of the project is to establish radiological safe discharge limits for radium, lead and polonium associated with other components in produced water from oil and gas installations on the Norwegian continental shelf. This study reports results indicating that the presence of added chemicals such as scale inhibitors in produced water has a marked influence on the formation of radium and barium sulphates when produced water is mixed with sea water. Thus, the mobility and bioavailability of radium (and barium) will be larger than anticipated. Also, the bioavailability of food-borne radium is shown to increase due to presence of such chemicals. (author)

  19. Radionuclides in produced water from Norwegian oil and gas installations — Concentrations and bioavailability

    Science.gov (United States)

    Eriksen, D. Ø.; Sidhu, R.; Strålberg, E.; Iden, K. I.; Hylland, K.; Ruus, A.; Røyset, O.; Berntssen, M. H. G.; Rye, H.

    2006-01-01

    Substantial amounts of produced water, containing elevated levels of radionuclides (mainly 226Ra and 228Ra) are discharged to the sea as a result of oil and gas production on the Norwegian Continental Shelf. So far no study has assessed the potential radiological effects on marine biota in connection with radionuclide discharges to the North Sea. The main objective of the project is to establish radiological safe discharge limits for radium, lead and polonium associated with other components in produced water from oil and gas installations on the Norwegian continental shelf. This study reports results indicating that the presence of added chemicals such as scale inhibitors in produced water has a marked influence on the formation of radium and barium sulphates when produced water is mixed with sea water. Thus, the mobility and bioavailability of radium (and barium) will be larger than anticipated. Also, the bioavailability of food-borne radium is shown to increase due to presence of such chemicals.

  20. Comment on “Large-scale bedforms along a tideless outer shelf setting in the western Mediterranean” by Lo Iacono et al. (2010) in Continental Shelf Research vol 30, pp. 1802-1813

    Science.gov (United States)

    Flemming, B. W.

    2013-01-01

    Lo Iacono et al. (2010) report the discovery of large (but degraded) subaqueous dunes on the outer continental shelf NE of Valencia, western Mediterranean Sea. They argue that the dunes, after having been generated sometime in the past, are being episodically rejuvenated by high-energy flow events to the present day. Because the height vs. wavelength relation of the dunes falls below the global mean trend predicted by the equation of Flemming (1988), they claim to have discovered a new, low-amplitude type of flow-transverse bedform which typically occurs on microtidal current-swept outer continental shelves. A close inspection of the evidence shows that the reasoning of Lo Iacono et al. (2010) is flawed and that their interpretations and conclusions are premature and unjustified.

  1. Late Cretaceous sub-volcanic structure in the continental shelf off Portugal and its implications on tectonics and seismicity

    Science.gov (United States)

    Neres, Marta; Terrinha, Pedro; Custódio, Susana; Noiva, João; Brito, Pedro; Santos, Joana; Carrilho, Fernando

    2017-04-01

    Long-lasting and widespread alkaline magmatism is recognized in the west Portuguese margin. Offshore, several volcanic seamounts punctuate the Tore-Madeira Rise and the Estremadura Spur, with known ages between 80 and 100 Ma. Onshore, the major events are the Monchique (69-73 Ma), Sines (75-77 Ma) and Sintra (75-82 Ma) plutons - whose location (aligned along 200 km) and age discrepancy inspired some geodynamic models for Iberia during the Cretaceous - and the Lisbon Volcanic Complex (90-100 Ma). Structural links between them have been proposed but no direct evidence was yet found for it. In this work we present new magnetic data from recent marine magnetic surveys (ROCHEL and MINEPLAT project) conducted off the west Portuguese coast on the continental shelf and slope. A total area of about 3000 km2 between Sintra and Sines was surveyed with line spacing of 1 mile. Very high-resolution multi-channel seismic profiles were simultaneously acquired with the magnetics covering an area of 400 km2 off Sines. Two main primary outcomes arise from these data. On one hand, higher-resolution mapping in regions where magnetic anomalies were already known allows a better understanding of the buried sub-volcanic system. On the other hand, previously unknown NNW-SSE aligned magnetic anomalies were identified along the coast off Sines, possibly corresponding to buried Late Cretaceous alkaline magmatic intrusives. The presence of magmatic bodies was up to now unknown in this region, and these findings reignite the discussion about a structural link connecting the three main on land intrusive complexes, Sintra, Sines and Monchique. In addition to the structural control of the magmatic complexes, seismicity is also an issue as a cluster of seismicity coincident with the Monchique complex has long been known. Smaller clusters coincide with the magnetic anomalies mapped during the ROCHEL and MINEPLAT surveys, as well. We interpret these results in the light of the tectono-magmatism of

  2. Diagenesis and reservoir quality evolution of palaeocene deep-water, marine sandstones, the Shetland-Faroes Basin, British continental shelf

    Energy Technology Data Exchange (ETDEWEB)

    Mansurbeg, H. [Department of Earth Sciences, Uppsala University, Villavaegen 16, SE 752 36 Uppsala (Sweden); Morad, S. [Department of Earth Sciences, Uppsala University, Villavaegen 16, SE 752 36 Uppsala (Sweden); Department of Petroleum Geosciences, The Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Salem, A. [Faculty of Education at Kafr El-Sheikh, Tanta University, Kafr El-Sheikh (Egypt); Marfil, R.; Caja, M.A. [Departmento Petrologia y Geoquimica, Facultad de Geologia, UCM, 28040 Madrid (Spain); El-ghali, M.A.K. (Geology Department, Al-Fateh University, P.O. Box 13696, Libya); Nystuen, J.P. [Department of Geosciences, University of Oslo, P.O. Box 1047 Blindern, NO-0316 Oslo (Norway); Amorosi, A. [Department of Earth Sciences, University of Bologna, Via Zamboni 67, 40127 Bologna (Italy); Garcia, D. [Centre SPIN, Department GENERIC, Ecole Nationale Superieure des Mines de Saint Etienne 158, Cours Fauriel 42023, Saint-Etienne (France); La Iglesia, A. [Instituto de Geologia Economica (CSIC-UCM), Facultad de Geologia, UCM, 28040 Madrid (Spain)

    2008-06-15

    The Palaeocene, deep-water marine sandstones recovered from six wells in the Shetland-Faroes Basin represent lowstand, transgressive and highstand systems tract turbiditic sediments. Mineralogic, petrographic, and geochemical analyses of these siliciclastics are used to decipher and discuss the diagenetic alterations and subsequent reservoir quality evolution. The Middle-Upper Palaeocene sandstones (subarkoses to arkoses) from the Shetland-Faroes Basin, British continental shelf are submarine turbiditic deposits that are cemented predominantly by carbonates, quartz and clay minerals. Carbonate cements (intergranular and grain replacive calcite, siderite, ferroan dolomite and ankerite) are of eogenetic and mesogenetic origins. The eogenetic alterations have been mediated by marine, meteoric and mixed marine/meteoric porewaters and resulted mainly in the precipitation of calcite ({delta}{sup 18}O{sub V-PDB}=-10.9 permille and -3.8 permille), trace amounts of non-ferroan dolomite, siderite ({delta}{sup 18}O{sub V-PDB}=-14.4 permille to -0.6 permille), as well as smectite and kaolinite in the lowstand systems tract (LST) and highstand systems tract (HST) turbiditic sandstone below the sequence boundary. Minor eogenetic siderite has precipitated between expanded and kaolinitized micas, primarily biotite. The mesogenetic alterations are interpreted to have been mediated by evolved marine porewaters and resulted in the precipitation of calcite ({delta}{sup 18}O{sub V-PDB}=-12.9 permille to -7.8 permille) and Fe-dolomite/ankerite ({delta}{sup 18}O{sub V-PDB}=-12.1 permille to -6.3 permille) at temperatures of 50-140 and 60-140 C, respectively. Quartz overgrowths and outgrowth, which post- and pre-date the mesogenetic carbonate cements is more common in the LST and TST of distal turbiditic sandstone. Discrete quartz cement, which is closely associated with illite and chlorite, is the final diagenetic phase. The clay minerals include intergranular and grain replacive

  3. An oilspill risk analysis for the Gulf of Mexico outer continental shelf lease area; regional environmental impact statement

    Science.gov (United States)

    LaBelle, R.P.

    1982-01-01

    An oilspill risk analysis was conducted for the Gulf of Mexico Outer Continental Shelf (OCS)lease area region. Results of the analysis can be used to determine relative risks associated with oil production in different regions to be offered in OCS Lease Sales 72, 74, and 79. The analysis considered the probability of spill occurrences based on historical trends; likely movement of oil slicks based on a climatological model; and locations of major environmental resources which could be vulnerable to spilled oil. The times between spill occurrence and contact with resources were estimated to aid in estimating slick characteristics. Critical assumptions made for this particular analysis were (1) that oil exists in the lease area, and (2) that oil will be, found and produced from tracts sold in sales 72, 74, and 79. On the basis of a most likely resource estimate of 241 million barrels of oil to be produced over an 18-year production life from sales to be held in 1983 (sales 72, 74, 79), it was calculated that approximately one oilspill of 1,000 barrels or larger will occur. The estimated probability that one or more oilspills of 1,000 barrels or larger will occur and contact land after being at sea less than 30 days is 41-percent. For a high resource estimate case of sales to be held in 1983, 717 million barrels are estimated to be produced over an 18-year production life with an 83-percent chance of one or more spills of 1,000 barrels or larger occurring and contacting land within 30 days. These results depend upon the routes and methods chosen to transport oil from OCS platforms to shore. Given a total development scenario in which 5.6 billion barrels of oil are estimated to be present and produced, it was calculated that 18 oilspills of 1,000 barrels or larger will occur over the 40-year production life of the proposed lease area. The estimated probability that one or more oilspills of 1,000 barrels or larger will occur and contact land after being at sea less than

  4. Modeling the seasonal cycle of the oxygen minimum zone over the continental shelf off Concepción, Chile (36.5° S)

    Science.gov (United States)

    Charpentier, J.; Mediavilla, D.; Pizarro, O.

    2012-06-01

    We analyze the seasonal dynamics of oxygen concentrations in the southernmost part of the Eastern South Pacific oxygen minimum zone (ESP's OMZ), offshore of Concepción, Chile (~37° S). We use data from a time series over the continental shelf off Concepción, as well as other hydrographic data and measurements from moored instruments and ocean gliders to evaluate temporal and spatial variability in this region. We identify two extreme modes (winter and summer) that characterize the seasonal variability. A simple model that account for the main physical and biological processes that influences the oxygen concentration was developed. According to our results, the seasonal variability of the dissolved oxygen in the study region is mainly driven by lateral (advective and diffusive) transport that connect the waters over the shelf with poorly oxygenated water from the slope, which is in turn, advected southward by the Peru-Chile Undercurrent.

  5. Trophic Groups Of Demersal Fish Of Santos Bay And Adjacent Continental Shelf, São Paulo State, Brazil: Temporal And Spatial Comparisons

    Directory of Open Access Journals (Sweden)

    Elizabeti Y. Muto

    2014-07-01

    Full Text Available The temporal and spatial variations of feeding habits and trophic groups of demersal fish species of Santos Bay and the adjacent continental shelf were investigated. The samples were taken in September 2005 and March 2006 by bottom otter trawling. The stomach content analysis of 2,328 specimens of 49 species showed most fish fed on a large range of food items but relied heavily on shrimp, crabs/swimming-crabs, amphipods, mysids, polychaetes, ophiuroids, squids, and teleosteans. The species were classified into ten trophic groups. Shrimp were an important food source in the Santos bay and inner shelf, while ophiuroids were important prey for predators of the middle shelf. Many species relied on crabs/swimming-crabs during the summer, especially on the middle shelf. The spatial and temporal variability in food resource utilization by fish were related to the pattern of distribution and abundance of their prey. The predation on shrimp and crabs/swimming-crabs seems to be related to the water mass dynamics of the region. Intraspecific comparisons demonstrated that most of the species display spatial and/or temporal variation in their diet. The demersal ichtyofauna can also be divided into the more general categories of piscivores, nektonic invertebrate feeders, benthic invertebrate feeders and planktonic invertebrate feeders.

  6. 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

  7. Assessment of resource selection models to predict occurrence of five juvenile flatfish species (Pleuronectidae) over the continental shelf in the western Gulf of Alaska

    Science.gov (United States)

    Wilson, Matthew T.; Mier, Kathryn L.; Cooper, Dan W.

    2016-05-01

    According to the nursery size hypothesis, flatfish recruitment is constrained by nursery area. Thus, if resource selection models can be shown to accurately predict the location and geographic extent of flatfish nursery areas, they will become important tools in the management and study of flatfish population dynamics. We demonstrate that some resource selection models derived previously to predict the presence and absence of juvenile flatfishes near shore were applicable to the broader continental shelf. For other age-species groups, derivation of new models for the continental shelf was necessary. Our study was conducted in the western Gulf of Alaska (GoA) during October 2011 on four groups of age-0 juvenile flatfishes: Pacific halibut (Hippoglossus stenolepis), arrowtooth flounder (Atheresthes stomias), northern rock sole (Lepidopsetta polyxystra), and flathead sole (Hippoglossoides elassodon); and three groups of age-1 juvenile flatfishes: northern rock sole, flathead sole, and yellowfin sole (Limanda aspera). Sampling occurred at 33 sites across the continental shelf. Fish were collected using a 3-m beam trawl, and a midwater trawl. Environmental data were collected on sediment composition and water temperature and depth. Many of the age-species groups co-occurred in the Shumagin and Barnabus sea valleys; however, age-0 arrowtooth flounder occurred at more locations than other juveniles, perhaps due to a relatively broad tolerance of environmental conditions and to the utilization of midwater habitat. Thus, the large nursery area of arrowtooth flounder may be one reason why they are currently the most abundant GoA flatfish. In fact, among all species, mean recruitment at age 3 increased with the percent occurrence of age-0 juveniles at the 33 sites, a proxy for relative nursery area, in accordance with the nursery size hypothesis, suggesting that mean recruitment among GoA flatfishes is structured by nursery size.

  8. The behavior of particle-reactive tracers in a high turbidity environment: 234Th and 210Pb on the Amazon continental shelf

    International Nuclear Information System (INIS)

    Smoak, J.M.; DeMaster, D.J.; Pope, R.H.; Kuehl, S.A.; McKee, B.A.

    1996-01-01

    Excess 234 Th and 210 Pb seabed inventories were measured in cores collected from the Amazon continental shelf to examine particle scavenging and seabed dynamics. Typical excess 210 Pb inventories range from 100 to 300 dpm cm -2 , and the total excess 210 Pb inventory for the Amazon shelf was determined to be 2.7 x 10 17 dpm. The 210 Pb measurements indicate that particle-reactive species are scavenged not only form the Amazon River but also from the lateral advection of offshore water. In order to sustain the 210 Pb inventories, the volume of water supplied by the lateral advection from offshore must be approximately five to ten times the water discharge of the Amazon River. This lateral advection supplies about 67% of the total excess 210 Pb to the Amazon continental shelf with relatively small contributions from riverine input (31%), atmospheric fallout (2.3%), and in-situ production (0.1%). The 234 Th inventories were measured on four cruises, which occurred during periods of differing river discharge, wind stress, and flow rates of the North Brazil Current. The 234 Th excess seabed inventories show large spatial and seasonal variability, with a range from 0 to 22 dpm cm -2 . This approach indicates that for most of the shelf, the inventories of the shorter-term tracer ( 234 Th) are less than predicted by the inventories of the longer-term tracer ( 210 Pb). There are two explanations for this trend. The first is that a larger portion of the 234 Th inventory occurs in the fluid muds or the water column relative to 210 Pb. The second is that the supply of offshore water, scavenging efficiency, and/or deposition have been lower over the two year study period relative to the last one hundred years. 38 refs., 7 figs

  9. Sand ridge morphology and bedform migration patterns derived from bathymetry and backscatter on the inner-continental shelf offshore of Assateague Island, USA

    Science.gov (United States)

    Pendleton, Elizabeth; Brothers, Laura; Thieler, E. Robert; Sweeney, Edward

    2017-01-01

    The U.S. Geological Survey and the National Oceanographic and Atmospheric Administration conducted geophysical and hydrographic surveys, respectively, along the inner-continental shelf of Fenwick and Assateague Islands, Maryland and Virginia over the last 40 years. High resolution bathymetry and backscatter data derived from surveys over the last decade are used to describe the morphology and presence of sand ridges on the inner-continental shelf and measure the change in the position of smaller-scale (10–100 s of meters) seafloor features. Bathymetric surveys from the last 30 years link decadal-scale sand ridge migration patterns to the high-resolution measurements of smaller-scale bedform features. Sand ridge morphology on the inner-shelf changes across-shore and alongshore. Areas of similar sand ridge morphology are separated alongshore by zones where ridges are less pronounced or completely transected by transverse dunes. Seafloor-change analyses derived from backscatter data over a 4–7 year period show that southerly dune migration increases in magnitude from north to south, and the east-west pattern of bedform migration changes ~ 10 km north of the Maryland-Virginia state line. Sand ridge morphology and occurrence and bedform migration changes may be connected to observed changes in geologic framework including topographic highs, deflated zones, and sand availability. Additionally, changes in sand ridge occurrence and morphology may help explain changes in the long-term shoreline trends along Fenwick and Assateague Islands. Although the data presented here cannot quantitatively link sand ridges to sediment transport and shoreline change, it does present a compelling relationship between inner-shelf sand availability and movement, sand ridge occurrence and morphology, geologic framework, and shoreline behavior.

  10. Thirty-Three Years of Ocean Benthic Warming Along the U.S. Northeast Continental Shelf and Slope: Patterns, Drivers, and Ecological Consequences

    Science.gov (United States)

    Kavanaugh, Maria T.; Rheuban, Jennie E.; Luis, Kelly M. A.; Doney, Scott C.

    2017-12-01

    The U.S. Northeast Continental Shelf is experiencing rapid warming, with potentially profound consequences to marine ecosystems. While satellites document multiple scales of spatial and temporal variability on the surface, our understanding of the status, trends, and drivers of the benthic environmental change remains limited. We interpolated sparse benthic temperature data along the New England Shelf and upper Slope using a seasonally dynamic, regionally specific multiple linear regression model that merged in situ and remote sensing data. The statistical model predicted nearly 90% of the variability of the data, resulting in a synoptic time series spanning over three decades from 1982 to 2014. Benthic temperatures increased throughout the domain, including in the Gulf of Maine. Rates of benthic warming ranged from 0.1 to 0.4°C per decade, with fastest rates occurring in shallow, nearshore regions and on Georges Bank, the latter exceeding rates observed in the surface. Rates of benthic warming were up to 1.6 times faster in winter than the rest of the year in many regions, with important implications for disease occurrence and energetics of overwintering species. Drivers of warming varied over the domain. In southern New England and the mid-Atlantic shallow Shelf regions, benthic warming was tightly coupled to changes in SST, whereas both regional and basin-scale changes in ocean circulation affect temperatures in the Gulf of Maine, the Continental Shelf, and Georges Banks. These results highlight data gaps, the current feasibility of prediction from remotely sensed variables, and the need for improved understanding on how climate may affect seasonally specific ecological processes.

  11. Phytoplankton community structure in relation to hydrographic features along a coast-to-offshore transect on the SW Atlantic Continental Shelf

    Science.gov (United States)

    Islabão, C. A.; Mendes, C. R. B.; Detoni, A. M. S.; Odebrecht, C.

    2017-12-01

    The continental shelf in Southern Brazil is characterized by high biological productivity associated with horizontal and vertical density gradients due to the mixing of distinct water masses. Phytoplankton biomass and composition were evaluated in summer 2013 along an on-offshore transect off the mouth of the Patos Lagoon (Lat. 32°12S). Photosynthetic active radiation, temperature, salinity and fluorescence vertical profiles were carried out and Brünt-Väisäla frequency was estimated. Three water bodies were identified: the Subtropical Shelf Water along the entire transect, the Plata Plume Water on the middle shelf surface and the Tropical Water farther offshore. The water was sampled (N = 40) for the analyses of dissolved inorganic nutrients, phytoplankton cell density and composition. Phytoplankton present in the water was identified and quantified by the classical microscope sedimentation technique, complemented with CHEMTAX analysis of high-performance liquid chromatography (HPLC) pigment data. From the results obtained, chlorophyll a concentration was higher at both coastal stations (1.6-2.0 mg m-3) where the water column was homogeneous and diatoms dominated the stations. This group was replaced by dinoflagellates in stratified conditions on the shelf and farther offshore. Along the onshore-offshore gradient, two types of dinoflagellates were found: the peridinin-containing dinoflagellates Prorocentrum and Scrippsiella with a small contribution at the coastal stations, and the fucoxantin-containing small Gymnodiniales cells (< 15 μm) with more than 50% of the total chlorophyll a at the stations on the continental shelf, especially associated with the chlorophyll maximum at the base of the euphotic zone. The positive (negative) relationship between the biomass of dinoflagellates (diatoms) with the Brünt-Väisäla frequency, respectively, support the hypothesis that stratification is the most important environmental factor that determines the biomass of

  12. Studies on sound signal scattering from varying seabed sediments of the western continental shelf of India: Cochin to Mangalore

    Digital Repository Service at National Institute of Oceanography (India)

    Chakraborty, B.; Pathak, D.

    A study on the interaction effect of the acoustic signal with three different sediment type seabottoms off the shelf area between Cochin and Mangalore of the west coast of India is performed. Analyses by means of Probability Density Function (PDF...

  13. 77 FR 10711 - Safety Zone; KULLUK, Outer Continental Shelf Mobile Offshore Drilling Unit (MODU), Beaufort Sea, AK

    Science.gov (United States)

    2012-02-23

    ... environment given the sensitivity of the environmental and subsistence importance to the indigenous population... Shelf and its distance from both land and safety fairways. Vessels traversing waters near the proposed...

  14. Sources and distribution of polycyclic aromatic hydrocarbons in sediments from the Spanish northern continental shelf. Assessment of spatial and temporal trends

    International Nuclear Information System (INIS)

    Vinas, Lucia; Angeles Franco, M.; Antonio Soriano, J.; Jose Gonzalez, J.; Pon, Jordi; Albaiges, Joan

    2010-01-01

    The distribution of polycyclic aromatic hydrocarbons was determined in surface sediments collected at 36 stations along the Spanish Northern continental shelf in March and September 2003, and February 2005. Concentrations of PAHs (Σ13 parent components) were in the range of 22-47528 μg/kg dw, the highest values corresponding to coastal urban-industrial hotspots and decreasing offshore. Sediment quality guidelines (SQGs) showed that concentrations of total PAHs were below the threshold effect level (TEC) in 27 stations (81%) and above in 7, two of which (Gijon and Bilbao) were above the probable effect concentration (PEC). The detailed study of diagnostic ratios suggested a rather uniform mixture of petrogenic and pyrolytic PAH sources along the continental shelf, with a slight decrease of the latter moving westwards and offshore. In order to assess the incidence of sediment sampling on the variability of the results, selected stations were also monitored in February and September 2004 and September 2005. The average field variance of the values obtained for each station was 31% that decreased to 23% when the values were normalized to TOC. - PAHs in the Spanish Atlantic coastal sediments reflect chronic inputs of petrogenic and pyrolytic hydrocarbons, with a decrease of the latter moving westwards and offshore and representing low to moderate pollution according to established sediment quality guidelines.

  15. Distribution of marine birds on the mid- and North-Atlantic US outer continental shelf. Technical progress report, January 1978-July 1980

    Energy Technology Data Exchange (ETDEWEB)

    Powers, K.D.; Pittman, G.L.; Fitch, S.J.

    1980-09-01

    The species composition, distribution, and abundance of marine birds on continental shelf waters from Cape Hatteras to the Bay of Fundy were examined using ships-of-opportunity. Northern Fulmar, Cory's Shearwater, Greater Shearwater, Sooty Shearwater, Wilson's Storm-Petrel, Gannet, Red Phalarope, Great Black-backed Gull, Herring Gull, and Black-legged Kittiwake were the most abundant and common species. These species were ecologically dominant within the bird community in numbers and biomass. Georges Bank and Gulf of Marine regions generally had greatest estimates of standing stock and biomass; whereas, in the Middle Atlantic region these estimates were consistently lowest. Species diversity throughout the study area was greatest in spring and least in fall. Oceanic fronts at the continental shelf break and at Nantucket Shoals influenced the distribution of Wilson's Storm-Petrels and Red Phalaropes. Fishing activities were particularly important to Larus gull distribution. Fishes, squids, and crustaceans were the most important groups of prey items in diets of nine bird species. An oiled bird or pollution index was developed. According to the index, frequency of oiled birds was greatest in winter and spring, and gulls made up the majority of species with oiled plumages.

  16. Sources and distribution of polycyclic aromatic hydrocarbons in sediments from the Spanish northern continental shelf. Assessment of spatial and temporal trends

    Energy Technology Data Exchange (ETDEWEB)

    Vinas, Lucia, E-mail: lucia.vinas@vi.ieo.e [Instituto Espanol de Oceanografia, Centro Oceanografico de Vigo, Cabo Estai - Canido, 36200 Vigo (Spain); Angeles Franco, M.; Antonio Soriano, J.; Jose Gonzalez, J. [Instituto Espanol de Oceanografia, Centro Oceanografico de Vigo, Cabo Estai - Canido, 36200 Vigo (Spain); Pon, Jordi [Department of Environmental Chemistry, CID-CSIC, Jordi Girona Salgado, 18-26, 08034-Barcelona (Spain); Albaiges, Joan, E-mail: albqam@cid.csic.e [Department of Environmental Chemistry, CID-CSIC, Jordi Girona Salgado, 18-26, 08034-Barcelona (Spain)

    2010-05-15

    The distribution of polycyclic aromatic hydrocarbons was determined in surface sediments collected at 36 stations along the Spanish Northern continental shelf in March and September 2003, and February 2005. Concentrations of PAHs (SIGMA13 parent components) were in the range of 22-47528 mug/kg dw, the highest values corresponding to coastal urban-industrial hotspots and decreasing offshore. Sediment quality guidelines (SQGs) showed that concentrations of total PAHs were below the threshold effect level (TEC) in 27 stations (81%) and above in 7, two of which (Gijon and Bilbao) were above the probable effect concentration (PEC). The detailed study of diagnostic ratios suggested a rather uniform mixture of petrogenic and pyrolytic PAH sources along the continental shelf, with a slight decrease of the latter moving westwards and offshore. In order to assess the incidence of sediment sampling on the variability of the results, selected stations were also monitored in February and September 2004 and September 2005. The average field variance of the values obtained for each station was 31% that decreased to 23% when the values were normalized to TOC. - PAHs in the Spanish Atlantic coastal sediments reflect chronic inputs of petrogenic and pyrolytic hydrocarbons, with a decrease of the latter moving westwards and offshore and representing low to moderate pollution according to established sediment quality guidelines.

  17. Facts 2006. The Norwegian petroleum sector

    International Nuclear Information System (INIS)

    Dokka, Ane; Midttun, Oeyvind

    2006-01-01

    The petroleum sector is extremely important to Norway. The industry is responsible for one fourth of all value creation in the country and more than one fourth of the state's revenues. It is currently Norway's largest industry, and the spillover effects to other industries are substantial. Norway ranks as the world's third largest exporter of oil and the eighth largest oil producer. Less than one third of the estimated petroleum reserves Norway has have been produced. The level of activity on the Norwegian continental shelf was very high in 2005. The number of producing fields was 50, and these fields produced 3 million barrels of oil (including NGL and condensate) per day and 85 billion standard cubic metres (scm) gas, for a total production saleable petroleum of 257 million scm of oil equivalents. Resource management is conducted through the models of cooperation and competition. Annual licensing rounds are held by the authorities where companies are given access to new exploration areas. The interest in the 19th licensing round in 2005 was considerable, indicating a continuous high interest in the Norwegian continental shelf. The Norwegian Petroleum Directorate estimates for the future a gradual increase in the petroleum production up until 2011, and a gradual fall thereafter. Gas production is expected to increase until 2013. Gas production represents 35 percent of the total production in 2006. It is expected that by 2013 it will represent 50 percent of the total. Other aspects accounted for include government petroleum revenues, environmental considerations, petroleum resources and overviews of fields in production, fields where production has ceased and fields under development

  18. The geostatistics of the metal concentrations in sediments from the eastern Brazilian continental shelf in areas of gas and oil production

    Science.gov (United States)

    Aguiar, Jose Edvar; de Lacerda, Luiz Drude; Miguens, Flavio Costa; Marins, Rozane Valente

    2014-04-01

    Geostatistical techniques were used to evaluate the differences in the geochemistry of metals in the marine sediments along the Eastern Brazilian continental margin along the states of Ceará and Rio Grande do Norte (Northeastern sector) and Espírito Santo (Southeastern sector). The concentrations of Al, Fe, Mn, Ba, Cd, Cu, Cr, Ni, Pb, V, Hg, and Zn were obtained from acid digestion and quantified using flame atomic absorption spectrometry (AAS), inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The metals showed a similar order of concentration: Al > Fe > Ba > Mn > V > Ni > Pb > Cr > Zn > Cu, in both the Ceará; and Rio Grande do Norte shelf regions but different in the Espírito Santo shelf (Fe > Al > Mn > Ba > Zn > V > Cr > Ni > Pb > Cu. The concentrations of Hg and Cd were below the detection limit in all areas. A multivariate analysis revealed that the metals of siliciclastic origin on the continental shelf of Ceará are carried by Al. In addition, a large portion of metal deposits is connected to the iron and manganese oxides on the continental margin of Rio Grande do Norte. The metals from the continental supply on the coast of Espírito Santo (Cu, Ni, Ba, and Mn) are associated with Al; whereas Cr, Pb, V, and Zn are associated with iron in this southern area. Geochemical evaluations are needed to distinguish the origin and mineralogical differences of marine sediments within the regions. Scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) applied to the sediments from the coast of Ceará showed the morphological diversity of sediment grains: biological fragments, multifaceted particles, aggregates, and crystals occurred in the three regions analyzed. Among these grains, calcite, Mg-calcite, and aragonite were predominant in the northeastern sector, whereas silicates and other minerals were predominant the southeastern sector. Mg, K, Ti, and Zr as well as the

  19. Concentrations and isotope ratios of mercury in sediments from shelf and continental slope at Campos Basin near Rio de Janeiro, Brazil.

    Science.gov (United States)

    Araujo, Beatriz Ferreira; Hintelmann, Holger; Dimock, Brian; Almeida, Marcelo Gomes; Rezende, Carlos Eduardo

    2017-07-01

    Mercury (Hg) may originate from both anthropogenic and natural sources. The measurement of spatial and temporal variations of Hg isotope ratios in sediments may enable source identification and tracking of environmental processes. In this study we establish the distribution of mercury concentrations and mercury isotope ratios in surface sediments of three transects along the continental shelf and slope in Campos Basin-RJ-Brazil. The shelf showed on average lower total Hg concentrations (9.2 ± 5.3 ng g -1 ) than the slope (24.6 ± 8.8 ng g -1 ). MMHg average concentrations of shelf 0.15 ± 0.12 ng g -1 and slope 0.13 ± 0.06 ng g -1 were not significantly different. Distinct differences in Hg isotope ratio signatures were observed, suggesting that the two regions were impacted by different sources of Hg. The shelf showed more negative δ 202 Hg and Δ 199 Hg values ranging from -0.59 to -2.19‰ and from -0.76 to 0.08‰, respectively. In contrast, the slope exhibited δ 202 Hg values from -0.29 to -1.82‰ and Δ 199 Hg values from -0.23 to 0.09‰. Mercury found on the shelf, especially along the "D" and "I" transects, is depleted in heavy isotopes resulting in more negative δ 202 Hg compared to the slope. Isotope ratios observed in the "D" and "I" shelf region are similar to Hg ratios commonly associated with plants and vegetation and very comparable to those detected in the estuary and adjoining mangrove forest, which suggests that Hg exported from rivers may be the dominating source of Hg in near coastal regions along the northern part of the shelf. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Long-lasting Microbial Methane Release at the Aquitaine Shelf Break (Bay of Biscay): Relation with the (Plio)-Pleistocene Sedimentary Progradation of the Continental Margin

    Science.gov (United States)

    Dupré, S.; Michel, G.; Pierre, C.; Ruffine, L.; Scalabrin, C.; Ehrhold, A.; Loubrieu, B.; Gautier, E.; Baltzer, A.; Imbert, P.; Battani, A.; Deville, E.; Dupont, P.; Thomas, Y.; Théréau, E.

    2017-12-01

    The recent identification of acoustic and visual gas release in the water column at the Aquitaine Shelf (140 and 220 m water depths) led to the discovery of a 200 km2 fluid system at the seafloor with 3000 bubbling sites associated with microbial methane (Dupré et al 2014; Ruffine et al. 2017). The moderate methane fluxes (measured in situ, on average 200 mLn/min per bubbling site) contribute to the formation of small-scale sub-circular authigenic carbonate mounds (with reliefs < 1 m in height) (Pierre et al. 2017). The emitted gases have neither a genetic link with thermogenic hydrocarbons from the Parentis Basin beneath, nor are issued from gas hydrate dissociation, but originate from microbial CO2 reduction. Based on estimated thickness and growth rate of authigenic carbonates, this system has lasted for at least several tens to possibly hundreds of kyears with a volume of escaping methane reaching 3.1012 Ln per 10 kyr. Seismic evidences for gas-charged layers and fossil authigenic carbonates point to organic matter source levels within the sedimentary deposits of the Late Pleistocene progradation system. The Aquitaine Shelf fluid system highlights the edge of continental shelves as preferential areas for bio-geological processes. The GAZCOGNE project is co-funded by TOTAL and IFREMER as part of the PAMELA (Passive Margin Exploration Laboratories) scientific project. References Dupré S, Berger L, Le Bouffant N, Scalabrin C, Bourillet J-F (2014) Fluid emissions at the Aquitaine Shelf (Bay of Biscay, France): a biogenic origin or the expression of hydrocarbon leakage? Cont. Shelf Res. 88:24-33 Pierre C, Demange J, Blanc-Valleron M-M, Dupré S (2017) Authigenic carbonate mounds from active methane seeps on the southern Aquitaine Shelf (Bay of Biscay, France): Evidence for anaerobic oxidation of biogenic methane and submarine groundwater discharge during formation. Cont. Shelf Res. 133:13-25 Ruffine L, Donval J-P, Croguennec C, Bignon L, Birot D, Battani A, Bayon

  1. Molecular Gut Content Profiling to Investigate the In Situ Grazing and Selectivity of Dolioletta gegenbauri in Summer Continental Shelf Intrusion Waters of the South Atlantic Bight, USA

    Science.gov (United States)

    Walters, T. L.; Frazier, L.; Gibson, D. M.; Paffenhofer, G. A.; Frischer, M. E.

    2016-02-01

    Gelatinous metazooplankton play a crucial role in marine planktonic food webs and it has been suggested that they may become increasingly important in the Future Ocean. However, largely due to methodological challenges and reliance on laboratory cultivation approaches, the in situ diet of zooplankton with complex life histories and diverse prey choices remains poorly investigated. This is particularly true for the gelatinous zooplankton including the pelagic tunicate, Dolioletta gegenbauri that form large blooms in productive subtropical continental shelf environments. To investigate the diet of D. gegenbauri we developed a molecular gut profiling approach based on the use of a Peptide Nucleic Acid (PNA) PCR blocker. Using a doliolid-specific PNA blocker, it was possible to enrich the amplification of prey and parasite DNA from whole animal DNA extracts of doliolids. Gut contents from the water column, wild and captive-fed doliolids were profiled after PNA-PCR by denaturing HPLC (dHPLC), clone library and next generation sequencing (NGS) approaches. Studies were conducted during 5 summer cruises in the mid-shelf of the South Atlantic Bight. Comparison of gut profiles to available prey in the water column revealed evidence of prey selection towards larger prey species, including diatoms, dinoflagelletes and also metazoan prey that were likely captured as larvae and eggs. Wild-caught doliolids contained significantly more metazoan sequences than did the captive-fed doliolids. Ingestion of metazoan prey suggests that metazoans may contribute both the nutrition of doliolids and the potential role of doliolids as trophic cascade agents in continental shelf pelagic food webs.

  2. Patterns in stable isotope values of nitrogen and carbon in particulate matter from the Northwest Atlantic Continental Shelf, from the Gulf of Maine to Cape Hatteras

    Directory of Open Access Journals (Sweden)

    Autumn Oczkowski

    2016-12-01

    Full Text Available Stable isotope measurements of nitrogen and carbon (δ15N, δ13C are often used to characterize estuarine, nearshore, and open ocean ecosystems. Reliable information about the spatial distribution of base-level stable isotope values, often represented by primary producers, is critical to interpreting values in these ecosystems. While base-level isotope data are generally readily available for estuaries, nearshore coastal waters, and the open ocean, the continental shelf is less studied. To address this, and as a first step towards developing a surrogate for base-level isotopic signature in this region, we collected surface and deep water samples from the United States’ eastern continental shelf in the Western Atlantic Ocean, from the Gulf of Maine to Cape Hatteras, periodically between 2000 and 2013. During the study, particulate matter δ15N values ranged from 0.8 to 17.4 ‰, and δ13C values from -26.4 to -15.6 ‰ over the region. We used spatial autocorrelation analysis and random forest modeling to examine the spatial trends and potential environmental drivers of the stable isotope values. We observed general trends towards lower values for both nitrogen and carbon isotopes at the seaward edge of the shelf. Conversely, higher δ15N and δ13C values were observed on the landward edge of the shelf, in particular in the southern portion of the sampling area. Across all sites, the magnitude of the difference between the δ15N of subsurface and surface particulate matter (PM significantly increased with water depth (r2 = 0.41, df = 35, p < 0.001, while δ13C values did not change. There were significant positive correlation between δ15N and δ13C values for surface PM in each of the three marine ecoregions that make up the study area. Stable isotope dynamics on the shelf can inform both nearshore and open ocean research efforts, reflecting regional productivity patterns and, even possibly, large-scale climate fluctuations.

  3. Closing the sea level budget on a regional scale: Trends and variability on the Northwestern European continental shelf.

    Science.gov (United States)

    Frederikse, Thomas; Riva, Riccardo; Kleinherenbrink, Marcel; Wada, Yoshihide; van den Broeke, Michiel; Marzeion, Ben

    2016-10-28

    Long-term trends and decadal variability of sea level in the North Sea and along the Norwegian coast have been studied over the period 1958-2014. We model the spatially nonuniform sea level and solid earth response to large-scale ice melt and terrestrial water storage changes. GPS observations, corrected for the solid earth deformation, are used to estimate vertical land motion. We find a clear correlation between sea level in the North Sea and along the Norwegian coast and open ocean steric variability in the Bay of Biscay and west of Portugal, which is consistent with the presence of wind-driven coastally trapped waves. The observed nodal cycle is consistent with tidal equilibrium. We are able to explain the observed sea level trend over the period 1958-2014 well within the standard error of the sum of all contributing processes, as well as the large majority of the observed decadal sea level variability.

  4. Influence of fluvial discharge on the dynamics of Chlorophyll-α in the continental shelf adjacent to the Recife Port Basin (Pernambuco-Brazil

    Directory of Open Access Journals (Sweden)

    Amanda Yumi Otsuka

    Full Text Available Abstract This study was undertaken in the coastal zone of the state of Pernambuco adjacent to the Recife port area, which corresponds to the inner shelf. This research aimed to analyze the dynamics of chlorophyll-a and several other environmental variables. Sampling was undertaken bimonthly on the surface from September 11th to May 10th, thus including the rainy and dry periods, and during low tide in spring tide. The parameters analyzed were chlorophyll-a, salinity, temperature, transparency, dissolved oxygen, oxygen saturation rate, pH, suspended solids, dissolved inorganic nutrients. Phytoplankton biomass ranged from 13.48 to 145.09 mg m-3 in the estuarine area and on the inner shelf, the variation being from 0.24 to 19.29 mg m-3 in the dry season and from 0.78 to 5.20 mg m-3 in the rainy season. PCA showed a direct relationship of chlorophyll-a with ammonia, phosphate and transparency and an inverse relationship with suspended particulate matter and nitrate. Biomass did not vary significantly different as a result of seasonal or spatial dynamics. The estuary of the Capibaribe River is considered highly impacted, and as it forms the Recife port basin, it joins with two more strongly eutrophic water bodies, the Beberibe River and the Pina Basin, leading to an amplification of its influence on the adjacent shelf. In terms of the river plume's dispersion in the Port of Recife, the presence of a dike causes some disturbance in the direction of the current, limiting the plume to the area close to the coast and influences the oceanographic variables on the inner continental shelf.

  5. Differential responses of seabirds to environmental variability over 2 years in the continental shelf and oceanic habitats of southeastern Bering Sea

    Science.gov (United States)

    Yamamoto, Takashi; Kokubun, Nobuo; Kikuchi, Dale M.; Sato, Nobuhiko; Takahashi, Akinori; Will, Alexis P.; Kitaysky, Alexander S.; Watanuki, Yutaka

    2016-04-01

    Seasonal sea-ice cover has been decreasing in the southeastern Bering Sea shelf, which might affect ecosystem dynamics and availability of food resources to marine top predators breeding in the region. In this study, we investigated the foraging responses of two seabird species, surface-foraging red-legged kittiwakes Rissa brevirostris (hereafter, RLKI) and pursuit-diving foraging thick-billed murres Uria lomvia (TBMU) to different marine environmental conditions over 2 years. At-sea distributions of RLKI and TBMU breeding on St. George Island, the largest seabird colony in the region, were recorded using GPS loggers, and blood samples were taken to examine their physiological condition and isotopic foraging niche in a given year. Between the study years, winter ice retreated earlier and summer water temperatures were relatively warmer in 2014 compared to those in 2013. RLKI foraging occurred mostly over the oceanic basin in both years. TBMU, however, foraged mostly over the shelf but showed a relatively higher use of the shelf break and oceanic basin in 2013. The foraging distances from the colony peaked at 250-300 km in 2013 and bimodally at 150-250 and 300-350 km in 2014 for RLKI and tended to be farther in 2013 compared to those in 2014 for TBMU. Plasma levels of corticosterone did not differ between the years in RLKI but differed in TBMU, showing higher levels of physiological stress incurred by murres in 2013, the year of relatively cooler sea surface temperatures with later sea-ice retreat. δ13N (a proxy of trophic level of prey) did not differ between the years in either RLKI or TBMU. These results suggest that the response of ecosystem dynamics to climate variability in the southeastern Bering Sea may differ between the ocean basin and continental shelf regions, which, in turn, may generate differential responses in seabirds relying on those habitats for foraging.

  6. 3-D thermal effect of late Cenozoic erosion and deposition within the Lofoten-Vesterålen segment of the Mid-Norwegian continental margin

    Science.gov (United States)

    Maystrenko, Yuriy Petrovich; Gernigon, Laurent; Olesen, Odleiv; Ottesen, Dag; Rise, Leif

    2018-05-01

    A 3-D subsurface temperature distribution within the Lofoten-Vesterålen segment of the Mid-Norwegian continental margin and adjacent areas has been studied to understand the thermal effect of late Cenozoic erosion of old sedimentary and crystalline rocks and subsequent deposition of glacial sediments during the Pleistocene. A lithosphere-scale 3-D structural model of the Lofoten-Vesterålen area has been used as a realistic approximation of the geometries of the sedimentary infill, underlying crystalline crust and lithospheric mantle during the 3-D thermal modelling. The influence of late Cenozoic erosion and sedimentation has been included during the 3-D thermal calculations. In addition, the 3-D thermal modelling has been carried out by taking also into account the influence of early Cenozoic continental breakup. The results of the 3-D thermal modelling demonstrate that the mainland is generally colder than the basin areas within the upper part of the 3-D model. The thermal influence of the early Cenozoic breakup is still clearly recognizable within the western and deep parts of the Lofoten-Vesterålen margin segment in terms of the increased temperatures. The thermal effects of the erosion and deposition within the study area also indicate that a positive thermal anomaly exists within the specific subareas where sedimentary and crystalline rocks were eroded. A negative thermal effect occurs in the subareas affected by subsidence and sedimentation. The erosion-related positive thermal anomaly reaches its maximum of more than +27 °C at depths of 17-22 km beneath the eastern part of the Vestfjorden Basin. The most pronounced deposition-related negative anomaly shows a minimum of around -70 °C at 17-20 km depth beneath the Lofoten Basin. The second negative anomaly is located within the northeastern part of the Vøring Basin and has minimal values of around -48 °C at 12-14 km depth. These prominent thermal anomalies are associated with the subareas where

  7. New species of Ulosa and Biemna (Porifera, Demospongiae, Poecilosclerida) from the N-NE Brazilian continental shelf

    NARCIS (Netherlands)

    Mothes, B.; Hajdu, E.; Lerner, C.; van Soest, R.W.M.

    2004-01-01

    Two new species collected off the coast between Amapa and Maranhao state, NNE coast of the Brazilian shelf. Two new species are described, Ulosa longimycalostylifera sp.nov. and Biemna microacanthosigma sp.nov. The former can be distinguished by the possession of long and thin mycalostyles, and the

  8. 78 FR 9731 - Gulf of Mexico, Outer Continental Shelf (OCS), Central Planning Area (CPA) Oil and Gas Lease Sale...

    Science.gov (United States)

    2013-02-11

    ... Environmental Impact Statement (Multisale FEIS). Authority: This NOA is published pursuant to the regulations... the NEPA process. The Multisale FEIS evaluated the environmental and socioeconomic impacts for CPA... DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Gulf of Mexico, Outer Continental...

  9. 77 FR 68147 - Gulf of Mexico, Outer Continental Shelf (OCS), Western Planning Area (WPA), Oil and Gas Lease...

    Science.gov (United States)

    2012-11-15

    ... Environmental Impact Statement (Multisale FEIS). Authority: This NOA is published pursuant to the regulations... NEPA process. The Multisale FEIS evaluated the environmental and socioeconomic impacts for WPA Lease... DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Gulf of Mexico, Outer Continental...

  10. 77 FR 1019 - Renewable Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf-Acquire a...

    Science.gov (United States)

    2012-01-09

    ...-0045] RIN 1010-AD79 Renewable Energy Alternate Uses of Existing Facilities on the Outer Continental... rule related to acquiring a lease non-competitively for offshore renewable energy projects. DATES... or Timothy Redding, Renewable Energy, BOEM, at (703) 787-1219 or email [email protected

  11. Steam trawling on the south-east continental shelf of Australia. An environmental history of fishing, management and science in NSW, 1865 -1961

    DEFF Research Database (Denmark)

    Jacobsen, A. Lif Lund

    2010-01-01

    . Motivated by Sydney’s insufficient supplies of fish, the objective of early fisheries management in the state of New South Wales (NSW) was to improve the industry. Driven by state developmentalism, efforts were focused on increasing the productivity of already existing coastal fisheries through fisheries......As many of the world’s fish stocks are fully or over-exploited there is an urgent need for governments to provide robust fisheries management. However, governments are often slow to implement necessary changes to fisheries practices. The will to govern is an essential factor in successful marine...... resource management. Studies of historical documents from State and Commonwealth fisheries authorities involved in the steam trawl fishery on the south-east continental shelf of Australia illustrate different expressions of intentional management and how a more ecological responsible view has emerged...

  12. Global change effects on early holocene sedimentation of the Brazilian continental shelf determined from TM-LANDSAT 5 data of the seafloor

    International Nuclear Information System (INIS)

    Cabral, A.P.; Vianna, M.L.; Gherardi, D.F.M.

    1992-01-01

    A study of the shaping of the seafloor morphology on the Brazilian northeast continental shelf caused by climatic changes in the beginning of the Holocene is being made with the support of TM-Landsat 5 data. Special emphasis is given on analysis of data from ancient shorelines between 20-45m depth, to be correlated with abrupt global climate change between 10,000-8,000 BP. The transport of a quartz sand deposit by the ocean currents through time, effected by active sandwave fields at the 20 m isobath is also described. Two images were used corresponding to two dates: 1984 and 1989. Geometric correction, filter application and contrast enhancement were performed. A comparison between 84' and 89' images was carried out, to detect changing patterns of the sand waves, along a 5 year period, caused by the seasonal wintertime wind-forced ocean currents. Based on this registration, estimates of displacement rates for the sand deposit could be made

  13. 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.

  14. Diel feeding chronology of the skate raja Agassizii (Müller & Henle (Pisces, Elasmobranchii on the continental shelf off Ubatuba, Southeastern Brazil

    Directory of Open Access Journals (Sweden)

    Lucy Satiko Hashimoto Soares

    1999-03-01

    Full Text Available The diet and diel feeding pattern of the skate Raja agassizii were investigated through analysis of stomach contents. A total of 280 stomachs were collected by a series of hauls during a daily cycle in three periods, 8-10 January 1987, 22-24 July and 2-4 December 1988, from the inner continental shelf of the coastal ecosystem of Ubatuba, São Paulo State, Brazil (25º35'S; 45º00'W. According to the results of the stomach fullness and of the number of fresh prey, it is suggested that this species presents continuity in the feeding activity during a day. The stomach contents were mainly composed of crustaceans. Nematodes, polychaetes and fishes also occurred. No changes were observed in dietary composition between day and night.

  15. Recent trends in the abundance of plaice Pleuronectes platessa and cod Gadus morhua in shallow coastal waters of the Northeastern Atlantic continental shelf – a review

    DEFF Research Database (Denmark)

    Dutz, Jörg; Støttrup, Josianne Gatt; Stenberg, Claus

    2016-01-01

    of the southern distribution boundary in the Bay of Biscay and deepening of stocks in the North Sea. In contrast, no trend in shallow water abundance of plaice similar to a decline in deep-water stocks during the 1970s and their slow recovery during the 2000s is apparent in the Skagerrak/Kattegat. Although......Shallow, near-shore water habitats on the continental shelf of the Northeast Atlantic have been productive fishing areas in the past. Here, we review the present knowledge about (i) recent trends in the abundance of plaice and cod in these habitats and (ii) hypotheses regarding the factors...... responsible for any trends. At present, only a few studies exist on the trends of abundance of plaice or cod, namely from the Bay of Biscay, the North Sea and the Skagerrak/Kattegat. They suggest a declining abundance in coastal, shallow areas and – at least for plaice – a latitudinal gradient with an erosion...

  16. Contribution to the study of deep coastal detritic bottoms: the algal communities of the continental shelf off the Balearic Islands, Western Mediterranean

    Directory of Open Access Journals (Sweden)

    S. JOHER

    2015-09-01

    Full Text Available Three main algal-dominated coastal detritic communities from the continental shelf off Mallorca and Menorca (Balearic Islands, Western Mediterranean are described herein: maërl beds dominated by Spongites fruticulosus and forests of Laminaria rodriguezii located in the Menorca channel, and Peyssonnelia inamoena beds found along the Southern coast of Menorca. There seems to be a gradient of disturbance from the highly disturbed Peyssonnelia beds to the almost undisturbed L. rodriguezii forests. Whether this gradient is the result of current and past anthropogenic pressure (e.g. trawling intensity or is driven by natural environmental factors needs further assessment. Finally, the location of the target communities by means of ROV dives combined with the use of a Box-Corer dredge and beam trawl proved to be a good methodology in the study of the composition and structure of these deep water detritic communities.

  17. Diets and niche overlap among nine co-occurring demersal fishes in the southern continental shelf of East/Japan Sea, Korea

    Science.gov (United States)

    Myun Park, Joo; Nam Kwak, Seok; Huh, Sung-Hoi; Han, In-Seong

    2017-09-01

    Dietary niches and food resource partitioning can support the coexistence of many fishes in benthic marine systems, which can lead to the greater abundances of those species that can potentially support their fisheries. Diets and niche overlap among nine demersal fish species were investigated in the southern continental shelf of East/Japan Sea, Korea. Specimens were collected monthly from January to November 2007 on soft bottoms between 40 and 100 m depth using a bottom trawl. A total of 20 prey taxa were found in 1904 stomachs of the nine species. Comparison of the stomach contents among the nine species showed that inter-specific dietary compositions differed significantly. Although all fish species consumed similar types of prey items, their contributions to the diet of different species varied. Among prey taxa, carid shrimps contributed greatly to the diets of Amblychaeturichthys hexanema, Amblychaeturichthys sciistius, Coelorinchus multispinulosus, Lepidotrigla guentheri, and Liparis tanakae, whereas polychaetes and teleosts contributed to the diets of Callionymus lunatus and Lophius litulon, respectively. On the other hand, carid shrimps and teleosts together contributed to the diets of Pseudorhombus pentophthalmus. Non-metric multivariate analysis of the mass contributions of dietary categories for food resources emphasized visually that the dietary compositions of the nine species differed. Although C. multispinulosus, L. guentheri, L. litulon, and L. tanakae showed similar dietary compositions between small and large size classes, ontogenetic diet changes of the remaining six species were evident. Feeding relationships among the nine demersal species were complicated, but inter- and intra-specific differences in dietary composition among the species reduced potential competition for food resources within the fish community in the southern continental shelf of East/Japan Sea, Korea.

  18. Spatial variability of primary organic sources regulates ichthyofauna distribution despite seasonal influence in Terminos lagoon and continental shelf of Campeche, Mexico

    Science.gov (United States)

    Romo Rios, J. A.; Aguíñiga-García, S.; Sanchez, A.; Zetina-Rejón, M.; Arreguín-Sánchez, F.; Tripp-Valdéz, A.; Galeana-Cortazár, A.

    2013-05-01

    Human activities have strong impacts on coastal ecosystems functioning through their effect on primary organic sources distributions and resulting biodiversity. Hence, it appears to be of utmost importance to quantify contribution of primary producers to sediment organic matter (SOM) spatial variability and its associated ichthyofauna. The Terminos lagoon (Gulf of Mexico) is a tropical estuary severely impacted by human activities even though of primary concern for its biodiversity, its habitats, and its resource supply. Stable isotope data (d13C, d15N) from mangrove, seaweed, seagrass, phytoplankton, ichthyofauna and SOM were sampled in four zones of the lagoon and the continental shelf through windy (November to February), dry (March to June) and rainy (July to October) seasons. Stable Isotope Analysis in R (SIAR) mixing model were used to determine relative contributions of the autotrophic sources to the ichthyofauna and SOM. Analysis of variance of ichthyofauna isotopic values showed significant differences (P < 0.001) in the four zones of lagoon despite the variability introduced by the windy, dry and rainy seasons. In lagoons rivers discharge zone, the mangrove contribution to ichthyofauna was 40% and 84% to SOM. Alternative use of habitat by ichthyofauna was evidenced since in the deep area of the lagoon (4 m), the contribution of mangrove to fish is 50%, and meanwhile contribution to SOM is only 77%. Although phytoplankton (43%) and seaweed (41%) contributions to the adjacent continental shelf ichthyofauna were the main organic sources, there was 37% mangrove contribution to SOM, demonstrating conspicuous terrigenous influence from lagoon ecosystem. Our results point toward organic sources spatial variations that regulate fish distribution. In Terminos lagoon, significant correlation (p-value = 0.2141 and r=0.79) of Ariopsis felis and Sphoeroides testudineus abundances and seaweed and seagrasses contributions (30-35%) during both dry and rainy seasons

  19. The Effects of Shoaling Internal Tides on Benthic Exchange Events and Near-Boundary Mixing Along the Continental Shelf

    Science.gov (United States)

    2013-06-01

    BLANK xv LIST OF ACRONYMS AND ABBREVIATIONS PISCO Partnership for Interdisciplinary Studies of Coastal Oceans ISW Internal Solitary Waves ITB ...shows how shoaling internal waves are also a vital instrument for transporting nutrients to inner shelf kelp ecosystems. As Internal Tidal Bores ( ITBs ...an internal tidal bore. As the ITB continues to propagate shoreward, the subsequent flood tide will assists in the propagation process. Under

  20. Projecting the effects of climate change on Calanus finmarchicus distribution within the U.S. Northeast Continental Shelf.

    Science.gov (United States)

    Grieve, Brian D; Hare, Jon A; Saba, Vincent S

    2017-07-24

    Calanus finmarchicus is vital to pelagic ecosystems in the North Atlantic Ocean. Previous studies suggest the species is vulnerable to the effects of global warming, particularly on the Northeast U.S. Shelf, which is in the southern portion of its range. In this study, we evaluate an ensemble of six different downscaled climate models and a high-resolution global climate model, and create a generalized additive model (GAM) to examine how future changes in temperature and salinity could affect the distribution and density of C. finmarchicus. By 2081-2100, we project average C. finmarchicus density will decrease by as much as 50% under a high greenhouse gas emissions scenario. These decreases are particularly pronounced in the spring and summer in the Gulf of Maine and Georges Bank. When compared to a high-resolution global climate model, the ensemble showed a more uniform change throughout the Northeast U.S. Shelf, while the high-resolution model showed larger decreases in the Northeast Channel, Shelf Break, and Central Gulf of Maine. C. finmarchicus is an important link between primary production and higher trophic levels, and the decrease projected here could be detrimental to the North Atlantic Right Whale and a host of important fishery species.

  1. Bio-Optical Properties of the Inner Continental Shelf off Santos Estuarine System, Southeastern Brazil, and their Implications for Ocean Color Algorithm Performance

    Directory of Open Access Journals (Sweden)

    Melissa Carvalho

    2014-07-01

    Full Text Available Optical characterizations of coastal water masses are important tools for a better understanding of physical and biochemical processes and aid the optimization of ocean color algorithms. In this study we present three optical classes of water observed during October/2005 and March/2006 on the inner continental shelf adjacent to Santos Bay (Brazil, based on remote sensing reflectance. ANOVA indicated a crescent estuarine influence in classes 1 to 3. Class 3 presented the highest chlorophyll-a and nutrient concentration and highest light absorption coefficients. Colored dissolved organic matter (CDOM dominated the light absorption in all classes and was strongly correlated to salinity in October/2005 due to the influence of the La Plata plume. The results indicated that CDOM dynamics in the Santos inner shelf are very complex. The performance of global chlorophyll algorithms was significantly smaller for October/2005 than for March/2006. As inconsistent changes in light absorption spectra by phytoplankton were detected between samplings, the results show that future bio-optical algorithms for this region must be optimized preferentially considering CDOM optical parameters.

  2. Geomorfologia, cobertura sedimentar e transporte de sedimentos na plataforma continental interna entre a Ponta de Saquarema e o Cabo Frio (RJ Geomorphology, sediment distribution and transpon on the inner continental shelf between Ponta de Saquarema and Cabo Frio (RJ

    Directory of Open Access Journals (Sweden)

    Dieter Muehe

    1993-01-01

    Full Text Available A plataforma continental interna defronte à restinga da Massambaba - um sistema de duplos cordões litorâneos localizados entre Saquarema e Arraial do Cabo, com 48 km de extensão - apresenta topografia regular, interrompida por raros afloramentos de rochas do embasamento cristalino e por ocorrências localizadas de arenitos de praia. Um amplo afloramento destes últimos ocorre na faixa batimétrica de 48 a 60 m, correspondendo à posição da linha de costa cerca de 10.000 anos atrás. Outro afloramento de arenitos de praia, de reduzida dimensão, ocorre próximo ao perfil S-4, à distância de 50 m da face da praia, em profundidade de 4 m. A cobertura sedimentar, sem aporte significativo de sedimentos terrígenos, é constituída predominantemente por areias quartzosas reliquiares. O gradiente batimétrico apresenta declividade elevada, atípica para uma plataforma passiva, atingindo o limite distai da plataforma continental interna, a isobatimétrica de 60 m, a uma distância da ordem de 4 milhas náuticas da linha de praia. O padrão de distribuição granulométrico apresenta gradientes de decréscimo em direção a leste, isto é, em direção ao Cabo Frio, e em direção a maiores profundidades. A diminuição do tamanho granulométrico em direção ao Cabo Frio é atribuída como sendo resultado do aporte de sedimentos terrígenos através de um sistema de drenagem pleistocênico, interrompido pela construção do cordão litorâneo mais interiorizado, e à remobilização dos sedimentos por ação de ondas e correntes com transporte residual em direção a leste.The inner continental shelf in front of the Massambaba beach, an East-West striking, 48 km long, double barrier beach, located between the towns of Saquarema and Arraial do Cabo presents a monotonous topography with only few outcrops of crystaline rocks, patches of beach rocks and a sediment cover of mainly relict quartz sand. The topographic gradient, steeper as expected for

  3. Impacts of Sea-Level Rise and Human Activity on a Tropical Continental Shelf, RN State, NE Brazil

    Science.gov (United States)

    Vital, H.; Barros Pereira, T. R.; Lira, H. F.; Tabosa, W. F.; Eichler, P.; Stattegger, K.; Sen Gupta, B. K.; Gomes, M. P.; Nogueira, M. L. D. S.; Pierri, G. C. S.

    2014-12-01

    The northeastern Brazilian, tropical coast-shelf system along the Atlantic Ocean is a sediment-starved zone, because of low relief, small drainage basins, and a semiarid climate. This work presents the major results of a study of environmental changes, particularly those related to Holocene sea-level rise, affecting the coast and shallow waters of Rio Grande do Norte (RN) State, NE Brazil. The methods included bottom-sediment characterization, bioindicator tracking, and integrated shallow-water geophysical investigation. This coastline is marked by active sea cliffs carved into tablelands alternating with reef- or dune-barrier sections, beach rocks and lagoons, whereas the shelf is a narrow, very shallow, and highly energetic system. Overall, the area is under the natural influence of tides (with a semidiurnal mesotidal regime) and the anthropogenic influence of salt exploration, oil industry, shrimp farms, tourism, and wind-farms. Sedimentation during the Holocene has been controlled mainly by sea-level variation, longshore currents, and the advance and westward propagation of active dunes along the coast. As in other areas around the world, growing numbers of permanent and seasonal residents choose to live at or near the ocean. Coastal erosion is a cause for concern along many Brazilian beaches, and several erosion hot spots are already recognized in RN State. Curves of Holocene relative sea-level variation were established for RN State, but the absence of long-term oceanographic observations in the last centuries or that of detailed altimetry maps hinders the evaluation of different risk scenarios at the local level. Nevertheless, impacts of the current sea-level rise and human activity can be observed along the RN coastal-shelf system. Particular aspects of the study, such as oil-spill monitoring, coastal-water sewage contamination, and coastal erosion, will be highlighted.

  4. Provenance and distribution of clay minerals in the sediments of the western continental shelf and slope of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.; Rao, B.R.

    -Goa (93 samples) For the convenience of description, the Saurashtra-Goa region has been divided into the Saurashtra, Gulf of Cambay-Ratnagiri and Ratnagiri-Goa sectors based on variations in clay mineral abundances. The boundaries between these sectors... are approximate and variations in the mineral abundances tend to grade one to the other. Smectite is the most abundant mineral in the inner shelf sediments of all the sectors [Fig. 3(Ba), 3(Ca) and Provenance and distribution of clay minerals 1763 0 Sm*ctlt* m...

  5. Differential responses of seabirds to inter-annual environmental change in the continental shelf and oceanic habitats of southeastern Bering Sea

    Science.gov (United States)

    Yamamoto, T.; Kokubun, N.; Kikuchi, D. M.; Sato, N.; Takahashi, A.; Will, A.; Kitaysky, A. S.; Watanuki, Y.

    2015-11-01

    Seasonal sea-ice cover has been decreasing in the southeastern Bering Sea shelf, which might affect ecosystem dynamics and availability of food resources to marine top predators breeding in the region. In this study, we investigated the foraging responses of two seabird species, surface-foraging red-legged kittiwakes Rissa brevirostris (hereafter, RLKI) and pursuit-diving foraging thick-billed murres Uria lomvia (TBMU) to the inter-annual change in environmental conditions. Between the study years, winter ice retreated earlier and summer water temperatures were warmer in 2014 compared to those in 2013. At-sea distributions of RLKI and TBMU breeding on St. George Island, the largest seabird colony in the region, were recorded using GPS loggers, and blood samples were taken to examine their physiological condition and isotopic foraging niche in a given year. RLKI foraging occurred mostly over the oceanic basin in both years. TBMU, however, foraged mostly over the shelf, but showed a relatively higher use of the shelf break and oceanic basin in the colder year, 2013. The foraging distances from the colony peaked at 250-300 km in 2013 and, bimodally, at 150-250 and 300-350 km in 2014 for RLKI, and tended to be farther in 2013 compared to those in 2014 for TBMU. Plasma levels of corticosterone did not differ between years in RLKI, but differed in TBMU, showing higher levels of physiological stress incurred by murres during the colder year, 2013. δ13N (a proxy of trophic level of prey) did not differ between the years in either RLKI or TBMU, while δ13C (a proxy of prey origin) were lower in 2014 than in 2013 in both species, suggesting possible differences in influx of oceanic prey items into foraging areas. These results suggest that the response of ecosystem dynamics to climate variability in the southeast Bering Sea may differ between the ocean basin and continental shelf regions, which, in turn, may generate differential responses in seabirds relying on those

  6. Continental Shelf-Scale Passive Acoustic Detection and Characterization of Diesel-Electric Ships Using a Coherent Hydrophone Array

    Directory of Open Access Journals (Sweden)

    Wei Huang

    2017-07-01

    Full Text Available The passive ocean acoustic waveguide remote sensing (POAWRS technique is employed to detect and characterize the underwater sound radiated from three scientific research and fishing vessels received at long ranges on a large-aperture densely-sampled horizontal coherent hydrophone array. The sounds radiated from the research vessel (RV Delaware II in the Gulf of Maine, and the RV Johan Hjort and the fishing vessel (FV Artus in the Norwegian Sea are found to be dominated by distinct narrowband tonals and cyclostationary signals in the 150 Hz to 2000 Hz frequency range. The source levels of these signals are estimated by correcting the received pressure levels for transmission losses modeled using a calibrated parabolic equation-based acoustic propagation model for random range-dependent ocean waveguides. The probability of the detection region for the most prominent signal radiated by each ship is estimated and shown to extend over areas spanning roughly 200 km in diameter when employing a coherent hydrophone array. The current standard procedure for quantifying ship-radiated sound source levels via one-third octave bandwidth intensity averaging smoothes over the prominent tonals radiated by a ship that can stand 10 to 30 dB above the local broadband level, which may lead to inaccurate or incorrect assessments of the impact of ship-radiated sound.

  7. Variability of the internal tide on the southern Monterey Bay continental shelf and associated bottom boundary layer sediment transport

    Science.gov (United States)

    Rosenberger, Kurt; Storlazzi, Curt; Cheriton, Olivia

    2016-01-01

    A 6-month deployment of instrumentation from April to October 2012 in 90 m water depth near the outer edge of the mid-shelf mud belt in southern Monterey Bay, California, reveals the importance regional upwelling on water column density structure, potentially accounting for the majority of the variability in internal tidal energy flux across the shelf. Observations consisted of time-series measurements of water-column currents, temperature and salinity, and near-bed currents and suspended matter. The internal tide accounted for 15–25% of the water-column current variance and the barotropic tide accounted for up to 35%. The subtidal flow showed remarkably little shear and was dominated by the 7–14 day band, which is associated with relaxations in the dominant equatorward winds typical of coastal California in the spring and summer. Upwelling and relaxation events resulted in strong near-bed flows and accounted for almost half of the current stress on the seafloor (not accounting for wave orbital velocities), and may have driven along-shelf geostrophic flow during steady state conditions. Several elevated suspended particulate matter (SPM) events occurred within 3 m of the bed and were generally associated with higher, long-period surface waves. However, these peaks in SPM did not coincide with the predicted resuspension events from the modeled combined wave–current shear stress, indicating that the observed SPM at our site was most likely resuspended elsewhere and advected along-isobath. Sediment flux was almost equal in magnitude in the alongshore and cross-shore directions. Instances of wave–current shear stress that exceeded the threshold of resuspension for the silty-clays common at these water depths only occurred when near-bed orbital velocities due to long-period surface waves coincided with vigorous near-bed currents associated with the internal tide or upwelling/relaxation events. Thus upwelling/relaxation dynamics are primarily responsible for

  8. Pacific Continental Shelf Environmental Assessment (PaCSEA): aerial seabird and marine mammal surveys off northern California, Oregon, and Washington, 2011-2012

    Science.gov (United States)

    Adams, Josh; Felis, Jonathan J.; Mason, John W.; Takekawa, John Y.

    2014-01-01

    Marine birds and mammals comprise an important community of meso- and upper-trophic-level predators within the northern California Current System (NCCS). The NCCS is located within one of the world’s four major eastern boundary currents and is characterized by an abundant and diverse marine ecosystem fuelled seasonally by wind-driven upwelling which supplies nutrient-rich water to abundant phytoplankton inhabiting the surface euphotic zone. The oceanographic conditions throughout the NCCS fluctuate according to well-described seasonal, inter-annual, and decadal cycles. Such oceanographic variability can influence patterns in the distribution, abundance, and habitat use among marine birds and mammals. Although there are an increasing number of studies documenting distributions and abundances among birds and mammals in various portions of the NCCS, there have been no comprehensive, large-scale, multi-seasonal surveys completed throughout this region since the early 1980s (off northern California; Briggs et al. 1987) and early 1990s (off Oregon and Washington; Bonnell et al. 1992, Briggs et al. 1992, Green et al. 1992). During 2011 and 2012, we completed the Pacific Continental Shelf Environmental Assessment (PaCSEA) which included replicated surveys over the continental shelfslope from shore to the 2000-meter (m) isobath along 32 broad-scale transects from Fort Bragg, California (39° N) through Grays Harbor, Washington (47° N). Additionally, surveys at a finer scale were conducted over the continental shelf within six designated Focal Areas: Fort Bragg, CA; Eureka, CA; Siltcoos Bank, OR; Newport, OR; Nehalem Bank, OR; and Grays Harbor, WA. We completed a total of 26,752 km of standardized, low-elevation aerial survey effort across three bathymetric domains: inner-shelf waters ( Overall, we recorded 15,403 sightings of 59,466 individual marine birds (12 families, 54 species). During winter, seven species groupings comprised >90% of the total number of birds

  9. Fact Sheet 1999. Norwegian Petroleum Activity

    Energy Technology Data Exchange (ETDEWEB)

    Breivik, Jan

    1999-10-01

    As discussed in this publication, petroleum resources in the order of 9.5 billion (bn) standard cubic metres (scm) oil equivalents (oe) have been discovered on the Norwegian continental shelf (NCS), 77 per cent in the North Sea, 19 per cent in the Norwegian Sea and four per cent in the Barents Sea. By the end of 1998, remaining reserves on the NCS totalled 1.6 bn scm of oil, 1.2 bn scm oe gas and 160 mill scm oe of natural gas liquids. Thirty-two exploration wells, including 21 wildcats and 11 for appraisal, were completed or temporarily abandoned on the NCS in 1998. 939 exploration wells had been completed or temporarily abandoned off Norway. In 1998 governmental approval was given for the Huldra, Snorre B phase II, Gullfaks satellites phase II and Yme Beta West. Norwegian offshore petroleum production in 1998 totalled 222.5 scm oe, including 168.9 mill scm oe of oil, 43.6 mill scm oe of gas and 10 mill scm oe of NGL/condensate. Oil production declined by 4 per cent compared with 1997, while gas sales rose by 2 per cent. The estimated value of Norwegian petroleum exports in 1998 was NOK 123 bn, or about 30 per cent of the country`s total earnings from foreign sales. Petroleum production and pipeline transport accounted for 12 per cent of Norway`s gross national product. Net government revenues from taxes and royalties on petroleum operations is put at 27.6 billion NOK. The publication also includes a list of white papers and a list of useful postal addresses. 23 figs., 14 tabs.

  10. Continental Shelf Morphology and Stratigraphy Offshore San Onofre, CA: The Interplay Between Rates of Eustatic Change and Sediment Supply

    Science.gov (United States)

    Klotsko, Shannon; Driscoll, Neal W.; Kent, Graham; Brothers, Daniel

    2016-01-01

    New high-resolution CHIRP seismic data acquired offshore San Onofre, southern California reveal that shelf sediment distribution and thickness are primarily controlled by eustatic sea level rise and sediment supply. Throughout the majority of the study region, a prominent abrasion platform and associated shoreline cutoff are observed in the subsurface from ~ 72 to 53 m below present sea level. These erosional features appear to have formed between Melt Water Pulse 1A and Melt Water Pulse 1B, when the rate of sea-level rise was lower. There are three distinct sedimentary units mapped above a regional angular unconformity interpreted to be the Holocene transgressive surface in the seismic data. Unit I, the deepest unit, is interpreted as a lag deposit that infills a topographic low associated with an abrasion platform. Unit I thins seaward by downlap and pinches out landward against the shoreline cutoff. Unit II is a mid-shelf lag deposit formed from shallower eroded material and thins seaward by downlap and landward by onlap. The youngest, Unit III, is interpreted to represent modern sediment deposition. Faults in the study area do not appear to offset the transgressive surface. The Newport Inglewood/Rose Canyon fault system is active in other regions to the south (e.g., La Jolla) where it offsets the transgressive surface and creates seafloor relief. Several shoals observed along the transgressive surface could record minor deformation due to fault activity in the study area. Nevertheless, our preferred interpretation is that the shoals are regions more resistant to erosion during marine transgression. The Cristianitos fault zone also causes a shoaling of the transgressive surface. This may be from resistant antecedent topography due to an early phase of compression on the fault. The Cristianitos fault zone was previously defined as a down-to-the-north normal fault, but the folding and faulting architecture imaged in the CHIRP data are more consistent with a

  11. Habitat compression and expansion of sea urchins in response to changing climate conditions on the California continental shelf and slope (1994-2013)

    Science.gov (United States)

    Sato, Kirk N.; Levin, Lisa A.; Schiff, Kenneth

    2017-03-01

    Echinoid sea urchins with distributions along the continental shelf and slope of the eastern Pacific often dominate the megafauna community. This occurs despite their exposure to naturally low dissolved oxygen (DO) waters (calcium carbonate (ΩCaCO3<1). Here we present vertical depth distribution and density analyses of historical otter trawl data collected in the Southern California Bight (SCB) from 1994 to 2013 to address the question: Do changes in echinoid density and species' depth distributions along the continental margin in the SCB reflect observed secular or interannual changes in climate? Deep-dwelling burrowing urchins (Brissopsis pacifica, Brisaster spp. and Spatangus californicus), which are adapted to low-DO, low-pH conditions appeared to have expanded their vertical distributions and populations upslope over the past decade (2003-2013), and densities of the deep pink urchin, Strongylocentrotus fragilis, increased significantly in the upper 500 m of the SCB. Conversely, the shallower urchin, Lytechinus pictus, exhibited depth shoaling and density decreases within the upper 200 m of the SCB from 1994 to 2013. Oxygen and pH in the SCB also vary inter-annually due to varying strengths of the El Niño Southern Oscillation (ENSO). Changes in depth distributions and densities were correlated with bi-monthly ENSO climate indices in the region. Our results suggest that both a secular trend in ocean deoxygenation and acidification and varying strength of ENSO may be linked to echinoid species distributions and densities, creating habitat compression in some and habitat expansion in others. Potential life-history mechanisms underlying depth and density changes observed over these time periods include migration, mortality, and recruitment. These types of analyses are needed for a broad suite of benthic species in order to identify and manage climate-sensitive species on the margin.

  12. Links between the recruitment success of northern European hake (Merluccius merluccius L.) and a regime shift on the NE Atlantic continental shelf

    KAUST Repository

    Goikoetxea, Nerea

    2013-07-01

    The distribution of northern European hake (Merluccius merluccius L.) extends from the Bay of Biscay up to Norwegian waters. However, despite its wide geographical distribution, there have been few studies on fluctuations in the European hake populations. Marine ecosystem shifts have been investigated worldwide and their influence on trophic levels has been studied, from top predator fish populations down to planktonic prey species, but there is little information on the effect of atmosphere-ocean shifts on European hake. This work analyses hake recruitment success (recruits per adult biomass) in relation to environmental changes over the period 1978-2006 in order to determine whether the regime shift identified in several abiotic and biotic variables in the North Sea also affected the Northeast Atlantic shelf oceanography. Hake recruitment success as well as parameters such as the sea surface temperature, wind patterns and copepod abundance changed significantly at the end of the 1980s, demonstrating an ecological regime shift in the Northeast Atlantic. Despite the low reproductive biomass recorded during the last decades, hake recruitment success has been higher since the change in 1989/90. The higher productivity may have sustained the population despite the intense fishing pressure; copepod abundance, warmer water temperatures and moderate eastward transport were found to be beneficial. In conclusion, in 1988/89 the Northeast Atlantic environment shifted to a favourable regime for northern hake production. This study supports the hypothesis that the hydro-climatic regime shift that affected the North Sea in the late 1980s may have influenced a wider region, such as the Northeast Atlantic. © 2013 John Wiley & Sons Ltd.

  13. Bacterial biomass and heterotrophic potential in the waters of the Chesapeake Bay plume and contiguous continental shelf

    Science.gov (United States)

    Kator, H. I.; Zubkoff, P. L.

    1981-01-01

    Seasonal baseline data on bacterial biomass and heterotrophic uptake in the Chesapeake Bay plume and contiguous Atlantic Ocean shelf waters are discussed. Viable count bacterial numbers in surface water samples collected during June 1980 ranged from a maximum of 190,000 MPN (most probable number)/ml at the Bay mouth to a minimum of 7900 MPN/ml offshore. Similarly, direct count densities ranged from 1,800,000 BU (bacterial units)/ml to 24,000 BU/ml. Heterotrophic potential (V max) was largest at the Bay mouth and lowest offshore. Biomass and V max values usually decreased with depth although subsurface maxima were occasionally observed at inshore stations. Correlation of biomass and heterotrophic potential data with selected hydrographic variables was determind with a nonparametric statistic. Results indicate viable counts are positively and significantly correlated with total chlorophyll, temperature, direct count and V max during June 1980; significant negative correlations are obtained with salinity and depth. Calculations of bacterial standing crop are discussed.

  14. Seismic imaging of small horizontal scale structures of the shallow thermocline on the western Brittany continental shelf (North-East Atlantic)

    Science.gov (United States)

    Piete, H.; Marié, L.; Marsset, B.; Gutscher, M.

    2012-12-01

    The recent development of the seismic oceanography technique has made possible the imaging of a variety of deep oceanographic structures (Holbrook et al., 2003); however, until now this method has remained ill suited for the study of shallow (environment) and 2- spectral contents offering high vertical resolutions (relevant to the mapping of small vertical wavelength structures). In this study we defined and tested a new experimental seismic acquisition system capable of imaging the ~10 m thick seasonal thermocline on the western Brittany continental shelf. To accomplish this task, we pursued two complementary approaches: 1. Analysis of legacy seismic data (multi-channel seismic reflection profiles acquired on the East-Corsican margin, Bahamas Plateau and Gulf of Cadiz in various oceanographic environments) featuring reflectors at depths between 25 and 150 m, in order to identify and quantify the influence of acquisition parameters (seismic trace length, offsets, emission level and frequency content). 2. Incorporation of new oceanographic data acquired during the FROMVAR cruise (July 28th to August 10th 2010) on the western Brittany shelf in thermally stratified waters for use in the simulation of the seismic acquisition, in order to further define the optimal parameters for the system. Finally a 3D seismic system has emerged and was tested during the ASPEX scientific cruise led from June 17th to 19th 2012 across the western Brittany shelf. The device featured: i- four seismic streamers, each consisting of 6 traces at a spacing of 1.80 m; ii- a 1000 J SIG Sparker producing a 400 Hz signal with a 220 dB re 1μPa @1m level of emission, towed at a 8 m distance of the first seismic trace. This survey provided high lateral resolution images of the seasonal thermocline located at a 30 m depth with vertical displacements induced by internal waves. References Holbrook, W.S., Paramo, P., Pearse, S. and Schmitt, R.W., 2003. Thermohaline Fine Structure in an Oceanographic

  15. A Vulnerability Assessment of Fish and Invertebrates to Climate Change on the Northeast U.S. Continental Shelf.

    Directory of Open Access Journals (Sweden)

    Jonathan A Hare

    Full Text Available Climate change and decadal variability are impacting marine fish and invertebrate species worldwide and these impacts will continue for the foreseeable future. Quantitative approaches have been developed to examine climate impacts on productivity, abundance, and distribution of various marine fish and invertebrate species. However, it is difficult to apply these approaches to large numbers of species owing to the lack of mechanistic understanding sufficient for quantitative analyses, as well as the lack of scientific infrastructure to support these more detailed studies. Vulnerability assessments provide a framework for evaluating climate impacts over a broad range of species with existing information. These methods combine the exposure of a species to a stressor (climate change and decadal variability and the sensitivity of species to the stressor. These two components are then combined to estimate an overall vulnerability. Quantitative data are used when available, but qualitative information and expert opinion are used when quantitative data is lacking. Here we conduct a climate vulnerability assessment on 82 fish and invertebrate species in the Northeast U.S. Shelf including exploited, forage, and protected species. We define climate vulnerability as the extent to which abundance or productivity of a species in the region could be impacted by climate change and decadal variability. We find that the overall climate vulnerability is high to very high for approximately half the species assessed; diadromous and benthic invertebrate species exhibit the greatest vulnerability. In addition, the majority of species included in the assessment have a high potential for a change in distribution in response to projected changes in climate. Negative effects of climate change are expected for approximately half of the species assessed, but some species are expected to be positively affected (e.g., increase in productivity or move into the region. These

  16. Highly diverse, poorly studied and uniquely threatened by climate change: an assessment of marine biodiversity on South Georgia's continental shelf.

    Directory of Open Access Journals (Sweden)

    Oliver T Hogg

    Full Text Available We attempt to quantify how significant the polar archipelago of South Georgia is as a source of regional and global marine biodiversity. We evaluate numbers of rare, endemic and range-edge species and how the faunal structure of South Georgia may respond to some of the fastest warming waters on the planet. Biodiversity data was collated from a comprehensive review of reports, papers and databases, collectively representing over 125 years of polar exploration. Classification of each specimen was recorded to species level and fully geo-referenced by depth, latitude and longitude. This information was integrated with physical data layers (e.g. temperature, salinity and flow providing a visualisation of South Georgia's biogeography across spatial, temporal and taxonomic scales, placing it in the wider context of the Southern Hemisphere. This study marks the first attempt to map the biogeography of an archipelago south of the Polar Front. Through it we identify the South Georgian shelf as the most speciose region of the Southern Ocean recorded to date. Marine biodiversity was recorded as rich across taxonomic levels with 17,732 records yielding 1,445 species from 436 families, 51 classes and 22 phyla. Most species recorded were rare, with 35% recorded only once and 86% recorded <10 times. Its marine fauna is marked by the cumulative dominance of endemic and range-edge species, potentially at their thermal tolerance limits. Consequently, our data suggests the ecological implications of environmental change to the South Georgian marine ecosystem could be severe. If sea temperatures continue to rise, we suggest that changes will include depth profile shifts of some fauna towards cooler Antarctic Winter Water (90-150 m, the loss of some range-edge species from regional waters, and the wholesale extinction at a global scale of some of South Georgia's endemic species.

  17. A Vulnerability Assessment of Fish and Invertebrates to Climate Change on the Northeast U.S. Continental Shelf

    Science.gov (United States)

    Hare, Jonathan A.; Morrison, Wendy E.; Nelson, Mark W.; Stachura, Megan M.; Teeters, Eric J.; Griffis, Roger B.; Alexander, Michael A.; Scott, James D.; Alade, Larry; Bell, Richard J.; Chute, Antonie S.; Curti, Kiersten L.; Curtis, Tobey H.; Kircheis, Daniel; Kocik, John F.; Lucey, Sean M.; McCandless, Camilla T.; Milke, Lisa M.; Richardson, David E.; Robillard, Eric; Walsh, Harvey J.; McManus, M. Conor; Marancik, Katrin E.; Griswold, Carolyn A.

    2016-01-01

    Climate change and decadal variability are impacting marine fish and invertebrate species worldwide and these impacts will continue for the foreseeable future. Quantitative approaches have been developed to examine climate impacts on productivity, abundance, and distribution of various marine fish and invertebrate species. However, it is difficult to apply these approaches to large numbers of species owing to the lack of mechanistic understanding sufficient for quantitative analyses, as well as the lack of scientific infrastructure to support these more detailed studies. Vulnerability assessments provide a framework for evaluating climate impacts over a broad range of species with existing information. These methods combine the exposure of a species to a stressor (climate change and decadal variability) and the sensitivity of species to the stressor. These two components are then combined to estimate an overall vulnerability. Quantitative data are used when available, but qualitative information and expert opinion are used when quantitative data is lacking. Here we conduct a climate vulnerability assessment on 82 fish and invertebrate species in the Northeast U.S. Shelf including exploited, forage, and protected species. We define climate vulnerability as the extent to which abundance or productivity of a species in the region could be impacted by climate change and decadal variability. We find that the overall climate vulnerability is high to very high for approximately half the species assessed; diadromous and benthic invertebrate species exhibit the greatest vulnerability. In addition, the majority of species included in the assessment have a high potential for a change in distribution in response to projected changes in climate. Negative effects of climate change are expected for approximately half of the species assessed, but some species are expected to be positively affected (e.g., increase in productivity or move into the region). These results will inform

  18. Simulations and observation of nonlinear internal waves on the continental shelf: Korteweg–de Vries and extended Korteweg–de Vries solutions

    Directory of Open Access Journals (Sweden)

    K. O'Driscoll

    2017-09-01

    Full Text Available Numerical solutions of the Korteweg–de Vries (KdV and extended Korteweg–de Vries (eKdV equations are used to model the transformation of a sinusoidal internal tide as it propagates across the continental shelf. The ocean is idealized as being a two-layer fluid, justified by the fact that most of the oceanic internal wave signal is contained in the gravest mode. The model accounts for nonlinear and dispersive effects but neglects friction, rotation and mean shear. The KdV model is run for a number of idealized stratifications and unique realistic topographies to study the role of the nonlinear and dispersive effects. In all model solutions the internal tide steepens forming a sharp front from which a packet of nonlinear solitary-like waves evolve. Comparisons between KdV and eKdV solutions are made. The model results for realistic topography and stratification are compared with observations made at moorings off Massachusetts in the Middle Atlantic Bight. Some features of the observations compare well with the model. The leading face of the internal tide steepens to form a shock-like front, while nonlinear high-frequency waves evolve shortly after the appearance of the jump. Although not rank ordered, the wave of maximum amplitude is always close to the jump. Some features of the observations are not found in the model. Nonlinear waves can be very widely spaced and persist over a tidal period.

  19. Heavy metals in fish tissues/stomach contents in four marine wild commercially valuable fish species from the western continental shelf of South China Sea.

    Science.gov (United States)

    Gu, Yang-Guang; Lin, Qin; Huang, Hong-Hui; Wang, Liang-Gen; Ning, Jia-Jia; Du, Fei-Yan

    2017-01-30

    The concentrations of heavy metals (Cd, Pb, Cr, Ni, Cu and Zn) were determined in four commercially valuable fish species (Thunnus obesus, Decapterus lajang, Cubiceps squamiceps and Priacanthus macracanthus), collected in the western continental shelf of the South China Sea. Concentrations of Cd, Pb, Cr, Ni, Cu, and Zn in fish muscles were 0.006-0.050, 0.13-0.68, 0.18-0.85, 0.11-0.25, 0.12-0.77, and 2.41-4.73μg/g, wet weight, respectively. Concentrations of heavy metals in all species were below their acceptable daily upper limit, suggesting human consumption of these wild fish species may be safe, with health risk assessment based on the target hazard quotients (THQ) and total THQ, indicating no significant adverse health effects with consumption. The average concentrations of Zn were higher in gills than in stomach contents, backbones or muscle, while conversely, the other heavy metals had higher concentrations in stomach contents than in other tissues. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Do high oil prices justify an increase in taxation in a mature oil province? The case of the UK continental shelf

    International Nuclear Information System (INIS)

    Nakhle, Carole

    2007-01-01

    In response to the structural shift in oil price coupled with greater import dependency, concerns about security of supply have once again emerged as a major policy issue. The UK, the largest producer of oil and natural gas in the European Union, became a net importer of natural gas in 2004, and according to Government estimates will become a net importer of oil by the end of the decade. A weakened North Sea performance means extra reliance, both for the UK and Europe as a whole, on global oil and gas network and imports. In 2002, the UK Government introduced a 10% supplementary charge and in 2005, doubled the charge to 20% in an attempt to capture more revenues from the oil industry as a result of the increase in the price of crude oil. However, higher tax rates do not necessarily generate higher fiscal revenue and in the long term may result in materially lower revenues if investment is discouraged as indeed occurred when the 2007 UK Annual Budget statement showed a shortfall in North Sea oil revenues below forecasts of Pounds 4 billion. It is therefore argued that the increase in the fiscal take came at the wrong time for the UK Continental Shelf and that the UK Government's concern should have been to encourage more oil production from its declining province, especially in the light of the rising concern surrounding the security of supply

  1. The use of 234Th/238U disequilibrium to examine the fate of particle-reactive species on the Yangtze continental shelf

    International Nuclear Information System (INIS)

    McKee, B.A.; DeMaster, D.J.; Nittrouer, C.A.

    1984-01-01

    Measurements of 234 Th (tsub(1/2)=24.1 d) in water column and seabed samples from an area near the mouth of the Yangtze River (People's Republic of China) provide the following information: Most of the 234 Th in waters near the mouth of the Yangtze River is in particulate form, and horizontal transport and sedimentation of 234 Th-bearing particles dominate the 234 Th budget in this area. A model incorporating processes in at least two dimensions is required to understand the fate of particle-reactive species on the Yangtze continental shelf. The residence times of particle-reactive species (with respect to scavenging) range from 0.3 days (nearshore) to 4.0 days (offshore). The residence times (with respect to removal to the seabed) range from 0.5 day (nearshore) to 11.0 days (offshore). Scavenging residence times for 234 Th decrease as the concentration of suspended particles increases. The time for removal of 234 Th to the seabed increases with distance from shore (a variable which integrates such factors as scavenging rate, bathymetry, and frequency of resuspension). (orig.)

  2. Assessing the impact of Hurricanes Irene and Sandy on the morphology and modern sediment thickness on the inner continental shelf offshore of Fire Island, New York

    Science.gov (United States)

    Schwab, William C.; Baldwin, Wayne E.; Denny, Jane F.

    2016-01-15

    This report documents the changes in seabed morphology and modern sediment thickness detected on the inner continental shelf offshore of Fire Island, New York, before and after Hurricanes Irene and Sandy made landfall. Comparison of acoustic backscatter imagery, seismic-reflection profiles, and bathymetry collected in 2011 and in 2014 show that sedimentary structures and depositional patterns moved alongshore to the southwest in water depths up to 30 meters during the 3-year period. The measured lateral offset distances range between about 1 and 450 meters with a mean of 20 meters. The mean distances computed indicate that change tended to decrease with increasing water depth. Comparison of isopach maps of modern sediment thickness show that a series of shoreface-attached sand ridges, which are the dominant sedimentary structures offshore of Fire Island, migrated toward the southwest because of erosion of the ridge crests and northeast-facing flanks as well as deposition on the southwest-facing flanks and in troughs between individual ridges. Statistics computed suggest that the modern sediment volume across the about 81 square kilometers of common sea floor mapped in both surveys decreased by 2.8 million cubic meters, which is a mean change of –0.03 meters, which is smaller than the resolution limit of the mapping systems used.

  3. The Northeast Greenland Shelf as a Potential Habitat for the Northeast Arctic Cod

    Directory of Open Access Journals (Sweden)

    Kjersti O. Strand

    2017-09-01

    Full Text Available Observations (1978–1991 of distributions of pelagic juvenile Northeast Arctic cod (Gadus morhua L. show that up to 1/3 of the year class are dispersed off the continental shelf and into the deep Norwegian Sea while on the way from the spring-spawning areas along the Norwegian coast to the autumn-settlement areas in the Barents Sea. The fate of this variable fraction of pelagic juveniles off-shelf has been an open question ever since Johan Hjort's (1914 seminal work. We have examined both the mechanisms causing offspring off-shelf transport, and their subsequent destiny using an individual-based biophysical model applied to quantify growth and dispersal. Our results show, consistently with the observations, that total off-shelf transport is highly variable between years and may be up to 27.4%. Offspring from spawning grounds around Lofoten have a higher chance of being displaced off the shelf. The off-shelf transport is dominated by episodic events where frequencies and dates vary between years. Northeasterly wind conditions over a 3–7-day period prior to the off-shelf events are a good proxy for dispersal of offspring off the shelf. Offspring transported into the open ocean are on average carried along three following routes: back onto the adjacent eastern shelves and into the Barents Sea (36.9%, recirculating within the Lofoten Basin (60.7%, or drifting northwest to the northeast Greenland shelf (2.4%. For the latter fraction the transport may exceed 12% depending on year. Recent investigations have discovered distributions of young cod on the northeast Greenland shelf indicating that conditions may support survival for Northeast Arctic cod offspring.

  4. Sandwave Morphologies and Dynamics in a Continental Shelf Environment : Example of the Banc du Four (western Brittany, France)

    Science.gov (United States)

    Franzetti, M.; Garlan, T.; Le Roy, P.; Delacourt, C.; Cancouët, R.; Graindorge, D.; Deschamps, A.

    2011-12-01

    Marine sand dunes and sandbanks are mainly observed in continental tidal shelves (North Sea, South China Sea, North Atlantic America) and may be highly dynamic (for example up to 75 m/y in the Marsdiep inlet). So they may pose a potential risk to offshore installations and shipping. Multitemporal mapping of sandwaves, necessary to mitigate this hazard, is complicated by their dynamic character, which is still poorly understood especially in the offshore domain. In consequence, these structures are often defined as moribund at depths greater than 30 meters. The aim of this investigation is to study evolution of deeper (110 meters) complex set of sand bedforms : "Banc du Four" located in the Iroise Sea. The study area is exposed to strong tidal currents and storm waves at the junction of the Northeast Atlantic Ocean and the Western English Channel, conditions favorable to sediment dynamics. The bathymetric data, which form the basis of this study, are two Digital Terrain Modeling's (DTM's) derived from MultiBeam Echosounder (MBES) surveys : "Pourquoi-Pas?" oceanographic research vessel (R/V) in February 2009 (5 meters resolution DTM) and R/V "Albert Lucas" in August 2010 (2 meters resolution DTM). Sandwave parameters (water depth, shape, wavelength, height, symmetry index, ...) have been derived from the 2009 bathymetric data. The Banc du Four is characterized by a large sandbank (45 meters height and 2 km width) flanked by dune fields. The morphological characteristics of the dunes vary greatly (range 30 to 110 meters depth, 40 meters maximal height, 600 meters maximal width, symmetrical to asymmetrical, ...). However, this complexity can be explained by the involved sandwave dynamic (range 0 to 30 meters per year migration velocity). Spatial correlation method, applied on the two DTM's, are used to measure the migration rate. The high migration rates for deeper giant dunes bring to light the dynamic sandwave existence at depths exceeding 30-40 meters, contrary to

  5. Submission of Republica Oriental del Uruguay to the Commission on the limits of the continental shelf pursuant to provisions of article 76, paragraph 8, of the United Nations Convention on the Law of the Sea: executive summary

    International Nuclear Information System (INIS)

    Mata Prates, C.; Tajes, J.; Burgos, M.; Caamaño; Lamartheé; Montiel, D.; Preciozzi, F.; De Santa Ana, H.

    2009-01-01

    Pursuant to provisions of article 76 of the United Nations Convention on the Law of the Sea (hereinafter the Convention), and to article 4 of Annex II of same, República Oriental del Uruguay (Uruguay) hereby submits to the Commission on the Limits of the Continental Shelf (the Commission) particulars on the outer limit of its continental shelf, extending beyond 200 nautical miles (M) from the baselines from which the breadth of territorial sea is measured. On December 10, 1982 Uruguay signed the Convention, which was subsequently approved by Uruguayan Law Nº 16,287, and ratified on December 10, 1992. The porvisions of article 76 invoked in Uruguay submission fixed points delimiting Uruguay’s Continental Shelf. There exist, at present, no unresolved disputes over the maritime border with either of Uruguay’s neighbouring countries, Argentina or Brazil. It was received assistance in the elaboration of this Submission April 2008, from member of the Commission and also assistance from other, non-member consultants and institutions from Germany, Brazil, Portugal and Norway

  6. Norwegian gas supplies for the European market

    International Nuclear Information System (INIS)

    Hansen, B.L.

    1994-01-01

    The conference paper deals with the Norwegian key role in the European gas market with increasing market shares. The supply capacity in a long-term perspective can be 65-70 bcm/year or more if export prices support the development of new and more costly gas resources. The main challenges for the Norwegian shelf are discussed. 5 figs

  7. Geochemistry and microbiology data collected from bottle casts from the R/V HERMANO GINES from the continental shelf of Venezuela in support of the Carbon Retention in a Colored Ocean (CARIACO) project from 19 January to 7 December 2010 (NODC Accession 0066503)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This accession contains bottle data collected aboard the R/V HERMANO GINES from the continental shelf of Venezuela during 19 January, 2009 (CAR-153); 16 May to 17...

  8. Physical, chemical and biological data collected from CTD and bottle casts from the R/V HERMANO GINES from the Caribbean Sea and continental shelf of Venezuela in support of the Carbon Retention in a Colored Ocean (CARIACO) project from 2008 - 2010 (NODC Accession 0069000)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — CTD and bottle data were collected from R/V HERMANO GINES on the continental shelf of Venezuela from 10 September 2008 to 7 January 2010, during cruises Car149...

  9. Physical, chemical, and nutrient data collected from CTD and bottle casts from the R/V HERMANO GINES from the continental shelf of Venezuela in support of the Carbon Retention in a Colored Ocean (CARIACO) project from 10 April 2007 to 05 August December 2008 (NODC Accession 0056729)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — CTD and bottle data were collected from R/V HERMANO GINES on the continental shelf of Venezuela from 10 April 2007 to 05 August 2008. Data were collected by the...

  10. Paleomagnetism and rock magnetism from sediments along a continental shelf-to-slope transect in the NW Barents Sea: Implications for geomagnetic and depositional changes during the past 15 thousand years

    Science.gov (United States)

    Caricchi, C.; Lucchi, R. G.; Sagnotti, L.; Macrì, P.; Morigi, C.; Melis, R.; Caffau, M.; Rebesco, M.; Hanebuth, T. J. J.

    2018-01-01

    Paleomagnetic and rock magnetic data were measured on glaciomarine silty-clay successions along an E-W sediment-core transect across the continental shelf and slope of the Kveithola paleo-ice stream system (south of Svalbard, north-western Barents Sea), representing a stratigraphic interval spanning the last deglaciation and the Holocene. The records indicate that magnetite is the main magnetic mineral and that magnetic minerals are distinctly less abundant on the shelf than at the continental slope. The paleomagnetic properties allow for the reconstruction of a well-defined characteristic remanent magnetization (ChRM) throughout the sedimentary successions. The stratigraphic trends of rock magnetic and paleomagnetic parameters are used for a shelf-slope core correlation and sediment facies analysis is applied for depositional processes reconstruction. The new paleomagnetic records compare to the PSV and RPI variation predicted for the core sites by a simulation using the global geomagnetic field variation models SHA.DIF.14k and CALS7K.2 and closest PSV and RPI regional stack curves. The elaborated dataset, corroborated by available 14C ages, provides a fundamental chronological framework to constrain the coupling of shelf-slope sedimentary processes and environmental changes in the NW Barents Sea region during and after deglaciation.

  11. Arctic Ocean outflow and glacier-ocean interactions modify water over the Wandel Sea shelf (northeastern Greenland)

    DEFF Research Database (Denmark)

    Dmitrenko, Igor A.; Kirillov, Sergey A.; Rudels, Bert

    2017-01-01

    The first-ever conductivity-temperature-depth (CTD) observations on the Wandel Sea shelf in northeastern Greenland were collected in April-May 2015. They were complemented by CTDs taken along the continental slope during the Norwegian FRAM 2014-2015 drift. The CTD profiles are used to reveal...... the origin of water masses and interactions with ambient water from the continental slope and the tidewater glacier outlet. The subsurface water is associated with the Pacific water outflow from the Arctic Ocean. The underlying halocline separates the Pacific water from a deeper layer of polar water that has...... interacted with the warm Atlantic water outflow through the Fram Strait, recorded below 140 m. Over the outer shelf, the halocline shows numerous cold density-compensated intrusions indicating lateral interaction with an ambient polar water mass across the continental slope. At the front of the tidewater...

  12. Modelo numérico tri-dimensional linear da plataforma continental do Estado do Maranhão Linear three-dimensional numerical model of Maranhão State continental shelf

    Directory of Open Access Journals (Sweden)

    José Edson Rodrigues Pereira

    1995-01-01

    Full Text Available Um modelo numérico hidrodinámico tri-dimensional linear, do tipo Heaps, foi implementado para a plataforma continental do Estado do Maranhão, visando a simulação da circulação gerada por efeitos astronômicos e meteorológicos na área. O modelo foi processado para cinco condições, a fim de calcular a circulação na plataforma devida aos seguintes efeitos: componente de maré semi-diurna lunar principal (M2, composição das principais componentes astronômicas de maré na área, condições meteorológicas médias de verão, condições meteorológicas médias de inverno e forçantes de maré em períodos específicos de interesse. Mapas cotidais e elipses de correntes da componente M2 foram obtidos, sendo esta componente preponderante na circulação local. Elevações e correntes sazonais médias são, em geral, muito menores que as astronômicas, permitindo o uso apenas de forçantes de maré em previsões hidrodinámicas. As simulações do modelo foram satisfatórias na plataforma e menos precisas nas baías e áreas internas rasas, onde atrasos de fase significativos são observados, devido a efeitos de menor escala que a adotada pelo modelo.A linear three-dimensional hydrodynamical numerical model, Heaps type, was implemented to the continental shelf of Maranhão State, aiming the simulation of the circulation generated by astronomical and meteorological effects in that area. Five runs of the model were performed, in order to compute the circulation in the shelf due to the following effects: principal lunar semi-diurnal component (M2, composition of the principal astronomical components in the area, mean summer meteorological conditions, mean winter meteorological conditions and tidal forcing in specific periods of interest. M2 cotidal maps and currents ellipses were obtained, that one being the most important component in the tidal circulation. Mean seasonal elevations and currents are generally much smaller than the

  13. The Morphologic Evolution of the Amazon Coastal Plain, Cabo Norte, Amapa, Brazil: The Need for Integrated Investigation on the Internal Continental Shelf.

    Science.gov (United States)

    Silveira, O.; Santos, V. F.; Takiyama, L. R.

    2007-05-01

    refers to the coastal zone between the Amapa Grande River and Araguari River, including Maraca Island and the Oriental lacustrine Belt. Westward the island, at least three paleolevels of clays with roots in life position suggests regressive/transgressive events. Extraordinaty paleodrainage network beginnig at the continent and recognized at the insular portion suggests links with the paleochannels found at the continental shelf. The Oriental Belt of lakes is located close to the coastline, at Cabo Norte. It main feature is a mud lump approximately 10 Km ratio, well recognized at the remote sensing. It shows similar evolutionary processes with Araguari River, dating from XIX century, when this river had two mouths defined by the Carpori Island. The reasons of the deactivation are still unknowed, but, this rapid morphological evolution indicates short time colmatation processes that can be linked to tectonic regional processes. On the other hand, the Cabo Norte feature consolidation may impose changes in the sedimentation processes yielding space reduction over the coastal plain accumulation, diminishing of the solid and liquid fluvial discharge and promoting the availability of the local sediment transport over the littoral. The investigation of these processes requires an integrated coastal plain-continental shelf morphological study applying adequate techniques for modification studies and dating ages over short geological time frame, in century scale level.

  14. Continental-shelf Scale Passive Ocean AcousticWaveguide Remote Sensing of Marine Mammals and other Submerged Objects including Detection, Localization, and Classification

    Science.gov (United States)

    Wang, Delin

    In this thesis, we develop the basics of the Passive Ocean Acoustic Waveguide Remote Sensing (POAWRS) technique for the instantaneous continental-shelf scale detection, localization and species classification of marine mammal vocalizations. POAWRS uses a large-aperture, densely sampled coherent hydrophone array system with orders of magnitude higher array gain to enhance signal-to-noise ratios (SNR) by coherent beamforming, enabling detection of underwater acoustic signals either two orders of magnitude more distant in range or lower in SNR than a single hydrophone. The ability to employ coherent spatial processing of signals with the POAWRS technology significantly improves areal coverage, enabling detection of oceanic sound sources over instantaneous wide areas spanning 100 km or more in diameter. The POAWRS approach was applied to analyze marine mammal vocalizations from diverse species received on a 160-element Office Naval Research Five Octave Research Array (ONR-FORA) deployed during their feeding season in Fall 2006 in the Gulf of Maine. The species-dependent temporal-spatial distribution of marine mammal vocalizations and correlation to the prey fish distributions have been determined. Furthermore, the probability of detection regions, source level distributions and pulse compression gains of the vocalization signals from diverse marine mammal species have been estimated. We also develop an approach for enhancing the angular resolution and improving bearing estimates of acoustic signals received on a coherent hydrophone array with multiple-nested uniformly-spaced subapertures, such as the ONR-FORA, by nonuniform array beamforming. Finally we develop a low-cost non-oil-filled towable prototype hydrophone array that consists of eight hydrophone elements with real-time data acquisition and 100 m tow cable. The approach demonstrated here will be applied in the development of a full 160 element POAWRS-type low-cost coherent hydrophone array system in the future.

  15. Principal Component Analysis and Morphostructural Characterization of a Portion of The Eastern Continental Shelf of Ceará, Brazil, Using Landsat 5-Tm Images

    Directory of Open Access Journals (Sweden)

    Cynthia Romariz Duarte

    2016-09-01

    Full Text Available This study used Landsat 5 Thematic Mapper (5-TM images in the morphostructural characterization of the shallow continental shelf of the eastern coast of Ceará (CE, in the Jaguaribe river mouth. The dam built near the river mouth to transpose the water towards Fortaleza, CE, ensures good water transparency since little of the river-carried sediment reaches the sea. The used image was captured on date and time to ensure low tide. Data using Secchi disc indicated good water transparency in the turbidity zone and seaside, coastal and marine areas. Bathymetry studies and underwater photos confirm the existence of many of the features described in this study. Digital image processing techniques have been applied in the study: colored compositions (RGB 124, 90° directional filter (band 1, and a colored composition employing the filtered band 1 and band 2 and 4. The filtered image of band 1 allowed recognizing different features when interpreted in detail scale. The principal component analysis (PCA was used here, calculating eigenvalues and eigenvectors. When applied to bands 1 to 5 and 7, PCA generated good results in PC2, whose correlation with the blue band was 0.85 (explained cumulative variance of more than 96%. Applied to the visible bands, PCA produced very similar results in PC1, and the correlation between the blue band and PC1 was 0.86 (explained cumulative variance of 94%. These results show that band 1 is the main contributor in studies of submerged morphological features. Each process resulted in a new image, from which it was possible to produce the map of the area representing morphostructural characteristics. The use of digitally processed satellite images in the visible region greatly improves the characterization and mapping of submerged features in places with shallow and good transparency waters.

  16. Coexisting sea-based and land-based sources of contamination by PAHs in the continental shelf sediments of Coatzacoalcos River discharge area (Gulf of Mexico).

    Science.gov (United States)

    Ruiz-Fernández, Ana Carolina; Portela, Julián Mauricio Betancourt; Sericano, José Luis; Sanchez-Cabeza, Joan-Albert; Espinosa, Luisa Fernanda; Cardoso-Mohedano, José Gilberto; Pérez-Bernal, Libia Hascibe; Tinoco, Jesús Antonio Garay

    2016-02-01

    The oldest refinery and the major petrochemical complexes of Mexico are located in the lower reach of the Coatzacoalcos River, considered the most polluted coastal area of Mexico. A (210)Pb-dated sediment core, from the continental shelf of the Coatzacoalcos River, was studied to assess the contamination impact by the oil industry in the southern Gulf of Mexico. The sedimentary record showed the prevalence of petrogenic PAHs between 1950s and 1970s, a period during which waste discharges from the oil industry were not regulated. Later on, sediments exhibited higher contents of pyrogenic PAHs, attributed to the incineration of petrochemical industry wastes and recurrent wildfires in open dumpsites at the nearby swamps. The total concentration of the 16 EPA-priority PAHs indicated low levels of contamination (1000 ng g(-1)) during the late 1970s, most likely due to the major oil spill produced by the blowout of the Ixtoc-I offshore oil rig in deep waters of the southwestern Gulf of Mexico. Most of the PAH congeners did not show defined temporal trends but, according to a Factor Analysis, apparently have a common origin, probably waste released from the nearby oil industry. The only exceptions were the pyrogenic benzo(b)fluoranthene and benzo(a)pyrene, and the biogenic perylene, that showed increasing concentration trends with time, which we attributed to erosional input of contaminated soil from the catchment area. Our study confirmed chronic oil contamination in the Coatzacoalcos River coastal area from land based sources for more than 60 years (since 1950s). Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Spatial distribution of southern brown shrimp (Farfantepenaeus subtilis on the Amazon continental shelf: a fishery, marine geology and GIS integrated approach

    Directory of Open Access Journals (Sweden)

    Déborah E. G. Martins

    2015-12-01

    Full Text Available Abstract The spatial distribution of the southern brown shrimp Farfantepenaeus subtilis (Pérez-Farfante, 1967 was studied based on industrial fishing fleet activities and is associated with geological and oceanographic characteristics of the benthonic environments on the Amazon continental shelf. Using a geographical information system (GIS this paper sought to calculate the relative abundance of brown shrimp based on catch per unit effort (CPUE and compare it with bathymetry, type of sedimentary structure, sedimentation rate and bottom salinity. As a result, we have concluded that the relative abundance (in terms of CPUE is not uniformly distributed in space. Spatial analysis indicates that commercial trawling efforts were made in the (foreset region of the subaqueous Amazon delta at depths of 40 to 60 m. In this region, prawn are responsible for the bioturbation of the sediments and the creation of a sedimentary structure called mottled mud. In the foreset region, sedimentation rates progressively increased up to 10 cm.yr-1; re-suspension was reduced and bottom salinity was high (~ 36. It appears that all of these factors define a stable muddy area with intense bioturbation. This notable biological activity is to be explained by the occurrence of a high F. subtilis abundance that appears to originate in a microbial loop. We concluded that by combining fishery information with environmental data from a GIS, it was possible to identify abundance distribution patterns for southern brown shrimp and other economically important fishery resources and to understand how they change on a large spatial-scale.

  18. Environment 2002. The Norwegian petroleum sector

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-07-01

    The Ministry of Petroleum and Energy produces an annual environmental review in cooperation with the Norwegian Petroleum Directorate. The purpose of this publication is threefold: (1) to increase knowledge about the environmental aspects of Norwegian oil and gas activities, (2) to take a more detailed look at a specific topic which particularly concerns both the industry and the authorities, and identify the challenges and options faced, (3) to emphasise the governments goal of ensuring that Norway reconciles its role as a large energy producer with a pioneering position on environmental issues. This year's edition focuses on the topic of ''oil and fish - common sea''. Both the petroleum and fishing industries depend on the waters off Norway. Ever since petroleum activities began on the Norwegian continental shelf more than 30 years ago, the authorities have been keen to ensure that these two sectors can work in the same sea areas. What challenges and opportunities face the petroleum industry over discharges to the sea and living marine resources? How can the authorities ensure that this sector is able to coexist with the fisheries? These and similar questions about the relationship between the petroleum and fishing industries in their shared seas are covered in section two of this publication. Environment 2002 also incorporates a factual section, which covers the status of emissions/discharges, environmental impacts and measures to reduce discharges to the sea and emissions to the air from petroleum activities. The MPE hopes that a publication of this kind can enhance basic knowledge about petroleum activities and environmental issues.

  19. Environment 2002. The Norwegian petroleum sector

    International Nuclear Information System (INIS)

    2002-01-01

    The Ministry of Petroleum and Energy produces an annual environmental review in cooperation with the Norwegian Petroleum Directorate. The purpose of this publication is threefold: (1) to increase knowledge about the environmental aspects of Norwegian oil and gas activities, (2) to take a more detailed look at a specific topic which particularly concerns both the industry and the authorities, and identify the challenges and options faced, (3) to emphasise the governments goal of ensuring that Norway reconciles its role as a large energy producer with a pioneering position on environmental issues. This year's edition focuses on the topic of ''oil and fish - common sea''. Both the petroleum and fishing industries depend on the waters off Norway. Ever since petroleum activities began on the Norwegian continental shelf more than 30 years ago, the authorities have been keen to ensure that these two sectors can work in the same sea areas. What challenges and opportunities face the petroleum industry over discharges to the sea and living marine resources? How can the authorities ensure that this sector is able to coexist with the fisheries? These and similar questions about the relationship between the petroleum and fishing industries in their shared seas are covered in section two of this publication. Environment 2002 also incorporates a factual section, which covers the status of emissions/discharges, environmental impacts and measures to reduce discharges to the sea and emissions to the air from petroleum activities. The MPE hopes that a publication of this kind can enhance basic knowledge about petroleum activities and environmental issues

  20. Can Continental Shelf River Plumes in the Northern and Southern Gulf of Mexico Promote Ecological Resilience in a Time of Climate Change?

    Directory of Open Access Journals (Sweden)

    G. Paul Kemp

    2016-03-01

    Full Text Available Deltas and estuaries built by the Mississippi/Atchafalaya River (MAR in the United States and the Usumacinta/Grijalva River (UGR in Mexico account for 80 percent of all Gulf of Mexico (GoM coastal wetlands outside of Cuba. They rank first and second in freshwater discharge to the GoM and owe their natural resilience to a modular geomorphology that spreads risk across the coast-scape while providing ecosystem connectivity through shelf plumes that connect estuaries. Both river systems generate large plumes that strongly influence fisheries production over large areas of the northern and southern GoM continental shelves. Recent watershed process simulations (DLEM, MAPSS driven by CMIP3 General Circulation Model (GCM output indicate that the two systems face diverging futures, with the mean annual discharge of the MAR predicted to increase 11 to 63 percent, and that of the UGR to decline as much as 80 percent in the 21st century. MAR delta subsidence rates are the highest in North America, making it particularly susceptible to channel training interventions that have curtailed a natural propensity to shift course and deliver sediment to new areas, or to refurbish zones of high wetland loss. Undoing these restrictions in a controlled way has become the focus of a multi-billion-dollar effort to restore the MAR delta internally, while releasing fine-grained sediments trapped behind dams in the Great Plains has become an external goal. The UGR is, from an internal vulnerability standpoint, most threatened by land use changes that interfere with a deltaic architecture that is naturally resilient to sea level rise. This recognition has led to successful efforts in Mexico to protect still intact coastal systems against further anthropogenic impacts, as evidenced by establishment of the Centla Wetland Biosphere Preserve and the Terminos Lagoon Protected Area. The greatest threat to the UGR system, however, is an external one that will be imposed by the

  1. Munitions and Explosives of Concern Survey Methodology and In-field Testing for Wind Energy Areas on the Atlantic Outer Continental Shelf

    Science.gov (United States)

    DuVal, C.; Carton, G.; Trembanis, A. C.; Edwards, M.; Miller, J. K.

    2017-12-01

    Munitions and explosives of concern (MEC) are present in U.S. waters as a result of past and ongoing live-fire testing and training, combat operations, and sea disposal. To identify MEC that may pose a risk to human safety during development of offshore wind facilities on the Atlantic Outer Continental Shelf (OCS), the Bureau of Ocean Energy Management (BOEM) is preparing to develop guidance on risk analysis and selection processes for methods and technologies to identify MEC in Wind Energy Areas (WEA). This study developed a process for selecting appropriate technologies and methodologies for MEC detection using a synthesis of historical research, physical site characterization, remote sensing technology review, and in-field trials. Personnel were tasked with seeding a portion of the Delaware WEA with munitions surrogates, while a second group of researchers not privy to the surrogate locations tested and optimized the selected methodology to find and identify the placed targets. This in-field trial, conducted in July 2016, emphasized the use of multiple sensors for MEC detection, and led to further guidance for future MEC detection efforts on the Atlantic OCS. An April 2017 follow on study determined the fate of the munitions surrogates after the Atlantic storm season had passed. Using regional hydrodynamic models and incorporating the recommendations from the 2016 field trial, the follow on study examined the fate of the MEC and compared the findings to existing research on munitions mobility, as well as models developed as part of the Office of Naval Research Mine-Burial Program. Focus was given to characterizing the influence of sediment type on surrogate munitions behavior and the influence of mophodynamics and object burial on MEC detection. Supporting Mine-Burial models, ripple bedforms were observed to impede surrogate scour and burial in coarse sediments, while surrogate burial was both predicted and observed in finer sediments. Further, incorporation of

  2. 日本外大陆架划界申请案内涵与中国的立场%The Contents of Japan's Submission on the Extended Continental Shelf and China's Position

    Institute of Scientific and Technical Information of China (English)

    金永明; ZHANG Chao

    2009-01-01

    日本经过连续五年的大陆架调查工作,终于向大陆架界限委员会提交了外大陆架划界申请案,其申请面积极其广袤,约为日本国土面积的2倍.为提交外大陆架申请案,日本在组织机构配置、调查任务分工、财政上均予以了大力协助和支持,提早完成了调查任务.应注意的是,在日本外大陆架划界申请案中,冲之鸟礁是作为日本申请外大陆架的基点.这种主张是不符合《联合国海洋法公约》关于岛屿的规定的,相关部分必不能通过审议.%After five consecutive years of surveying the continental shelf,Japan finally made the submission to establish the limits of its continental shelf to the Commission on the Limits of the Continental Shelf (CLCS).The submission covers an extremely vast area that is about twice the size of Japan's land area.To prepare its submission,Japan committed itself to providing robust support and collaborative efforts to configure the organizational structure,divide the survey's tasks,and guarantee the finances,completing the survey ahead of schedule.It should be noted that in Japan's submission on the limits of the continental shelf,Oki-no-Tori acts as the base point.This claim does not comply with the provisions on islands in the United Nations Convention on the Law of the Sea,and the relevant content in the submission definitely will not be approved in the CLCS's considerations.

  3. The outlook for investment in the Norwegian North Sea

    International Nuclear Information System (INIS)

    Enger, T.

    1992-01-01

    An outline of the investment potential for oil and gas production on the Norwegian continental shelf is given. The continental shelf includes the Haltenbanken area and the Barents Sea as well as the North Sea. A description of existing projects and present knowledge of future prospects is given. The total production of oil and gas in 1990 was 107 million toe, the ratio of oil to gas production being 4:1. The relationship between oil and gas will change dramatically in the future however as the gas share in fields under development is much greater than in currently producing fields. The greatest potential for gas is expected to be in the Barents Sea which, being located at a considerable distance from existing gas markets presents a great challenge for commercial development. The conclusion drawn from the outline is that the present level of investment will be maintained or increase slightly over the next four to five years. For the period up to the turn of the century there is increasing uncertainty over the investment level which will become more and more dependent upon further expansion of gas exports but a best estimate is for continued investment stability beyond the year 2000. The production level can be expected to increase and reach a peak during the late 1990s. The resource base is sufficient to maintain a high production level for several decades after the year 2000. (UK)

  4. Experience with the use of copper alloys in seawater systems in the Norwegian sector of the North Sea

    Energy Technology Data Exchange (ETDEWEB)

    Johnsen, Roy [Norwegian University of Science and Technology, NO-7491 Trondheim (Norway)

    2004-07-01

    Offshore oil and gas has been produced on the Norwegian Continental Shelf (NCS) for nearly 30 years. Seawater has been used extensively as cooling medium and firewater. Copper alloys have been an alternative material both for piping and equipment like pumps, valves, heat exchangers and screens. In this presentation the experience from the use from different oil companies will be presented. The paper will also contain a discussion about the future for copper alloys in seawater systems. This part will be based on input and discussions with senior corrosion specialists in oil companies. (authors)

  5. Summer composition and distribution of the jellyfish (Cnidaria: Medusozoa in the shelf area off the central Mexican Pacific Composición y distribución de las medusas (Cnidaria: Medusozoa en la plataforma continental central del Pacifico mexicano

    Directory of Open Access Journals (Sweden)

    Lourdes Segura-Puertas

    2010-04-01

    Full Text Available The composition, distribution, and abundance of the jellyfish community of a shelf area of the Mexican tropical Pacific were surveyed during August 1988. Zooplankton samples were collected along transects on the outer and inner sectors of the continental shelf to determine the structure of the jellyfish community and its variation in this area during the rainy season. A total of 23 species were recorded, with Aglaura hemistoma, Solmundella bitentaculata, Liriope tetraphylla, Pelagia noctiluca, and Rhopalonema velatum being the most abundant. The total abundance of medusae and of the most abundant species was statistically independent of depth and distance to the coast. Hence, the total jellyfish abundance of the most abundant species, and Shannon's Diversity index had a uniform distribution in both the inner and the outer shelf; furthermore, neritic-oceanic forms and oceanic species occurred indistinctly over the entire continental shelf. On the outer shelf A. hemistoma and S. bitentaculata were most abundant; the former species, together with L. tetraphylla, weakly characterized the inner shelf jellyfish community. The narrowness of the shelf, the wide distribution of the most abundant forms, and the possible effect of local advective processes from the oceanic zone masked a definite gradient across the shelf. Three species have not been recorded previously in the Mexican Pacific: Amphinema dinema (Péron and Lesueur, 1810, Sarsia coccometra Bigelow, 1909, and Clytia mccradyi (Brooks, 1888. The finding of A. dinema is the first in the Eastern Pacific.Se estudió la composición, distribución y abundancia de la comunidad de medusas de la plataforma continental en el Pacífico mexicano durante agosto 1988. Las muestras de zooplancton provienen de transectos en las zonas externa e interna de la plataforma para determinar la estructura de la comunidad de medusas y su variación durante la época de lluvias. Se identificaron 23 especies; las m

  6. Distribution of Al, Mn, Ni, Co & Cu in the non-lithogenous fractions of sediments of the northern half of the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, P.S.N.; Rao, Ch.M.; Paropkari, A.L.; Topgi, R.S.

    of the outer shelf region with high calcium carbonate content and all the elements covary with each other in the environment. From an evaluation of the role of different processes with the incorporation of elements, particularly trace elements...

  7. Links between the recruitment success of northern European hake (Merluccius merluccius L.) and a regime shift on the NE Atlantic continental shelf

    KAUST Repository

    Goikoetxea, Nerea; Irigoien, Xabier

    2013-01-01

    variables in the North Sea also affected the Northeast Atlantic shelf oceanography. Hake recruitment success as well as parameters such as the sea surface temperature, wind patterns and copepod abundance changed significantly at the end of the 1980s

  8. Comparison of the Northeast Arctic cod year class strength (at the age of 3+) with the SST anomalies in main spawning ground (the Norwegian Shelf Waters) by results of analysis satellite monitoring data during last years.

    Science.gov (United States)

    Vanyushin, George

    2015-04-01

    Continuous long-term database (1998-2014) on the sea surface temperature (SST) comprising results of regional satellite monitoring (the Norwegian and the Barents seas) is used to resolve several applied problems. Authors have analyzed indirect influence the SST (the NOAA satellite data) on modern cod total stock biomass (abundance of the Northeast Arctic cod at age 3+). In this study, we went on the consideration of the relationship between the SST anomalies for March-April in the main spawning ground of the cod off the Lofoten islands in the Norwegian Shelf Waters and forecasting assessment of future cod generation success and its future abundance of 3 year old. Mean monthly SST and SST anomalies are computed for the selected area on the basis of the weekly SST maps which made by using the NOAA satellites data for the period 1998-2014. Comparison of the SST anomalies in the main spawning ground with abundance of the cod year class at age 3+ shows that survival of the cod generations was inhibited on the whole as negative (below -0,1C) well as positive SST anomalies (above +1,3C) during March and April. Finally, the results indicate that poor and low middle generations of cod at age 3+ (2002, 2004, 2010) occurred in years with negative or extremely high positive the SST anomalies in the spawning area. The SST anomalies in years which were close to normal significances provide conditions for appearance middle or strong generations of cod (2001-2003, 2005-2009, 2011-2013). So, the SST and SST anomalies (by the NOAA satellite data) characterize of increase in input of warm Atlantic waters which form numerous eddies along the main stream thus creating favorable conditions for spawning and development of the cod larvae and fry and provide them with food stock, finally direct influence on forming total stock biomass of cod and helping its population forecast. Key words: satellite monitoring of SST, the Northeast Arctic cod, spawning ground, forecast of the cod year class

  9. Over 10 million seawater temperature records for the United Kingdom Continental Shelf between 1880 and 2014 from 17 Cefas (United Kingdom government) marine data systems

    Science.gov (United States)

    Morris, David J.; Pinnegar, John K.; Maxwell, David L.; Dye, Stephen R.; Fernand, Liam J.; Flatman, Stephen; Williams, Oliver J.; Rogers, Stuart I.

    2018-01-01

    around the British Isles, although cross-matching with satellite-derived data for surface temperatures at specific times and in specific areas is another area in which the data could be of value (see e.g. Smit et al., 2013). Maps are provided indicating geographical coverage, which is generally within and around the UK Continental Shelf area, but occasionally extends north from Labrador and Greenland to east of Svalbard and southward to the Bay of Biscay. Example potential uses of the data are described using plots of data in four selected groups of four ICES rectangles covering areas of particular fisheries interest. The full dataset enables extensive data synthesis, for example in the southern North Sea where issues of spatial and numerical bias from a data source are explored. The full dataset also facilitates the construction of long-term temperature time series and an examination of changes in the phenology (seasonal timing) of ecosystem processes. This is done for a wide geographic area with an exploration of the limitations of data coverage over long periods. Throughout, we highlight and explore potential issues around the simple combination of data from the diverse and disparate sources collated here. The datasets are available on the Cefas Data Hub (https://www.cefas.co.uk/cefas-data-hub/). The referenced data sources are listed in Sect. 5.

  10. 2010 Joint United States-Canadian Program to explore the limits of the Extended Continental Shelf aboard U.S. Coast Guard Cutter Healy--Cruise HLY1002

    Science.gov (United States)

    Edwards, Brian D.; Childs, Jonathan R.; Triezenberg, Peter J.; Danforth, William W.; Gibbons, Helen

    2013-01-01

    In August and September 2010, the U.S. Geological Survey, in cooperation with Natural Resources Canada, Geological Survey of Canada, conducted bathymetric and geophysical surveys in the Beaufort Sea and eastern Arctic Ocean aboard the U.S. Coast Guard Cutter Healy. The principal objective of this mission to the high Arctic was to acquire data in support of a delineation of the outer limits of the U.S. and Canadian Extended Continental Shelf in the Arctic Ocean, in accordance with the provisions of Article 76 of the United Nations Convention on the Law of the Sea. The Healy was accompanied by the Canadian Coast Guard icebreaker Louis S. St-Laurent. The scientific parties on board the two vessels consisted principally of staff from the U.S. Geological Survey (Healy), and the Geological Survey of Canada and the Canadian Hydrographic Service (Louis). The crew also included marine-mammal observers, Native-community observers, ice observers, and biologists conducting research of opportunity in the Arctic Ocean. Despite interruptions necessitated by three medical emergencies, the joint survey proved largely successful. The Healy collected 7,201 trackline-kilometers of swath (multibeam) bathymetry (47,663 square kilometers) and CHIRP subbottom data, with accompanying marine gravity measurements, and expendable bathythermograph data. The Louis acquired 3,673 trackline-kilometers of multichannel seismic (airgun) deep-penetration reflection data along 25 continuous profiles, as well as 34 sonobuoy refraction stations and 9,500 trackline-kilometers of single-beam bathymetry. The coordinated efforts of the two vessels resulted in seismic-reflection-profile data that were of much higher quality and continuity than if the data had been acquired with a single vessel alone. The equipment-failure rate of the seismic equipment aboard the Louis was greatly reduced when the Healy led as the ice breaker. When ice conditions proved too severe to deploy the seismic system, the Louis led

  11. Over 10 million seawater temperature records for the United Kingdom Continental Shelf between 1880 and 2014 from 17 Cefas (United Kingdom government marine data systems

    Directory of Open Access Journals (Sweden)

    D. J. Morris

    2018-01-01

    hydrological conditions around the British Isles, although cross-matching with satellite-derived data for surface temperatures at specific times and in specific areas is another area in which the data could be of value (see e.g. Smit et al., 2013. Maps are provided indicating geographical coverage, which is generally within and around the UK Continental Shelf area, but occasionally extends north from Labrador and Greenland to east of Svalbard and southward to the Bay of Biscay. Example potential uses of the data are described using plots of data in four selected groups of four ICES rectangles covering areas of particular fisheries interest. The full dataset enables extensive data synthesis, for example in the southern North Sea where issues of spatial and numerical bias from a data source are explored. The full dataset also facilitates the construction of long-term temperature time series and an examination of changes in the phenology (seasonal timing of ecosystem processes. This is done for a wide geographic area with an exploration of the limitations of data coverage over long periods. Throughout, we highlight and explore potential issues around the simple combination of data from the diverse and disparate sources collated here. The datasets are available on the Cefas Data Hub (https://www.cefas.co.uk/cefas-data-hub/. The referenced data sources are listed in Sect. 5.

  12. Intra-annual variability of carbon and nitrogen stable isotopes in suspended organic matter in waters of the western continental shelf of India

    Directory of Open Access Journals (Sweden)

    M. V. Maya

    2011-11-01

    Full Text Available Intra-annual variations of δ13C and δ15N of water-column suspended particulate organic matter (SPOM have been investigated to understand the biogeochemical cycling of C and N in the Western Continental Shelf of India (WCSI. The key issues being addressed are: how the δ15N of SPOM is affected by seasonally varying processes of organic matter production and respiration and how it relates to the δ15N of sedimentary organic matter that appears to show a decreasing trend despite an apparent intensification of seasonal oxygen deficiency over the past few decades? A secondary objective was to evaluate the sources of organic carbon. Elemental carbon and nitrogen concentrations, C/N ratios in SPOM, along with ancillary chemical and biological variables including phytoplankton pigment abundance were also determined on a seasonal basis (from March 2007 to September 2008, with the partial exception of the southwest (SW monsoon period. The results reveal significant shifts in isotopic signatures, especially δ15N, of SPOM before and after the onset of SW monsoon. Very low δ15N values, reaching a minimum of −4.17 ‰, are found during the pre-monsoon period. Our results provide the first direct evidence for the addition of substantial amounts of isotopically light nitrogen by the diazotrophs, especially Trichodesmium, in the region. The δ15N of SPOM is generally lower than the mean value (7.38 ‰ for surficial sediments, presumably because of diagenetic enrichment. The results support the view that sedimentary δ15N may not necessarily reflect denitrification intensity in the overlying waters due to diverse sources of nitrogen and variability of its isotopic composition. The observed intra-annual variability of δ13C of SPOM during the pre-monsoon and post-monsoon periods is generally small. Phytoplankton production and probably species

  13. Structural lineaments from the magnetic anomaly maps of the eastern continental margin of India (ECMI) and NW Bengal Fan

    Digital Repository Service at National Institute of Oceanography (India)

    Murthy, K.S.R.; Rao, T.C.S.; Subrahmanyam, A; Rao, M.M.M.; Lakshminarayana, S.

    extension of 85 degrees E ridge, abutting the continental shelf off Chilka Lake and (3) trend 3, locted over the continental shelf/slope between Visakhapatnm and Paradip represents a folded (ridges and depressions) nature of the continental basement...

  14. Late Quaternary Halimeda bioherms and aragonitic faecal pellet-dominated sediments on the carbonate platform of the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P; Veerayya, M.; Nair, R.R.; Dupeuble, P; Lamboy, M.

    brought by river runoff and shelf edge currents favoured the growth of algal bioherms dominated by Halimeda between 13,700 (?) and 8300 yr B.P. The absence of Late Holocene and modern carbonates on the platform may be due to the combined influence...

  15. Holocene sediment distribution on the inner continental shelf of northeastern South Carolina: implications for the regional sediment budget and long-term shoreline response

    Science.gov (United States)

    Denny, Jane F.; Schwab, William C.; Baldwin, Wayne E.; Barnhardt, Walter A.; Gayes, Paul T.; Morton, R.A.; Warner, John C.; Driscoll, Neal W.; Voulgaris, George

    2013-01-01

    High-resolution geophysical and sediment sampling surveys were conducted offshore of the Grand Strand, South Carolina to define the shallow geologic framework of the inner shelf. Results are used to identify and map Holocene sediment deposits, infer sediment transport pathways, and discuss implications for the regional coastal sediment budget. The thickest deposits of Holocene sediment observed on the inner shelf form shoal complexes composed of moderately sorted fine sand, which are primarily located offshore of modern tidal inlets. These shoal deposits contain ~67 M m3 of sediment, approximately 96% of Holocene sediment stored on the inner shelf. Due to the lack of any significant modern fluvial input of sand to the region, the Holocene deposits are likely derived from reworking of relict Pleistocene and older inner-shelf deposits during the Holocene marine transgression. The Holocene sediments are concentrated in the southern part of the study area, due to a combination of ancestral drainage patterns, a regional shift in sediment supply from the northeast to the southwest in the late Pleistocene, and proximity to modern inlet systems. Where sediment is limited, only small, low relief ridges have formed and Pleistocene and older deposits are exposed on the seafloor. The low-relief ridges are likely the result of a thin, mobile veneer of sediment being transported across an irregular, erosional surface formed during the last transgression. Sediment textural trends and seafloor morphology indicate a long-term net transport of sediment to the southwest. This is supported by oceanographic studies that suggest the long-term sediment transport direction is controlled by the frequency and intensity of storms that pass through the region, where low pressure systems yield net along-shore flow to the southwest and a weak onshore component. Current sediment budget estimates for the Grand Strand yield a deficit for the region. Volume calculations of Holocene deposits on the

  16. Cs-137 geochronology, epithermal neutron activation analysis, and principal component analysis of heavy metals pollution of the Black Sea anoxic continental shelf sediments

    Science.gov (United States)

    Duliu, O. G.; Cristache, C.; Oaie, G.; Culicov, O. A.; Frontasyeva, M. V.

    2009-04-01

    Anthropogenic Cs-137 Gamma-ray Spectroscopy assay (GrSA) performed at the National Institute of Research and Development for Physics and Nuclear Engineering - Bucharest (Romania) in correlation with Epithermal Neutrons Activation Analysis (ENAA) performed at the Joint Institute of Nuclear Researches - Dubna (Russia) were used to investigate a 50 cm core containing unconsolidated sediments collected at a depth of 600 m off Romanian town of Constantza, located in the anoxic zone of the Black Sea Continental Shelf. A digital radiography showed the presence of about 265 distinct laminae, 1 to 3 mm thick, a fact attesting a stationary sedimentary process, completely free of bioturbation. After being radiographed, the core was sliced into 45 segments whose thickness gradually increased from 0.5 to 5 cm, such that the minimum thickness corresponded to the upper part of the core. From each segment two aliquots of about 0.5 g and 50 g were extracted for subsequent ENAA and Cs-137 GrSA. The Cs-137 vertical profile evidenced two maxima, one of them was very sharp and localized at a depth of 1 cm and the other very broad, almost undistinguished at about 8 cm depth, the first one being attributed to 1986 Chernobyl accident. Based on these date, we have estimated a sedimentation ratio of about 0.5 mm/year, value taken as reference for further assessment of recent pollution history. By means of ENAA we have determined the vertical content of five presumed pollutants, e.i. Zn, As, Br, Sn and Sb and of Sc, as natural, nonpolluting element. In the first case, all five elements presented a more or less similar vertical profile consisting of an almost exponential decrease for the first 10 cm below sediment surface followed by a plateau until the core base, i.e. 50 cm below surface, dependency better described by the equation: c(z) = c0 [1+k exp (-z/Z)] (1) where: where c(z) represents the concentration vertical profile; z represents depth (in absolute value); c0 represents the plateau

  17. Mineral Resource Assessment of Marine Sand Resources in Cape- and Ridge-Associated Marine Sand Deposits in Three Tracts, New York and New Jersey, United States Atlantic Continental Shelf

    Science.gov (United States)

    Bliss, James D.; Williams, S. Jeffress; Arsenault, Matthew A.

    2009-01-01

    Demand is growing in the United States and worldwide for information about the geology of offshore continental shelf regions, the character of the seafloor, and sediments comprising the seafloor and subbottom. Interest in locating sand bodies or high quality deposits that have potential as sources for beach nourishment and ecosystem restoration is especially great in some regions of the country. The Atlantic coast, particularly New York and New Jersey, has been the focus of these studies for the past 40 years with widely varying results. This study is the first attempt at applying probability statistics to modeling Holocene-age cape-and ridge-associated sand deposits and thus focuses on distinct sand body morphology. This modeling technique may have application for other continental shelf regions that have similar geologic character and late Quaternary sea-level transgression history. An estimated volume of 3.9 billion m3 of marine sand resources is predicted in the cape-and ridge-associated marine sand deposits in three representative regions or tracts on the continental shelf offshore of New York and New Jersey. These estimates are taken from probabilistic distributions of sand resources and are produced using deposit models and Monte Carlo Simulation (MCS) techniques. The estimated sand resources presented here are for only three tracts as described below and for Holocene age sand resources contained in cape-and ridge-associated marine sand deposit types within this area. Other areas may qualify as tracts for this deposit type and other deposit types and geologic ages (for example, paleo-stream channels, blanket and outwash deposits, ebb-tide shoals, and lower sea level-stand deltas), which are present on the New Jersey and New York continental shelf area but are not delineated and modeled in this initial evaluation. Admittedly, only a portion of these probable sand resources will ultimately be available and suitable for production, dependent largely on

  18. Four new species of free-living marine nematodes of the family Desmodoridae (Nematoda: Desmodorida) and a redescription of Desmodora nini (Inglis, 1963) from the continental shelf off northeastern Brazil.

    Science.gov (United States)

    Larrazábal-Filho, Alexandre L; Silva, Maria Cristina Da; Esteves, André M

    2015-09-24

    Four new species of marine nematodes were collected from the continental shelf of the Potiguar Basin in northeastern Brazil. Zalonema vicentei sp. n. and Zalonema mariae sp. n. are characterized by having multispiral fovea amphidialis, lateral alae and ventral ala. These features also are found in Pseudochromadora, Desmodorella and Psammonema. They differ in the cephalic arrangement, and shape of the cephalic capsule and the fovea amphidialis. Croconema fortis sp. n. resembles Desmodora in the shape of the fovea amphidialis and cephalic capsule, but differs in the number of subcephalic setae and ornamentation on the cuticule. Desmodora paraconica sp. n. is characterized by the loop-shaped fovea amphidialis and the long conical-cylindrical tail. This species is similar to the genus Bolbonema, but differs in having the cephalic setae anterior to the fovea amphidialis. Desmodora nini is redescribed, to record details lacking in the original description.

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

    Science.gov (United States)

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

    1990-01-01

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

  20. Condições hidrográficas na plataforma continental ao largo de Ubatuba: variações sazonais e em média escala Hydrographic conditions on the continental shelf off Ubatuba: seasonal and meso-scale variability

    Directory of Open Access Journals (Sweden)

    Belmiro Mendes de Castro Filho

    1987-01-01

    estruturas térmica e halina, tem provavelmente um importante papel na troca de massas de água entre a costa e o talude, contribuindo para o enriquecimento das águas da plataforma continental através dos movimentos ascendentes que ocorrem em seu núcleo.Hydrographic conditions on the continental shelf offshore of Ubatuba have shown different water mass distributions for summer (December, 1985 and winter (July, 1986. Two physical domains were identified: inner shelf and outer shelf, both separated by a front particularly well defined during the winter, The inner shelf has a two layer vertical stratification during summer, with a strong thermocline at mid-depths. During winter this region shows almost no stratification, During summer the upper layer (depths smaller than 20 m is filled with Coastal Water (CW, which interacts with Tropical Water (TW offshore. South Atlantic Central Water (SACA predominates in the lower layer during surrmer. Vertical interaction between CW and SACA is restricted to a band near the coast. During winter SACA does not penetrate towards the coast in the lower layer and, as a consequence, the inner shelf shows the presence of CW only. For winter interactions between CW and SACA are observed only across the front that separates inner and outer shelf. For this season there is also a noticeable intrusion of TW towards the coast on the upper layer of the outer shelf. A descriptive model for the wind driven seasonal circulation of the inner shelf is sugested, based on: 1 the water mass distributions observed and: 2 meteorological conditions from a coastal station located southward of Ubatuba, The outer shelf dynamics seems to suffer strong influence from the Brazil Current. Eddies or meanders with characteristics of frontal eddies, have been observed on both seasons on the outer shelf. These eddies should play an important role on the water mass exchange between the shelf and the slope, contributing for the enrichment of shelf waters by the upward

  1. Radioactivity in produced water from Norwegian oil and gas installations - concentrations, bioavailability and doses to marine biota

    Energy Technology Data Exchange (ETDEWEB)

    Sidhu, R.; Eriksen, D. Oe.; Straalberg, E.; Iden, K. I.; Rye, H.; Hylland, K.; Ruus, A.; Roeyset, O.; Berntssen, M. H. G.

    2006-03-15

    Substantial amounts of produced water, containing elevated levels of radionuclides (mainly 226Ra and 228Ra) are discharged to the sea as a result of oil and gas production on the Norwegian Continental Shelf. So far no study has assessed the potential radiological effects on marine biota in connection with radionuclide discharges to the North Sea. The main objective of the project is to establish radiological safe discharge limits for radium, lead and polonium associated with other components in produced water from oil and gas installations on the Norwegian continental shelf. Preliminary results indicate that presence of added chemicals such as scale inhibitors in the produced water has a marked influence on the formation of radium and barium sulphates when produced water is mixed with sea water. Thus, the mobility and bio-availability of radium (and barium) may be larger than anticipated. Also, the bio-availability of radium may be increased due to presence of such chemicals, and this is presently being studied. (author) (tk)

  2. Determinação dos elementos-traço (Zn, Co e Ni em sedimentos da Plataforma Continental Amazônica sob influência da descarga do rio Amazonas Determination of trace elements (Zn, Co and Ni in sediments at the Amazon Continental Shelf on influence of the Amazon River discharge

    Directory of Open Access Journals (Sweden)

    Gilmar Wanzeller Siqueira

    2006-01-01

    Full Text Available Esta pesquisa foi desenvolvida na Plataforma Continental Amazônica (PCA no trecho compreendido entre os cabos Orange (AP e Maguari (PA, para determinar os teores de Zn, Co e Ni nos sedimentos superficiais, identificando o papel dos sedimentos como fonte ou reserva de elementos-traço. A concentração dos elementos metálicos apresentou a seguinte associação: Zn > Ni > Co. Os sedimentos localizados na PCA podem ser considerados como sítio de ocorrência natural dos elementos metálicos, não havendo influência de fontes poluidoras na liberação destes para o sistema.Determination of trace elements (Zn, Co and Ni in sediments at the Amazon Continental Shelf on influence of the Amazon River discharge This research was developed at Amazon Continental Shelf (ACS between the Orange Cape (Amapá State and the Maguari Cape (Pará State, to determine the levels of zinc, cobalt and nickel in the superficial sediments identifying its inputs and outputs. The rate of these metallic elements in the sediments decreases following Zn> Ni> Co. The concentrations of total metals in the surface sediments range from Zn = 52.8 159.5; Ni = 21.7 47.4 and Co = 14.3 48.8 (mg.kg-1. The levels of trace elements observed in the sediments at ACS are of natural occurrence. Pollution sources of metallic elements were not observed.

  3. Physical and nutrient data collected from CTD and bottle casts from the R/V HERMANO GINES from the continental shelf of Venezuela in the Caribbean Sea in support of the project: Carbon Retention in a Colored Ocean (CARIACO) from 16 March 2006 to 06 March 2007 (NODC Accession 0014920)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — CTD and bottle data were collected from the R/V HERMANO GINES in the Caribbean Sea on the continental shelf of Venezuela from 16 March 2006 to 06 March 2007. Data...

  4. Ability of surface and subsurface death assemblages to track km-scale spatial and decade-scale temporal variability in living communities: Tests using the urban southern California continental shelf

    Science.gov (United States)

    Kidwell, Susan M.; Tomasovych, Adam

    2016-04-01

    Actualistic analysis of death assemblages has always focused on quantifying, and achieving a mechanistic understanding of, the reliability of deep-time records, and is now additionally motivated to assess natural conditions before human impacts. The southern California continental shelf permits us to evaluate the ability of time-averaged death assemblages to detect known variability in urban nutrients, which increased from the early 20th Century up until the 1972 Clean Water Act. Biomonitoring since then documents strong declines in populations of pollution- and hypoxia-tolerant species, especially the chemosymbiontic lucinid bivalve Parvilucina tenuisculpta. This shelf is taphonomically challenging -- median shell ages are 50-100 y, only 1% of shells survive, the mixed-zone is ~25 cm thick, and siliciclastic accumulation is slow, in contrast to sediment-trapping estuaries and lagoons. Nonetheless, both surficial death and buried core assemblages capture first-order urban trends, albeit with significant damping of the large, spatially localized mid-20th Century pulse in Parvilucina abundance. Paleoecologists will thus detect but under-estimate the original magnitude of even strong past excursions in community composition, an important bounding condition for both recent- and deep-time analysis.

  5. Major hazard risk indicators for monitoring of trends in the Norwegian offshore petroleum sector

    International Nuclear Information System (INIS)

    Vinnem, Jan Erik; Aven, Terje; Husebo, Torleif; Seljelid, Jorunn; Tveit, Odd J.

    2006-01-01

    The Petroleum Safety Authority Norway (PSA, formerly Norwegian Petroleum Directorate) took in 1999 the initiative to develop a method in order to assess trends and status for the risk levels in the Norwegian offshore petroleum industry. A method was developed, and a pilot study report was issued in April 2001, covering the period 1996-2000. Annual updates have been performed since then, and the latest report covers the period 1996-2004. The statistical approach is based on recording occurrence of near misses and relevant incidents, performance of barriers and results from risk assessments. Of similar importance is an evaluation of safety culture, motivation, communication and perceived risk. This is covered through the use of social science methods, such as questionnaire surveys and a number of interviews, audit and inspection reports as well as accident and incident investigations. There are also indicators for occupational accidents and occupational illness/-physical working environment factors. The focus is on the major hazard risk components for personnel staying on the offshore installations. An overview of the indicators used to illustrate these risk aspects is presented, followed by a discussion of the analytical approach used for these indicators. Results from the risk assessment for the Norwegian Continental Shelf in the period 1996-2004 are used throughout for illustration, and discussion of challenges

  6. Managing the environmental effects of the Norwegian oil and gas industry: from conflict to consensus

    International Nuclear Information System (INIS)

    Gray, John S.; Bakke, Torgeir; Beck, Hans Jakob; Nilssen, Ingunn

    1999-01-01

    In the early days of exploitation of the oil resources on Norway's continental shelf there was little control over environmental impacts. The oil companies expected effects of their activity to be found to a 1 Km radius round platforms. In the late 1980s data started appearing that suggested that effects were over much larger areas. These findings were disputed but subsequent studies showed that a more realistic figure of the area affected was 3 km radius giving roughly 10 times the area predicted by the companies. The Norwegian authorities reacted by imposing restrictions on discharges of oil-based drilling cuttings and since 1993 oil-based drilling mud or cuttings have not been intentionally discharged to sea on the Norwegian shelf. In 1996 Norway changed its offshore monitoring from field based monitoring of sediments to a regional monitoring of both sediments and the water column. The change makes it possible to obtain a better overview of the environmental conditions, at the same time it also reduces costs for the operators. (Author)

  7. Fact 2004. The Norwegian petroleum sector

    Energy Technology Data Exchange (ETDEWEB)

    Gooderham, Rolf E [ed.

    2004-07-01

    The oil and gas sector is Norway's largest industry by value creation and has been a key driving force in Norwegian economic development for several decades. Developments in the petroleum industry are crucial for the future progress of Norwegian society and will remain so. While the petroleum sector has so far been characterised by growth, we can now see the beginning of a gradual reduction in the level of activity. This will have significant spin-offs for other industries and consequences for the Norwegian economy as a whole. Thus, it is important to ensure that profitable petroleum activities are pursued in order to moderate the pace of decline. This publication provides a broad picture of Norway's petroleum activities, and covers most aspects of the industry. It presents useful information and statistics on the sector both for those already familiar with this business and for readers who know less about it. Since petroleum production began on the Norwegian continental shelf (NCS) in 1971, a total of 3.8 bn standard cubic metres of oil equivalent (scm oe) has been produced. This corresponds to just under 30 per cent of the original recoverable reserves, and so substantial oil and gas resources remain. The government's Report no 38 (2001-2002) to the Storting (the Norwegian Parliament) described a long-term scenario for the NCS in which estimates for recoverable reserves from the Norwegian Petroleum Directorate are recovered. It is very important to ensure that the long-term scenario is achieved based on due consideration of environmental and safety issues. Norway's role as a major energy producer must be reconciled with the ambition to be a pioneer in the environmental area. This goal has always characterized government policy towards the petroleum industry. The strong focus on the environment has created a positive trend in safeguarding environmental concerns on the NCS. Production of oil and natural gas liquids averaged 3.3 mill barrels a day in 2003, while gas

  8. Fact 2004. The Norwegian petroleum sector

    Energy Technology Data Exchange (ETDEWEB)

    Gooderham, Rolf E. (ed.)

    2004-07-01

    The oil and gas sector is Norway's largest industry by value creation and has been a key driving force in Norwegian economic development for several decades. Developments in the petroleum industry are crucial for the future progress of Norwegian society and will remain so. While the petroleum sector has so far been characterised by growth, we can now see the beginning of a gradual reduction in the level of activity. This will have significant spin-offs for other industries and consequences for the Norwegian economy as a whole. Thus, it is important to ensure that profitable petroleum activities are pursued in order to moderate the pace of decline. This publication provides a broad picture of Norway's petroleum activities, and covers most aspects of the industry. It presents useful information and statistics on the sector both for those already familiar with this business and for readers who know less about it. Since petroleum production began on the Norwegian continental shelf (NCS) in 1971, a total of 3.8 bn standard cubic metres of oil equivalent (scm oe) has been produced. This corresponds to just under 30 per cent of the original recoverable reserves, and so substantial oil and gas resources remain. The government's Report no 38 (2001-2002) to the Storting (the Norwegian Parliament) described a long-term scenario for the NCS in which estimates for recoverable reserves from the Norwegian Petroleum Directorate are recovered. It is very important to ensure that the long-term scenario is achieved based on due consideration of environmental and safety issues. Norway's role as a major energy producer must be reconciled with the ambition to be a pioneer in the environmental area. This goal has always characterized government policy towards the petroleum industry. The strong focus on the environment has created a positive trend in safeguarding environmental concerns on the NCS. Production of oil and natural gas liquids averaged 3.3 mill barrels a

  9. Observações sobre stomatopoda Squilla brasiliensis calman, 1917 na plataforma continental do Rio Grande do Sul Observation on the Stamatopoda Squilla brasiliensis Calman, 1917 on the continental shelf of the Rio Grande do Sul State

    Directory of Open Access Journals (Sweden)

    Luiz Roberto Tommasi

    1987-01-01

    Full Text Available O Stomatopoda Squilla brasiliensis ocorreu em 60 estações na plataforma continental do Rio Grande do Sul. É aparentemente, bastante freqüente entre 19 e 285 m de profundidade, mas especialmente entre 100 e 150 m, temperatura da água de fundo de 12,22 a 24,45ºC, salinidade de 30,20 a 36,16º/.., fundo de areia fina e lodo com baixo teor de calcario (0-20% na fração menor do que 44µ. Ocorreu especialmente em fundos sob influencia da massa de água Subtropical. As maiores abundancias ocorreram entre 30º e 31ºS e entre 49º e 50ºW. Vários exemplares, tanto machos como fêmeas, apresentaram telso com bordos entumescidos, o que sugere não ser essa uma característica ligada ao sexo nesta espécie .The distribution of Squilla brasiliensis Caiman, 1917 (Crustacea Stomatopoda is by the first time discussed in the continental plataform in the region of Rio Grande do Sul State, in relationship with depth, temperature and salinity. Apparently the distribution of that species is more related to salinity than to depth and temperature, and specially to the water mass of Subtropical origin. The largest densities were found between 84 and 128 m depth.

  10. Hydrographic and biological observations on the Washington continental shelf and slope during the periods: 30 March-5 April, 8-15 June, and 6-11 September 1978

    Energy Technology Data Exchange (ETDEWEB)

    Postel, J.R.; Peterson, W.K. (comps.)

    1981-01-01

    During 1978 several cruises were successfully completed along a shelf-slope section off the Washington coast. These cruises were undertaken to collect seasonal information on the processes affecting phytoplankton production and distribution and data on the settling rate of organic matter in the sea during spring, early summer, and autumn conditions. This report summarizes the data collected on three cruises aboard the R/V CAYUSE, which was operated by Oregon State University. All three cruises originated and terminated in Newport, Oregon. Sampling was conducted at established station locations along a transect off Copalis Beach, Washington. Water depth varied from about 10 m at the innermost station (approx. 3 km from the beach) to over 1500 m at the outermost station (approx. 120 km from the beach).

  11. Characterization and distribution of organic matter using specific physico-chemical methods: A case study of the southeast Adriatic continental and shelf slope (Albania)

    Science.gov (United States)

    Plavšić, Marta; Strmečki, Slađana; Dautović, Jelena; Vojvodić, Vjeročka; Olujić, Goran; Ćosović, Božena

    2012-05-01

    In May 2009, we characterized the organic matter in the area where Albanian shelf riverine plume waters enter the Southern Adriatic Pit region. Due to stable weather and hydrological conditions at the time of sampling a longitudinal thermal front was present around the Albanian shelf break. Our measurements point to the input of inorganic nutrients, including phosphorus (average P-PO4 concentration was 0.71 μg/L) and nitrogen (average as total inorganic nitrogen (TIN) concentration was 25.33 μg/L) due to the intrusion of Levantine Intermediate Water (LIW) through the Otranto Strait. The input of LIW brings high salinity (˜38.7) water that is poor in organic matter content. Low concentrations of dissolved organic carbon (DOC) (0.7 mg C/L) and particulate organic carbon (POC) (0.06 mg C/L), surface active substances (SAS) (in the range from 0.025 to 0.078 mg/L equiv. Triton-X-100) and copper complexing capacity (CuCC) (24 nmol Cu2+/L) were measured in the area. All the values for DOC, POC, SAS and CuCC were significantly lower in the Albanian coastal waters than in the North Adriatic. The measurable influence of the inflowing Albanian rivers was observed from the inverse dependance of the DOC concentrations and salinity data. The Albanian rivers contribute to the elevated nutrient concentrations especially those of silicate, which displayed concentrations up to 380 μg/L in the shallowest coastal station.

  12. Short and long term evolution of deep giant submarine dunes in continental shelf environment: the example of the 'Banc du Four' (Western Brittany, France)

    Science.gov (United States)

    Franzetti, M.; Le Roy, P.; Garlan, T.; Delacourt, C.; Thibaud, R.; Cancouet, R.; Graindorge, D.; Prunier, C.; Sukhovich, A.; Deschamps, A.

    2013-12-01

    The deep sandwave dynamics is still in debate. Understanding the migration processes and the resulting evolution of their 3D internal architecture are scientifically challenging. To address these questions we realized two swath bathymetry surveys complemented with seismic reflection across the large sandwaves field named 'Banc du Four'. It is located offshore the Western Brittany and is composed of more 500 dunes. Some of the dunes' wavelengths and heights exceed 1000m and 30m respectively placing them among the largest dunes ever described. Equilibrium laws obtained from our morphological analysis are not completely in agreement with those described in previous studies of similar structures in shallow waters. Relatively high migration velocities on deep continental shelves (from 3 to 20m.yr-1) attest of their still present dynamical equilibrium. Internal-external morphological and kinematical analyses show the existence of two different dynamic regimes. Interpretation of the seismic reflection data allowed reconstructing long-term evolution of the sandbank and the establishment of progressive connections between stepped submarine channels and tidal dynamics during the last sea-level rise.

  13. Contributions to knowledge of the continental margin of Uruguay. Description of background samples in the continental margin of Uruguay

    International Nuclear Information System (INIS)

    Preciozzi, F

    2015-01-01

    This study provide data concerning of the background sediments of the continental margin of Uruguay. There were carried out different works with witnesses in order to extract various sediment samples from the continental shelf

  14. The real right of the state and municipal taxation on activities performed on the Continental Shelf; O real direito de tributacao estadual e municipal sobre atividades executadas na Plataforma Continental

    Energy Technology Data Exchange (ETDEWEB)

    Belo, Heraldo da Costa [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Belo, Rodrigo Marcellino da Costa

    2008-07-01

    and services that are carried out in the continental Brazilian platform. The continental platform does not constitute territory of the States and Local authority, but yes territory in the Union, so the standard itself of regency limits the rights of power, jurisdiction and legislation only the Union in exclusion to too many federate beings. So, notice, in regard to the beginning of the legality and to the value of the legal security, the necessity of resolving this dilemma, since to a businessman who it is responsibility to business activity cannot be subdued to size been of uncertainty that, like natural reflex, matters in increase of costs of production that they will be gone over again to the final product, raising the price whose products the production of the oil producing industry is an input, or even his products themselves been intended for the final consumption. (author)

  15. Milankovitch cyclicity in modern continental margins: stratigraphic cycles in terrigenous shelf settings; El registro de la ciclicidad de Milankovitch en margenes continentales actuales: ciclos estratigraficos en plataformas terrigenas

    Energy Technology Data Exchange (ETDEWEB)

    Lobo, F. J.; Ridente, D.

    2013-06-01

    We present a synthesis of the sedimentary responses to Late Quaternary Milankovitch-type sea-level cycles (100 and 20 kyr periodicities) as a basis for our investigations into the patterns and concepts of composite sequences in shallow-shelf settings. We describe the record of both 100 and 20 kyr cycles as documented worldwide and discuss the pattern of composite cyclicity mainly on the basis of previously published data from the Adriatic Sea and Gulf of Cadiz margins. Cycles of 100 kyr are those most frequently documented in Quaternary margins; they occur in the form of unconformity-bounded depositional sequences dominated by fairly uniform pro gradational-regressive units and more variable, though less well developed, transgressive deposits. Sequence boundaries correspond to prominent polygenic (regressive-transgressive) erosional surfaces that bear witness to considerable transgressive reworking of the original sub-aerial unconformity. Although the progradational units making up the greater part of these sequences have usually been interpreted as a record of a falling sea-level stage, recent evidence is pointing towards a more complex stratigraphic picture, including a distinction between relative highstand and lowstand deposits. The 20-kyr stratigraphic motifs show greater variation compared to that displayed by the more common 100-kyr sequences, particularly in the basic structure of systems tracts and the nature of bounding surfaces. The two case studies described here, the Adriatic Sea and Gulf of Cadiz margins, highlight the fact that, concomitantly with an increase in frequencies of cycles and sequences, sediment supply and the dynamics of their dispersal significantly affected the stratigraphic response to the main controlling factor, which was sea-level, thus determining the variety of expression in the 20 kyr cycles. (Author)

  16. Small proportions of silt linked to distinct and predictable differences in marine macrofaunal assemblages on the continental shelf of the Pacific Northwest

    Science.gov (United States)

    Henkel, S. K.; Politano, K. K.

    2017-07-01

    Increasing interest in offshore development has motivated intensified efforts to map the seafloor for marine spatial planning. However, surficial geologic maps do not accurately represent habitats for various species groups of concern. This study used a bottom-up approach to integrate macrofaunal densities and benthic conditions on the Pacific Northwest shelf to identify macrofaunal assemblages and associated habitat features. Benthic cores and water-column profiles were collected from 137 stations from 50 to 110 m depth. Analyses grouping stations based on both similar species abundances and benthic conditions resulted in six broad habitats. Within the sampled depth and latitudinal range, sediment characteristics were the primary structuring variable. A major break in assemblages was detected between sediment that had less than 1% silt/clay and those containing more than 1% silt/clay. Assemblages differed primarily in the bivalve species present and secondarily in polychaete species. Within the greater than and less than 1% silt/clay habitats, further discretization of assemblages was based mostly on differing abundances of characteristic bivalves and polychaetes associated with differing median grain sizes, which did not correspond to traditional definitions of fine or medium sand. These data show that a bottom-up methodology is necessary to discern habitats for macrofauna and that site-specific physical sampling is necessary to predict macrofaunal assemblage composition. However, if detailed sediment characteristics are known, macrofaunal assemblages may be predicted without time-intensive biological sampling and processing. These results also indicate that seemingly small sedimentary changes due to offshore installations may have measureable effects on the relative abundances and even the species composition of macrofauna.

  17. Processing of the reflection seismic data which were acquired in the continental shelf off the north-west Australia; Australia hokusei tairikudana chiiki ni oite shutokusareta hanshaho chishitsu tansa data no shori ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Amano, H [Japan National Oil Corp., Tokyo (Japan)

    1996-05-01

    Reflection exploration of earthquakes was conducted in the continental shelf off the north-west Australia, and a report is made concerning the processing of the acquired data. A GI gun was used as the vibration source, and a wave quite similar to a pulse was generated. Hydrophones were arranged with group intervals of 12.5m, and high-resolution field data were acquired. An analog low cut filter was used to suppress the large-amplitude swell noise attributable to sea conditions. A digital filter was designed for the purpose of eliminating coherent noises from other survey ships. At the ultimate stage the f-k filter was applied to each of the shot records, and the effectiveness was verified. The traverse line was as long as 6700km and therefore the design window was set relatively long at 2.0-4.0s in the residual static correction phase. It was found that this setup is effective in improving the continuity of the reflection surface. 5 figs., 1 tab.

  18. The effects of the fiscal terms applied to offshore petroleum exploitation of new fields: a comparative study of the UK, Norway, Denmark, Netherlands, Australia, China, Indonesia, Egypt, Nigeria, and United States outer continental shelf

    International Nuclear Information System (INIS)

    Kemp, A.G.; Reading, D.; Macdonald, B.

    1992-01-01

    This paper examines the comparative impact of petroleum taxation in the UK, Norway, Denmark, the Netherlands, Australia, Nigeria, China, Indonesia, Egypt and U.S. Outer Continental Shelf at the field development stage. The emphasis is on the effects in offshore operating situations. The study examines the operation of the systems under (a) a range of field sizes typical for each of the regimes, (b) a variety of oil prices ($15, $18, and $23 per barrel in real terms), and (c) a wide range of field development costs. The results indicate that generally the complex fiscal instruments employed are not well-targetted on economic rents. Frequently the systems are regressive with respect to both oil price and development case changes. In the UK and Australia the schemes are related to profits in a reasonably sensitive manner and are less likely to cause disincentives to field developments than in other countries. Even where systems are ostensibly profit-related they may have effects similar to imposts based on gross revenues (such as ceilings on cost recovery). In most jurisdictions it is likely that discretionary changes will be required when the operating environment exhibits marked variations. (author)

  19. Seasonal evolution of cholorophyll-a and cyanobacteria (Prochlorococcus and Synechococcus on the northeast continental shelf of the Gulf of Cádiz: relation to thermohaline and nutrients fields

    Directory of Open Access Journals (Sweden)

    Eleonora Anfuso

    2013-01-01

    Full Text Available The seasonal evolution of nutrients, chlorophyll-a (chl-a and cyanobacteria (Synechococcus and Prochlorococcus on the northeast continental shelf of the Gulf of Cádiz was observed during four cruises in summer and autumn 2006 and winter and spring 2007. Samples were collected to determine the distribution of chl-a and cyanobacteria abundance and to analyse their coupling with thermohaline and chemical properties in the gulf region. Surface nutrient distributions showed clear seasonal variability. Maximum levels were recorded for the entire study region during winter due to winter mixing and the strong influence of the Guadalquivir River and Bay of Cádiz outflow. Maximum chl-a levels were reached during spring for the entire region and for the entire water column. Minimum values of chl-a were observed during summer, under prevailing oligotrophic conditions, and winter when in spite of relatively high nutrient concentrations, phytoplankton growth was probably light-limited. The distribution of both cyanobacteria populations also varied seasonally in association with the oceanographic conditions. Prochlorococcus maximum cell abundance was observed at the sea surface during the four cruises, except in the northern region during summer. However, Synechococcus showed a maximum concentration at the sea surface in autumn and winter and at the subsurface chlorophyll maximum in autumn and spring.

  20. Depositional and sea-level history from MIS 6 (Termination II) to MIS 3 on the southern continental shelf of South Africa

    Science.gov (United States)

    Cawthra, H. C.; Jacobs, Z.; Compton, J. S.; Fisher, E. C.; Karkanas, P.; Marean, C. W.

    2018-02-01

    Pleistocene shoreline deposits comprised of calcified shallow marine (palaeobeach) and aeolian (palaeodune) facies found along mid-latitude coastlines can be useful indicators of past sea levels. Here, we describe a succession of such deposits that are presently exposed both above (subaerial) and below (submerged) mean sea level along the southern Cape coast of South Africa, 18 km east of the town of Mossel Bay. The submerged units provide a window on Late Pleistocene coastal processes, as palaeoshoreline deposits in this study extend to water depths of up to 55 m on the mid-shelf. Five sedimentary facies were identified in the strata and were compared to modern depositional environments of the local littoral zone, which include aeolian dune, upper shoreface, foreshore, intertidal swash and back-barrier settings. Twenty-two geological units were observed and mapped. Some of these units were directly dated with optically stimulated luminescence (OSL) dating. OSL ages were obtained for ten samples from the subaerial and twelve samples from the submerged deposits. Those geological units not directly dated were interpreted based on sedimentology and field/stratigraphic relationships to dated units. The stratigraphy and chronology of the succession indicates a record of initial deposition during Termination II (T-II) meltwater events, preceding and leading to marine isotope stage (MIS) 5e. Indicators for multiple sea-level fluctuations between MIS 5d and MIS 4, and sediment deposition at the end of MIS 4 and start of MIS 3 are also found. Both regressive and transgressive depositional cycles are well-preserved in the succession. We propose that palaeodune and palaeobeach deposits along the South Coast of South Africa have no clear preference for deposition during sea-level transgressions or regressions. Sediment deposition more closely mirrors the rate of sea level change, with deposition and preservation either during times of rapid sea-level movement, or oscillation

  1. 77 FR 71612 - Atlantic Wind Lease Sale 2 (ATLW2) Commercial Leasing for Wind Power on the Outer Continental...

    Science.gov (United States)

    2012-12-03

    ... Wind Lease Sale 2 (ATLW2) Commercial Leasing for Wind Power on the Outer Continental Shelf Offshore...), Interior. ACTION: Proposed Sale Notice for commercial leasing for wind power on the Outer Continental Shelf... sale of commercial wind energy leases on the Outer Continental Shelf (OCS) offshore Rhode Island and...

  2. Exploration of the continental margins of India

    Digital Repository Service at National Institute of Oceanography (India)

    Siddiquie, H.N.; Hashimi, N.H.; Vora, K.H.; Pathak, M.C.

    impetus from sponsored surveys of other organizations, chiefly the oil industry, ports and harbours as well as industries disposing of their effluents in the marine environment. By now the entire western continental shelf and a large part...

  3. Risk evaluation for federally listed (roseate tern, piping plover) or candidate (red knot) bird species in offshore waters: A first step for managing the potential impacts of wind facility development on the Atlantic Outer Continental Shelf

    Energy Technology Data Exchange (ETDEWEB)

    Burger, Joanna [Division of Life Sciences, Rutgers University, Piscataway, NJ 08854-8082 (United States); Conserve Wildlife, 516 Farnsworth Avenue, Bordentown, NJ 08505 (United States); Gordon, Caleb; Newman, James; Forcey, Greg [Pandion Systems, Inc. 102 NE 10th Ave, Gainesville, FL 32601 (United States); Lawrence, J. [Conserve Wildlife, 516 Farnsworth Avenue, Bordentown, NJ 08505 (United States); Vlietstra, Lucy [Department of Science, US Coast Guard Academy, 27 Mohegan Drive, New London, CT 06320 (United States)

    2011-01-15

    With a worldwide increase in attention toward developing a reliance on renewable energy, there is a need to evaluate the effects of these facilities (solar, wind, hydropower) on ecosystems. We conduct a hazard and risk evaluation for three species of birds that are listed, or candidates for listing, as federally threatened or endangered in the US, and that might occur offshore on the Atlantic Outer Continental Shelf (AOCS) where wind power facilities could be developed. Our objectives were to: 1) provide conceptual models for exposure for each species, and 2) examine potential exposure and hazards of roseate tern (Sterna dougallii) and piping plover (Charadrius melodus, both federally endangered in the US) and red knot (Calidris canutus rufa, candidate species) in the AOCS. We used a weight-of-evidence approach to evaluate information from a review of technical literature. We developed conceptual models to examine the relative vulnerability of each species as a function of life stage and cycle (breeding, staging, migratory, wintering). These methods are useful for conducting environmental assessments when empirical data are insufficient for a full risk assessment. We determined that 1) Roseate terns are likely to be exposed to risk during the migratory and breeding season when they occur in the AOCS, as well as while staging. 2) Piping plovers are not likely to be at risk during the breeding season, but may be at risk during spring or fall migrations. Risk to this species is likely to be low from turbines located far from land as this species migrates mainly along the coast. 3) Red knots are potentially exposed to some risk during migration, especially long-distance migrants whose migratory routes take them over the AOCS. More information is required on exact spatio-temporal migration routes, flight altitudes (especially during ascent and descent), and behavioral avoidance of turbines by birds to ascertain their risk. (author)

  4. Aplicação do diagrama T-S estatístico: volumétrico à análise das massas de água da plataforma continental do Rio Grande do Sul The statistical volumetric T-S diagram applied to the analysis of water masses of Rio Grande do Sul continental shelf

    Directory of Open Access Journals (Sweden)

    Luiz Bruner de Miranda

    1979-06-01

    Full Text Available The general characteristics of the seasonal variation of the thermohaline properties of the continental shelf water off Rio Grande do Sul, under non-conservative and quasi-synoptic conditions were analysed. The method applied - volumetric statistical T-S analysis allows the computation of the water masses budget from the knowledge of their temperature and salinity ranges. The data of 194 hydrographic stations from six oceanographic cruises between April 1968 and March 1969, were used. Water of Tropical and Subtropical origin (47,5% and 64% of the total volume during the winter and summer, respectively was always present during the observation period. Subantarctic water has its maximum and minimum influences during the winter (15% and summer (<3%, respectively. The average minimum and maximum temperature and salinity values of the water masses in the investigated region were observed in June (16,85ºC and 34,72‰, December (35,58‰ and March (20,82ºC.

  5. The zooplankton of Santa Catarina continental shelf in southern Brazil with emphasis on Copepoda and Cladocera and their relationship with physical coastal processes El zooplancton de la plataforma continental de Santa Catarina, sur de Brasil con énfasis en Copepoda y Cladocera y sus relaciones con procesos físicos costeros

    Directory of Open Access Journals (Sweden)

    Renata Domingos-Nunes

    2012-11-01

    Full Text Available Very few studies have been carried out to exclusively investigate the zooplankton community of Santa Catarina State continental shelf, despite the economic and ecological importance of the area. This coastal region of southern Brazil presents highly relevant oceanographic processes, such as the strong influence of continental inputs, resurgence in the Cabo de Santa Marta Grande and River Plata plume water to the south. Two sampling cruises were carried out, in December 2005 and May 2006, in order to study temporal hydrological variations, and their influence on the biota of the region. Zooplankton samples for analysis were obtained by oblique hauls with Bongo nets at 33 sampling stations arranged in profiles perpendicular to the coast on each cruise. The predominant groups found in the samples were Copepoda, Cladocera, Salpidae and Chaetognatha, which presented higher densities at the stations closer to the coast. In the case of the December 2005 cruise, the salinity and temperature gradients perpendicular to the coast, promoted by the continental inputs to the north of the area and by the upwelling to the south, determined the limits of distribution of Acartia lilljeborgi and Penilia avirostris. However, the temperature and salinity gradients longitudinal to the coast determined on the May 2006 cruise did not explain the species distribution, indicating that biotic forcing mechanisms may have been active in the ecology of the system during this period.A pesar de la importancia económica y ecológica del área todavía no habían sido realizados estudios exclusivamente destinados a la investigación de la comunidad zooplanctónica de la plataforma continental del Estado de Santa Catarina. Esta región costera del sur de Brasil presenta procesos oceanográficos de alta relevancia, tales como fuerte influencia de aportes continentales, resurgencia en el Cabo de Santa Marta Grande y la pluma de agua del río Plata en el sur. Se efectuaron dos

  6. Continental Shelf Sediments of Sarawak, Malaysian Borneo

    Science.gov (United States)

    Masron, Tarmiji; Rumpet, Richard; Musel, Jamil

    2017-01-01

    Sediment distributions in deep sea influence the benthic community structure and thus play an important role in shaping the marine ecosystem. Several studies on sediment characteristics had been conducted in South China Sea (SCS), but only limited to coastal areas of regions within SCS territories. Therefore, this study was carried out to analyze the benthic sediment profile in an area beyond 12 nautical miles off the coast of Sarawak, southern SCS. Sediment samples were collected from 31 stations, comprising three depth ranges: (I) 20–50 m, (II) 50–100 m, and (III) 100–200 m. The total organic matter (TOM) contents were determined and subjected to dry and wet sieving methods for particle size analysis. TOM contents in the deep area (>50 m) were significantly higher (p = 0.05) and positively correlated (r = 0.73) with silt-clay fraction. About 55% and 82% of stations in strata II and III, respectively, were dominated by silt-clay fractions (50 m) tend to be poorly sorted, very fine skewed, and platykurtic. Unlike data obtained 20 years ago which reported high content of silt-clay (58%), this study recorded a lower content (35%); therefore, changes in sediment load had been observed in southern SCS. PMID:29075660

  7. 2008 Joint United States-Canadian program to explore the limits of the Extended Continental Shelf aboard the U.S. Coast Guard cutter Healy--Cruise HLY0806

    Science.gov (United States)

    Childs, Jonathan R.; Triezenberg, Peter J.; Danforth, William W.

    2012-01-01

    In September 2008, the U.S. Geological Survey (USGS), in cooperation with Natural Resources Canada, Geological Survey of Canada (GSC), conducted bathymetric and geophysical surveys in the Arctic Beaufort Sea aboard the U.S. Coast Guard cutter USCGC Healy. The principal objective of this mission to the high Arctic was to acquire data in support of delineation of the outer limits of the U.S. and Canadian Extended Continental Shelf (ECS) in the Arctic Ocean in accordance with the provisions of Article 76 of the Law of the Sea Convention. The Healy was accompanied by the Canadian Coast Guard icebreaker Louis S. St- Laurent. The science parties on the two vessels consisted principally of staff from the USGS (Healy), and the GSC and the Canadian Hydrographic Service (Louis). The crew included marine mammal and Native-community observers, ice observers, and biologists conducting research of opportunity in the Arctic Ocean. The joint survey proved an unqualified success. The Healy collected 5,528 km of swath (multibeam) bathymetry (38,806 km2) and CHIRP subbottom profile data, with accompanying marine gravity measurements. The Louis acquired 2,817 km of multichannel seismic (airgun) deep-penetration reflection-profile data along 12 continuous lines, as well as 35 sonobuoy refraction stations and accompanying single-beam bathymetry. The coordinated efforts of the two vessels resulted in seismic-reflection profile data of much higher quality and continuity than if the data had been acquired with a single vessel alone. Equipment failure rate of the seismic equipment gear aboard the Louis was greatly improved with the advantage of having a leading icebreaker. When ice conditions proved too severe to deploy the seismic system, the Louis led the Healy, resulting in much improved quality of the swath bathymetry and CHIRP sub-bottom data in comparison with data collected by the Healy in the lead or working alone. Ancillary science objectives, including ice observations, deployment

  8. Magmatism and sedimentation in an area in the Continental Shelf of Cabo Frio, Rio de Janeiro, Brazil, in the Upper Cretaceous - Tertiary interval; Magmatismo e sedimentacao em uma area na Plataforma Continental de Cabo Frio, Rio de Janeiro, Brasil, no intervalo Cretaceo Superior - Terciario

    Energy Technology Data Exchange (ETDEWEB)

    Oreiro, Sergio Goulart [PETROBRAS S.A., Santos, SP (Brazil). E e P. Ativo de Exploracao Santos - Polo Sul], E-mail: oreiro@petrobras.com.br

    2005-11-15

    The Continental Shelf of the Cabo Frio Area shows unique features in its tectono-sedimentary evolution when compared to the other areas of the Campos and Santos basins. The presence of a regular pattern of antithetic faults in the basement and in the sin-rift and post-rift sedimentary sections, are some of these features. In addition, the area shows important magmatic events in the Upper Cretaceous and Tertiary sequences, which climax took place in the earliest portion of the Middle Eocene. The description of these magmatic events and their influence in the post-rift sedimentation is the main objective of this paper. The analyses of seismic reflection and well log data, in the work area, points to a set of diagnostic features that can lead to the identification of magmatic events and the distinction of intrusive from extrusive rocks, as well as their intercalations with epiclastic sedimentary sequences. Volcanic edifices have preserved their conical shapes when they were formed under submarine conditions; under subaereal conditions, they show irregular shapes due to erosion. In this way, these observations indicate the paleobathymetry for the time of the formation of these edifices. In the case of the work area, the integration of the analyzed data indicates that extrusive events are more widespread than intrusive events. The sedimentary pattern of the work area is similar to that of the Campos Basin. The sedimentary sequences that overlap this volcano-sedimentary section are not directly related to the magmatic pulses in the area; however, they affected the palaeo-relief of the sea floor, which controlled turbiditic deposition. (author)

  9. The Norwegian state as a natural gas entrepreneur : the impact of the EEA agreement and EU gas market liberalization

    Energy Technology Data Exchange (ETDEWEB)

    Austvik, Ole Gunnar

    2009-07-01

    This study focuses on how the European Economic Area (EEA) agreement and European Union (EU) natural gas market liberalization processes have challenged and changed the Norwegian state's natural gas entrepreneurship since the 1990s. The point of departure is that the Norwegian petroleum industry was developed as a political entreprise by the Norwegian state from the early 1970s. As a political entrepreneur, the state was engaged in the industry as production entrepreneur, as well as being a political and economic risk-taker. As a political entrepreneur the state could define social goals for activities and use regulative, legal and political measures to reach goals that private entrepreneurs do not have at their disposal. As a political entrepreneur the Norwegian state did not limit itself to the regulation of activities on the Norwegian Continental Shelf (NCS), but instead took on the role of innovator and leader of economic change and development. Natural gas activities and their relations to the infantile, imperfect and international European gas market demanded additional political efforts compared to oil activities. The Norwegian state used several instruments in a combination to reach goals set up: regulations, direct participation and political interventions, and preferential treatment of Norwegian companies. Policies were developed with high ambitions with regard to national sovereignty and control of the industry, an optimal resource management, and to capture as much rent as possible. In addition to being the regulator, law and policymaker the state became itself an industrial actor, and in periods a substantial financial contributor to developments. Government policy and industrial structures changed as the industry matured, and markets, international affairs and technology changed. The state not only ensured the establishment of the industry, but maintained its role as a driving force looking after and contributing to change and evolution, to the

  10. Asteroidea de la plataforma continental de Rio Grande do Sul (Brasil, coleccionados durante los viajes del N/Oc. "prof. W. Besnard" para el proyecto Rio Grande do Sul Asteroidea of the continental shelf of Rio Grande do Sul (Brazil, collected during the cruises of the R/V "prof. W. Besnard" for the project Rio Grande do Sul

    Directory of Open Access Journals (Sweden)

    Carlos J Carrera-Rodríguez

    1977-01-01

    , Mediaster trindadensis Bernasconi, Sclerasterias subangülosa (Verrill y Tosia parva (Perrier siendo nuevas ocurrencias para el área de estudio y Luidla barbadensis Perrier y L. elegans Perrier siendo nuevas ocurrencias para Brasil. 9 - El género Pectinidiscus Ludwig se reporta por la primera vez para las Américas y se describe una nueva especie: Pectinidiscus aliciae. Se compara con las otras dos especies conocidas del género, P. annae y P. sibogae.The Asteroidea collected during the cruises of the R/V "Prof. W. Besnard" along the coast of Rio Grande do Sul (Brazil from April 1968 to January 1972 were studied. Twenty-four species are reported from the continental shelf for the area between Torres (29ºS and Chui (34ºS. Labidiaster radiosus Lutken, Luidia clathrata (Say, Marginaster pectinatus Perrier, Mediaster trindadensis Bernasconi, Sclerasterias subangulosa (Verrill and Tosia parva (Perrier are new records for the area; Luidia barbadensis Perrier and L. elegans Perrier are new records for Brazil and Pectinidiscus aliciae sp. n. constitutes the first record of the genus from the Americas and is compared with the other two known species of the genus: P. annae and P. sibogae. Ecological data and the geographic distribution for each species are given. Keys for identification are provided. The general hydrology of the area and the biogeography are discussed and correlations of asteroid abundance with two commercially important fish species are made.

  11. Extended Reach Drilling on the example of Reelwell Drilling Method: Influence examination of different drill pipes on drilling performance on Idun field on the Norwegian Continental Shelf by PGNiG Norway AS.

    OpenAIRE

    Krol, Dariusz Pawel

    2011-01-01

    Master's thesis in Petroleum engineering Horizontal or extended reach drilling is incredibly fast growing technology. Although in some areas of the world ERD is still novelty, most of oil companies have been using the technology reliably and successfully for dozens of years. And those companies want to improve well-worn solutions to obtain better performance, thereby reducing costs. One of the main aspects that affects drilling performance and efficiency is adequate choice of drill pipe...

  12. On Apologizing in Norwegian

    OpenAIRE

    Awedyk, Witosław

    2011-01-01

    This paper discusses selected points concerning the verbal realization of the speech act of apology in Norwegian. It sets out to establish prevailing tendencies in the choice of apology strategies applied by the native speakers of Norwegian. The present findings, which seem to indicate that Norwegian apology strategies are fairly routinized, ought to be perceived as preliminary as a more detailed analysis of apology formulae will be presented in an upcoming article.

  13. New Jersey shallow shelf

    DEFF Research Database (Denmark)

    Expedition 313 Scientists; Bjerrum, Christian J.

    2009-01-01

    to key horizons in wells drilled into the adjacent coastal plain suggest the clinoform structures investigated during Expedition 313 were deposited during times of oscillations in global sea level; however, this needs to be determined with much greater certainty. The age, lithofacies, and core-log......Integrated Ocean Drilling Program (IODP) Expedition 313 to the New Jersey Shallow Shelf off the east coast of the United States is the third IODP expedition to use a mission-specific platform. It was conducted by the European Consortium for Ocean Research Drilling (ECORD) Science Operator (ESO......) between 30 April and 17 July 2009, with additional support from the International Continental Scientific Drilling Program (ICDP). There were three objectives: (1) date late Paleogene–Neogene depositional sequences and compare ages of unconformable surfaces that divide these sequences with times of sea...

  14. Safety management and control policy. A study of the safety regulation of offshore oil activity by the Norwegian Petroleum Directorate. Sikkerhetsstyring og reguleringsteknikk. Oljedirektoratets regulering av sikkerheten ved produksjon av petroleum

    Energy Technology Data Exchange (ETDEWEB)

    Graver, H P

    1983-01-01

    The Norwegian Petroleum Directorate (NPD) is the main administrative body with responsibility to regulate and control the safety aspects of drilling for and production of petroleum on the Norwegian Continental Shelf. Its responsibility does not, however, include the aspects of maritime safety, which are regulated by the Norwegian Maritime Directorate. This study is limited to the regulation of safety on fixed installations for production of petroleum. The object has been to describe the methods applied by the NPD to achieve better safety, and to give answers to why these specific methods of approach have developed as they have. A conclusion that may be drawn from this study is that there exists a relationship of close cooperation between the NPD and the oil industry represented by the operating companies. Only this can explain the differences we find in the NPD approach as compared to the approach of other parts of public administration. Such a relationship probably leads to better safety within the scope of technical rationality than would have a more hostile relationship between the Directorate and the industry. This has its price, however. Aspects of the safety question not included within the limits of a purely technical approach are not as easily taken into account. Partly due to this fact, other parties with interests in safety are not represented.

  15. Plant speciation in continental island floras as exemplified by Nigella in the Aegean Archipelago

    OpenAIRE

    Comes, Hans Peter; Tribsch, Andreas; Bittkau, Christiane

    2008-01-01

    Continental shelf island systems, created by rising sea levels, provide a premier setting for studying the effects of geographical isolation on non-adaptive radiation and allopatric speciation brought about by genetic drift. The Aegean Archipelago forms a highly fragmented complex of mostly continental shelf islands that have become disconnected from each other and the mainland in relatively recent geological times (ca

  16. Coupling of Coastal Zone Color Scanner data to a physical-biological model of the southeastern U.S. continental shelf ecosystem. I - CZCS data description and Lagrangian particle tracing experiments. II - An Eulerian model. III - Nutrient and phytoplankton fluxes and CZCS data assimilation

    Science.gov (United States)

    Ishizaka, Joji

    1990-01-01

    Surface phytoplankton biomass of the southeastern U.S. continental shelf area is discussed based on coastal zone color scanner (CZCS) images obtained in April 1980. Data of chlorophyll distributions are analyzed in conjunction with concurrent flow and temperature fields. Lagrangian particle tracing experiments show that the particles move consistently with the evolution of the chlorophyll patterns. A four-component physical-biological model for a horizontal plane at a nominal depth of 17 m is presented. Model simulations using various physical-biological dynamics and boundary conditions show that the variability of chlorophyll distributions is controlled by horizontal advection. Phytoplankton and nutrient fluxes, calculated using the model, show considerable variability with time. The chlorophyll distributions obtained from the CZCS images are assimilated into the model to improve the phytoplankton flux estimates.

  17. Contributions to knowledge of the continental margin of Uruguay. Uruguayan continental margin: morphology, geology and identification of the base of the slope

    International Nuclear Information System (INIS)

    Preciozzi, F.

    2014-01-01

    This work is about the morphology, geology and the identification of the base of the slope in the The Uruguayan continental margin which corresponds to the the type of divergent, volcanic and segmented margins. Morphologically is constituted by a clearly defined continental shelf, as well as a continental slope that presents configuration changes from north to south and passes directly to the abyssal plain

  18. Arctic Ocean outflow and glacier–ocean interactions modify water over the Wandel Sea shelf (northeastern Greenland

    Directory of Open Access Journals (Sweden)

    I. A. Dmitrenko

    2017-12-01

    Full Text Available The first-ever conductivity–temperature–depth (CTD observations on the Wandel Sea shelf in northeastern Greenland were collected in April–May 2015. They were complemented by CTDs taken along the continental slope during the Norwegian FRAM 2014–2015 drift. The CTD profiles are used to reveal the origin of water masses and interactions with ambient water from the continental slope and the tidewater glacier outlet. The subsurface water is associated with the Pacific water outflow from the Arctic Ocean. The underlying halocline separates the Pacific water from a deeper layer of polar water that has interacted with the warm Atlantic water outflow through the Fram Strait, recorded below 140 m. Over the outer shelf, the halocline shows numerous cold density-compensated intrusions indicating lateral interaction with an ambient polar water mass across the continental slope. At the front of the tidewater glacier outlet, colder and turbid water intrusions were observed at the base of the halocline. On the temperature–salinity plots these stations indicate a mixing line that is different from the ambient water and seems to be conditioned by the ocean–glacier interaction. Our observations of Pacific water are set within the context of upstream observations in the Beaufort Sea and downstream observations from the Northeast Water Polynya, and clearly show the modification of Pacific water during its advection across the Arctic Ocean. Moreover, ambient water over the Wandel Sea slope shows different thermohaline structures indicating the different origin and pathways of the on-shore and off-shore branches of the Arctic Ocean outflow through the western Fram Strait.

  19. Arctic Ocean outflow and glacier-ocean interactions modify water over the Wandel Sea shelf (northeastern Greenland)

    Science.gov (United States)

    Dmitrenko, Igor A.; Kirillov, Sergey A.; Rudels, Bert; Babb, David G.; Toudal Pedersen, Leif; Rysgaard, Søren; Kristoffersen, Yngve; Barber, David G.

    2017-12-01

    The first-ever conductivity-temperature-depth (CTD) observations on the Wandel Sea shelf in northeastern Greenland were collected in April-May 2015. They were complemented by CTDs taken along the continental slope during the Norwegian FRAM 2014-2015 drift. The CTD profiles are used to reveal the origin of water masses and interactions with ambient water from the continental slope and the tidewater glacier outlet. The subsurface water is associated with the Pacific water outflow from the Arctic Ocean. The underlying halocline separates the Pacific water from a deeper layer of polar water that has interacted with the warm Atlantic water outflow through the Fram Strait, recorded below 140 m. Over the outer shelf, the halocline shows numerous cold density-compensated intrusions indicating lateral interaction with an ambient polar water mass across the continental slope. At the front of the tidewater glacier outlet, colder and turbid water intrusions were observed at the base of the halocline. On the temperature-salinity plots these stations indicate a mixing line that is different from the ambient water and seems to be conditioned by the ocean-glacier interaction. Our observations of Pacific water are set within the context of upstream observations in the Beaufort Sea and downstream observations from the Northeast Water Polynya, and clearly show the modification of Pacific water during its advection across the Arctic Ocean. Moreover, ambient water over the Wandel Sea slope shows different thermohaline structures indicating the different origin and pathways of the on-shore and off-shore branches of the Arctic Ocean outflow through the western Fram Strait.

  20. Continental tectonics and continental kinetics

    International Nuclear Information System (INIS)

    Allegre, C.J.; Jaupart, C.; Paris-7 Univ., 75

    1985-01-01

    We present a model of continental growth which combines the results of geochemical studies and tectonic ideas about the evolution of continents through geological time. The process of continental growth is mainly controlled by surface phenomena. Continental material is extracted from the mantle along subduction zones at the periphery of oceans, and is destroyed in collision zones where it is remobilized and made available for subduction. We derive an equation for S, the portion of the Earth's surface occupied by continents, which reads as follows: dS/dt=a . √(1-S)-b . S. Coefficients a and b depend on the geometry of plates, on their number and on their velocities. We assume that they decrease exponentially with time with the same time-scale α. This model satisfies both geochemical and tectonic constraints, and allows the integration of several current observations in a single framework. (orig.)