WorldWideScience

Sample records for alaskan continental shelf

  1. Southeast continental shelf studies

    Energy Technology Data Exchange (ETDEWEB)

    Menzel, D.W.

    1979-02-12

    Research efforts on the southeast continental shelf currently describe the manner in which fluctuations in Gulf Stream motion influence biological and chemical processes. Current meter arrays are maintained in the Georgia Bight and in Onslow Bay to describe general circulation patterns and to identify forcing functions. biological studies describe processes affecting temporal and spatial variations on the shelf and have attempted to track the biological history of intruded Gulf Stream water masses. Chemical studies examine the influence of both physical and biological variables on the distribution and fate of trace elements. The current state of knowledge is reviewed, the hypotheses developed and are described, a rationale for testing these hypotheses is given. 1 figure, 1 table.

  2. The Myanmar continental shelf

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Rao, P.S.

    flooding of the Sunda Shelf: a late-glacial sea-level record. Science 288, 1033–1035. Hyder, P., Jeans, D.R.G., Cauquil, E.. Nerzic, R. 2005. Observations and predictability of internal solitons in the northern Andaman Sea. Applied Ocean Research, 27, 1...

  3. 75 FR 61512 - Outer Continental Shelf Official Protraction Diagrams

    Science.gov (United States)

    2010-10-05

    ... Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf Official... Outer Continental Shelf Official Protraction Diagrams (OPDs) located within Atlantic Ocean areas, with... informational purposes only. Outer Continental Shelf Official Protraction Diagrams in the North Atlantic,...

  4. 76 FR 2919 - Outer Continental Shelf Official Protraction Diagram and Supplemental Official Outer Continental...

    Science.gov (United States)

    2011-01-18

    ... Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf Official Protraction Diagram and Supplemental Official Outer Continental Shelf Block Diagrams AGENCY: Bureau of Ocean... American Datum of 1983 (NAD 83) Outer Continental Shelf Official Protraction Diagram and...

  5. Continental Shelf Boundary - Alaska NAD83

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Continental Shelf Boundaries (CSB) lines in ESRI shapefile format for the BOEM Alaska Region. The CSB defines the seaward limit of federally...

  6. Atlantic NAD 83 Continental Shelf Boundary (CSB)

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Continental Shelf Boundary (CSB) lines in ESRI shapefile format for the BOEM Atlantic Region. The CSB defines the seaward limit of federally...

  7. Coordination: southeast continental shelf studies. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Menzel, D.W.

    1980-03-01

    The GABEX I experiment is designed to provide synoptic coverage of a series of Gulf Stream wave-like disturbances, the effect of these on the circulation of the entire shelf, and on biological and chemical processes. This study was initiated in February 1980 when current meter arrays were deployed. These meters will be removed in July 1980. In April three ships will simultaneously study the effects of Gulf Stream disturbances on the hydrography, chemistry, and biology of the shelf. One vessel will track a specific wave-like disturbance and provide synoptic coverage of the shelf area. The second vessel will determine the effect of shelf break processes on adjacent shelf water; and the third will study trace metal distributions in and outside of disturbances. Research progress is reported in continental shelf studies, nearshore and estuarine studies (diffusion of freshwater out of nearshore zone), tidal currents and material transport, and mixing of inlet plumes.

  8. Elephant teeth from the atlantic continental shelf

    Science.gov (United States)

    Whitmore, F.C.; Emery, K.O.; Cooke, H.B.S.; Swift, D.J.P.

    1967-01-01

    Teeth of mastodons and mastodons have been recovered by fishermen from at least 40 sites on the continental shelf as deep as 120 meters. Also present are submerged shorelines, peat deposits, lagoonal shells, and relict sands. Evidently elephants and other large mammals ranged this region during the glacial stage of low sea level of the last 25.000 years.

  9. Federal Outer Continental Shelf Oil and Gas Production Statistics

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — Federal Outer Continental Shelf Oil and Gas Production Statistics by month and summarized annually. Outer Continental Shelf consists of Gulf of Mexico, Pacific and...

  10. 49 CFR 192.10 - Outer continental shelf pipelines.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Outer continental shelf pipelines. 192.10 Section... NATURAL AND OTHER GAS BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS General § 192.10 Outer continental shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf (as defined in...

  11. 49 CFR 195.9 - Outer continental shelf pipelines.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Outer continental shelf pipelines. 195.9 Section... HAZARDOUS LIQUIDS BY PIPELINE General § 195.9 Outer continental shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf must identify on all their respective pipelines the specific...

  12. 75 FR 1076 - Outer Continental Shelf Civil Penalties

    Science.gov (United States)

    2010-01-08

    ...: 2010-119] DEPARTMENT OF THE INTERIOR Minerals Management Service Outer Continental Shelf Civil... maximum daily civil penalty assessment. SUMMARY: The Outer Continental Shelf Lands Act requires the MMS to... operations in the Outer Continental Shelf at least once every 3 years. This review ensures that the...

  13. Oceanography of the Southeastern Continental Shelf

    Science.gov (United States)

    This volume, the second in the Coastal and Estuarine Sciences series, provides a synthesis of the physical, chemical, and biological oceanography of the South Atlantic Bight (SAB). The results presented derive from a decade-long multidisciplinary investigation of the SAB continental shelf regime.The SAB extends from West Palm Beach, Fla., where the narrow south Florida shelf begins to broaden, to Cape Hatteras, N.C., where the shelf again narrows. This broad and shallow area is distinguished by the proximity of the Gulf Stream to the shelf break. Large contrasts in the distribution of properties, the strength of oceanic and atmospheric forces, and the high frequency (4-12 days) at which these forces vary have created a unique natural laboratory in which a variety of oceanic processes may be studied.

  14. 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.

  15. 76 FR 54787 - Outer Continental Shelf Official Protraction Diagram, Lease Maps, and Supplemental Official Outer...

    Science.gov (United States)

    2011-09-02

    ... Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf Official Protraction Diagram, Lease Maps, and Supplemental Official Outer Continental Shelf Block Diagrams AGENCY... revised North American Datum of 1927 (NAD 27) Outer Continental Shelf Official Protraction Diagram,...

  16. 76 FR 7518 - Outer Continental Shelf Air Regulations Consistency Update for Alaska

    Science.gov (United States)

    2011-02-10

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Alaska AGENCY... of the Outer Continental Shelf (``OCS'') Air Regulations. Requirements applying to OCS sources..., Intergovernmental relations, Nitrogen dioxide, Nitrogen oxides, Outer Continental Shelf, Ozone, Particulate...

  17. 77 FR 52630 - Outer Continental Shelf Air Regulations Consistency Update for California

    Science.gov (United States)

    2012-08-30

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for California AGENCY... of the Outer Continental Shelf (``OCS'') Air Regulations. Requirements applying to OCS sources..., Intergovernmental relations, Nitrogen dioxide, Nitrogen oxides, Outer Continental Shelf, Ozone, Particulate...

  18. 76 FR 15898 - Outer Continental Shelf Air Regulations; Consistency Update for California

    Science.gov (United States)

    2011-03-22

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations; Consistency Update for California AGENCY... of the Outer Continental Shelf (``OCS'') Air Regulations. Requirements applying to OCS sources... oxides, Outer Continental Shelf, Ozone, Particulate matter, Permits, Reporting and...

  19. Discoveries on the Norwegian continental shelf

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-02-01

    As discussed in this document, there are 108 discoveries on the Norwegian continental shelf which so far have not been approved for development. The oil and gas resources of the Norwegian Sea and the Barents Sea are mostly found in discoveries containing large volumes of gas. Eighty-one of the discoveries which are not approved for development are located in the North Sea and more than 60% of the discoveries in this province contain less than 5 mill Sm{sup 3} oil equivalents. In the Norwegian Sea and the Barents Sea there are 27 discoveries which are not approved for development and whose total resources are estimated at 500 mill Sm{sup 3} oil equivalents. About 60% of the oil resources is expected to be comprised by development plans in 1997 or 1998. Another 20% is in new discoveries currently being evaluated or in discoveries containing large volumes of gas. Production forecasts indicate substantial vacant oil processing capacity after 2000. Vacant gas processing capacity will mainly arise after 2005. 23 figs., 3 tabs.

  20. Outer Continental Shelf Lease Blocks - Alaska Region NAD83

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Outer Continental Shelf block outlines in ArcGIS shapefile format for the BOEM Alaska Region. OCS blocks are used to define small geographic...

  1. 75 FR 71734 - Outer Continental Shelf (OCS), Scientific Committee (SC)

    Science.gov (United States)

    2010-11-24

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf (OCS), Scientific Committee (SC) AGENCY: Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE),...

  2. In search of the Malaysian Extended Continental Shelf

    Science.gov (United States)

    Yahaya, N. A. Z.; Musa, T. A.; Omar, K. M.; Din, A. H. M.; Abdullah, N. M.; Othman, A. H.; Wahab, M. I. A.

    2016-06-01

    Over the years, the sovereignty proclamation of Coastal States for their extended continental shelf has been a crucial matter. The declaration and extension of a continental shelf under the United Nations Convention on the Law of the Sea provide significant potential for many developing nations in economics, trades, resource exploitation, communication and security. Hence, the application of satellite altimeter, as one of the solutions for collecting bathymetry data to define the approximate limits of the continental shelf, is reviewed. This paper also discusses the possible significance or contribution of space-derived bathymetry, i.e. the seafloor topography, either independently or harmoniously with different datasets, to meet the element of the Article 76 of UNCLOS.

  3. GENERATION OF NONLINEAR INTERNAL WAVES ON CONTINENTAL SHELF

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A 2-D KdV equation is derived under condition of arbitrary continuous density profiles. A non-fission version of initial internal solitary waves propagating onto the continental shelf is studied by means of the 2-D KdV equation. Under non-Bohr and Sommerfeld’s condition, numerical calculations are carried out based on the KdV equation. The results shows that the initial internal solitary waves in deep ocean break down into internal undular bores on the continental shelf. And the bores have a like-soliton leading fronts and undular trails.

  4. The petroleum resources on the Norwegian continental shelf

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-02-01

    In this document the Norwegian Petroleum Directorate estimates the total recoverable petroleum resources on the Norwegian continental shelf to be 12.5 billion Sm{sup 3} oil equivalents. There is considerable uncertainty regarding the undiscovered resources, the expected value being 3.5 billion Sm{sup 3} oil equivalents. The new estimates signify an increase of 14% since the calculations made last year. This increase is chiefly due to an upward adjustment of the expectations for a future increase in the recovery factor for the in place resources on the continental shelf. In 1995, the Norwegian oil production accounted for 4.3% of the global oil production. It is estimated that Norway has a total of about 1.3% of the discovered recoverable oil resources and about 1.8% of the discovered recoverable gas resources in the world. The Norwegian annual oil production is expected to reach a maximum of 3.7 million barrels per day in the year 2000. Many new discoveries are still being made on the Norwegian continental shelf. In the last two years, 20 new discoveries have been made, giving a resources growth of about 260 million Sm{sup 3} oil equivalents. Great technological progress has been made on the Norwegian continental shelf during the last five years concerning exploration, development and production. As for mapping, the introduction of 3D seismic data and the development of interpolation tools have helped to provide a much better understanding of the substratum. 88 figs.

  5. 75 FR 10809 - Outer Continental Shelf (OCS) Scientific Committee-Notice of Renewal

    Science.gov (United States)

    2010-03-09

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Outer Continental Shelf (OCS) Scientific Committee--Notice of Renewal AGENCY: Minerals Management Service (MMS), Interior. ACTION: Notice of renewal of the Outer Continental Shelf Scientific...

  6. 77 FR 15382 - Outer Continental Shelf Scientific Committee; Notice of Renewal

    Science.gov (United States)

    2012-03-15

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Outer Continental Shelf Scientific Committee; Notice of Renewal AGENCY: Bureau of Ocean Energy... the Outer Continental Shelf (OCS) Scientific Committee (Committee). The Committee provides advice...

  7. 75 FR 3423 - Outer Continental Shelf Air Regulations Consistency Update for Alaska

    Science.gov (United States)

    2010-01-21

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Alaska AGENCY.... Requirements applying to Outer Continental Shelf (``OCS'') sources located within 25 miles of States' seaward..., Incorporation by reference, Intergovernmental relations, Nitrogen dioxide, Nitrogen oxides, Outer...

  8. 76 FR 43230 - Outer Continental Shelf Air Regulations Consistency Update for Virginia

    Science.gov (United States)

    2011-07-20

    ... From the Federal Register Online via the Government Publishing Office ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Virginia AGENCY... Outer Continental Shelf (OCS) Air Regulations. Requirements applying to OCS sources located within...

  9. 76 FR 63654 - Outer Continental Shelf Official Protraction Diagram, Lease Maps, and Supplemental Official Outer...

    Science.gov (United States)

    2011-10-13

    ... Doc No: 2011-26503] DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Outer Continental Shelf Official Protraction Diagram, Lease Maps, and Supplemental Official Outer Continental Shelf Block... American Datum of 1927 (NAD 27) Outer Continental Shelf (OCS) Official Protraction Diagram (OPD),...

  10. 75 FR 3392 - Outer Continental Shelf Air Regulations Consistency Update for Alaska

    Science.gov (United States)

    2010-01-21

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Alaska AGENCY... 50.410. Requirements applying to Outer Continental Shelf (``OCS'') sources located within 25 miles of..., Intergovernmental relations, Nitrogen dioxide, Nitrogen oxides, Outer Continental Shelf, Ozone, Particulate...

  11. On the freshening of the northwestern Weddell Sea continental shelf

    Directory of Open Access Journals (Sweden)

    H. H. Hellmer

    2011-05-01

    Full Text Available We analyzed hydrographic data from the northwestern Weddell Sea continental shelf of the three austral winters 1989, 1997, and 2006 and two summers following the last winter cruise. During summer a thermal front exists at ~64° S separating cold southern waters from warm northern waters that have similar characteristics as the deep waters of the central basin of the Bransfield Strait. In winter, the whole continental shelf exhibits southern characteristics with high Neon (Ne concentrations, indicating a significant input of glacial melt water. The comparison of the winter data from the shallow shelf off the tip of the Antarctic Peninsula, spanning a period of 17 yr, shows a salinity decrease of 0.09 for the whole water column, which has a residence time of <1 yr. We interpret this freshening as being caused by a combination of reduced salt input due to a southward sea ice retreat and higher precipitation during the late 20th century on the western Weddell Sea continental shelf. However, less salinification might also result from a delicate interplay between enhanced salt input due to sea ice formation in coastal areas formerly occupied by Larsen A and B ice shelves and increased Larsen C ice loss.

  12. On the freshening of the northwestern Weddell Sea continental shelf

    Directory of Open Access Journals (Sweden)

    H. H. Hellmer

    2010-12-01

    Full Text Available We analysed hydrographic data from the northwestern Weddell Sea continental shelf of three austral winters (1989, 1997 and 2006 and two summers following the last winter cruise. During summer a thermal front exists at ~64° S separating cold southern waters from warm northern waters that have similar characteristics as the deep waters of the central basin of the Bransfield Strait. In winter, the whole continental shelf exhibits southern characteristics with high Neon (Ne concentrations, indicating a significant input of glacial melt water. The comparison of the winter data at the tip of the Antarctic Peninsula, spanning a period of 17 years, shows a salinity decrease of 0.09 for the whole water column. We interpret this freshening as a reduction in salt input to the water masses being advected northward on the western Weddell Sea continental shelf. Possible causes for the reduced winter salinification are a southward retreat of the summer sea ice edge together with more precipitation in this sector. However, the latter might have happened in conjunction with an increase in ice shelf mass loss, counteracting an enhanced salt input due to sea ice formation in coastal areas formerly occupied by Larsen A and B ice shelves.

  13. The geomorphology of a glaciated continental shelf, Western Scotland, UK

    Science.gov (United States)

    Howe, John; Dove, Dayton; Bradwell, Tom

    2013-04-01

    We present recently collected swath bathymetry and legacy seismic data from two regions of the north-west UK continental shelf: the Sea of the Hebrides; and the Firth of Lorn, western Scotland. Both regions have experienced extensive Pleistocene ice sheet glaciation and both provide abundant geomorphological evidence of subglacial and postglacial processes. The Sea of the Hebrides bathymetry data cover 2200 km2 and provide new geomorphological evidence for an ice stream flowing from western Scotland and the Inner Hebrides focusing towards a trough-mouth fan (the Barra Fan) at the continental shelf break during the height of the last glaciation. Notably, bedrock structures provide a control on the location and orientation of glacially overdeepened basins and troughs on the inner shelf. Whilst around the Islands of Canna and Rum, convergent seabed glacial lineations and other subglacially streamlined features eroded in bedrock preserve the direction of ice sheet movement - indicating ice streaming in a south-westerly direction across the continental shelf. We propose that this fast-flow zone formed part of a larger convergent ice stream system draining much of western Scotland and the north of Ireland. The Firth of Lorn bathymetry acquisition comprises 553km2 of data, collected as part of the INIS Hydro program (Ireland, Northern Ireland and Scotland Hydrographic Survey). This region of nearshore continental shelf is revealed as predominantly bedrock-dominated seabed, characterised by a series of narrow, strongly fault-controlled troughs, part of the Great Glen Fault Zone complex. Evidence for glaciation is widespread and well preserved in the Firth of Lorn and surrounding seabed with moraines, bedrock lineations (?megagrooves?) and overdeepened basins common across the area. Initial mapping shows that our understanding of the configuration and style of deglaciation in these sectors of the former British-Irish Ice Sheet can be greatly improved by the collection of

  14. Propagation of internal waves up continental slope and shelf

    Institute of Scientific and Technical Information of China (English)

    DAI Dejun; WANG Wei; QIAO Fangli; YUAN Yeli; XIANG Wenxi

    2008-01-01

    In a two-dimensional and linear framework, a transformation was developed to derive eigensolutions of internal waves over a subcriticai hyperbolic slope and to approximate the continental slope and shelf. The transformation converts a hyperbolic slope in physical space into a fiat bottom in transform space while the governing equations of internal waves remain hyperbolic. The eigensolutions are further used to study the evolution of linear internal waves as it propagates to subcritical continental slope and shelf. The stream function, velocity, and vertical shear of velocity induced by internal wave at the hyperbolic slope are analytically expressed by superposition of the obtained eigensolutions. The velocity and velocity shear increase as the internal wave propagates to a hyperbolic slope. They become very large especially when the slope of internal wave rays approaches the topographic slope, which is consistent with the previous studies.

  15. Habitat Specialization in Tropical Continental Shelf Demersal Fish Assemblages

    OpenAIRE

    Ben M Fitzpatrick; Euan S Harvey; Heyward, Andrew J.; Twiggs, Emily J.; Jamie Colquhoun

    2012-01-01

    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. ...

  16. Pleistocene mammals from the southern Brazilian continental shelf

    Science.gov (United States)

    Lopes, Renato Pereira; Buchmann, Francisco Sekiguchi

    2011-02-01

    Fossils of terrestrial mammals preserved in submarine environment have been recorded in several places around the world. In Brazil such fossils are rather abundant in the southernmost portion of the coast, associated to fossiliferous concentrations at depths up to 10 m. Here is presented a review of such occurrences and the first record of fossils in deeper areas of the continental shelf. The fossils encompass several groups of both extinct and extant mammals, and exhibit several distinct taphonomic features, related to the marine environment. Those from the inner continental shelf are removed and transported from the submarine deposits to the coast during storm events, thus forming large konzentrat-lagerstätte on the beach, called “Concheiros”. The only fossils from deeper zones of the shelf known so far are a portion of a skull, a left humerus and of a femur of Toxodon sp. and a lower right molar of a Stegomastodon waringi, all collected by fishermen at depths around 20 m. The presence of fossils at great depths and distances from the present coastline, without signs of abrasion and far from areas of fluvial discharges does indicate that these remains have not been transported from the continent to the shelf, but have been preserved directly on the area that today correspond to the continental shelf. These remains indicate the existence of large fossiliferous deposits that have developed during periods of sea-level lowstand (glacial maxima) and have been submerged and reworked by the sea-level rise at the end of the last glaciation.

  17. Map of Distribution of Bottom Sediments on the Continental Shelf, Gulf of Alaska

    Science.gov (United States)

    Evans, Kevin R.; Carlson, Paul R.; Hampton, Monty A.; Marlow, Michael S.; Barnes, Peter W.

    2000-01-01

    Introduction The U.S. Geological Survey has a long history of exploring marine geology in the Gulf of Alaska. As part of a cooperative program with other federal and state agencies, the USGS is investigating the relations between ocean-floor geology and benthic marine biohabitats. This bottom sediment map, compiled from published literature will help marine biologists develop an understanding of sea-floor geology in relation to various biological habitats. The pattern of sea-floor sedimentation and bottom morphology in the Gulf of Alaska reflects a complex interplay of regional tectonism, glacial advances and retreats, oceanic and tidal currents, waves, storms, eustatic change, and gravity-driven processes. This map, based on numerous cruises during the period of 1970-1996, shows distribution of bottom sediments in areas of study on the continental shelf. The samples were collected with piston, box, and gravity corers, and grab samplers. The interpretations of sediment distribution are the products of sediment size analyses combined with interpretations of high-resolution seismic reflection profiles. The sea floor was separated into several areas as follows: Cook Inlet -- Hazards studies in this embayment emphasized sediment distribution, sediment dynamics, bedforms, shallow faults, and seafloor stability. Migrating mega-sandwaves, driven by strong tidal currents, influence seabed habitats and stability of the seafloor, especially near pipelines and drilling platforms. The coarseness of the bottom sediment reinforces the influence of the strong tidal currents on the seafloor habitats. Kodiak Shelf -- Tectonic framework studies demonstrate the development of an accretionary wedge as the Pacific Plate underthrusts the Alaskan landmass. Seismic data across the accretionary wedge reveal anomalies indicative of fluid/gas vent sites in this segment of the continental margin. Geologic hazards research shows that movement along numerous shallow faults poses a risk to sea

  18. 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

  19. 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)

  20. Water mass modification over the continental shelf north of Ronne Ice Shelf, Antarctica

    OpenAIRE

    Nicholls, Keith W.; L. Padman; Schröder, Michael; Woodgate, R. A.; Jenkins, Adrian; Østerhus, Svein

    2003-01-01

    We use new data from the southern Weddell Sea continental shelf to describe water mass conversion processes in a formation region for cold and dense precursors of Antarctic Bottom Water. The cruises took place in early 1995, 1998, and 1999, and the time series obtained from moored instruments were up to 30 months in length, starting in 1995. We obtained new bathymetric data that greatly improve our definition of the Ronne Depression, which is now shown to be limited to the sout...

  1. 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.

    the Deccan trap coastal province is the predominant clay mineral in the sediments of the continental shelf south of the Gulf of Kutch. Lateral variations reveal that the montmorillonite contents are high in the innershelf and on the continental slope...

  2. Methane hydrate resource assessment of the outer continental shelf : in-place Gulf of Mexico results

    Energy Technology Data Exchange (ETDEWEB)

    Frye, M. [Minerals Mangement Service, Herndon, VA (United States); Grace, J. [Earth Science Associates, Long Beach, CA (United States); Hunt, J.; Shedd, W. [Minerals Management Service, New Orleans, LA (United States); Kaufman, G. [Massachusetts Inst. of Technology, Boston, MA (United States); Schuenemeyer, J. [Southwest Statistical Consulting, Cortez, CO (United States)

    2008-07-01

    The Minerals Management Service (MMS) is division of the United States (U.S.) Department of the Interior. Its mandate is to manage natural gas, oil, and other mineral resources on the U.S. outer continental shelf (OCS). The MMS launched a project in order to provide an assessment of the natural gas hydrate resource potential across the entire OCS, including the Alaskan, Atlantic, Gulf of Mexico, and Pacific margins. The purpose of this ongoing project is to provide a probabilistic evaluation of in-place, technically recoverable, and economically recoverable gas hydrate resources. This paper provided an overview of the project, including a preliminary assessment of in-place gas hydrate resources in the Gulf of Mexico. The paper described the probabilistic model that was built on a mass balance approach to assessment. The model provided a high degree of spatial resolution and supported detailed mapping. The model produced a Monte Carlo distribution of in-place resources that ranged from 314 trillion to 974 trillion cubic meters (TCM) with a mean value of 607 TCM. The paper also provided a link to the full report which included the model methodology, underlying assumptions, and input datasets. Additional work on the development of a technically recoverable model component is currently underway. 1 fig.

  3. 75 FR 24966 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Science.gov (United States)

    2010-05-06

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Minerals Management Service Notice on Outer Continental Shelf Oil and Gas Lease Sales AGENCY: Minerals... in any other of the following groups at Outer Continental Shelf oil and gas lease sales to be...

  4. 77 FR 64826 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Science.gov (United States)

    2012-10-23

    ... From the Federal Register Online via the Government Publishing Office ] DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management (BOEM) Notice on Outer Continental Shelf Oil and Gas Lease Sales AGENCY... with any entity in any of the other following groups at Outer Continental Shelf oil and gas lease...

  5. 77 FR 27480 - Outer Continental Shelf Scientific Committee; Announcement of Plenary Session

    Science.gov (United States)

    2012-05-10

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Outer Continental Shelf Scientific Committee; Announcement of Plenary...: The Outer Continental Shelf (OCS) Scientific Committee (SC) will meet at the Fess Parker's...

  6. 75 FR 51968 - Outer Continental Shelf Air Regulations Consistency Update for Massachusetts

    Science.gov (United States)

    2010-08-24

    ... From the Federal Register Online via the Government Publishing Office ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Massachusetts AGENCY... update to a portion of the Outer Continental Shelf (``OCS'') Air Regulations. Requirements applying...

  7. 75 FR 3387 - Outer Continental Shelf Air Regulations Consistency Update for Alaska

    Science.gov (United States)

    2010-01-21

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Alaska AGENCY: Environmental Protection Agency (EPA). ACTION: Final rule. SUMMARY: EPA is finalizing the update of the Outer..., Nitrogen oxides, Outer Continental Shelf, Ozone, Particulate matter, Permits, Reporting and...

  8. 76 FR 43185 - Outer Continental Shelf Air Regulations Consistency Update for Virginia

    Science.gov (United States)

    2011-07-20

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Virginia AGENCY... approve an update to a portion of the Outer Continental Shelf (OCS) Air Regulations. Requirements applying... on the OCS, see appendix A to this part. * * * * * (22) Virginia. (i) State requirements. (A)...

  9. 78 FR 25100 - Outer Continental Shelf Scientific Committee; Announcement of Plenary Session

    Science.gov (United States)

    2013-04-29

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Outer Continental Shelf Scientific Committee; Announcement of Plenary...: The Outer Continental Shelf (OCS) Scientific Committee (SC) will meet at the Marriott Downtown...

  10. Data Assimilation in Hydrodynamic Models of Continental Shelf Seas

    DEFF Research Database (Denmark)

    Sørensen, Jacob Viborg Tornfeldt

    2004-01-01

    and forecast skill in the Inner Danish Waters. The framework for combining data assimilation and off-line error correction techniques is discussed and presented. Early results show a potential for such an approach, but a more elaborate investigation is needed to further develop the idea. Finally, work has been......This thesis consists of seven research papers published or submitted for publication in the period 2002-2004 together with a summary report. The thesis mainly deals with data assimilation of tide gauge data in two- and three-dimensional hydrodynamic models of the continental shelf seas....... Assimilation of sea surface temperature and parameter estimation in hydrodynamic models are also considered. The main focus has been on the development of robust and efficient techniques applicable in real operational settings. The applied assimilation techniques all use a Kalman filter approach. They consist...

  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. Habitat specialization in tropical continental shelf demersal fish assemblages.

    Science.gov (United States)

    Fitzpatrick, Ben M; Harvey, Euan S; Heyward, Andrew J; Twiggs, Emily J; Colquhoun, Jamie

    2012-01-01

    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 connected habitats

  14. 76 FR 55090 - Commercial Lease of Submerged Lands for Renewable Energy Development on the Outer Continental Shelf

    Science.gov (United States)

    2011-09-06

    ... Renewable Energy Development on the Outer Continental Shelf AGENCY: Bureau of Ocean Energy Management... will use Form 0008 to issue commercial renewable energy leases on the Outer Continental Shelf. In the... the Outer Continental Shelf,'' BOEMRE stated that ``we intend to develop a model lease form through...

  15. 77 FR 5529 - Commercial Lease of Submerged Lands for Renewable Energy Development on the Outer Continental Shelf

    Science.gov (United States)

    2012-02-03

    ... the Outer Continental Shelf AGENCY: Bureau of Ocean Energy Management, Interior. ACTION: Notice... energy leases on the Outer Continental Shelf (OCS). In the preamble to the April 29, 2009, Final Rule, ``Renewable Energy and Alternate Uses of Existing Facilities on the Outer Continental Shelf,'' BOEM...

  16. On instability and mixing on the UK Continental Shelf

    Science.gov (United States)

    Liu, Zhiyu

    2016-06-01

    The stability of stratified flows at locations in the Clyde, Irish and Celtic Seas on the UK Continental Shelf is examined. Flows are averaged over periods of 12-30 min in each hour, corresponding to the times taken to obtain reliable estimates of the rate of dissipation of turbulent kinetic energy per unit mass, ε. The Taylor-Goldstein equation is solved to find the maximum growth rate of small disturbances to these averaged flows, and the critical gradient Richardson number, Ric. The proportion of unstable periods where the minimum gradient Richardson number, Rimin, is less than Ric is about 35%. Cases are found in which Ric < 0.25; 37% of the flows with Rimin < 0.25 are stable, and Ric < 0.24 in 68% of the periods where Rimin < 0.25. Marginal conditions with 0.8 < Rimin/Ric < 1.2 occur in 30% of the periods examined. The mean dissipation rate at the level where the fastest growing disturbance has its maximum amplitude is examined to assess whether the turbulence there is isotropic and how it relates to the wave-turbulence boundary. It is concluded that there is a background level of dissipation that is augmented by instability; instability of the averaged flow does not account for all the turbulence observed in mid-water. The effects of a horizontal separation of the measurements of shear and buoyancy are considered. The available data do not support the hypothesis that the turbulent flows observed on the UK shelf adjust rapidly to conditions that are close to being marginal, or that flows in a particular location and period of time in one sea have stability characteristics that are very similar to those in another.

  17. On instability and mixing on the UK Continental Shelf

    CERN Document Server

    Liu, Zhiyu

    2015-01-01

    The stability of stratified flows at locations in the Clyde, Irish and Celtic Seas on the UK Continental Shelf is examined. Flows are averaged over periods of 12-30 min in each hour, corresponding to the times taken to obtain reliable estimates of the rate of dissipation of turbulent kinetic energy per unit mass, $\\varepsilon$. The Taylor-Goldstein equation is solved to find the maximum growth rate of small disturbances to these averaged flows, and the critical gradient Richardson number, $\\textrm{Ri}_\\textrm{c}$. The proportion of unstable periods where the minimum gradient Richardson number, $\\textrm{Ri}_{\\textrm{min}}$, is less than $\\textrm{Ri}_\\textrm{c}$ is about 35%. Cases are found in which $\\textrm{Ri}_\\textrm{c} <$ 0.25; 37% of the flows with $\\textrm{Ri}_{\\textrm{min}}<$ 0.25 are stable, and $\\textrm{Ri}_\\textrm{c}<$ 0.24 in 68% of the periods where $\\textrm{Ri}_{\\textrm{min}}<$ 0.25. Marginal conditions with 0.8 $<$ Ri$_{\\textrm{min}}$$/$Ri$_\\textrm{c}$ $<$ 1.2 occur in 30% of th...

  18. 75 FR 52546 - Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf (OCS...

    Science.gov (United States)

    2010-08-26

    ... Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf (OCS) Scientific Committee (SC); Announcement of Plenary Session AGENCY: Bureau of Ocean Energy Management, Regulation and... Ocean Energy Management, Regulation and Enforcement, 381 Elden Street, Mail Stop 4043, Herndon,...

  19. 77 FR 24734 - Outer Continental Shelf (OCS) Renewable Energy Program Leasing for Marine Hydrokinetic Technology...

    Science.gov (United States)

    2012-04-25

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Outer Continental Shelf (OCS) Renewable Energy Program Leasing for... labeled ``Comments on OCS Renewable Energy Program Leasing for Marine Hydrokinetic Technology...

  20. 76 FR 28449 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Science.gov (United States)

    2011-05-17

    ... Oil and Gas Lease Sales AGENCY: Bureau of Ocean Energy Management, Regulation and Enforcement... with any entity in any other of the following groups at Outer Continental Shelf oil and gas lease...

  1. 76 FR 4129 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Science.gov (United States)

    2011-01-24

    ... Gas Lease Sales AGENCY: Bureau of Ocean Energy Management, Regulation and Enforcement, Interior... any entity in any other of the following groups at Outer Continental Shelf oil and gas lease sales...

  2. Digital Offshore Cadastre (DOC) - Pacific NAD83 – Continental Shelf Boundaries

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Continental Shelf Boundary (CSB) lines in ESRI Arc/Info export and Arc/View shape file formats for the BOEM Pacific Region. The CSB defines...

  3. Outer Continental Shelf Lease Blocks - Pacific Region - West Coast NAD83

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Outer Continental Shelf block outlines in ArcGIS shape file format for the BOEM Pacific Region. OCS blocks are used to define small geographic...

  4. Outer Continental Shelf 200 Nautical Mile Limit - Gulf of Mexico Region NAD27

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Continental Shelf Boundary (CSB) lines in ESRI shapefile format for the BOEM Gulf of Mexico Region. The CSB defines the seaward limit of...

  5. 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...

  6. Outer Continental Shelf Oil and Natural Gas Pipelines - Gulf of Mexico Region NAD 27

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This polyline data set contains the locations of oil and gas pipelines in the Gulf of Mexico Outer Continental Shelf federal waters that are associated with the oil...

  7. 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...

  8. 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...

  9. 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...

  10. Federal Outer Continental Shelf (OCS) Sand and Gravel Borrow Areas (Lease Areas)

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — Federal outer Continental Shelf (OCS) Sand and Gravel Borrow Areas (Lease Areas) are polygons which are maintained by the Bureau of Ocean Energy Management (BOEM),...

  11. 76 FR 23331 - Outer Continental Shelf (OCS) Scientific Committee (SC); Announcement of Plenary Session

    Science.gov (United States)

    2011-04-26

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf (OCS) Scientific Committee (SC); Announcement of Plenary Session AGENCY: Bureau of Ocean Energy Management, Regulation...

  12. 77 FR 4056 - Outer Continental Shelf (OCS) Scientific Committee (SC); Announcement of Plenary Session

    Science.gov (United States)

    2012-01-26

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Outer Continental Shelf (OCS) Scientific Committee (SC); Announcement of Plenary Session AGENCY: Bureau of Ocean Energy Management (BOEM), Interior. ACTION: Notice...

  13. Heavy minerals occurrences in the continental shelf inner/mean west of CearÃ

    OpenAIRE

    Antonio Borges de Aguiar Neto

    2015-01-01

    This study embraces the west continental shelf of Cearà (147 samples of marine sediments) and two fluvial courses (4 sediment samples of Curu and SÃo GonÃalo rivers) to determine heavy minerals distribution with their possible provenances and economic potential. Sedimentary facies on the continental shelf were distinguished through the particle size and calcium carbonate content. Heavy minerals were investigated for their total content (%), relative abundance (%) of each mineral species, conc...

  14. 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

  15. Cross-Shelf Circulation and Momentum and Heat Balances Over the Inner Continental Shelf Near Martha’s Vineyard, Massachusetts

    Science.gov (United States)

    2007-09-01

    T2 or AT = 0 at x = c : 0, the temperature stratification as a function of cross-shelf position in the model is AT- QS_X (.32) Poe , Uo The vertical... Poe - U o - U o x ) (4 ., The cross-shelf temperature gradient in the model is positive near shore: a(T) Uo d> 0 for x < --- (4.35) 5W3 h 153 The...Wind-driven currents over the continental shelf. In Kenneth H. Brink and Allan R. Robinson, editors, The Global Coastal Ocean: Processes and Methods

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

    NARCIS (Netherlands)

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

    2010-01-01

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

  17. Onshore-offshore movement of jumbo squid (Dosidicus gigas) on the continental shelf

    Science.gov (United States)

    Stewart, Julia S.; Gilly, William F.; Field, John C.; Payne, John C.

    2013-10-01

    Jumbo squid (Dosidicus gigas) have greatly extended their range in the California Current System, where they forage on a variety of ecologically and economically important species that inhabit both coastal and offshore mesopelagic regions. Swimming abilities and behavior are important factors in assessing the impacts of this range expansion, particularly in regard to foraging in conjunction with onshore-offshore movement over the continental shelf. Here we describe a study of horizontal movements by jumbo squid along and across the continental shelf off Washington, USA, using acoustic tags in association with the Census of Marine Life's Pacific Ocean Shelf Tracking Program (POST) receiver arrays. We detected frequent movements along the shelf break, movement onto the shelf at night, and no evidence of movement as a cohesive school. Our results demonstrate feasibility of using acoustic tags and arrays to document horizontal movements of jumbo squid along and across the continental shelf. This is important in order to determine how those movements overlap with those of other ecologically and commercially important fish species.

  18. Salinity variability along the eastern continental shelf of Canada and the United States, 1973-2013

    Science.gov (United States)

    Bisagni, James J.

    2016-09-01

    Continental shelf waters located off the east coast of Canada and the United States are part of a long shelf current system that is partly comprised of colder, less-saline waters originating from high latitudes, including waters from the North Atlantic sub-polar gyre, along with ice-melt and freshwater input from local rivers. A 41-year analysis (1973-2013) of near-surface salinity (NSS) using three hydrographic datasets (Bedford Institute of Oceanography "Climate", NOAA/ESDIM, and Canadian Marine Environmental Data Service (MEDS)) allowed an examination of NSS variability within 11 continental shelf sub-regions, extending from the southern Newfoundland Shelf of eastern Canada to the DelMarVa/Hatteras Shelf of the United States. Although the periods of record containing sufficient data vary between sub-regions, regional mean NSS values are lowest within the Gulf of St. Lawrence and highest on the DelMarVa/Hatteras shelf, with largest annual variability within the Gulf of St. Lawrence. After removal of outliers, long-term linear trends computed from annual mean NSS were detected along the Newfoundland Shelf (+0.011 y-1), Western Scotian Shelf (-0.007 y-1), Gulf of Maine (-0.014 y-1), Georges Bank (-0.011 y-1), and DelMarVa/Hatteras Shelf (+0.024 y-1). A long-term quadratic fit to annual mean NSS from the Eastern Scotian Shelf displays a salinity increase through 1992 of +0.026 y-1, decreasing thereafter until 2013 by -0.028 y-1. A quadratic fit for the Western Grand Banks displays a NSS increase through 2007 of +0.022 y-1, decreasing thereafter through 2013 by -0.006 y-1. Annual mean NSS from the Eastern Grand Banks, Tail of the Grand Banks, Gulf of St. Lawrence, and Middle Atlantic Bight display no long-term trends. Inter-annual variability (IAV) of NSS residuals shows similar small mean squared error (mse) of 0.02-0.04 for the four northern-most sub-regions (Newfoundland Shelf, Eastern, Tail and Western Grand Banks) and are correlated at 0-year lag. IAV of NSS

  19. Seasonal anoxia over the western Indian continental shelf

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.; Naik, H.; Jayakumar, A.; Pratihary, A.K.; Narvenkar, G.; Kurian, S.; Agnihotri, R.; Shailaja, M.S.; Narvekar, P.V.

    , 1, 33–49. Banse, K. (1968), Hydrography of the Arabian Sea shelf of India and Pakistan and effects on demersal fishes, Deep Sea Res. Oce- anogr. Abstr., 15, 45–79. Bograd, S. J., C. G. Castro, E. Di Lorenzo, D. M. Palacios, H. Bai- ley, W. Gilly...

  20. 76 FR 14040 - Outer Continental Shelf (OCS), Central and Western Gulf of Mexico, Oil and Gas Lease Sales for...

    Science.gov (United States)

    2011-03-15

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf (OCS), Central and... Environmental Policy Act (NEPA), the Outer Continental Shelf Lands Act (OCSLA), and the Coastal Zone...

  1. 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.

  2. 76 FR 29156 - Outer Continental Shelf Air Regulations Consistency Update for California

    Science.gov (United States)

    2011-05-20

    ..., Nitrogen dioxide, Nitrogen oxides, Outer Continental Shelf, Ozone, Particulate matter, Permits, Reporting...). Rule 325 Crude Oil Production and Separation (Adopted 07/19/01). Rule 326 Storage of Reactive Organic... Analysis and Modeling (Adopted 04/17/97). Rule 808 New Source Review for Major Sources of Hazardous...

  3. 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.

  4. 77 FR 5830 - Commercial Wind Leasing and Site Assessment Activities on the Atlantic Outer Continental Shelf...

    Science.gov (United States)

    2012-02-06

    ... Bureau of Ocean Energy Management Commercial Wind Leasing and Site Assessment Activities on the Atlantic... identify areas that may be most suitable for wind energy leasing on the Outer Continental Shelf (OCS), and... efficient and responsible renewable energy leasing process. In consultation with other Federal agencies...

  5. 76 FR 7230 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Science.gov (United States)

    2011-02-09

    ... From the Federal Register Online via the Government Publishing Office ] DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Notice on Outer Continental Shelf Oil and Gas Lease Sales AGENCY: Bureau of Ocean Energy Management, Regulation and Enforcement,...

  6. 78 FR 27430 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Science.gov (United States)

    2013-05-10

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Notice on Outer Continental Shelf Oil and Gas Lease Sales AGENCY... gas lease sales to be held during the bidding period May 1, 2013, through October 31, 2013. This...

  7. 78 FR 45965 - Research Lease on the Outer Continental Shelf (OCS) Offshore Virginia, Request for Competitive...

    Science.gov (United States)

    2013-07-30

    ... Bureau of Ocean Energy Management Research Lease on the Outer Continental Shelf (OCS) Offshore Virginia...: Public Notice of an Unsolicited Request for an OCS Research Lease; Request for Competitive Interest (RFCI...) to acquire an OCS lease for wind energy research activities; (2) solicit indications of interest in...

  8. 77 FR 24980 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Science.gov (United States)

    2012-04-26

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Notice on Outer Continental Shelf Oil and Gas Lease Sales AGENCY... gas lease sales to be held during the bidding period May 1, 2012, through October 31, 2012. The...

  9. 76 FR 67759 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Science.gov (United States)

    2011-11-02

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Notice on Outer Continental Shelf Oil and Gas Lease Sales AGENCY... gas lease sales to be held during the bidding period November 1, 2011, through April 30, 2012....

  10. 78 FR 64243 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Science.gov (United States)

    2013-10-28

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Notice on Outer Continental Shelf Oil and Gas Lease Sales AGENCY... gas lease sales to be held during the bidding period November 1, 2013, through April 30, 2014....

  11. 76 FR 13205 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Science.gov (United States)

    2011-03-10

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Notice on Outer Continental Shelf Oil and Gas Lease Sales AGENCY: Bureau of Ocean Energy Management, Regulation and Enforcement,...

  12. Biogeochemical characteristics of the surface sediments along the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Jacob, J.; Jayaraj, K.A.; Rehman, H.H.; Chandramohanakumar, N.; Balachandran, K.K.; Raveendran, T.V; Joseph, T.; Nair, M.; Achuthankutty, C.T.

    , No. 2, April 2009, 135–149 Biogeochemical characteristics of the surface sediments along the western continental shelf of India Josia Jacob a *, K.A. Jayaraj a , H. Habeeb Rehman a , N. Chandramohanakumar b , K.K. Balachandran a , T.V. Raveendran a...

  13. 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)

  14. Benthic mineralization and nutrient exchange over the inner continental shelf of western India.

    Digital Repository Service at National Institute of Oceanography (India)

    Pratihary, A; Naqvi, S.W.A; Narvenkar, G.; Kurian, S.; Naik, H.; Naik, R.; Manjunatha, B.R.

    –denitrification, resulting in substantial N loss (1.98 mmol m–2 d–1) in the sediment. The continental shelf sediment switched over from being a NO3-source during the oxic regime to a NO3- sink during...

  15. The geological structure of the Netherlands continental shelf - Results of a detailed mapping project

    NARCIS (Netherlands)

    Veen, J.H. ten; Doornenbal, J.C.; Dulk, M. den; Gessel, S.F. van; Witmans, N.

    2014-01-01

    In 2011, TNO-GDN concluded a 5 year geological mapping of the Netherlands Continental Shelf. In this project all public data from hydrocarbon exploration were used resulting in a major update of the dataset and a variety of deliverables available at www.NLOG.NL. The stratigraphy of more than 400 wel

  16. 76 FR 5189 - BOEMRE Information Collection Activities: 1010-0081, Operations in the Outer Continental Shelf...

    Science.gov (United States)

    2011-01-28

    ... the public consultation process, on September 7, 2010, we published a Federal Register notice (75 FR...: 1010-0081, Operations in the Outer Continental Shelf for Minerals Other Than Oil, Gas, and Sulphur... collection (1010-0081). SUMMARY: To comply with the Paperwork Reduction Act of 1995 (PRA), we are...

  17. 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.

    .R.J., 1991. Radio- carbon dates of sediment cores from inner continental shelf off Karwar, west coast of India. Curr. Sci., 61: 353-354. Nisbet, E.G., 1989. Some northern sources of atmospheric methane: production, history, and future implications. Can...

  18. 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.

  19. 78 FR 33859 - Outer Continental Shelf (OCS) Geological and Geophysical Exploration Activities in the Gulf of...

    Science.gov (United States)

    2013-06-05

    ... [Federal Register Volume 78, Number 108 (Wednesday, June 5, 2013)] [Notices] [Page 33859] [FR Doc No: 2013-13248] DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management [MMAA104000] Outer... in the Federal Register (78 FR 27427) entitled ``Outer Continental Shelf Geological and...

  20. Mineral resource management of the Outer Continental Shelf : leasing procedures, evaluation of resources, and supervision of production operations on leased lands of the Outer Continental Shelf

    Science.gov (United States)

    Adams, Maurice V.; John, C.B.; Kelly, R.F.; LaPointe, A.E.; Meurer, R.W.

    1975-01-01

    An important function of the Geological Survey is the evaluation and management of the mineral resources of the Outer Continental Shelf, particularly with respect to oil and gas, salt, and sulfur. Production of oil and gas from the Outer Continental Shelf of the United States has increased substantially over the past 20 years and represents an increasing percentage of total United States production. As discovery of major onshore production of oil and gas has become more difficult, the search has moved into the surrounding waters where submerged sedimentary formations are conducive to the accumulation of oil and gas. Increased energy demands of recent years have accelerated the pace of offshore operations with a corresponding improvement in technology as exploration and development have proceeded farther from shore and into deeper water. While improved technology and enforcement of more stringent regulations have made offshore operations safer, it is unrealistic to believe that completely accident-free operations can ever be achieved. Only slightly more than six percent of the world's continental terrace is adjacent to the United States, but less than one percent has been explored for oil and gas. Since the lead time for the development of offshore oil and gas resources can be as much as a decade, they do not provide an immediate energy supply but should be viewed in the light of a near-term source with a potential of becoming a medium-range source of supply pending the development of alternative energy sources. Revenues from the Outer Continental Shelf are deposited to the general fund of the United States Treasury. A major portion of these funds is allocated to the Land and Water Conservation Fund, the largest Federal grant-in-aid program of assistance to States, counties, and cities for the acquisition and development of public parks, open space, and recreation lands and water.

  1. Observations of a coastal current in the continental shelf of Yucatan

    Science.gov (United States)

    Ruiz-Castillo, E.; Gomez-Valdes, J.; Rioja-Nieto, R.

    2013-05-01

    Oceanographic measurements were recorded at the continental shelf of Yucatan , over four CTD surveys carried out between 2003 and 2009. Results showed that the continental waters are confined in two layers. A 25 - year time series of sea surface temperature from AVHRR, with 1-day temporal resolution and 4-km spatial resolution, is also analyzed. Maps of the mean, the standard deviation, and the maximum temperature, obtained from the time series, showed the presence of low temperature waters along the northern coast of the Yucatan Peninsula, which were probably of subsurface origin. Monthly average temperature maps showed that cold surface water occur first in March at the southeast of the Yucatan continental shelf, and afterwards it flows westward and reaches the Campeche bay in July and August. Furthermore, in the continental waters the maximum temperature occurs in August and the minimum temperature occurs in February. The annual cycle explains more than 60 % of the variance with an error of the order of 1 C. The CTD surveys confirmed that the origin of the cold water was from the Caribbean Sea's subsurface that first appears at the southeast of the continental shelf. The water column along the coast was found to be well mixed in the same region where the band of cold water was detected using satellite data. It is concluded that the surface circulation along the northern coast of the Yucatan Peninsula is westward throughout the year except in February.

  2. U.S. Eastern Continental Shelf Carbon Cycling (USECoS): Modeling, Data Assimilation, and Analysis

    Science.gov (United States)

    Mannino, Antonio

    2008-01-01

    Although the oceans play a major role in the uptake of fossil fuel CO2 from the atmosphere, there is much debate about the contribution from continental shelves, since many key shelf fluxes are not yet well quantified: the exchange of carbon across the land-ocean and shelf-slope interfaces, air-sea exchange of CO2, burial, and biological processes including productivity. Our goal is to quantify these carbon fluxes along the eastern U.S. coast using models quantitatively verified by comparison to observations, and to establish a framework for predicting how these fluxes may be modified as a result of climate and land use change. Our research questions build on those addressed with previous NASA funding for the USECoS (U.S. Eastern Continental Shelf Carbon Cycling) project. We have developed a coupled biogeochemical ocean circulation model configured for this study region and have extensively evaluated this model with both in situ and remotely-sensed data. Results indicate that to further reduce uncertainties in the shelf component of the global carbon cycle, future efforts must be directed towards 1) increasing the resolution of the physical model via nesting and 2) making refinements to the biogeochemical model and quantitatively evaluating these via the assimilation of biogeochemical data (in situ and remotely-sensed). These model improvements are essential for better understanding and reducing estimates of uncertainties in current and future carbon transformations and cycling in continental shelf systems. Our approach and science questions are particularly germane to the carbon cycle science goals of the NASA Earth Science Research Program as well as the U.S. Climate Change Research Program and the North American Carbon Program. Our interdisciplinary research team consists of scientists who have expertise in the physics and biogeochemistry of the U.S. eastern continental shelf, remote-sensing data analysis and data assimilative numerical models.

  3. 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.

  4. Seasonal oxygen deficiency over the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.; Naik, H.; Jayakumar, D.A.; Shailaja, M.S.; Narvekar, P.V.

    environment, popularly known as 'dead zones' because of exclusion of many organisms including commercially important fishes. The largest and the best investigated 'dead zone' along an open-ocean coast devel- ops every summer in the inner Gulf of Mexico as a... Somalia [55]). The effects of seasonal changes in circulation on the hydrographic structure and biogeochemical cyclillg extend beyond the continental margin [41]. During the SWM, when the surface flow is directed toward the equator, the subsurface...

  5. Large-scale penetration of Gulf Stream water onto the continental shelf north of Cape Hatteras

    Science.gov (United States)

    Gawarkiewicz, Glen; Church, Thomas M.; Luther, George W., III; Ferdelman, Timothy G.; Caruso, Michael

    1992-01-01

    The presence of Gulf Stream water on the continental shelf as much as 60 km north of Cape Hatteras was observed during a hydrographic cruise in the summer of 1990. Gulf Stream water was concentrated at mid-depth between 10 and 30 m and penetrated the shelfbreak front which normally separates the shelf water from slope water and Gulf Stream water. Velocities of Gulf Stream water in the upper 110 m of the water column along the 1000 m isobath indicated a flow of 18 to 25 cm/s directed towards the northwest. Gulf Stream water on the shelf is considered to be associated with low values of fluorescence, transmissivity, and nutrient concentrations relative to adjacent shelf water.

  6. 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.

  7. The holocene sequence of the central continental shelf of the State of Bahia, Brazil; A sequencia holocenica da plataforma continental central do Estado da Bahia

    Energy Technology Data Exchange (ETDEWEB)

    Freire, Antonio Fernando Menezes; Dominguez, Jose Maria Landim [PETROBRAS S.A., BA (Brazil). Unidade de Negocios de Exploracao e Producao da Bahia. Ativo de Exploracao Avaliacao e Acompanhamento Geologico]. E-mail: fernandofreire@petrobras.com.br

    2006-05-15

    Fifty cores were recovered from the sea bottom in the central portion of the continental shelf of the State of Bahia, between the Marau Peninsula and the city of Olivenca. Thirty six of these cores were collected by divers at up to 40 m deep waters. Fourteen cores were collected by piston cores in areas ranging from the continental shelf to the upper slope. All cores were described, photographed and sampled for grain size and bio stratigraphic analysis. These data were used to prepare textural and facies maps of the continental shelf. The piston cores were run parallel to sub-bottom profiling surveys. Results show that there is a strong reflector located 3 - 4 m below the sediment- water interface, which limited the penetration of the piston cores. This reflector represents a sequence boundary separating the holocene from the pleistocene sequences. A transgressive system tract has been deposited on the top of this surface along with the early stages of the high stand system tract, particularly on the inner shelf. Because of the starved character of this shelf, notably on its external portion, a detailed application of sequence stratigraphy concepts has not been possible. Only at the inner shelf/shore face there is evident pro gradation of siliciclastics over carbonates. Several submarine valleys dissect the outer shelf/upper slope, thus acting as channels that transport continental shelf sediments to the deeper portions of the basin. (author)

  8. Modeling River Networks in the Continental Shelf during Sea Level Cycles

    Science.gov (United States)

    Fagherazzi, S.; Wiberg, P. L.

    2003-12-01

    Several processes influence the development of fluvial networks in the continental shelf during sea level low stands. In order to understand the specific role of each process and quantify its influence on channel formation and incision, the Detachment Limited Model (DeLiM) (Howard, 1994) has been applied to several shelf configurations and with different sea-level curves. The computer model incorporates deltaic deposition on the continental shelf as well as sea-level oscillations and is parameterized with Virginia coastal plain data. Simulations show that the major factor controlling incision and channel development is the tendency of streams to reach an equilibrium (graded) configuration. If, for a given river discharge and shelf slope, the sediment load is less than that required to be at grade, channel incision will occur in the exposed shelf until the river long profile is in equilibrium with the current sea level (base level). The geometry and thickness of sediments deposited in deltas and estuaries have a minor influence on the total channel incision, but are of fundamental importance for the spatial development of the channel network. Model results show that the detailed structure of sea level oscillations is important for sediment redistribution and channel changes. Conceptual models that consider a mere succession of sea level high stands and low stands are oversimplified and miss the complex response of the system to gradual sea level oscillations. The initial shelf topography strongly characterizes the future network development. During the simulations the drainage network is initially strongly fragmented, but gradually becomes integrated through depression infilling and dissection of steep scarps. Finally the role of coastal processes is of crucial importance for sediment redistribution and shelf topography modification during sea-level oscillations.

  9. Ancient Changjiang channel system in the East China Sea continental shelf during the last glaciation

    Institute of Scientific and Technical Information of China (English)

    LI Guangxue; LIU Yong; YANG Zigeng; YUE Shuhong; YANG Wenda; HAN Xibin

    2005-01-01

    Based on the data of high-resolution seismic profiles, an ancient river channel system of the last glaciation occurred along the Zhedong and Xihu depression in the southeast of Hupijiao rise. The distribution of the channel fill system shows that the ancient Changjiang River went through the Changjiang depression into the low land plain of the outside continental shelf during the low sea level cycle of the last glaciation. The big channel fill into Okinawa Trough is not found due to the depletion of the river kinetic energy in the low land plain. The river discharge dispersal was of an important role to the dilution of the northern Okinawa Trough sea at that time. Six ancient river channel systems (A―F), which are main distributaries of ancient Changjiang in the East China Sea continental shelf during the last glaciation, may be buried off the modern Changjiang estuary. The distribution of these channels coincides with the zonal elevations in the sea floor.

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

    Energy Technology Data Exchange (ETDEWEB)

    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. (ACR)

  11. 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.

    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... circulation, direct current measurements are needed to determine the higher frequency time-dependent motion. For most of the Indian coastline, the current pattern in the near shore region, on shorter time scales, still remains poorly documented. However, a...

  12. Cathodoluminescent bimineralic ooids from the Pleistocene of the Florida continental shelf

    Science.gov (United States)

    Major, R. P.; Halley, Robert B.; Lukas, Karen J.

    1988-01-01

    A bored and encrusted late Pleistocene ooid grainstone was recovered from the seafloor at a depth of approximately 40 m on the outer continental shelf of eastern Florida. Ooid cortices are dominantly bimineralic, generally consisting of inner layers of radial magnesian calcite and outer layers of tangential aragonite. Ooid nuclei are dominantly rounded cryptocrystalline grains, although quartz grains and a variety of skeletal grains also occur as nuclei. Ooids are partially cemented by blocky calcite, and interparticle porosity is partially filled by micrite.

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

    Energy Technology Data Exchange (ETDEWEB)

    Funnemark, E. [Det Norske Veritas Industry AS, (Norway); Young, E. [Health and Safety Executive, (United Kingdom)

    2003-07-01

    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.

  14. Environmental magnetism and application in the continental shelf sediments of India

    Digital Repository Service at National Institute of Oceanography (India)

    Alagarsamy, R.

    in the coastal environment. Key words: Mineral Magnetic; Heavy metal; Magnetic method; Sediment; Continental shelf; India. * Corresponding Address: Earth Dynamic System Research Center, National Cheng Kung University, Tainan, Taiwan 70101, Republic of China... zones and exhibits strong seasonality from warm humid to arid and cold arid conditions. The climate of the subcontinent is dominated by Monsoon systems; this region remains humid during summer and dry during winter. It has basically two main seasons...

  15. Offshore oil in the alaskan arctic.

    Science.gov (United States)

    Weeks, W F; Weller, G

    1984-07-27

    Oil and gas deposits in the Alaskan Arctic are estimated to contain up to 40 percent of the remaining undiscovered crude oil and oil-equivalent nature gas within U.S. jurisdiction. Most (65 to 70 percent) of these estimated reserves are believed to occur offshore beneath the shallow, ice-covered seas, of the Alaskan continental shelf. Offshore recovery operations for such areas are far from routine, with the primary problems associated with the presence of ice. Some problems that must be resolved if efficient, cost-effective, environmentally safe, year-round offshore production is to be achieved include the accurate estimation of ice forces on offshore structures, the proper placement of pipelines beneath ice-produced gouges in the sea floor, and the cleanup of oil spills in pack ice areas.

  16. Oceanographic Time Series Data: Northeast Atlantic Outer Continental Shelf, Gulf of Maine and Georges Bank Marine Sanctuary

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Time-series oceanographic data for the Northeast Atlantic outer continental shelf, Gulf of Maine and Georges Bank collected by the U.S. Geological Survey (USGS) or...

  17. 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...

  18. 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 ...

  19. 76 FR 53481 - Outer Continental Shelf, Alaska OCS Region, Chukchi Sea Planning Area, Oil and Gas Lease Sale 193

    Science.gov (United States)

    2011-08-26

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf, Alaska OCS Region...) announces the availability of a Final Supplemental Environmental Impact Statement (SEIS) for...

  20. Policy and Profit Allocation for the Cooperative Development of Natural Gas Resource on Chinese Offshore Continental Shelf

    Institute of Scientific and Technical Information of China (English)

    Zhou Qingsong; Zhang Mingzhi

    1994-01-01

    @@ Rich natural gas resources on Chinese offshore continental shelf China has a wide sea waters with their offshore continental shelf covering over 1 million km2. Rich oil-gas resources are lying under the sea waters. In accordance with the conventional international assessment method for oil and gas resources, it is expected that the gas reserve volume in China is approximately 14 000 billion cu.m.

  1. Influence of fluvial processes on the quaternary geologic framework of the continental shelf, North Carolina, USA

    Science.gov (United States)

    Boss, S.K.; Hoffman, C.W.; Cooper, B.

    2002-01-01

    Digital, single-channel, high-resolution seismic reflection profiles were acquired from the insular continental shelf of North Carolina, USA along a data grid extending from Oregon Inlet northward 48 km to Duck, North Carolina and from the nearshore zone seaward approximately 28 km (total surveyed area= 1334 km2). These data were processed and interpreted to delineate principal reflecting horizons and develop a three-dimensional seismic stratigraphic framework for the continental shelf that was compared to stratigraphic data from the shoreward back-barrier (estuarine) and barrier island system. Six principal reflecting horizons (designated R0 through R5) were present within the upper 60 m of the shelf stratigraphic succession. Three-dimensional mapping of reflector R1 demonstrated its origin from fluvial incision of the continental shelf during an episode (or episodes) of lowered sea-level. Fluvial processes during development of reflector R1 were responsible for extensive reworking and re-deposition of sediment throughout most of the northern half of the study area. Five seismic stratigraphic units (designated S1 through S5) were tentatively correlated with depositional sequences previously identified from the North Carolina back-barrier (estuarine) and barrier island system. These five stratigraphic units span the Quaternary Period (S1 = early Holocene; S2 = 51-78 ka; S3 = 330-530 ka; S4 = 1.1-1.8 Ma; S5 = earliest Pleistocene). Unit S1 is composed of fine-grained fluvial/estuarine sediment that back-filled incised streams during early Holocene sea-level rise. The four other stratigraphic units (S2-S5) display tabular depositional geometries, low total relief, and thicken toward the east-southeast as their basal reflectors dip gently between 0.41 m km-1 (0.02??) and 0.54 m km-1 (0.03??). Knowledge of the three-dimensional subsurface stratigraphic architecture of the continental shelf enhances understanding of the development of shelf depositional successions and

  2. EXPLOITATION OF THE CONTINENTAL SHELF IN DISPUTED AREAS AN EXAMPLE OF THE ARCTIC OCEAN

    Directory of Open Access Journals (Sweden)

    M. S. Peters

    2016-01-01

    Full Text Available This paper aims to examine the legal regime related to define the outer limits of the continental shelf beyond 200 NM. Firstly, special focus will be on the development of the legal concept of the continental shelf. Relevant provisions of the LOS Convention and Article76 inparticular will be scrutinized. Subsequently there is an assumption on which the principles of the Arctic outer continental margin delimitation will be conducted in relation of hypothetic application during the practice of an international adjudicative body. The delimitation within 200 NM and beyond200 NM will be compared. The fourth chapter will be concentrated on the role of the Commission as an important participant of delimitation process. Also there will be a general overview of the state practice concerning the establishment of the outer continental margin in theArctic, the reaction of other Arctic States and recommendations of the Commission.It will be concluded that 'there are some difficulties in implementing the Article 76 (locating the foot of the slope and dealing with ridge issues, however it is possible to delimit the continental margin of the world based on the Article 76.' Difficulties in implementing and some discrepancies in provisions of the Article 76 do not constitute grounds for considering of a new legal approach. Discrepancies are mainly con tained in the Rules of Procedure and in the Scientific and Technical Guidelines of the Commission. They can be disposed practically without considering the legal concept. In case of unresolved land or maritime dispute the cooperation among coastal states is the best way to avoid conflicts while delimiting the outer continental margin.

  3. Wave-driven sediment mobilization on a storm-controlled continental shelf (Northwest Iberia)

    Science.gov (United States)

    Oberle, Ferdinand; Storlazzi, Curt D.; Hanebuth, Till

    2014-01-01

    Seafloor sediment mobilization on the inner Northwest Iberian continental shelf is caused largely by ocean surface waves. The temporal and spatial variability in the wave height, wave period, and wave direction has a profound effect on local sediment mobilization, leading to distinct sediment mobilization scenarios. Six grain-size specific sediment mobilization scenarios, representing seasonal average and storm conditions, were simulated with a physics-based numerical model. Model inputs included meteorological and oceanographic data in conjunction with seafloor grain-size and the shelf bathymetric data. The results show distinct seasonal variations, most importantly in wave height, leading to sediment mobilization, specifically on the inner shelf shallower than 30 m water depth where up to 49% of the shelf area is mobilized. Medium to severe storm events are modeled to mobilize up to 89% of the shelf area above 150 m water depth. The frequency of each of these seasonal and storm-related sediment mobilization scenarios is addressed using a decade of meteorological and oceanographic data. The temporal and spatial patterns of the modeled sediment mobilization scenarios are discussed in the context of existing geological and environmental processes and conditions to assist scientific, industrial and environmental efforts that are directly affected by sediment mobilization. Examples, where sediment mobilization plays a vital role, include seafloor nutrient advection, recurrent arrival of oil from oil-spill-laden seafloor sediment, and bottom trawling impacts.

  4. Analysis of Water Dynamics in Banda Sea and its Influences on Continental Shelf Fishing Area

    Directory of Open Access Journals (Sweden)

    Irawan Muripto

    2016-10-01

    Full Text Available Over the rise of the Arafura Sea of the vertical configuration results shown curves which easy to understand about its water dynamics. The water character is oceanic’s as cool, salty and stable DO were maintaining by the variability of thermal structure in the continental shelf. The pattern of water masses is the current system surrounding the Banda Sea as an upwelling from undercurrent those enhances and nitrified the shelf.  Along the coast of western part of Papua was conducted the parcel of water masses traveling across the fishing area where’s kind of fishing boat catches the fish in the whole year, and almost confining in the continental shelf has low current from the southern part. The current flows from west to east at the southern part of Nusa Tenggara Islands bringing water and curve to the southwestern coast of Australia. These water masses characterized the temperature, salinity and oxygen gradients from some points where may have an important implication to the slopes area between the deepest and the shallow water near the coast. The lower temperature ranges from 10.0˚C to 8.0˚C at 300m depth and 34.50‰ to 34.85‰ conducted was circulated back to the deepest layer were higher salinity and stable dissolved oxygen. This continental shelf as a fishing area boundary water dynamic may cause by these water dynamic,  especially from data catches of the two fishing vessels catches 17,4 to 39,21kg/haul in the western area and 44.0 to 80kg/haul in eastern coast area.

  5. Larval Transport on the Atlantic Continental Shelf of North America: a Review

    Science.gov (United States)

    Epifanio, C. E.; Garvine, R. W.

    2001-01-01

    This review considers transport of larval fish and crustaceans on the continental shelf. Previous reviews have contained only limited treatments of the physical processes involved. The present paper provides a physical background that is considerably more comprehensive. It includes a discussion of three principal forcing agents: (1) wind stress; (2) tides propagating from the deep ocean; and (3) differences in density associated with the buoyant outflow of estuaries, surface heat flux, or the interaction of coastal and oceanic water masses at the seaward margin of the shelf. The authors discuss the effects of these forcing agents on transport of larvae in the Middle Atlantic and South Atlantic Bights along the east coast of North America. The discussion concentrates on three species (blue crab, menhaden, bluefish) that have been the subject of a very recent multi-disciplinary study. Taken as a whole, the reproductive activities of these three species span the entire year and utilize the entire shelf, from the most seaward margin to the estuarine nursery. The blue crab is representative of species affected by physical processes occurring during summer and early autumn on the inner and mid-shelf. Menhaden are impacted by processes occurring in winter on the outer and mid-shelf. Bluefish are influenced primarily by processes occurring during early spring at the outer shelf margin near the western boundary current. The authors conclude that alongshore wind stress and density differences, i.e. buoyancy-driven flow, are the primary agents of larval transport in the region. Circulation associated with the western boundary current is only important at the shelf margin and tidally driven processes are generally inconsequential.

  6. Diversity, distribution and ecology of benthic molluscan communities on the Portuguese continental shelf

    Science.gov (United States)

    Martins, R.; Sampaio, L.; Quintino, V.; Rodrigues, A. M.

    2014-10-01

    The diversity, ecology and distribution patterns of the Portuguese continental shelf malacofauna and its relationship with abiotic factors were studied from samples covering the western and the southern coast. A total of 2544 specimens were identified corresponding to 169 taxa, mostly bivalves (62% of the total taxa). Abra alba was the most abundant and the most frequent species. The alpha diversity ranged from one species to 21 spp. 0.1 m- 2. The highest abundance and diversity were obtained in coarser sediments. Multivariate analysis based on the abundance data identified five major malacological groups: (a) Angulus pygmaeus and Thracia villosiuscula in the coarser sediments of the western inner and mid shelf; (b) Calyptraea chinensis and Leptochiton cancellatus in the heterogeneous and organically enriched sediments of the southern shelf; (c) Angulus fabula, Spisula subtruncata and Pharus legumen in the near shore exposed fine sands; (d) A. alba in muddy fine sands, mainly in the northwestern shelf and (e) Saccella commutata in the southwestern deeper shelf. The malacofauna could be used as a proxy for the major benthic communities known to occur in this area, except in muddy patches, where molluscs were absent or low abundant. Median grain-size, gravel content, depth and hydrodynamic regime were the environmental factors best related to the malacofauna spatial distribution patterns. This study sets the first record of Astarte borealis, Leptochiton asellus, Mercenaria mercenaria and Montacuta phascolionis in the Portuguese shelf and the most northern limit for Anadara polii, Glycymeris nummaria, and Leptochiton algesirensis along the northwestern shelf. This study also gives new ecological insights for several species, in terms of bathymetric range distribution, as well as habitat type and highlighted the transitional characteristics of the molluscan communities from this particular northeastern Atlantic area where boreal, temperate and subtropical faunas can

  7. Methods and procedures to determine the outer limits of the continental shelf beyond 200 nautical miles

    Institute of Scientific and Technical Information of China (English)

    WU Ziyin; LI Jiabiao; JIN Xianglong; FANG Yinxia; SHANG Jihong; LI Shoujun

    2013-01-01

    This paper establishes techniques and methods to determine a variety of boundaries associated with 200 nautical miles beyond the continental shelf. The methods, based on topography, slope and second-deriv-ative profile integrated analysis, are now able to identify automatically the foot of the continental slope (FOS). By analyzing the sedimentary profile, the points of 1%sediment thickness are recognized. Through the intersection, cut, deletion and mergence calculation of the extrapolated data set of fixed-point series, the method succeeds in generating automatically the extrapolated boundaries, including the FOS+60 M line, the 350 M line, and the 2500 m+100 M line. In addition, based on the automatic analysis of the topographic profile, it can be applied to determine rapidly the points of maximum water depth. Taking the northern Okinawa Trough (OT) as an example, these methods are used to calculate and examine the boundaries in-cluded in the Submission by the People's Republic of China Concerning the Outer Limits of the Continental Shelf beyond 200 Nautical miles in Part of the East China Sea (ECS);the boundaries thus derived have a solid scientific and rational basis.

  8. 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.

  9. The potential impacts of climate change on the hydrography of the northwest European continental shelf

    Science.gov (United States)

    Holt, Jason; Wakelin, Sarah; Lowe, Jason; Tinker, Jonathan

    2010-09-01

    Changes in global atmospheric conditions have the potential to substantially influence shelf sea environments with far reaching consequences for their ecosystems. Here we focus on the northwest European continental shelf, and review the mechanisms by which climate change might affect the temperature, salinity and stratification of this shelf sea. We explore results from a single pair of Proudman Oceanographic Laboratory Coastal Ocean Modelling System (POLCOMS) simulations forced by the Hadley Centre regional climate model, for conditions typical of 1961-1990 and 2070-2098, under a ‘business as usual’ emissions scenario (SRES A1B). This provides a single, physically plausible, representation of the future and a consistent representation of the recent past. Comparing these simulations, the shelf sea regions of this model are shown to warm substantially more than the open-ocean, by between 1.5 and 4 °C depending on location. Across the whole domain the surface waters are projected to be ∼0.2 p.s.u. fresher by the end of the 21st century. The strength of seasonal stratification is shown to increase by ∼20% on the shelf, compared with 20-50% in the open-ocean. The former being controlled by temperature and the latter by salinity. In shelf seas away from the direct influence of river discharge, stratification is projected to start ∼5 days earlier and breakdown ∼5-10 days later each year, hence extending the stratified period. An ERA-40 re-analysis forced simulation provides a reference, along with validation from gridded monthly mean data from the ICES data base.

  10. Galveston Symposium: Physical Oceanography of the Louisiana/Texas Continental Shelf

    Science.gov (United States)

    Mitchell, Thomas M.; Brown, Murray

    The Minerals Management Service (MMS), Gulf of Mexico Outer Continental Shelf (OCS) Region sponsored a symposium on the Physical Oceanography of the Louisiana/Texas (LA/TX) Shelf in Galveston, Texas, on May 24-26, 1988. The symposium brought together a number of physical oceanographers, meteorologists, and ecologists to discuss the state of knowledge and to begin the planning process for a long-term study of shelf circulation covering the region from the mouth of the Mississippi River to approximately 24° latitude along the Mexican coast and from the shore out to a depth of approximately 500 m. The proposed study, to be a component of the ongoing MMS Environmental Studies Program, is expected to take place during the period 1989-1991. It is anticipated that the work will be done principally through contracts after a competitive procurement process. Specific charges to the participants were as follows:to assess the current state of knowledge concerning the circulation on the LA/TX shelfto identify significant gaps in that knowledgeto recommend a field measurement program to address these gapsto recommend a circulation modeling program for the LA/TX shelf that will improve MMS' oil spill risk assessmentsto identify and initiate coordination mechanisms and data-sharing arrangements with other proposed research efforts

  11. What a drag: Quantifying the global impact of chronic bottom trawling on continental shelf sediment

    Science.gov (United States)

    Oberle, Ferdinand K.J.; Storlazzi, Curt; Hanebuth, Till J.J.

    2016-01-01

    Continental shelves worldwide are subject to intense bottom trawling that causes sediment to be resuspended. The widely used traditional concepts of modern sedimentary transport systems on the shelf rely only on estimates for naturally driven sediment resuspension such as through storm waves, bottom currents, and gravity-driven flows but they overlook a critical anthropogenic factor. The strong influence of bottom trawling on a source-to-sink sediment budget is explored on the NW Iberian shelf. Use of Automated Information System vessel tracking data provides for a high-resolution vessel track reconstruction and the accurate calculation of the spatial distribution of bottom trawling intensity and associated resuspended sediment load. The mean bottom trawling-induced resuspended sediment mass for the NW Iberian shelf is 13.50 Mt yr− 1, which leads to a six-fold increase in off-shelf sediment transport when compared to natural resuspension mechanisms. The source-to-sink budget analysis provides evidence that bottom trawling causes a rapid erosion of the fine sediment on human time scales. Combining global soft sediment distribution data of the shelves with worldwide bottom trawling intensity estimates we show that the bottom trawling-induced resuspended sediment mass amounts to approximately the same mass of all sediment entering the shelves through rivers. Spatial delineations between natural and anthropogenic sediment resuspension areas are presented to aid in marine management questions.

  12. What a drag: Quantifying the global impact of chronic bottom trawling on continental shelf sediment

    Science.gov (United States)

    Oberle, Ferdinand K. J.; Storlazzi, Curt D.; Hanebuth, Till J. J.

    2016-07-01

    Continental shelves worldwide are subject to intense bottom trawling that causes sediment to be resuspended. The widely used traditional concepts of modern sedimentary transport systems on the shelf rely only on estimates for naturally driven sediment resuspension such as through storm waves, bottom currents, and gravity-driven flows but they overlook a critical anthropogenic factor. The strong influence of bottom trawling on a source-to-sink sediment budget is explored on the NW Iberian shelf. Use of Automated Information System vessel tracking data provides for a high-resolution vessel track reconstruction and the accurate calculation of the spatial distribution of bottom trawling intensity and associated resuspended sediment load. The mean bottom trawling-induced resuspended sediment mass for the NW Iberian shelf is 13.50 Mt yr- 1, which leads to a six-fold increase in off-shelf sediment transport when compared to natural resuspension mechanisms. The source-to-sink budget analysis provides evidence that bottom trawling causes a rapid erosion of the fine sediment on human time scales. Combining global soft sediment distribution data of the shelves with worldwide bottom trawling intensity estimates we show that the bottom trawling-induced resuspended sediment mass amounts to approximately the same mass of all sediment entering the shelves through rivers. Spatial delineations between natural and anthropogenic sediment resuspension areas are presented to aid in marine management questions.

  13. Budgeting postglacial sedimentation history on the Santa Cruz, California mid-continental shelf

    Science.gov (United States)

    Grossman, E.E.; Eittreim, S.L.; Hanes, D.M.; Field, M.E.; Edwards, B.D.; Fallon, S.J.; Anima, R.J.

    2003-01-01

    High-resolution seismic reflection profiling and surface texture mapping of the central California continental shelf, reveal a prominent subsurface reflector interpreted as a low stand erosion surface and an overlying mudbelt that covers 421 km2 of the mid-shelf in depths of 40-90 m. Radiometric and sedimentologic analyses of samples from vibracores taken along the seaward edge of the mudbelt show that initial deposition above the pre-Holocene erosion surface began ca. 14.5 ka. These data and model results of sea-level history, tectonics, and the Monterey Bay littoral sediment budget support the notion that the entire midshelf deposit was formed during the postglacial transgression. An alternative explanation, that land-use activities while providing important boundary conditions for modeling shoreface evolution.

  14. Relating Ctenophore Population to Water Mass Indices in the Northeast U.S. Continental Shelf Ecosystem

    Directory of Open Access Journals (Sweden)

    Rebecca Sparks

    2015-01-01

    Full Text Available Ctenophores exist throughout the Northeast U.S. Continental Shelf Ecosystem, but the underlying mechanisms that control ctenophore populations at this scale are not clear. Ctenophore population data over the last 30 years coincides with changes in several water masses on the shelf, but discovering which water mass was most influential was problematic without mechanistic clarity. This paper strives to identify the relationship between oceanography and ctenophore populations over the last 30 years. Using a numerical modeling approach, we found a strong relationship between the North Atlantic Oscillation index, percent Labrador Subarctic Slope Water, and ctenophore population. We suggest these results might inform future efforts to develop a predictive capability for major changes in ctenophore population.

  15. Environmental geologic studies on the southeastern United States Atlantic Outer Continental Shelf, 1977-1978

    Science.gov (United States)

    Popenoe, Peter; Popenoe, Peter

    1981-01-01

    This report is a summary of the second year of marine environmental research activities by the U.S. Geological Survey (USGS) on the southeaster U.S. Atlantic Continental Margin, in accordance with with Memorandum of Understanding (MOU) AA551-MU8-13 between the USGS and the Bureau of Land Management (BLM). The report covers studies whose fieldwork was conducted during the period from 1 October 1977 to 30 September 1978. The results of the first year of study are reported in Popenoe (1978a and b) and as U.S. Department of Commerce NTIS report PB 300-820. The purpose of these investigations is to provide basic geologic and oceanographic data to the BLM Outer Continental Shelf (OCS) Marine Environmental Studies Program in support of management decisions which relate to possible development of oil and gas resources of the continental shelf. The objectives of the USGS-BLM geologic research program for fiscal year 1978 (FY-78) were 1) to determine the sedimentation rates and processes on the upper slope and inner Blake Plateau; 2) to determine the distribution, areal extent, and vertical characteristics of geological features supportive of biological communities; 3) to monitor the transport of bottom sediment across the OCS, evaluate its possible effect on pollutant transfer along the seabed and the potential of sediment as a pollutant sink, determine the implications of erosion/deposition on pipeline emplacement, and aid the interpretation of chemical, biological, and physical data; 4) to determine the concentration levels of chosen trace metals and silica in three chemically defined fractions of the suspended particulate matter (seston); 5) to study the shelf edge and slope near areas of oil and gas interest, and the northern portion of the Blake Plateau for evidence of slope instability and other geologic hazards, and 6) to determine the depth and rate of sediment mixing caused by large storms and/or by benthic organisms and where possible to estimate the rate of

  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 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

  19. Acoustic Clutter and Ocean Acoustic Waveguide Remote Sensing (OAWRS) in Continental Shelf Environments

    Science.gov (United States)

    2009-09-30

    D. Symonds, S. Jagannathan, S. Lee and R.W. Nero , “Fish Population and Behavior Revealed by Instantaneous Continental Shelf-Scale Imaging,” Science...Redwood W. Nero , J. Michael Jech, "Critical Population Density Triggers Rapid Formation of Vast Oceanic Fish Shoals", Science, Vol. 323, No. 5922, 1734...1737 (March 27, 2009). 3. S. Jagannathan, D. Symonds, I. Bertsatos, T. Chen, H. T. Nia, A. D. Jain, M. Andrews,Z. Gong, N. Donabed, R. Nero , L

  20. The circulation over the continental shelf of Tamaulipas-North of Veracruz

    Science.gov (United States)

    Mancilla-Rojas, M. D.; Rivas, D.

    2012-12-01

    A 3D regional ocean model with a terrain-following vertical coordinate and high horizontal resolution (~ 2 km) was used to describe the circulation over the continental shelf of Tamaulipas-North of Veraruz. This study is focused on the sensitivity of the local dynamics to the main forcings such as the Panuco river discharge and the wind stress field. The model reproduces reasonably well the dynamics variables such as salinity and temperature field but further validation work is still need. This model results are of particular importance since much of the study area remain to be described.

  1. Fish assemblages associated with oil industry structures on the continental shelf of north-western Australia.

    Science.gov (United States)

    Pradella, N; Fowler, A M; Booth, D J; Macreadie, P I

    2014-01-01

    This study provides the first assessment of fish associations with oil and gas structures located in deep water (85-175 m) on Australia's north-west continental shelf, using rare oil industry video footage obtained from remotely operated vehicles. A diverse range of taxa were observed associating with the structures, including reef-dependent species and transient pelagic species. Ten commercially fished species were observed, the most abundant of which was Lutjanus argentimaculatus, with an estimated biomass for the two deepest structures (Goodwyn and Echo) of 109 kg.

  2. 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...

  3. Numerical Simulation of Internal Tide Generation at a Continental Shelf Break

    CERN Document Server

    Brandt, Laura K; Brucker, Kyle A; Dommermuth, Douglas G

    2014-01-01

    A fully nonlinear, three-dimensional numerical model is developed for the simulation of tidal flow over arbitrary bottom topography in an ocean with realistic stratification. The model is capable of simulating accurately the generation of fine-scale internal wave tidal beams, their interaction with an ocean thermocline and the subsequent generation of solitary internal waves that propagate on this thermocline. Several preliminary simulation results are shown for uniform and non-uniform flow over an idealized two-dimensional ridge, which are compared with linear theory, and for flow over an idealized two-dimensional continental shelf.

  4. 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.

    . Aragonite, low-magnesium calcite and quartz are also present in some samples. Microprobe geochemistry of the phosphatised material of the algal nodules reveals the presence of land-derived siliciclastic detritus and the possibility of more than one source... the continental shelf off the central west coast of India. source of phosphate as 90% of the material in the 0025-3227/90/$03.50 © 1990 -- Elsevier Science Publishers B.V. 18 V. PURNACHANDRA RAO El" AL. algal nodules is composed of calcium carbonate. In between...

  5. 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

    producers especially in oligotrophic areas. The metazooplankton community structure and production reflect biotic and abiotic conditions of the system. We show that small size classes, especially larvaceans, have a higher contribution to secondary production and carbon cycling in tropical oligotrophic areas......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...

  6. 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

  7. 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

  8. Carbonate sediment production in the equatorial continental shelf of South America: Quantifying Halimeda incrassata (Chlorophyta) contributions

    Science.gov (United States)

    Carneiro, Pedro Bastos de Macêdo; Morais, Jader Onofre de

    2016-12-01

    The middle and outer continental shelves of eastern equatorial South America (ESA) are characterized by intense production of carbonate sediments. Qualitative analyses of sediment deposits suggest that the calcareous green alga Halimeda incrassata is among the top CaCO3 producers. Nevertheless, no study so far has quantified its real contributions. To better understand the sediment dynamic in this area, we measured biomass, growth rates and calcium carbonate production by this alga. The species exhibited high growth rates (3.38 segments.individual-1.day-1), coverage (174 individuals.m-2) and biomass (214.02 g.m-2). Substitution of segments may allow a sedimentation rate of 1.53 mm.yr-1 and a complete turnover of the population every 60.2 days. The rapid growth indicates that this alga can produce as much CaCO3 (1.19 kg CaCO3.m-2.year-1) as other tropical organisms, such as corals and rhodoliths. In a conservative estimate, 773.500 tonnes of CaCO3 are produced per year in a 5000 km2 area off the northern coast of Brazil. Sedimentation rate seems to be higher than that promoted by continental inputs in middle and outer continental shelf. On the other hand, population turnover is twice as slow as in other H. incrassata assemblages, suggesting that South American populations are sensible to physical disturbances. New studies are necessary to accurately estimate H. incrassata coverage along the Brazilian coast and to integrate data on other CaCO3 producers, such as foraminifera and coralline algae. This would allow a better understanding of the role of South American continental shelf on the global carbon budget. Furthermore, analysis on the health of these organisms is urgent, since a decline in their populations could negatively affect ecosystems functioning and services.

  9. Geophysical and Geotechnical Determination of Sand Resources on the Florida Atlantic Continental Shelf: Preliminary Results

    Science.gov (United States)

    Finkl, C. W.; Andrews, J. L.; Suthard, B. C.; Robertson, W.

    2007-12-01

    The State of Florida is committed to maintaining beaches to sustain beach width and protect coastal infrastructure. Nearshore sand resources must be identified and cataloged for potential beach nourishment projects in response to sea-level rise and increased tropical storm activity. Given the vast length of Florida coastline, application of a variety of remote sensing techniques are required for measuring large areas in a short amount of time. The study area encompasses a shelf area of about 2,053,220 ha (20,532 km2) from Miami to the Georgia State line (about 653 km shoreline length) and extends up to 27 km offshore to about the 45 m isobath offshore Jacksonville. The continental shelf along the east coast of the Florida peninsula contains a wide range of seafloor environments that lie above the Florida-Hatteras Slope on the shoreface and inner, middle, and outer shelf floors. This study used Airborne Laser Bathymetry (ALB), 3D digital terrain models based on reformatted NOAA bathymetric data, sidescan sonar, and seismic reflection profiling to map seafloor geomorphological conditions that range from coralline-algal reef systems to drowned karst, submerged paleo shorelines (drowned beach ridge plains), and buried paleo channels. Seatruthing of morphosedimentary features is achieved via jetprobe and vibracore surveys in the study of inter-reefal sand troughs, ebb-tidal deltas, transverse bars, shoals, sand waves, ridges, and banks. Preliminary results, which visualize seafloor topography as color-ramped morphoforms, indicate the presence of sedimentary deposits that may constitute viable sand resources for shore protection in the form of beach renourishment. Use of ALB and reformatted NOAA bathymetric data in the form of 3D terrain models permits classification of submarine landform topologies that was heretofore not possible using isobaths. The combination of multiple remote sensing methods showed the spatial distribution of morphosedimentary features and provided

  10. 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.

  11. Community structure of rhodolith-forming beds on the central Brazilian continental shelf

    Science.gov (United States)

    Villas-Boas, Alexandre B.; Riosmena-Rodriguez, Rafael; de Oliveira Figueiredo, Marcia Abreu

    2014-03-01

    The community structure of rhodoliths beds in the central Brazilian continental shelf was studied under the hypothesis that nongeniculate coralline algae are the major contributors of the individual rhodoliths. Samples were collected from five localities within a single area at 17-18 m depth. At each locality, rhodoliths were collected in 10 random quadrat samples along a 20-m transect. Our results show that dead cores of rhodoliths were significantly composed by nongeniculate coralline red algae rather than bryozoans, corals, or inorganic material. The live outer layers of the rhodoliths are composed mainly of 7 species of nongeniculate red coralline algae ( Lithophyllum coralline, L. johansenii, L. depressum, L. stictaeformis, Neogoniolithon brassica- florida, Spongites fruticosus, and Lithothamnion muellerii) associated with other encrusting organisms such as bryozoans, sponges, corals, barnacles, and Peyssonnelia red algae. Significant differences were found in the proportion of Lithophyllum species in relation to other red coralline algae found in this study. Our results show that on the Brazilian continental shelf, the rhodolith-forming species are quite higher in size than in any other studied areas in the world. There was no difference in the proportion of live-to-dead rhodolith materials, suggesting an old bed deposit. Also, the amount of calcium carbonate material in the specimens is relevant to take in account in terms of the CO2 balance worldwide.

  12. Deepening of the ocean mixed layer at the northern Patagonian continental shelf: a numerical study

    CERN Document Server

    Zanella, Juan; Pescio, Andres; Dragani, Walter

    2014-01-01

    A possible deepening of the ocean mixed layer was investigated at a selected point of the Patagonian continental shelf where a significant positive wind speed trend was estimated. Using a 1-dimensional vertical numerical model (S2P3) forced by atmospheric data from NCEP/NCAR I reanalysis and tidal constituents from TPXO 7.2 global model on a long term simulation (1979-2011), it was found that the mixed layer thickness presents a significant and positive trend of 10.1 +/- 1.4 cm/yr. Several numerical experiments were carried out in order to evaluate the impact of the different atmospheric variables (surface zonal and latitudinal wind components, air temperature, atmospheric pressure, specific humidity and cloud coverage) considered in this study. As a result it was found that an increase in the wind speed can be considered as the main responsible of the ocean mixed layer deepening at the selected location of the Patagonian continental shelf. A possible increasing in the mixed layer thickness could be directly ...

  13. Benthic foraminifers on the continental shelf and upper slope, Russian River area, northern California ( USA).

    Science.gov (United States)

    Quinterno, P.J.; Gardner, J.V.

    1987-01-01

    We analyzed benthic foraminifers from 71 surface samples collected from the sea floor of the continental margin. One hundred and six different taxa were identified, and Q-mode factor analysis was used to identify assemblages. Six foraminiferal assemblage factors explain 94% of the variation in the data matrix. The Inner Shelf Assemblage is characterized by Trichohyalus ornatissima, Rotalia columbiensis, Cassidulina limbata, Cibicides fletcheri, Elphidiella hannai and Elphidium sp. 1 and occupies water depths less than 50 m. The Middle Shelf Assemblage is characterized by Nonionella basispinata, Elphidium excavatum and Florilus labradoricus and occupies water depths between 50 and 90 m. A Middle Shelf to Upper Bathyal Assemblage is characterized by Uvigerina juncea, Globobulimina spp. and Nonionella basispinata and occupies depths between about 90 and 450 m. Two overlapping assemblages make up the Upper Middle Bathyal Assemblage and are most abundant between water depths of 500 and 1300 m. They are associated with low- oxygen conditions. The Mid-Bathyal Assemblage is dominated by Uvigerina proboscidea and occurs on the slope at water depths ranging from 1200 to 2500 m. -from Authors

  14. Temperature characteristics of bacterial sulfate reduction in continental shelf and slope sediments

    Directory of Open Access Journals (Sweden)

    J. E. Sawicka

    2012-01-01

    Full Text Available The temperature responses of sulfate-reducing microbial communities were used as fingerprints for their in situ temperature adaptation, their origin, and dispersal in the deep-sea. Sediments were collected from a suite of coastal, continental shelf, and slope sediments from the southwest and southeast Atlantic and permanently cold Arctic fjords from water depths ranging from the intertidal zone to 4327 m. In situ temperatures ranged from 8 °C on the shelf to 1 °C on the lower slope and in the Arctic. Temperature characteristics of the active sulfate-reducing community were determined in short-term incubations with 35S-sulfate in a temperature gradient block spanning a temperature range from 0 to 40 °C. An optimum temperature (Topt between 27 °C and 30 °C for the South Atlantic shelf sediments and for the intertidal flat sediment from Svalbard was indicative of a psychrotolerant/mesophilic sulfate-reducing community, whereas Topt ≤ 20 °C in South Atlantic slope and Arctic shelf sediments suggested a predominantly psychrophilic community. High sulfate reduction rates (20–50% at in-situ temperatures compared to those at Topt further support this interpretation, and point to the importance of the ambient temperature regime for regulating the short-term temperature response of sulfate-reducing communities. A number of cold (<4 °C continental slope sediments showed broad temperature optima reaching as high as 30 °C suggesting the additional presence of apparently mesophilic sulfate-reducing bacteria. Since the temperature characteristics of these mesophiles do not fit with the permanently cold deep-sea environment, we suggest that these mesophilic microorganisms are of allochthonous origin and transported to this site. It is likely that they were deposited along with the mass-flow movement of warmer shelf-derived sediment. These data therefore suggest that temperature

  15. Temperature characteristics of bacterial sulfate reduction in continental shelf and slope sediments

    Directory of Open Access Journals (Sweden)

    J. E. Sawicka

    2012-08-01

    Full Text Available The temperature responses of sulfate-reducing microbial communities were used as community temperature characteristics for their in situ temperature adaptation, their origin, and dispersal in the deep sea. Sediments were collected from a suite of coastal, continental shelf, and slope sediments from the southwest and southeast Atlantic and permanently cold Arctic fjords from water depths ranging from the intertidal zone to 4327 m. In situ temperatures ranged from 8 °C on the shelf to −1 °C in the Arctic. Temperature characteristics of the active sulfate-reducing community were determined in short-term incubations with 35S-sulfate in a temperature gradient block spanning a temperature range from 0 to 40 °C. An optimum temperature (Topt between 27 °C and 30 °C for the South Atlantic shelf sediments and for the intertidal flat sediment from Svalbard was indicative of a psychrotolerant/mesophilic sulfate-reducing community, whereas Topt ≤20 °C in South Atlantic slope and Arctic shelf sediments suggested a predominantly psychrophilic community. High sulfate reduction rates (20–50% at in situ temperatures compared to those at Topt further support this interpretation and point to the importance of the ambient temperature regime for regulating the short-term temperature response of sulfate-reducing communities. A number of cold (<4 °C continental slope sediments showed broad temperature optima reaching as high as 30 °C, suggesting the additional presence of apparently mesophilic sulfate-reducing bacteria. Since the temperature characteristics of these mesophiles do not fit with the permanently cold deep-sea environment, we suggest that these mesophilic microorganisms are of allochthonous origin and transported to this site. It is likely that they were deposited along with the mass-flow movement of warmer shelf-derived sediment. These data therefore suggest that temperature

  16. 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.

  17. Distribution of DDT and other persistent organic contaminants in Canyons and on the continental shelf off the central California coast.

    Science.gov (United States)

    Hartwell, S Ian

    2008-04-01

    Sediment samples were collected to delineate the distribution of contaminants along the central California coast. Sampling included a variety of Canyons and shelf/slope areas to evaluate contaminant transport patterns and potential delivery to Canyons and the continental slope to a depth of 1200 m. Sediments were collected and analyzed for organic contaminants using standard techniques of the NOAA National Status and Trends Program (NS&T). DDT is distributed on the shelf within a zone of fine-grained sediments between Half Moon and Monterey Bays. DDT was found at higher concentrations in Ascension, Año Nuevo, and Monterey/Soquel Canyons than in Pioneer and Carmel Canyons, the Gulf of the Farallones, or the continental slope. The Monterey Bay watershed appears to be the primary source of DDT. In contrast, PAHs and PCBs on the shelf appear to be derived primarily from San Francisco Bay. DDT appears to be delivered to the deep ocean via the Canyons more than from cross-shelf sediment transport. Sediment budget estimates for the continental shelf north of Monterey Bay need further refinement and more data to account for the movement of material from Monterey Bay onto the shelf.

  18. Observed wintertime tidal and subtidal currents over the continental shelf in the northern South China Sea

    Science.gov (United States)

    Li, Ruixiang; Chen, Changsheng; Xia, Huayong; Beardsley, Robert C.; Shi, Maochong; Lai, Zhigang; Lin, Huichan; Feng, Yanqing; Liu, Changjian; Xu, Qichun; Ding, Yang; Zhang, Yu

    2014-08-01

    Synthesis analyses were performed to examine characteristics of tidal and subtidal currents at eight mooring sites deployed over the northern South China Sea (NSCS) continental shelf in the 2006-2007 and 2009-2010 winters. Rotary spectra and harmonic analysis results showed that observed tidal currents in the NSCS were dominated by baroclinic diurnal tides with phases varying both vertically and horizontally. This feature was supported by the CC-FVCOM results, which demonstrated that the diurnal tidal flow over this shelf was characterized by baroclinic Kelvin waves with vertical phase differences varying in different flow zones. The northeasterly wind-induced southwestward flow prevailed over the NSCS shelf during winter, with episodic appearances of mesoscale eddies and a bottom-intensified buoyancy-driven slope water intrusion. The moored current records captured a warm-core anticyclonic eddy, which originated from the southwestern coast of Taiwan and propagated southwestward along the slope consistent with a combination of β-plane and topographic Rossby waves. The eddy was surface-intensified with a swirl speed of >50 cm/s and a vertical scale of ˜400 m. In absence of eddies and onshore deep slope water intrusion, the observed southwestward flow was highly coherent with the northeasterly wind stress. Observations did not support the existence of the permanent wintertime South China Sea Warm Current (SCSWC). The definition of SCSWC, which was based mainly on thermal wind calculations with assumed level of no motion at the bottom, needs to be interpreted with caution since the observed circulation over the NSCS shelf in winter included both barotropic and baroclinic components.

  19. Surficial sediment character of the Louisiana offshore continental shelf region: a GIS compilation

    Science.gov (United States)

    Williams, S. Jeffress; Arsenault, Matthew A.; Buczkowski, Brian J.; Reid, Jane A.; Flocks, James; Kulp, Mark A.; Penland, Shea; Jenkins, Chris J.

    2007-01-01

    switching by the Mississippi River and its distributaries over the past ~10,000 years that resulted in laterally overlapping deltaic depocenters. The interactions among riverine, coastal, and inner shelf processes have been superimposed on the Holocene transgression resulting in distinctive landforms and sedimentary sequences. Four Holocene shelf-phase delta complexes have been identified using seismic reflection data and vibracores. Each delta complex is bounded by transgressive surfaces. Following each cycle of deposition and abandonment, the delta lobes undergo regional subsidence and marine reworking that forms transgressive coastal systems and barrier islands. Ultimately, the distal end of each of the abandoned delta lobes is marked by submerged marine sand bodies representing drowned barriers. These sand bodies (e.g. Ship Shoal, Outer Shoal, Trinity Shoal, Tiger Shoal, St. Bernard Shoal) offer the largest volumes and highest quality sand for beach nourishment and shoreline and wetlands restoration. These four large sand shoals on inner continental shelf, representing the reworked remnants of former prograded deltaic headlands that existed on the continental shelf at lower sea level, were generated in the retreat path of the Mississippi River delta plain during the Holocene transgression. Penland and others (1989) have shown these sand bodies represent former shoreline positions associated with lower still stands in sea level. Short periods of rapid relative sea-level rise led to the transgressive submergence of the shorelines which today can be recognized at the -10 m to -20 m isobaths on the Louisiana continental shelf. Trinity Shoal and Ship Shoal represent the -10 m middle-to-late Holocene shoreline trend, whereas Outer Shoal and the St. Bernard Shoals define the -20 m early Holocene shoreline trend (Penland and others, 1989). Collectively, these sand shoals constitute a large volume of high quality sandy sediment potentially suitable for barrier island nourishment

  20. Random-access technique for modular bathymetry data storage in a continental shelf wave refraction program

    Science.gov (United States)

    Poole, L. R.

    1974-01-01

    A study was conducted of an alternate method for storage and use of bathymetry data in the Langley Research Center and Virginia Institute of Marine Science mid-Atlantic continental-shelf wave-refraction computer program. The regional bathymetry array was divided into 105 indexed modules which can be read individually into memory in a nonsequential manner from a peripheral file using special random-access subroutines. In running a sample refraction case, a 75-percent decrease in program field length was achieved by using the random-access storage method in comparison with the conventional method of total regional array storage. This field-length decrease was accompanied by a comparative 5-percent increase in central processing time and a 477-percent increase in the number of operating-system calls. A comparative Langley Research Center computer system cost savings of 68 percent was achieved by using the random-access storage method.

  1. 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.

  2. 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.

  3. Arctic geodynamics: Continental shelf and deep ocean geophysics. ERS-1 satellite altimetry: A first look

    Science.gov (United States)

    Anderson, Allen Joel; Sandwell, David T.; Marquart, Gabriele; Scherneck, Hans-Georg

    1993-01-01

    An overall review of the Arctic Geodynamics project is presented. A composite gravity field model of the region based upon altimetry data from ERS-1, Geosat, and Seasat is made. ERS-1 altimetry covers unique Arctic and Antarctic latitudes above 72 deg. Both areas contain large continental shelf areas, passive margins, as well as recently formed deep ocean areas. Until ERS-1 it was not possible to study these areas with satellite altimetry. Gravity field solutions for the Barents sea, portions of the Arctic ocean, and the Norwegian sea north of Iceland are shown. The gravity anomalies around Svalbard (Spitsbergen) and Bear island are particularly large, indicating large isostatic anomalies which remain from the recent breakup of Greenland from Scandinavian. Recently released gravity data from the Armed Forces Topographic Service of Russia cover a portion of the Barents and Kara seas. A comparison of this data with the ERS-1 produced gravity field is shown.

  4. Application of the Three-Dimensional Shallow Sea and Continental Shelf Mode for Inversion of Undercurrent

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Due to the incapability of high frequency surface wave radar (HFSWR) to detect undercurrent parameters, a new algorithm is proposed to apply a three-dimensional (3D) nonlinear barotropic shallow sea and continental shelf model in coordinate system to the inversion of undercurrent. The calculation domain of this model is the area detected by HFSWR. Considering the benthal topography of the detected area and the ocean dynamic parameters, such as surface current, wind and wave detected by HFSWR, the relation between surface current and undercurrent is established in this model. Accordingly, the undercurrent parameters of corresponding area are obtained. The inversion results agree with the law of ocean dynamics and reproduce the movement of undercurrent.

  5. 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 (

  6. Drowned forests and archaeology on the continental shelf of British Columbia, Canada

    Science.gov (United States)

    Fedje, Daryl W.; Josenhans, Heiner

    2000-02-01

    We have used high-resolution digital terrain imaging and sea-floor sampling to reveal drowned late glacial to early postglacial terrestrial landscapes at water depths as great as 150 m. In situ tree stumps and shellfish-rich paleobeaches are present on these drowned landscapes. A stone tool encrusted with barnacles and bryozoa was recovered from a drowned delta flood plain now 53 m below mean sea level. This is the first tangible evidence that the formerly subaerial broad banks of the western North American Continental Shelf may have been occupied by humans in earliest Holocene and possibly late-glacial time. Analyses (14C) of the drowned terrestrial and intertidal deposits were used to refine the local sea-level curve, which shows very rapid change within this glacio-isostatically dynamic region.

  7. Sedimentary and geochemical characterization and provenance of the Portuguese continental shelf soft-bottom sediments

    Science.gov (United States)

    Martins, R.; Azevedo, M. R.; Mamede, R.; Sousa, B.; Freitas, R.; Rocha, F.; Quintino, V.; Rodrigues, A. M.

    2012-03-01

    Grain-size and geochemical analyses for soft-bottom sediments from the Portuguese continental shelf are used to determine their provenance and to identify the main factors governing the sediment distribution patterns. The deeper areas of the northwestern and central sectors of the Portuguese shelf and most of its southwestern sector are covered by fine and very fine sands. Coarse deposits are found in the inner and middle shelf of the northernmost sector and immediately south of the Nazaré and Setúbal canyons, while muddy sediments are restricted to areas located off the mouths of major rivers (Douro and Tagus mud patches). In contrast, the southern shelf corresponds to a low energy environment receiving most of its sediment supply from the Guadiana River. As a result, an expressive mud patch is developed off the Guadiana estuarine system. The application of multivariate analysis to geochemical data allowed the classification of the studied samples into four main groups: (a) a group of mud deposits constituted by detrital clay minerals and authigenic iron-manganese oxyhydroxides, displaying high contents for organic matter and for most major and trace elements; (b) a group of biogenic carbonate-rich sands showing high CaO, Sr and U contents which is well represented throughout the entire Portuguese shelf; (c) a group of quart-rich sediments, with very high SiO 2 contents and moderate Al 2O 3, K 2O and TiO 2 contents, supporting a major terrigenous contribution and (d) a group of coarse sand samples with high As levels from off important rivers, pointing to anthropogenic contamination. Trace metal enrichments observed in the muddy areas from both the western and southern coasts appear to result from natural causes and do not exceed the international sediment quality thresholds. There is, however, local evidence for As, Zn, Cr and Pb anthropogenic contamination in near-shore sediments associated with rivers draining regions characterized by urban, industrial or

  8. 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)

  9. 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)

  10. Mode-2 hydraulic control of flow over a small ridge on a continental shelf

    Science.gov (United States)

    Gregg, M. C.; Klymak, Jody M.

    2014-11-01

    Some of the most intense turbulence in the ocean occurs in hydraulic jumps formed in the lee of sills where flows are hydraulically controlled, usually by the first internal mode. Observations on the outer Texas-Louisiana continental shelf reveal hydraulic control of internal mode-2 lasting more than 3 h over a 20 m high ridge on the 100 m deep continental shelf. When control began the base of the weakly stratified surface layer bulged upward and downward, a signature of mode-2. As the westward flow producing control was lost, large-amplitude disturbances, initially resembling a bore in the weakly stratified layer, began propagating eastward. Average dissipation rates inferred from density inversions over the ridge were 10-8 and 10-7W kg-1, one to two decades above local background. Corresponding diapycnal diffusivities, Kρ, were 10-4 to 10-3 m2 s-1. Short-term mixing averages did not evolve systematically with hydraulic control, possibly owing to our inability to observe small overturns in strongly stratified water directly over the ridge. To test the feasibility of our interpretation of the observations, hydrostatic runs with a three-dimensional MITgcm simulated mode-2 control and intense mixing over the ridge below the interface. Details differed from observations, principally because we lacked three-dimensional density fields to initialize the model which was forced with currents observed by a bottom-mounted ADCP several kilometers east of the ridge. Consequently, the model did not capture all flow features around the bank. The principal conclusion is that hydraulic responses to higher modes can dominate flows around even modest bathymetric irregularities.

  11. Southeast Alaskan shelf from southern tip of Baranof Island to Kayak Island: Currents, mixing and chlorophyll-a

    Science.gov (United States)

    Stabeno, P. J.; Bond, N. A.; Kachel, N. B.; Ladd, C.; Mordy, C. W.; Strom, S. L.

    2016-10-01

    During 2011 and 2013, an integrated ecosystem study was undertaken on the Southeast Alaska shelf and slope. As part of that study, a total of 8 moorings were deployed each year along the coast of Baranof and Chichagof Islands, in Cross Sound and at Icy Point. In addition, 18 satellite-tracked drifters were deployed during the two field years. The goals of this manuscript are to describe: the coastal currents in southeastern Alaska; the processes affecting them; and how the physics modify the nutrients and primary production in the region. Mixing in Cross Sound is an important source of nutrients for the shelf north of the sound, resulting in prolonged production during summer. While the Alaska Coastal Current is not a continuous feature along the entire Gulf of Alaska coast, it does exist from southern tip of Baranof Island to Cross Sound, and again northwest of Yakutat. The narrowness of this shelf coupled with the meanders and eddies in the Alaska Current result in large amounts of on-shelf flow of slope water and off-shelf flow of coastal water. While local currents and summer winds were similar in 2011 and 2013, 2011 was characterized by low chlorophyll-a concentrations throughout the spring-summer, while chlorophyll concentrations in 2013 were typical. The cause of this difference remains unclear, but bottom-up processes likely contributed to the low chlorophyll-a concentrations in 2011.

  12. 76 FR 8962 - Renewable Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf-Acquire a...

    Science.gov (United States)

    2011-02-16

    ... Bureau of Ocean Energy Management, Regulation and Enforcement 30 CFR Part 285 RIN 1010-AD71 Renewable... acquisition of an Outer Continental Shelf (OCS) renewable energy lease. We are taking this action because the current regulations governing the noncompetitive acquisition of an OCS renewable energy lease initiated...

  13. 76 FR 28178 - Renewable Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf-Acquire a...

    Science.gov (United States)

    2011-05-16

    ... Bureau of Ocean Energy Management, Regulation and Enforcement 30 CFR Part 285 RIN 1010-AD71 Renewable... acquisition of an Outer Continental Shelf (OCS) renewable energy lease. We are taking this action because... for an OCS renewable energy lease, where BOEMRE is required to publish only a single notice. The...

  14. 75 FR 72679 - Renewable Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf-Acquire a...

    Science.gov (United States)

    2010-11-26

    ... Bureau of Ocean Energy Management, Regulation and Enforcement 30 CFR Part 285 RIN 1010-AD71 Renewable... an Outer Continental Shelf (OCS) renewable energy lease. We are taking this action because the current regulations covering noncompetitive leasing of an OCS renewable energy lease and an...

  15. 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.

  16. 78 FR 8190 - Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore North Carolina...

    Science.gov (United States)

    2013-02-05

    ... Bureau of Ocean Energy Management Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS... Information and Nominations for Commercial Leasing for Wind Power Offshore North Carolina (Call), published on... developers describing commercial leasing interest and requested comments and information pertaining to...

  17. 76 FR 70156 - Proposed 5-Year Outer Continental Shelf (OCS) Oil and Gas Leasing Program for 2012-2017

    Science.gov (United States)

    2011-11-10

    ... Bureau of Ocean Energy Management Proposed 5-Year Outer Continental Shelf (OCS) Oil and Gas Leasing... on the Proposed 5-Year OCS Oil and Gas Leasing Program for 2012-2017 (``Proposed Program''). This is... OCS Oil and Gas Leasing Program for 2012-2017. The Proposed Program document may be downloaded...

  18. 75 FR 16833 - Preliminary Revised 5-Year Outer Continental Shelf (OCS) Oil and Gas Leasing Program for 2007-2012

    Science.gov (United States)

    2010-04-02

    ... Minerals Management Service Preliminary Revised 5-Year Outer Continental Shelf (OCS) Oil and Gas Leasing... Revised 5-Year OCS Oil and Gas Leasing Program for 2007- 2012. This is the Preliminary Revised Program... relative environmental sensitivity analysis and the Secretary's revisions to the leasing schedule...

  19. 75 FR 68824 - Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore Maryland-Request...

    Science.gov (United States)

    2010-11-09

    ... Enforcement [Docket No. BOEM-2010-0038] Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS... Enforcement, Interior. ACTION: RFI in Commercial Wind Energy Leasing Offshore Maryland, and Invitation for... this potential commercial leasing area no later than January 10, 2011 for your submission to...

  20. 75 FR 21653 - Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore Delaware-Request...

    Science.gov (United States)

    2010-04-26

    ... Minerals Management Service Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore... renewable energy leasing offshore Delaware, and invitation of comments from interested and affected parties... your submission indicating your interest in this potential commercial leasing area no later than...

  1. 78 FR 64242 - Outer Continental Shelf (OCS), Gulf of Mexico (GOM), Oil and Gas Lease Sales, Western Planning...

    Science.gov (United States)

    2013-10-28

    ... Bureau of Ocean Energy Management Outer Continental Shelf (OCS), Gulf of Mexico (GOM), Oil and Gas Lease Sales, Western Planning Area (WPA) Lease Sales 238, 246, and 248 AGENCY: Bureau of Ocean Energy... proposed OCS oil and gas Lease Sales 238, 246, and 248, which are tentatively scheduled to be held...

  2. 77 FR 40380 - Outer Continental Shelf, Gulf of Mexico, Oil and Gas Lease Sales, Western Planning Area Lease...

    Science.gov (United States)

    2012-07-09

    ... Bureau of Ocean Energy Management Outer Continental Shelf, Gulf of Mexico, Oil and Gas Lease Sales, Western Planning Area Lease Sale 233 and Central Planning Area Lease Sale 231 AGENCY: Bureau of Ocean... proposed Western Planning Area (WPA) Lease Sale 233 and Central Planning Area (CPA) Lease Sale 231...

  3. 77 FR 51568 - Outer Continental Shelf, Gulf of Mexico, Oil and Gas Lease Sales, Western Planning Area Lease...

    Science.gov (United States)

    2012-08-24

    ... Bureau of Ocean Energy Management Outer Continental Shelf, Gulf of Mexico, Oil and Gas Lease Sales, Western Planning Area Lease Sale 233 and Central Planning Area Lease Sale 231 AGENCY: Bureau of Ocean... announced its intent to prepare a Supplemental EIS for proposed Western Planning Area (WPA) Lease Sale...

  4. 78 FR 42544 - Outer Continental Shelf (OCS), Gulf of Mexico (GOM), Oil and Gas Lease Sale, Western Planning...

    Science.gov (United States)

    2013-07-16

    ... Bureau of Ocean Energy Management Outer Continental Shelf (OCS), Gulf of Mexico (GOM), Oil and Gas Lease Sale, Western Planning Area (WPA) Lease Sales 238, 246, and 248 MMAA104000 AGENCY: Bureau of Ocean... Supplemental EIS for proposed WPA lease sales beginning with Lease Sale 238 (WPA Lease Sales 238, 246, and...

  5. 78 FR 52562 - Outer Continental Shelf (OCS), Gulf of Mexico (GOM), Oil and Gas Lease Sales, Central Planning...

    Science.gov (United States)

    2013-08-23

    ... Bureau of Ocean Energy Management Outer Continental Shelf (OCS), Gulf of Mexico (GOM), Oil and Gas Lease Sales, Central Planning Area (CPA) Lease Sales 235, 241, and 247 AGENCY: Bureau of Ocean Energy... EIS for proposed Central Planning Area (CPA) Lease Sales 235, 241 and 247 in the Gulf of Mexico...

  6. 76 FR 19122 - Record of Decision (ROD) for Authorizing the Use of Outer Continental Shelf (OCS) Sand Resources...

    Science.gov (United States)

    2011-04-06

    ... the Use of Outer Continental Shelf (OCS) Sand Resources in National Aeronautics and Space... Availability (NOA) of the Record of Decision. SUMMARY: BOEMRE has issued a ROD to authorize the use of OCS sand... for the purpose of making sand available from a shoal on the OCS for placement on the beach in...

  7. 77 FR 40081 - Gulf of Mexico, Outer Continental Shelf (OCS), Western Planning Area (WPA) and Central Planning...

    Science.gov (United States)

    2012-07-06

    ... From the Federal Register Online via the Government Publishing Office 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...

  8. Filamentous bacteria inhabiting the sheaths of marine Thioploca spp. on the Chilean continental shelf

    DEFF Research Database (Denmark)

    Teske, Andreas; Jørgensen, Bo Barker; Gallardo, Victor A.

    2009-01-01

    A new component of the benthic Thioploca mat microbial ecosystem on the Chilean continental shelf was detected by epifluorescence microscopy: filamentous, bacterial endobionts of 4-5-μm filament diameter and length sometimes exceeding 1 mm. These filaments were identified as growing within Thiopl...

  9. 76 FR 70473 - Outer Continental Shelf (OCS) Western Planning Area (WPA) Gulf of Mexico (GOM) Oil and Gas Lease...

    Science.gov (United States)

    2011-11-14

    ..., 6th Floor, Immediately. Please Note: 1. Bidders mailing bid(s) are advised to call Ms. Nancy Kornrumpf... provisions of the 1982 Law of the Sea Convention, and could be subject to a continental shelf delimitation... additional information, please call the Mapping and Automation Section at (504) 736-5768. All blocks...

  10. 78 FR 52239 - Oil and Gas and Sulphur Operations on the Outer Continental Shelf-Oil and Gas Production Safety...

    Science.gov (United States)

    2013-08-22

    ... would be added because the hydraulic control pressure to an individual subsea well may not be able to be... subsea tree production systems on the Outer Continental Shelf (OCS) and divide the current subpart H into... following headings: General requirements; Surface and subsurface safety systems--Dry trees; Subsea...

  11. Distribution of DDT and Other Persistent Organic Contaminants in Canyons and on the Continental Shelf off the Central California Coast

    OpenAIRE

    Hartwell, S. Ian

    2008-01-01

    Distribution of DDT and Other Persistent Organic Contaminants in Canyons and on the Continental Shelf off the Central California Coast correspondence: Corresponding author. Tel.: +301 713 3028; fax: +301 713 4388. (Hartwell, S. Ian) (Hartwell, S. Ian) NOAA/NOS/NCCOS Center for Coastal Monitoring and Assessment 1305 East West Hwy Silver Spring - MD 20910--> - (Hartwell, S. Ian) UNITED STATES (Hartwell, S. Ia...

  12. 78 FR 45557 - Gulf of Mexico, Outer Continental Shelf (OCS), Western Planning Area (WPA) Oil and Gas Lease Sale...

    Science.gov (United States)

    2013-07-29

    ... making its decision, BOEM considered alternatives to the proposed action and the potential impacts as... Bureau of Ocean Energy Management Gulf of Mexico, Outer Continental Shelf (OCS), Western Planning Area...: Notice of Availability of a Record of Decision. SUMMARY: BOEM has prepared a Record of Decision (ROD)...

  13. 78 FR 59632 - Oil and Gas and Sulphur Operations on the Outer Continental Shelf-Oil and Gas Production Safety...

    Science.gov (United States)

    2013-09-27

    ... proposed rulemaking on production safety systems on August 22, 2013 (78 FR 52240). The proposed rule would... Bureau of Safety and Environmental Enforcement 30 CFR Part 250 RIN 1014-AA10 Oil and Gas and Sulphur Operations on the Outer Continental Shelf--Oil and Gas Production Safety Systems AGENCY: Bureau of Safety...

  14. 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...

  15. 78 FR 45558 - Western Gulf of Mexico Planning Area (WPA) Outer Continental Shelf (OCS) Oil and Gas Lease Sale...

    Science.gov (United States)

    2013-07-29

    ... Migration, Reverse Migration, Reverse Time Migration) of the data, velocity models used, and other requested...-Program/Mapping-and-Data/Official-Protraction-Diagrams.aspx . For the current status of all WPA leasing... the U.S.-Mexico Maritime and Continental Shelf Boundary The following definitions apply to...

  16. Inputs of iron, manganese and aluminium to surface waters of the Northeast Atlantic Ocean and the European continental shelf

    NARCIS (Netherlands)

    Jong, Jeroen T.M. de; Boyé, Marie; Gelado-Caballero, Maria D.; Timmermans, Klaas R.; Veldhuis, Marcel J.W.; Nolting, Rob F.; Berg, Constant M.G. van den; Baar, Hein J.W. de

    2007-01-01

    Dissolved Fe, Mn and Al concentrations (dFe, dMn and dAl hereafter) in surface waters and the water column of the Northeast Atlantic and the European continental shelf are reported. Following an episode of enhanced Saharan dust inputs over the Northeast Atlantic Ocean prior and during the cruise in

  17. 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

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf, Alaska OCS Region, Chukchi Sea Planning Area, Oil and Gas Lease Sale 193 AGENCY: Bureau of Ocean Energy...

  18. 75 FR 25291 - Outer Continental Shelf (OCS) Mid-Atlantic Proposed Oil and Gas Lease Sale 220

    Science.gov (United States)

    2010-05-07

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Minerals Management Service Outer Continental Shelf (OCS) Mid-Atlantic Proposed Oil and Gas Lease Sale 220 AGENCY: Minerals Management Service (MMS), Interior. ACTION: Notice of indefinite postponement of...

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

    Institute of Scientific and Technical Information of China (English)

    Zhang-Hua; Wang; Yong-Hong; Dong; Jing; Chen; Xiao-Feng; Li; Juan; Cao; Zhi-Yong; Deng

    2014-01-01

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  1. Geologic evidence for onshore sediment transport from the inner continental shelf: Fire Island, New York

    Science.gov (United States)

    Schwab, William C.; Baldwin, Wayne E.; Hapke, Cheryl J.; Lentz, Erika E.; Gayes, Paul T.; Denny, Jane F.; List, Jeffrey H.; Warner, John C.

    2013-01-01

    Sediment budget analyses along the south shore of Fire Island, New York, have been conducted and debated in the scientific and coastal engineering literature for decades. It is well documented that a primary component of sediment transport in this system is directed alongshore from E to W, but discrepancies in volumetric sediment budget calculations remain. An additional quantity of sand, averaging about 200,000 m3/y is required to explain the growth of the western segment of the barrier island, a prograding spit. Littoral sediment derived from updrift erosion of the coast, addition of beach nourishment fill, and onshore transport of inner continental shelf, shoreface sediments, or both have all been proposed as potential sources of the additional sediment needed to balance the sediment budget deficit. Analysis of high-resolution seafloor mapping data collected in 2011, including seismic reflection profiles and inteferometric sonar acoustic backscatter and swath bathymetry; comparison with seafloor mapping data collected in 1996–1997; and shoreline change analysis from 1933 to 2011 support previous suggestions that the inner-shelf Holocene sedimentary deposit is a likely source to resolve this sediment budget discrepancy.

  2. Holocene Formation of Heald Sand Bank on the East Texas Inner Continental Shelf

    Science.gov (United States)

    Swartz, J. M.; Cleveland, V.; Gulick, S. P. S.; Goff, J. A.

    2015-12-01

    Heald Bank is a Gulf of Mexico sand bank located ~50 km off the coast of east Texas on the inner continental shelf. The bank is proposed to be a remnant of barrier islands drowned and thus preserved during an episode of rapid sea level rise. For this hypothesis to be true, the transgressive ravinement that marks the erosion by the shoreline moving from shelf edge towards the modern location would by definition postdate and thus be stratigraphically above the bank. To test this hypothesis we present ~90 km of Compressed High Intensity Radar Pulse (CHIRP) and Multi-channel seismic (MCS) data collected from the University of Texas Geophysics marine field course during 2008, 2013, and 2014. In these data, there are several visible underlying channels beneath Heald Bank. These channels have channel fill which are truncated by an overlying erosional surface, which we interpret to be the transgressive ravinement from sea level rise. However, this interpretation places the ravinement below the sand bank, meaning it could not have been drowned and buried by a rapid sea level rise event. Thus, Heald Bank and potentially the related inner shelf banks (Thomas, Shepard, and Sabine) from eastern Texas to western Louisiana cannot be used as an example of coastal response to climate change and sea level rise. We examine alternate origins for the banks and their sand using published cores as well as age models and integrating them with our seismic data. One possibility is that the sand was sourced from the nearby Sabine River system immediately following local transgression or the sand was remobilized from sediment fill within underlying paleo-river channels imaged below the Heald Bank. In either case Heald Bank appears not to serve as an indicator for rapid sea-level rise, yet could be an important analog for sand transport mechanisms offshore.

  3. Benthic Foraminiferal Census Data from Louisiana Continental Shelf Cores, Gulf of Mexico

    Science.gov (United States)

    Osterman, Lisa E.; Kelly, Wendy S.; Ricardo, John P.

    2009-01-01

    An area of oxygen-depleted bottom- and subsurface-water (hypoxia = dissolved oxygen restore normal oxygen conditions (Rabalais and others, 1994, 1996; Rabalais, 2002). Since systematic measurement of the extent of the dead zone began in 1985, the overall pattern indicates that the area of the dead zone is increasing (Rabalais and Turner, 2001; Turner and others, 2005). Several studies have concluded that the expansion of the Louisiana Shelf dead zone is related to increased nutrients (primarily nitrogen, but possibly also phosphorous) in the Mississippi River drainage basin and is responsible for the degradation of Gulf of Mexico marine habitats (Goolsby and others, 2001). This paper presents the benthic foraminiferal data from 10 sediment cores collected from the Continental Shelf of Louisiana (table 1), obtained as part of an initiative to investigate the geographic and temporal extent of hypoxia prior to 1985 in the Gulf of Mexico. Benthic foraminifers provide a method to track the development of hypoxia prior to 1985 (Blackwelder and others, 1996; Sen Gupta and others, 1996). Previous work (Osterman, 2003) has shown statistically that the relative occurrence of three low-oxygen-tolerant species represents the modern seasonal Louisiana hypoxia zone. The cumulative percentage of these three species (% Pseudononion atlanticum + % Epistominella vitrea, + % Buliminella morgani = PEB index of hypoxia) provides a way to investigate fluctuation in paleohypoxia. Interpretation of some of these cores is provided in Osterman and others (2005), Osterman and others (2008a,b), and Swarzenski and others (2008). Our hypothesis is that the increased relative abundance of PEB species in dated sediment cores accurately tracks past seasonal low-oxygen conditions on the Louisiana Shelf.

  4. 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

    We studied the cross-shelf variation in hydrography and plankton dynamics off west Thailand, focusing on physical- biological linkages. The overall research programme investigated linkages between physics, chemistry and plankton biology; in the present paper we consider the findings based...... 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...... revealed a marked cross-shelf structuring into a number of larval assemblages. Distinct assemblages were identified in nearshore areas, at mid-shelf in the area of the hydrographic front, and off the shelf break in oceanic water. Less pronounced variation was seen in the along-shelf direction and between...

  5. Benthic mineralization and nutrient exchange over the inner continental shelf of western India

    Science.gov (United States)

    Pratihary, A. K.; Naqvi, S. W. A.; Narvenkar, G.; Kurian, S.; Naik, H.; Naik, R.; Manjunatha, B. R.

    2014-05-01

    The western Indian continental shelf is one of the most productive coastal systems of the world ocean. This system experiences extreme changes in its oxygen regime, being normoxic from November to May and suboxic (denitrifying)/anoxic from June to October, owing to the biogeochemical response to cyclical monsoonal influence. In order to understand the impact of the seasonally varying oxygen regime on benthic mineralization, nutrient exchange and, in turn, on the shelf ecosystem, we carried out the first ever intact-core incubations during two contrasting seasons - spring intermonsoon and fall intermonsoon (late southwest monsoon) at a 28 m-deep fixed site on the inner shelf off Goa, dominated by fine-grained cohesive sediments. The results showed that incomplete sediment oxygen consumption (SOC) occurred during April as opposed to the complete SOC and subsequent sulfide flux observed in the fall intermonsoon incubations. The sediments acted as a perennial net source of DIN (dissolved inorganic nitrogen i.e. NO3- + NO2- + NH4+), PO43- and SiO44- to the overlying water column. The efflux of DIN increased from 1.4 to 3.74 mmol m-2 d-1 from April to October, of which NH4+ flux comprised 59-100%. During the oxic regime, ∼75% of diffusing NH4+ appeared to be nitrified (2.55 mmol m-2 d-1), of which ∼77% remained coupled to benthic denitrification. Consequently, 58% of NH4+ flux was lost in active coupled nitrification-denitrification, resulting in substantial N loss (1.98 mmol m-2 d-1) in the sediments. The continental shelf sediments switched over from being a NO3- source during the oxic regime to a NO3- sink during the anoxic regime. During suboxia, benthic denitrification that is fed by NO3- from the overlying water caused N loss at the rate of 1.04 mmol m-2 d-1. Nitrogen loss continued even under sulfidic conditions during October, possibly through the chemolithoautotrophic denitrification, at a potential rate of 3.21 mmol m-2 d-1. Phosphate flux increased more

  6. 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

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

    Directory of Open Access Journals (Sweden)

    A. Goswami

    2015-04-01

    Full Text Available 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

  8. Architectures of the Moroccan continental shelf of the Alboran Sea: insights from high-resolution bathymetry and seismic data.

    Science.gov (United States)

    Lafosse, Manfred; Gorini, Christian; Leroy, Pascal; d'Acremont, Elia; Rabineau, Marina; Ercilla, Gemma; Alonso, Belén; Ammar, Abdellah

    2016-04-01

    The MARLBORO and the SARAS oceanographic surveys have explored the continental shelf in the vicinity of the transtensive Nekor basin (South Alboran Sea, Western Mediterranean) and over three submarine highs located at several tens of kilometers from the shelf. Those surveys have produced high-resolution (≤29m²/pixel) bathymetry maps. Simultaneously, seismic SPARKER and TOPAS profiles were recorded. To quantify and understand Quaternary vertical motions of this tectonically active area, we searched for morphological and sedimentary paleobathymetric or paleo-elevations markers. Shelf-edge wedges associated marine terraces and paleo-shorelines have been identified on the bathymetry and on seismic cross-sections. These features reflect the trends of long term accommodation variations. Along the Moroccan continental shelf the lateral changes of shelf-edges geometries and the spatial distribution of marine landforms (sedimentary marine terraces, sediment wave fields, marine incisions) reflect the interaction between sea level changes and spatial variations of subsidence rates. Positions of paleo-shorelines identified in the studied area have been correlated with the relative sea-level curve (Rohling et al., 2014). Several still stands or slow stands periods have been recognized between -130-125m, -100-110m and -85-80m. The astronomical forcing controls the architecture of Mediterranean continental shelves. Marine landforms distribution also reveals the way sea level changed since the LGM. The comparison with observations on other western Mediterranean margins (e.g. the Gulf of Lion, the Ionian-Calabrian shelf) allowed a first order access to vertical motion rates.

  9. Ocean acidification research alongside extended continental shelf exploration in the western Arctic Ocean

    Science.gov (United States)

    Wynn, J. G.; Robbins, L. L.; Knorr, P. O.; Byrne, R. H.; Takahashi, T.; Onac, B. P.

    2013-12-01

    Research investments funded to fulfill the requirements of the UN Convention on the Law of the Sea in the western Arctic have allowed simultaneous acquisition of marine chemistry data, including baseline monitoring of changes in ocean acidification. Our participation in the Extended Continental Shelf cruises on the USCGC Healy in the western Arctic have allowed us to collect data focused on understanding processes driving rapid changes in seawater chemistry that result from increased oceanic uptake of CO2 (ocean acidification), increased freshwater runoff, changes in sea ice growth and decay processes and changes in biogeochemical processes. Carbonate mineral saturation data collected during HLY1002, HLY1102, and HLY1202 (summers 2010-2012) document undersaturation with respect to aragonite (Ωaragonite) in ~20% of the surface waters of the Canada and Makarov Basins, in direct association with areas of recently accelerated sea ice loss. Conservative tracer studies using salinity, stable oxygen isotopic composition, dissolved silica and barium augment this work by elucidating contributions from distinct water sources. These data show that while surface water in this entire area retains abundant freshwater from meteoric sources, it is freshwater additions from melting of multiyear sea ice which is most closely linked to the areas of aragonite undersaturation. Depth profiles from 20 oceanographic stations taken during the cruises show a ~100 m thick lens of Ωaragonite undersaturated water at ~150 m depth in the western Arctic, but not further north than 85°N. The surface waters in the Canada and Makarov Basins have pCO2 values much lower than the atmospheric pCO2 (~390 uatm), ranging between 350 μatm and 100 μatm, and are a strong sink for atmospheric CO2. The strong sink areas are found in the Chukchi Sea and western Beaufort shelf areas. These studies represent the frontiers of ocean acidification research in the western Arctic, in which baseline data have been

  10. Decadal changes in zooplankton of the Northeast U.S. continental shelf.

    Directory of Open Access Journals (Sweden)

    Hongsheng Bi

    Full Text Available The abundance of the subarctic copepod, Calanus finmarchicus, and temperate, shelf copepod, Centropages typicus, was estimated from samples collected bi-monthly over the Northeast U.S. continental shelf (NEUS from 1977-2010. Latitudinal variation in long term trends and seasonal patterns for the two copepod species were examined for four sub-regions: the Gulf of Maine (GOM, Georges Bank (GB, Southern New England (SNE, and Mid-Atlantic Bight (MAB. Results suggested that there was significant difference in long term variation between northern region (GOM and GB, and the MAB for both species. C. finmarchicus generally peaked in May - June throughout the entire study region and Cen. typicus had a more complex seasonal pattern. Time series analysis revealed that the peak time for Cen. typicus switched from November - December to January - March after 1985 in the MAB. The long term abundance of C. finmarchicus showed more fluctuation in the MAB than the GOM and GB, whereas the long term abundance of Cen. typicus was more variable in the GB than other sub-regions. Alongshore transport was significantly correlated with the abundance of C. finmarchicus, i.e., more water from north, higher abundance for C. finmarchicus. The abundance of Cen. typicus showed positive relationship with the Gulf Stream north wall index (GSNWI in the GOM and GB, but the GSNWI only explained 12-15% of variation in Cen. typicus abundance. In general, the alongshore current was negatively correlated with the GSNWI, suggesting that Cen. typicus is more abundant when advection from the north is less. However, the relationship between Cen. typicus and alongshore transport was not significant. The present study highlights the importance of spatial scales in the study of marine populations: observed long term changes in the northern region were different from the south for both species.

  11. Meiofauna abundance on the Gulf of Mexico continental shelf affected by hypoxia

    Science.gov (United States)

    Murrell, Michael C.; Fleeger, John W.

    1989-12-01

    Meiofauna were sampled in shallow (8-13 m) continental shelf waters off the coast of Louisiana at three stations on 13 dates from June 1985 to August 1986. Total meiofauna abundances ranged from 525 to 3406 individuals per 10 cm 2 with a mean of 1810 individuals per 10 cm 2. Peak abundances occurred in late spring and early summer while seasonal lows occurred during late summer and winter. The three predominant taxa were Nematoda (91.8%), Copepoda (3.2%) and Kinorhyncha (2.5%). The meiobenthic copepod assemblage displayed low diversity and was dominated by three epibenthic species which together comprised 87% of the copepod fauna. Hypoxic conditions (dissolved oxygen <2mg l -1) developed seasonally on this shelf as a result of water column density stratification and eutrophication during late spring and summer. Abundances of all taxa declined during the summers of both years apparently in response to hypoxic conditions. Copepods were most dramatically affected, dropping from springtime peak abundances (several hundred per 10 cm 2) to virtually zero in a one-month period of time. Copepod density declines were spatially correlated with the onset of hypoxia, as inshore stations developed hypoxia later and underwent declines later. Densities remained low after the return of normal oxygen conditions, rising in the spring of the following year. The effect on nematodes and kinorhynchs was not as dramatic. A single collection of meiofauna from July 1983 in nearby normoxic Terrebonne Bay at similar water depths reveals a high density and diversity of copepods, further suggesting the sensitivity of copepods to hypoxia.

  12. Submarine groundwater discharge revealed by radium isotopes (Ra-223 and Ra-224 near a paleochannel on the Southern Brazilian continental shelf

    Directory of Open Access Journals (Sweden)

    Karina Kammer Attisano

    2013-09-01

    Full Text Available Submarine Groundwater Discharge (SGD has been recognized as an important component of the ocean-continent interface. The few previous studies in Brazil have focused on nearshore areas. This paper explores SGD on the Southern Brazilian Continental Shelf using multiple lines of evidence that include radium isotopes, dissolved nutrients, and water mass observations. The results indicated that SGD may be occurring on the Continental Shelf in the Albardão region, near a paleochannel located 50 km offshore. This paleochannel may thus be a preferential pathway for the delivery of nutrient- and metal-enriched groundwater and porewater into continental shelf waters.

  13. Fish community diversity in the middle continental shelf of the East China Sea

    Institute of Scientific and Technical Information of China (English)

    SHAN Xiujuan; JIN Xianshi; ZHOU Zhipeng; DAI Fangqun

    2011-01-01

    The status of fishery stocks in the coastal waters of China is far from ideal,mainly due to climate change and the impacts of human activities (e.g.,pollution and overfishing).Thus,the restoration and protection of fishery resources have become critical and complex.The stability and balanced structure of the fish community is a basic foundation for the protection of fishery resources.Based on data collected from bottom trawls by the R/V Beidou in continental shelf of the East China Sea in November 2006 and February 2007,changes in the composition and diversity of fish species and functional groups were analyzed.The research area was divided into offshore waters and inshore waters by the two-way indicator species analysis (TWIA).The results showed that the dominant species were different between offshore waters and inshore waters and also varied with the survey time.The most abundant family was Sciaenidae and Teraponidae in November 2006,Sciaenidae,Engraulidae and Triglidae were most abundant in February 2007.The species belonged mainly to mobile piscivores (G6),benthivores/piscivores (G4),benthivores (G3) and planktivores (G1),and the dominant species in November 2006 were commercial species (e.g.Larimichthys polyactis and Trichiurus japonicus),but small-sized species were dominant in February 2007 (e.g.,Harpadon nehereus,Benthosema pterotum,Champsodon capensis,and Acropoma japonicum).The species diversity showed a similar trend as the functional group diversity.Stations with higher diversity were mainly distributed in inshore waters in February 2007,whereas higher diversity was found in offshore waters in November 2006.The highest biomass and species number were found in G6 group,followed by the G4,G5 and G1 groups.The distribution of the number of individuals of each functional group showed the opposite trend as that of the biomass distribution.In addition,the size spectra were mainly concentrated around 3-29 cm,and the individual number of fish species gradually

  14. Remote Sensing Systems to Detect and Analyze Oil Spills on the U.S. Outer Continental Shelf - A State of the Art Assessment

    Science.gov (United States)

    2016-08-18

    demo”) with a graphical user interface is also provided as a prototype for a web -based version that could be developed in a future project. 18-08...graphical user interface, is also provided as a prototype for a web -based version that could be developed in a future project...Alaskan shelf. The review by Leifer et al. (2012), which surveyed the sensors deployed during the 2010 BP Deep Water Horizon (DWH) Oil Spill in the

  15. Surficial sediment character of the Louisiana offshore continental shelf region: a GIS compilation

    Science.gov (United States)

    Williams, S. Jeffress; Arsenault, Matthew A.; Buczkowski, Brian J.; Reid, Jane A.; Flocks, James; Kulp, Mark A.; Penland, Shea; Jenkins, Chris J.

    2007-01-01

    switching by the Mississippi River and its distributaries over the past ~10,000 years that resulted in laterally overlapping deltaic depocenters. The interactions among riverine, coastal, and inner shelf processes have been superimposed on the Holocene transgression resulting in distinctive landforms and sedimentary sequences. Four Holocene shelf-phase delta complexes have been identified using seismic reflection data and vibracores. Each delta complex is bounded by transgressive surfaces. Following each cycle of deposition and abandonment, the delta lobes undergo regional subsidence and marine reworking that forms transgressive coastal systems and barrier islands. Ultimately, the distal end of each of the abandoned delta lobes is marked by submerged marine sand bodies representing drowned barriers. These sand bodies (e.g. Ship Shoal, Outer Shoal, Trinity Shoal, Tiger Shoal, St. Bernard Shoal) offer the largest volumes and highest quality sand for beach nourishment and shoreline and wetlands restoration. These four large sand shoals on inner continental shelf, representing the reworked remnants of former prograded deltaic headlands that existed on the continental shelf at lower sea level, were generated in the retreat path of the Mississippi River delta plain during the Holocene transgression. Penland and others (1989) have shown these sand bodies represent former shoreline positions associated with lower still stands in sea level. Short periods of rapid relative sea-level rise led to the transgressive submergence of the shorelines which today can be recognized at the -10 m to -20 m isobaths on the Louisiana continental shelf. Trinity Shoal and Ship Shoal represent the -10 m middle-to-late Holocene shoreline trend, whereas Outer Shoal and the St. Bernard Shoals define the -20 m early Holocene shoreline trend (Penland and others, 1989). Collectively, these sand shoals constitute a large volume of high quality sandy sediment potentially suitable for barrier island nourishment

  16. Spatially quantitative seafloor habitat mapping: example from the northern South Carolina inner continental shelf

    Science.gov (United States)

    Ojeda, Germán Y.; Gayes, Paul T.; Van Dolah, Robert F.; Schwab, William C.

    2004-03-01

    Naturally occurring hard bottom areas provide the geological substrate that can support diverse assemblages of sessile benthic organisms, which in turn, attract many reef-dwelling fish species. Alternatively, defining the location and extent of bottom sand bodies is relevant for potential nourishment projects as well as to ensure that transient sediment does not affect reef habitats, particularly in sediment-starved continental margins. Furthermore, defining sediment transport pathways documents the effects these mobile bedforms have on proximal reef habitats. Thematic mapping of these substrates is therefore crucial in safeguarding critical habitats and offshore resources of coastal nations. This study presents the results of a spatially quantitative mapping approach based on classification of sidescan-sonar imagery. By using bottom video for image-to-ground control, digital image textural features for pattern recognition, and an artificial neural network for rapid, quantitative, multivariable decision-making, this approach resulted in recognition rates of hard bottom as high as 87%. The recognition of sand bottom was less successful (31%). This approach was applied to a large (686 km 2), high-quality, 2-m resolution sidescan-sonar mosaic of the northern South Carolina inner continental shelf. Results of this analysis indicate that both surficial sand and hard bottoms of variable extent are present over the study area. In total, 59% of the imaged area was covered by hard bottom, while 41% was covered by sand. Qualitative spatial correlation between bottom type and bathymetry appears possible from comparison of our interpretive map and available bathymetry. Hard bottom areas tend to be located on flat, low-lying areas, and sandy bottoms tend to reside on areas of positive relief. Published bio-erosion rates were used to calculate the potential sediment input from the mapped hard bottom areas rendering sediment volumes that may be as high as 0.8 million m 3/yr for

  17. 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

  18. The last glaciation and deglaciation of the Northeast Greenland continental shelf revealed by hydro-acoustic data

    Science.gov (United States)

    Arndt, Jan Erik; Jokat, Wilfried; Dorschel, Boris

    2017-03-01

    About 16% of the Greenland Ice Sheet drains in the area of the Northeast Greenland shelf between 76°N and 80.5°N via marine terminating glaciers. Most of it is via the Northeast Greenland Ice Stream, the largest ice stream of Greenland. During ice ages, the ice sheet extended onto the continental shelf and modern-day cross-shelf troughs were filled by ice streams. In this study, high-resolution hydro-acoustic data acquired during three decades of research were jointly investigated to reveal the past glacial conditions. Our data shows that Westwind Trough and Norske Trough were filled by fast flowing ice streams that extended to the shelf edge during the last glacial maximum. In between the cross-shelf troughs, ice domes resided on shallow banks that may have contributed about a decimetre to global sea level. Most probably these ice domes initiated fast ice flow through sinks in the inter-trough area. In Westwind Trough, ice sheet retreat to the inner shelf after the last glacial maximum was intermittent. In contrast, in Norske Trough the ice sheet retreat appears relatively rapid with no evidences for phases of grounding line stabilization. Probably during the Younger Dryas, the ice sheet readvanced to a mid-shelf position in both troughs documented by grounding zone wedges. During this time, a thick ice shelf was present in Norske Trough releasing tabular icebergs. Ice sheet retreat from the mid-shelf to the coastline during Holocene deglaciation was rapid.

  19. Sediment Chemistry and Meiofauna from the Northern Gulf of Mexico Continental Shelf

    Directory of Open Access Journals (Sweden)

    Ceil C. Martinec

    2014-01-01

    Full Text Available This study examined sediment chemistry, granulometry, and meiofauna on the northern Gulf of Mexico continental shelf from central Louisiana to Apalachicola, Florida. Sediment samples were collected in October/November 2012 with a Shipek grab sampler from 26 locations (extending from 28°18′46.079′′N, 91°10′44.471′′W to 29°3′48.383′′N, 85°28′25.679′′W at depths ranging from 49 to 361 m. Sediment analysis revealed two distinct profiles to the east and west of the Mississippi River Delta at approximately 88°30′W. The concentrations of silt + clay, organic carbon, Ba, Cr, Cu, Fe, Ni, Pb, V, and Zn were higher in western sites and positively correlated with Al concentrations. Eastern sites contained sandier sediments with lower organic carbon concentrations and higher Sr and Ca concentrations. Nematode densities were higher at western sites and positively correlated with Al, Cr, Cu, Fe, Ni, Pb, Zn, silt + clay, and organic carbon concentrations. Copepod densities correlated with very coarse + coarse sand, exhibiting higher densities at eastern sites. PAH concentrations were relatively low, with all sites having <1700 µg/kg total PAHs. This study has revealed two distinct sediment profiles in the eastern and western zones of the study, which appear to influence the nematode and copepod densities.

  20. Searching for tsunamis evidences on the Algarve (Southern Portugal) continental shelf sedimentary record

    Science.gov (United States)

    Drago, Teresa; Silva, Pedro; Lopes, Ana; Magalhães, Vitor; Roque, Cristina; Rodrigues, Ana Isabel; Noiva, João; Terrinha, Pedro; Mena, Anxo; Francés, Guillermo; Kopf, Achim; Völker, David; Omira, Rachid; Baptista, Maria Ana

    2016-04-01

    Tsunami hazard assessment is important in order to prevent and/or minimize its effects, which is only possible if a complete and long record dataset of past events is available, allowing the estimation of their recurrence intervals. The knowledge of past tsunami events are based on instrumental, historical and geological records. Although instrumental and historical records are reliable sources they are limited in time. Geological records can give a much more extended reconstruction overview of thousand years, which can provide a good estimation of tsunami return periods. Most of the existing studies have been conducted onshore and only a few were based on offshore sedimentary record. These last ones, have the advantage to provide a more continuous and almost undisturbed records but the identification of tsunami sediments in marine environment require a multi-proxy approach in order to better identify the allochtonous layers/deposits and to differentiate them from storm deposits. In the context of ASTARTE project (FP7), five gravity and piston cores on the southern Portuguese continental shelf collected in 2008 and 2014 were studied. The methodology included XRF, MSCL, sedimentological and magnetic analyses. Preliminary results show some identifiable layers that may related with allochthonous sedimentary material, compatible with a genesis resulting from tsunami backwash sediment transport and deposition. Acknowledgments - Publication supported by project FCT UID/GEO/50019/2013 - Instituto Dom Luiz.

  1. Chriolepis prolata, a new species of Atlantic goby (Teleostei: Gobiidae) from the North American continental shelf.

    Science.gov (United States)

    Hastings, Philip A; Findley, Lloyd T

    2015-01-08

    A new species of seven-spined goby of the genus Chriolepis is described from five specimens collected from the continental shelf of the northeastern Gulf of Mexico and Atlantic Ocean off South Carolina in depths of ca 54 to 110 m. The "Platform Goby", Chriolepis prolata, is distinguishable from all other western Atlantic species currently assigned to the genus Chriolepis and the morphologically similar genus Varicus in having pelvic-fin rays one through four branched, the fifth (innermost) pelvic-fin ray unbranched and relatively long (longer than the second ray to longer than all other pelvic-fin rays); most lateral body scales ctenoid, extending anteriorly in a wedge to a level anterior to the first dorsal-fin insertion or nearly to the pectoral-fin axil, with two or more rows of small cycloid scales extending anteriorly to near the pectoral-fin axil, cycloid scales along the bases of the dorsal and anal fins, and no scales on the belly; and the first two anal-fin pterygiophores inserted anterior to the first haemal spine. It closely resembles C. bilix but differs from that species which has a scaled belly, a shorter fifth pelvic-fin ray, prolonged dorsal-fin spines and smaller teeth in the lower jaw. An earlier report of C. bilix from Florida waters apparently refers to C. prolata. 

  2. Sea-floor features on Mississippi and Alabama outer Continental Shelf

    Energy Technology Data Exchange (ETDEWEB)

    Rezak, R.; Sager, W.W.; Laswell, J.S.; Gittings, S.R. (Texas A and M Univ., College Station (USA))

    1989-09-01

    Approximately 400 mi{sup 2} were surveyed on the Alabama outer continental shelf during October 1987 and March 1988 using an Edo-Western 4 kHz High Resolution Subbottom Profiler, an EG and G Model 260 Seafloor Mapping System and Starfix Navigation. The mapping is part of a larger project, The Mississippi-Alabama Marine Ecosystems Study, funded by the US Department of the Interior, Minerals Management Service, Gulf of Mexico Regional Office. Bathymetric maps and side-scan mosaics are being prepared from the raw data. Sea-floor features recognized on the side-scan and subbottom records include: (1) low topographic features - possibly bed-rock outcrops, and an enigmatic feature the authors are calling footprints, (2) moderate topographic features - low reefs or bed-rock outcrops, (3) major topographic features - pinnacles and large reefal masses, (4) pox - patches of closely spaced strong reflections with no relief, (5) ridges - closely spaced outcrops along clearly defined features such as shorelines and scarps (possibly truncated dunes or beach ridges), (6) patch reefs, closely spaced, which look like pox but have relief, (7) wave fields - closely spaced sand or gravel waves, and (8) wrecks - sunken rigs or platforms. Except for the wave fields, they believe that the remaining sea-floor features are relict and related to the post-Pleistocene rise of sea level.

  3. {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)

  4. Observed and modeled mixed-layer variability on the continental shelf of Sardinia (Western Mediterranean)

    Science.gov (United States)

    Onken, Reiner

    2016-04-01

    An important task of Military Oceanography is the prediction of mixed-layer properties and their spatial and temporal variability. In the mainframe of the REP14-MED sea trial which was conducted under the lead of CMRE in June 2014 in the waters west of Sardinia, an oceanographic mooring was deployed on the continental shelf which recorded the seawater temperature between the surface and 40-m depth with high resolution for about twelve days; meteorological parameters were collected at the same time on top of the mooring by a meteorological buoy. A series of ROMS model runs was conducted and validated against the observations. Those runs applied different setups for the forcing at the lateral open boundaries and at the surface, different arrangements of the vertical coordinates, and different strategies for the assimilation of data from CTD casts and gliders. The goal was to test the sensitivity of the forecast skill to the different setups and to find a "cheap" setup which predicts the observed temperature and the mixed-layer depth and their temporal variabilities to a satisfactory degree. That setup is supposed to provide also reliable forecasts for the other areas of the model domain.

  5. Distribution and abundance of flatfish on the South American continental shelf from Suriname to Colombia

    Science.gov (United States)

    Manickchand-Heileman, Sherry C.

    This study is based on data collected during four trawl surveys conducted in 1988 on the South American continental shelf from Suriname to Colombia. Members of four flatfish families were caught in depths ranging from 15 to 410 m at 264 of the 1200 stations trawled: Bothidae (13 genera, 30 species), Cynoglossidae (1 genus, 4 species), Soleidae (3 genera, 4 species) and Pleuronectidae (1 genus, 3 species). Flatfish comprised less than 5% of total catch by weight at most stations. Hierarchical cluster analysis revealed between 4 and 6 groups of stations in each survey characterized according to depth, temperature and species associations. Cynoglossids, soleids and some bothids characterized shallow-water stations while bothids and pleuronectids characterized intermediate and deep-water stations. Highest catches were taken off northern Venezuela and Colombia during times of increased upwelling and in areas influenced by river runoff. Mean density of flatfish was less than 0.0005 ind·m -2. The major species caught were Paralichthys tropicus, Paralichthys lethostigma, Cyclopsetta chittendeni, Syacium micrurum, Syacium papillosum,, Syacium sp. and Symphurus plagiusa and range extensions were found for six species.

  6. Improved oil recovery (IOR). Possibility and challenges on the Norwegian continental shelf

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-02-01

    Recently, estimates of the oil reserves on the Norwegian continental shelf have been substantially adjusted upwards due to technological development. In this report, the Norwegian Petroleum Directorate presents the current status. Based on current technology and recovery plans, an average of 41% of the oil that was originally in place in Norwegian fields will be recovered. Of these reserves, totaling just over 3 billion Sm{sup 3} of oil, about half have been produced. The potential for improved oil recovery is estimated at 1 billion Sm{sup 3} and it is anticipated that this potential can be realised. The objective is to attain an average recovery factor of at least 50%. Among the great technological advances that have taken place are developments within drilling and well technology and better techniques for reservoir management and reservoir monitoring. Technology using chemicals is available that will counteract increased water production and unwanted breakthrough of gas in oil producing wells. A significant part of the development of improved oil recovery technology is made jointly by the oil companies, often with the authorities as active providers. FORCE (FOrum for Reservoir Characterisation and reservoir Engineering) has been established in this context as a central forum for exchange of experience. Gas injection will be an efficient way of achieving high recovery factors for a number of fields. The foremost objective in projects for improved oil recovery is to be capable of achieving a total value creation while also ensuring that environmental considerations are taken into account. 21 figs., 2 tabs.

  7. Fish population dynamics revealed by instantaneous continental-shelf scale acoustic imaging

    Science.gov (United States)

    Ratilal, Purnima; Symonds, Deanelle; Makris, Nicholas C.; Nero, Redwood

    2005-04-01

    Video images of fish population densities over vast areas of the New Jersey continental shelf have been produced from acoustic data collected on a long range bistatic sonar system during the Acoustic Clutter 2003 experiment. Areal fish population densities were obtained after correcting the acoustic data for two-way transmission loss modeled using the range-dependent parabolic equation, spatially varying beampattern of the array, source level and mean target strength per fish. The wide-area fish density images reveal the temporal evolution of fish school distributions, their migration, as well as shoal formation and fragmentation at 50 s interval. Time series of the fish population within various density thresholds were made over the period of a day in an area containing millions of fish that at some instances formed a massive shoal extending over 12 km. The analysis shows that fish population in the area can be decomposed into a stable ambient population from lower-fish-density regions and a time-varying population composed from higher-density regions. Estimates of the differential speed between population centers of various shoals show that the average speed is on the order of a slow-moving surface vessel or submarine.

  8. Continental shelf-wide response of a fish assemblage to rapid warming of the sea.

    Science.gov (United States)

    Simpson, Stephen D; Jennings, Simon; Johnson, Mark P; Blanchard, Julia L; Schön, Pieter-Jan; Sims, David W; Genner, Martin J

    2011-09-27

    Climate change affects marine biological processes from genetic to ecosystem levels [1-3]. Recent warming in the northeast Atlantic [4, 5] has caused distributional shifts in some fish species along latitudinal and depth gradients [6, 7], but such changes, as predicted by climate envelope models [8], may often be prevented because population movement requires availability of suitable habitat. We assessed the full impacts of warming on the commercially important European continental shelf fish assemblage using a data-driven Eulerian (grid-based) approach that accommodates spatial heterogeneity in ecological and environmental conditions. We analyzed local associations of species abundance and community diversity with climatic variables, assessing trends in 172 cells from records of >100 million individuals sampled over 1.2 million km(2) from 1980-2008. We demonstrate responses to warming in 72% of common species, with three times more species increasing in abundance than declining, and find these trends reflected in international commercial landings. Profound reorganization of the relative abundance of species in local communities occurred despite decadal stability in the presence-absence of species. Our analysis highlights the importance of focusing on changes in species abundance in established local communities to assess the full consequences of climate change for commercial fisheries and food security.

  9. 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

  10. Collision of a loop current anticyclonic ring against the continental shelf slope of the western Gulf of Mexico

    Science.gov (United States)

    Vidal, VíCtor M. V.; Vidal, Francisco V.; PéRez-Molero, José M.

    1992-02-01

    A Loop Current anticyclonic ring ˜330 km in diameter and extending to a depth of >1500 m was observed to collide in January of 1984 against the continental shelf slope of the western Gulf of Mexico between 21.5° and 23°N. The collision occurred precisely at the time we conducted our Argos 84-1 hydrographic cruise in the western gulf (26°00' to 19°20'N) aboard the R/V Justo Sierra. The Caribbean Subtropical Underwater (SUW) was used as a tracer to identify the Loop Current anticyclonic ring within the western gulf. The collision was identified from temperature and salinity distributions and from the dynamic topography distribution relative to 500 m. The ring's collision zone was identified by the presence of a horizontal baroclinic flow divergence, to the east of Tamiahua, that divides the surface circulation into northward and southward baroclinic currents parallel to the western gulf's continental shelf break, with speeds of 85 and 32 cm s-1, respectively. Horizontal divergence and vertical convergence (ring asymmetries) resulted at the focus of the anticyclonic ring's collision and originated the alongshore self advection and northward translation of the colliding anticyclone. Upon colliding the anticyclonic ring shed approximately one third of its volume (˜2 × 104 km3), mass, and transferred angular momentum to the south flanking water mass, thus generating a cyclonic ring to the south of the collision zone. The observed alongshelf southward current results from mass conservation and volume continuity requirements associated with the anticyclonic ring's volume shedding and most probably constitutes the colliding ring's potential vorticity conservation mechanism. The weakening of the anticyclonic ring's relative vorticity due to the collision is most likely made up by gain of vorticity from lateral shear in the northward and southward current jets parallel to the continental shelf break. The core of both the anticyclonic and cyclonic rings had typical SUW

  11. Drifting buoy and other data as part of the Outer Continental Drifting buoy and other data as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 04 June 1976 to 01 October 1976 (NODC Accession 7700020)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Drifting buoy and other data was collected by the University of Washington (UW) as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP)....

  12. 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...

  13. Selected bibliography on birds in the Bering Sea and the Arctic Ocean as related to outer continental shelf areas under consideration for leasing: Draft

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This bibliography lists published and unpublished references to the bird resources within or near the areas of Alaska's outer continental shelf that have been...

  14. 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...

  15. 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...

  16. Drifting buoy and other data as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 17 May 1976 to 23 December 1976 (NODC Accession 7800105)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Drifting buoy data was collected by the Atlantic Oceanographic and Meteorological Laboratory (AOML) as part of the Outer Continental Shelf Environmental Assessment...

  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. Hydrography, bacteria and protist communities across the continental shelf and shelf slope of the Andaman Sea (NE Indian Ocean)

    DEFF Research Database (Denmark)

    Nielsen, Torkel Gissel; Bjørnsen, P.K.; Boonruang, P.

    2004-01-01

    along 3 transects perpendicular to the shelf break, from the coast across the shelf into deep water. The water column at the nearshore stations was vertically mixed, while the water column at off shore stations was strongly stratified, hence a frontal zone was established at the mid shelf. A prominent...... in the surface layer. We did not find any relationships between hydrography and the other key components of the microbial food web. No difference in productivity or food web structure was observed between the 2 seasons despite a significant difference in climatic forcing. Pico- and nanoplankton dominated...... the biomass in both seasons and Synechococcus contributed 72 to 74 % of the biomass. Analysis of the microbial food web and establishment of carbon-flow budgets illustrates the importance of the microbial food web for making the primary producers available to the higher trophic levels....

  19. Fine-scale analysis of shelf -slope physiography across the western continental margin of India

    Digital Repository Service at National Institute of Oceanography (India)

    Chakraborty, B.; Mukhopadhyay, R.; Jauhari, P.; Mahale, V.; Shashikumar, K.; Rajesh, M.

    to characterise the outer shelf, upper slope, shelf margin basin, and several structural rises. The scatter diagram analysis shows that the seafloor can be grouped in two distinct clusters. Distinctly different clustering patterns are observed over the structural...

  20. 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

  1. 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

  2. Trend and dynamic cause of sediment particle size on the adjacent continental shelf of the Yangtze Estuary

    Science.gov (United States)

    Yang, Yun-ping; Zhang, Ming-jin; Li, Yi-tian; Fan, Yong-yang

    2016-12-01

    Based on the measured data in recent 20 years, the variation trends of the median grain size of the surface sediment, the sand-silt boundary and the mud area on the adjacent continental shelf of the Yangtze Estuary were analyzed in depth, and the effects of natural mechanism and human activities were discussed. The results show that: (1) In recent years (2006-2013), the median grain size of sediment and the distribution pattern of grouped sediments in the adjacent continental shelf area to the Yangtze Estuary have presented no obvious change compared with those before 2006; (2) The median diameter of the surface sediment in the continental shelf area displayed a coarsening trend with the decrease of sediment discharge from the basin and the drop in suspended sediment concentration in the shore area; (3) In 2004-2007, the sand-silt boundary in the north part (31°30'N) of the continental shelf area presented no significant changes, while that in the south part (31°30'S) moved inwards; In 2008-2013, both the sand-silt boundaries in the north and south parts of the continental shelf area moved inwards, mainly due to the fact that in the dry season, a relatively enhanced hydrodynamic force of the tides was generated in the Yangtze River, as well as a decreased suspended sediment concentration and a flow along the banks in North Jiangsu; (4) The mud area where the maximum deposition rate is found in the Yangtze Estuary, tends to shrink due to the drop in sediment discharge from the basin, and the decrease in suspended sediment concentration in the shore area and erosion in the delta. Moreover, it tended to shift to the south at the same time because the implement of the training works on the deep-water channel of the North Passage changed the split ratio between the North and South Passages with an increase in the power of the discharged runoff in the South Passage.

  3. 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

  4. 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.

  5. 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

  6. Inventory and burial fluxes of Black Carbon in the Swedish continental shelf sediments

    Science.gov (United States)

    Sánchez-García, L.; Cato, I.; Gustafsson, Ö.

    2009-04-01

    Highly condensed black carbon (BC) particles, mainly derived from incomplete combustion of biomass and fossil fuel, are involved in several important processes in the biogeosphere [1], including sedimentary carbon burial, sequestration of organic pollutants in soils and sediments, affecting Earth's radiative heat balance and even human respiratory health. BC is commonly found to constitute several to 20% of total sedimentary carbon, and thus plays an important but poorly constrained role in the global biogeospheric carbon cycle. Sequestration of biogenic carbon as BC is a direct sink of the element from the rapidly cycling atmosphere-biosphere reservoirs, whereas burial of petrogenic/fossil BC is simply a conversion of one form of geological carbon to another [2]. Considerable emphasis has been made on the relevant role this recalcitrant form of organic matter (OM) may play on the global C cycle and yet large uncertainty exists around BC detection and quantification. This work seeks to provide a large-scale estimate of the reservoir and burial sink flux of BC in sediments from the extensive Swedish continental shelf (SCS), as a first approach to global inventories. To this end, a total of 120 sediment samples were collected from the Exclusive Economic Zone (EEZ) along the ?2000 km SCS stretch. The most recalcitrant fraction of the sedimentary OM was isolated and determined by means of a commonly applied method in biogeochemical studies of soils and sediments: chemo-thermal oxidation at 375˚ C in air (CTO-375). The obtained BC concentration was used to estimate the inventory and burial flux of BC in the SCS surface sediments, following [3], which takes into account key geophysical and geochemical properties of the nine distinct sedimentary regimes of the SCS that was separately assessed. Globally representative values of the sediment properties (e.g. density of dried sediments, bioturbated mixing depth, sedimentation rate or porosity over the mixed depth) were

  7. Remote sensing of pigment concentration and sea surface temperature on the continental shelf of China

    Science.gov (United States)

    Tang, Danling

    The combination of a population of more than 1.2 billion people and the recent rapid industrialization and large-scale infrastructure projects have placed a very heavy burden on the coastal environment in China. Algal blooms and red tides pose a serious threat to public health, fisheries and aquaculture industry. Consequently, a thorough assessment of their impacts on the coastal zone is urgently needed. This research is the first application of the historical satellite remote sensing archive to investigate temporal and spatial patterns of pigment concentrations (PC) and sea surface temperatures (SST) on the entire continental shelf of China. Firstly, I examined the temporal (annual/monthly) and spatial patterns of PC and SST on the continental shelf of China. The image availability for the study area was examined. A total of 2139 scenes were obtained from the study area during the years of the Nimbus-7 satellite mission (from 1978 to 1986), from which 76 monthly and 8 annual composite CZCS images were generated. AVHRR (Advanced Very High Resolution Radiometer) data from NOAA (National Oceanic & Atmospheric Administration) satellites were also examined. A distinctive high PC belt of about 50 km wide existed along the coastline of China, and a large plume of high PC was observed which extended nearly 500 km to the east from the Yangtze River. PC were high in the Yellow Sea (about 1--2 mg m-3 it decreased seawards and southeastwards with a minimum value in the Philippine Sea (about 0.2 mg m-3 ). Annual PC increased from 1979 and reached a peak in 1981; it dropped in 1982 with a strong El Nino. In the northern area (Yellow Sea), there were two peaks of PC in each year (spring and fall). In the southern area (northern South China Sea), PC was relatively low and constant over each year. A basin-wide gyre appeared in the center of the Yellow Sea in April 1986. Secondly, I focused on the Luzon Strait, a channel between the Philippine Sea and the South China Sea. High

  8. The Bay of Bengal and the Statement of Understanding Concerning the Establishment of the Outer Edge of the Continental Margin: Regional Implications for Delimiting the Juridical Continental Shelf

    Science.gov (United States)

    Mridha, M.; Varma, H.; Macnab, R.

    2005-12-01

    The Bay of Bengal is the site of massive depositions of sediment from the Ganga-Brahmaputra river systems, which discharge an estimated 2300 million tons of material into the Indian Ocean every year. The accumulated material comprises an enormous fan that extends some 4000 km from the Mouths of the Ganges, a delta system which encompasses the entire coast of Bangladesh and a segment of the coast of India. The major tectonic elements of the Bay of Bengal and surrounding areas are: the passive eastern continental margin of India; the 85E Ridge; the Ninetyeast Ridge; the intervening basin buried beneath deep sediment; and the Sunda Arc system with the associated back-arc Andaman Basin. Except for the Nikitin Seamounts which rise above the seabed just south of the Equator, the 85E Ridge is totally covered by thick sediment. The Ninetyeast Ridge, on the other hand, protrudes above the seabed as far north as 10N, where it plunges beneath the thickening sediment and separates the deposits into the Bengal Fan and the smaller Nicobar Fan. The 85E and Ninetyeast Ridges present the most significant relief in the crystalline basement underlying the Bay of Bengal, and should therefore figure substantially in any analysis of sediment thickness pursuant to the delimitation of the outer continental shelf. In this region, the sediment thickness provision of Article 76 has been modified by a Statement of Understanding in Annex II of the Final Act of the Third UN Conference on the Law of the Sea. To avoid a perceived inequity that might arise from the application of the standard one percent sediment thickness formula of Article 76, the Statement introduced a new formula: a qualified State in this region, even if it has a narrow physiographic continental shelf, may establish the outer edge of its continental margin by a line where the thickness of sedimentary rock is not less than one km. This presentation will describe the development of a joint formula line for the States that

  9. 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.

  10. Continental Shelf Freshwater Water Resources and Enhanced Oil Recovery By Low Salinity Water Flooding

    Science.gov (United States)

    Person, M. A.; Morrow, N.; Wilson, J. L.

    2014-12-01

    This study investigates the prospects of utilizing offshore freshwater in continental shelf oil production. Petroleum engineers have recently shown that tertiary water floods using freshwater can enhance oil recovery by as much as 18% (Morrow and Buckley, 2011). Hydrogeologists recently estimated that up to 5x105 km3of fresh to brackish water are sequestered in shallow ( oil platform locations in order to assess the economic viability of this energy-water nexus. We also discuss a project that is currently underway within the North Sea (Clair Ridge) to field validate this concept. We present a series of variable-density groundwater flow and solute transport simulations that are intended to assess how long freshwater resources could be produced in an offshore environment using horizontal drilling technologies before seawater invades the well. We considered a 100m thick freshwater reservoir sandwiched between two 200-300m thick confining units. We pumped the horizontal well at a rate of 5.4 m3/day (1 gpm per meter of well). The resulting drawdown was less than 5 m at the well head (r=0.15 m). For a 1000 m long horizontal well, this resulted in the production of 5455 m3/day of fresh water (over 34,000 barrels per day). Concentrations increased at the wellhead by about 5000 mg/l after 20 years of continuous pumping using a reservoir permeability of 10-13 m2. This simulation demonstrates that where freshwater is available it is likely that it can be produced in commercially viable quantities to support tertiary water floods.

  11. Marine geological study of the continental shelf around Heugsan island, SE Korea

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chi Won; Jin, Jae Hwa; Shin, Won Cheol; Kim, Won Sik; Kim, Jung Ki; Kim, Sang Woo; Lee, Ho Yong; Chang, Cheong Hae; Kim, Sung Woo; Lee, Yoon Oh; Park, Young Soo; Bahng, Hyo Ky [Korea Inst. of Geology Mining and Materials, Taejon (Korea, Republic of)

    1995-12-01

    This annual report is a result of marine geological and geophysical surveys conducted in 1995 to obtain a variety of data available for mapping Korean continental shelf geology. The study area is situated off city of Mokpo, comprising a rectangle enclosed by lines connecting between 34 degree 30`N and 35 degree 00`N, and between 125 degree 00`E and 126 degree 00`E. Geophysical surveys included water-depth sounding, sea floor side scanning, 3.5 khz sub-bottom profiling, air gun seismic reflection profiling and measurement of total magnetic intensity. During geological terms, 102 grab samples were collected from a grid of 4 miles x 4 miles spaced on the sea floor, and 31 sediment cores were raised from the proper sites determined by preliminary interpretation of geophysical data. The survey vessel, R/V Tamhae, was positioned by a GPS system (Loran-GPS 10X; Trimble Navigation Co.). The sea floor is largely covered with seven distinct types of surface and near-surface sediments; (1) massive sand, (2) homogeneous clay, (3) laminated silt, (4) bioturbated muddy sand, (5) massive silt, (6) bioturbated gravelly muddy sand, and (7) shell aggregate. Based on synthetic interpretation of high-resolution (3.5 khz) seismic data and correlated sedimentary facies, the shallow substratum comprises low-stand, transgressive and high-stand systems tracts (LST, TST and HST, respectively) formed during the last glacio-eutectics regression and transgression. Air gun seismic profiles show that pre-Pleistocene sediments comprise 4 sequences designated as B, C, D, and E, respectively. (author). 63 refs.

  12. Structuring Factors Of The Cumacean Communities Of The Continental Shelf Of Southeastern Brazil

    Directory of Open Access Journals (Sweden)

    Pedro Abib Cristales

    2014-07-01

    Full Text Available Cumaceans are benthic crustaceans distributed worldwide, from intertidal to abyssal plains. They live in sandy and muddy bottoms and can sometimes be found in the water column. Despite their ecological importance as food items for fishes and other organisms and their usefulness as environmental indicators, very few studies have investigated their biodiversity and distribution in Brazil. The present paper reports an ecological study of the cumacean species found on the continental shelf off Santos, southeastern Brazil. It investigates the composition and spatio-temporal structure of the communities, the main environmental factors responsible for the maintenance of that structure and analyzes the effects of the seasonal oceanographic changes on the community descriptors. A grid of 21 stations located between 10 and 100 m depth was created in winter 2005 and summer 2006 and the sediment samples collected with a 0.1 m2 box corer. Twenty four species were obtained, five of them being the most numerous: Diastylis sexpectinata, D. sympterygiae, Eudorella sp., Oxyurostylis salinoi and Anchistylis notus, the latter highly dominant in summer. Diastylis sympterygiae was characteristic of the shallowest and least saline stations (< 16 m depth; S = 33.07 - 34.2 in both seasons. Of the total of 919 individuals, nearly 70% occurred in summer. The area was divided into four depth bands and no significant temporal difference was found as regards the density distribution of cumaceans in those bands as between the samples of the two campaigns. There were, however, spatial differences within bands in the summer campaign: the higher values of density, diversity and richness were close to the 50 m isobath in both campaigns, a fact that could well be attributed to the ongoing effect of the South Atlantic Central Water in this area. The results showed also that depth and the sediment particle size were the main structural factors determining the composition and

  13. Biodiversity, community structural shifts, and biogeography of prokaryotes within Antarctic continental shelf sediment.

    Science.gov (United States)

    Bowman, John P; McCuaig, Robert D

    2003-05-01

    16S ribosomal DNA (rDNA) clone library analysis was conducted to assess prokaryotic diversity and community structural changes within a surficial sediment core obtained from an Antarctic continental shelf area (depth, 761 m) within the Mertz Glacier Polynya (MGP) region. Libraries were created from three separate horizons of the core (0- to 0.4-cm, 1.5- to 2.5-cm, and 20- to 21-cm depth positions). The results indicated that at the oxic sediment surface (depth, 0 to 0.4 cm) the microbial community appeared to be dominated by a small subset of potentially r-strategist (fast-growing, opportunistic) species, resulting in a lower-than-expected species richness of 442 operational taxonomic units (OTUs). At a depth of 1.5 to 2.5 cm, the species richness (1,128 OTUs) was much higher, with the community dominated by numerous gamma and delta proteobacterial phylotypes. At a depth of 20 to 21 cm, a clear decline in species richness (541 OTUs) occurred, accompanied by a larger number of more phylogenetically divergent phylotypes and a decline in the predominance of Proteobacteria. Based on rRNA and clonal abundance as well as sequence comparisons, syntrophic cycling of oxidized and reduced sulfur compounds appeared to be the dominant process in surficial MGP sediment, as phylotype groups putatively linked to these processes made up a large proportion of clones throughout the core. Between 18 and 65% of 16S rDNA phylotypes detected in a wide range of coastal and open ocean sediments possessed high levels of sequence similarity (>95%) with the MGP sediment phylotypes, indicating that many sediment prokaryote phylotype groups defined in this study are ubiquitous in marine sediment.

  14. Settling particle fluxes across the continental margin of the Gulf of Lion: the role of dense shelf water cascading

    Directory of Open Access Journals (Sweden)

    C. Pasqual

    2009-07-01

    Full Text Available Settling particles were collected using sediment traps deployed along three transects in the Lacaze-Duthiers and Cap de Creus canyons and the adjacent southern open slope from October 2005 to October 2006. The settling material was analysed to obtain total mass fluxes and main constituent contents (organic matter, opal, calcium carbonate, and siliciclastics. Cascades of dense shelf water from the continental shelf edge to the lower continental slope occurred from January to March 2006. They were traced through strong negative near-bottom temperature anomalies and increased current speeds, and generated two intense pulses of mass fluxes in January and March 2006. This oceanographic phenomenon appeared as the major physical forcing of settling particles at almost all stations, and caused both high seasonal variability in mass fluxes and important qualitative changes in settling material. Fluxes during the dense shelf water cascading (DSWC event ranged from 90.1 g m−2 d−1 at the 1000 m depth station in the Cap de Creus canyon to 3.2 g m−2 d−1 at the canyon mouth at 1900 m. Fractions of organic matter, opal and calcium carbonate components increased seaward, thus diminishing the siliciclastic fraction. Temporal variability of the major components was larger in the canyon mouth and open slope sites, due to the mixed impact of dense shelf water cascading processes and the pelagic biological production. Results indicate that the cascading event remobilized and homogenized large amounts of material down canyon and southwardly along the continental slope contributing to a better understanding of the internal dynamics of DSWC events. While the late winter/early spring bloom signature was diluted when DSWC occurred, the primary production dynamics were observable at all stations during the rest of the year and highlighted the biological community succession in surface waters.

  15. 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

  16. Production and turnover of suspended organic matter in the coastal water of the southeastern continental shelf. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Pomeroy, L.R.

    1992-02-15

    Sixteen years of work on the microbial food web of the southeastern shelf and its relation to the production, movement, and fate of organic materials, have helped us understand the roles of microorganisms in that ecosystem. We found that microbial metabolism dominates the flow of energy and materials on the continental shelf, utilizing nearly all available organic matter, except in mid-winter. Bacteria strongly influence the cycle of carbon in continental shelf waters, both by rapidly utilizing organic materials and by promoting aggregation of particulate material. We demonstrated a strong interaction between microorganisms in the water and those in the nearshore bottom sediments. We showed that chelation of copper by dissolved organic ligands in the coastal water protects phytoplankton not only from existing amounts but from much larger amounts. Simulation modeling predicted that there is usually little transfer of energy from the microbial food web to macroorganisms (fishes), an observation that has since been validated by investigators. A complete list of publications, theses and dissertations resulting from this project is provided.

  17. Flocculation, heavy metals (Cu, Pb, Zn) and the sand-mud transition on the Adriatic continental shelf, Italy

    Science.gov (United States)

    George, D.A.; Hill, P.S.; Milligan, T.G.

    2007-01-01

    Across a limited depth range (5-10 m) on many continental shelves, the dominant sediment size changes from sand to mud. This important boundary, called the sand-mud transition (SMT), separates distinct benthic habitats, causes a significant change in acoustic backscatter, represents a key facies change, and delimits more surface-reactive mud from less surface-reactive sand. With the goal of improving dynamical understanding of the SMT, surficial sediments were characterized across two SMTs on the Adriatic continental shelf of Italy. Geometric mean diameter, specific surface area (SSA), mud fraction (<63 ??m) and heavy metal concentrations were all measured. The SMT related to the Tronto River is identified between 15 and 20 m water depth while the SMT associated with the Pescara River varies between 15 and 25 m water depth. The sediment properties correlate with a new, process-based sedimentological parameter that quantifies the fraction of the sediment in the seabed that was delivered as flocs. These correlations suggest that floc dynamics exert strong influence over sediment textural properties and metal concentrations. Relative constancy in the depth of the SMT along this portion of the margin and its lack of evolution over a period during which sediment input to the margin has dramatically decreased suggest that on the Adriatic continental shelf energy is the dominant control on the depth of the SMT. ?? 2006 Elsevier Ltd. All rights reserved.

  18. Geologic framework of the northern North Carolina, USA inner continental shelf and its influence on coastal evolution

    Science.gov (United States)

    Thieler, E. Robert; Foster, David S.; Himmelstoss, Emily A.; Mallinson, David J.

    2013-01-01

    The inner continental shelf off the northern Outer Banks of North Carolina was mapped using sidescan sonar, interferometric swath bathymetry, and high-resolution chirp and boomer subbottom profiling systems. We use this information to describe the shallow stratigraphy, reinterpret formation mechanisms of some shoal features, evaluate local relative sea-levels during the Late Pleistocene, and provide new constraints, via recent bedform evolution, on regional sediment transport patterns. The study area is approximately 290 km long by 11 km wide, extending from False Cape, Virginia to Cape Lookout, North Carolina, in water depths ranging from 6 to 34 m. Late Pleistocene sedimentary units comprise the shallow geologic framework of this region and determine both the morphology of the inner shelf and the distribution of sediment sources and sinks. We identify Pleistocene sedimentary units beneath Diamond Shoals that may have provided a geologic template for the location of modern Cape Hatteras and earlier paleo-capes during the Late Pleistocene. These units indicate shallow marine deposition 15–25 m below present sea-level. The uppermost Pleistocene unit may have been deposited as recently as Marine Isotope Stage 3, although some apparent ages for this timing may be suspect. Paleofluvial valleys incised during the Last Glacial Maximum traverse the inner shelf throughout the study area and dissect the Late Pleistocene units. Sediments deposited in the valleys record the Holocene transgression and provide insight into the evolutionary history of the barrier-estuary system in this region. The relationship between these valleys and adjacent shoal complexes suggests that the paleo-Roanoke River did not form the Albemarle Shelf Valley complex as previously proposed; a major fluvial system is absent and thus makes the formation of this feature enigmatic. Major shoal features in the study area show mobility at decadal to centennial timescales, including nearly a kilometer of

  19. Glacial geomorphology of the northwestern Weddell Sea, eastern Antarctic Peninsula continental shelf: Shifting ice flow patterns during deglaciation

    Science.gov (United States)

    Campo, Jennifer M.; Wellner, Julia S.; Domack, Eugene; Lavoie, Caroline; Yoo, Kyu-Cheul

    2017-03-01

    During the Last Glacial Maximum, grounded ice from the expanded Antarctic Peninsula Ice Sheet extended across the continental shelf. Grounded and flowing ice created a distinctive array of glacial geomorphic features on the sea floor, which were then exposed as the ice sheet retreated. The recent disintegration of the northern parts of the Larsen Ice Shelf (Larsen A and B) have permitted acquisition of marine geophysical data in previously inaccessible and unmapped areas. We present a reconstruction of the evolving ice-flow path and ice sheet geometry of the eastern Antarctic Peninsula, with particular focus paid to newly surveyed areas that shed light on the dynamics of a marine-terminating glacial geomorphic environment, where ice shelves play a major role in grounding line stability. Shifting flow directions were mapped in several areas, including across the Seal Nunataks, which divide Larsen A and B, and offshore of Larsen C, indicating flow reorientation that reflects the changing ice sheet geometry as retreat neared the modern coastline. The measured flow indicators in this area reveal comparatively high elongation ratios (> 20), indicating rapid ice flow. Evidence of possible previous ice-shelf collapses are noted near the shelf break, further illustrating the critical, protective effect that ice shelves impart to marine-terminating glacial environments. Modern ice retreat is governed in part by reorganization of flow patterns accompanying grounding line movement; such reorganizations happened in the past and can aid understanding of modern processes.

  20. 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

  1. 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

  2. Using MODIS True-Color 250 m Remote Sensing Data to Assess Interannual Variability of Suspended Matter over Southeastern Brazilian Continental Shelf

    Science.gov (United States)

    Belem, A. L.; Silva, T. M. L.; Albuquerque, A. L.

    2014-12-01

    Continental shelf is the final destination of terrigenous sediments drained by rivers and estuaries, forming a mass of water drifting over the shelf due to its differential density from underlaying salty oceanic waters, forming a coastal plume. On the Southeastern Brazilian Continental Shelf, Cabo Frio region represents the limit between Santos and Campos basin oil reserves. The continental drainage in this area is not expressive, nevertheless presents a complex interaction between the western boundary Brazil Current (BC) and shelf border mechanisms providing amid-shelf intrusion and a coastal upwelling of South Atlantic Central Water (SACW) over the shelf. Satellite images of the region shows expressive shelf plumes with sedimentary contributions from Paraiba do Sul river located approximately 180 km northward of Cabo Frio, as well as from Guanabara bay, located 150 km westward of Cabo Frio. In order to understand the role of plumes in sedimentary processes over the continental shelf, this study analyzed 10 years of MODIS true-color 250 m remote sensing data in order to understand the temporal variability of the shelf front and the area of plumes. The remote data were obtained from the Aerosol Robotic Network and USDA Foreign Agricultural Service subsets. Selected 17% of daily images were cloud-free to allow shelf plumes to be delimited and processed to enhancement of features as well as land masking, geo-referencing, and daily area calculation on pixel basis. During austral winter (dry season) the plumes get its maximum extension in area over the shelf, suggesting that the mechanism of sediment transport is connected with high energetic wave-wind interactions on the coast followed by wind-driven dispersion less than continental drainage. The interannual pattern shows a general decreasing trend, mainly in the last 4 years, associated with sediment availability on the inner shelf, which is driven by river discharge during the austral summer (rain season). We also

  3. Impact of seasonal oxygen deficiency on the phosphorous geochemistry of surface sediments along the Western Continental Shelf of India

    Directory of Open Access Journals (Sweden)

    Josia Jacob

    2010-08-01

    Full Text Available The intensification of the natural coastal hypoxic zone over the western Indian shelf in the recent years and its impact on the biogeochemistry and marine life is a matter of concern. This study examines the influence of the seasonal oxygen deficiency on the phosphorus geochemistry of the surface sediments along the western continental shelf of India (WCSI. Speciation of phosphorus along with the geochemical characteristics (total organic carbon – TOC, total nitrogen – TN, and total phosphorus – TP of the surface sediments and the hydrography of the western continental shelf of India (WCSI were studied, during late summer monsoon (LSM and spring intermonsoon (SIM. The hydrography of the WCSI revealed upwelling and associated seasonal oxygen deficiency with denitrifying suboxic conditions along the inner shelf and hypoxic conditions along the outer shelf. High concentrations of dissolved phosphate (PO4 and dissolved Iron (Fe were also observed in the subsurface water of the inner shelf during LSM. The shelf water of the WCSI was oligotrophic and oxygen rich during SIM. A latitudinal enrichment of TOC, TN and TP in the surface sediments was observed at 13–17° N, along the WCSI during LSM, where seasonal suboxia was intense. Authigenic apatite bound phosphorus (Paut was the major phosphorus species along the WCSI during LSM whereas detrital flourapatite bound phosphorus (Pdet was the major species during SIM. Substantial depletion of reactive iron(III-bound phosphorus (ΔPFe was observed in the surface sediments of the WCSI during LSM which showed significant correlation with the enrichment of PO4 (ΔPO4 in the overlying water during LSM compared to SIM. PO4 diffusing into the water column from the sediments by reductive dissolution of PPFe probably leads to high dissolved PO4 along the inner shelf water during LSM which agrees with the

  4. Isotope and fatty acid trends along continental shelf depth gradients: Inshore versus offshore hydrological influences on benthic trophic functioning

    Science.gov (United States)

    Chouvelon, T.; Schaal, G.; Grall, J.; Pernet, F.; Perdriau, M.; A-Pernet, E. J.; Le Bris, H.

    2015-11-01

    Anthropogenic activities and land-based inputs into the sea may influence the trophic structure and functioning of coastal and continental shelf ecosystems, despite the numerous opportunities and services the latter offer to humans and wildlife. In addition, hydrological structures and physical dynamics potentially influence the sources of organic matter (e.g., terrestrial versus marine, or fresh material versus detrital material) entering marine food webs. Understanding the significance of the processes that influence marine food webs and ecosystems (e.g., terrestrial inputs, physical dynamics) is crucially important because trophic dynamics are a vital part of ecosystem integrity. This can be achieved by identifying organic matter sources that enter food webs along inshore-offshore transects. We hypothesised that regional hydrological structures over wide continental shelves directly control the benthic trophic functioning across the shelf. We investigated this issue along two transects in the northern ecosystem of the Bay of Biscay (north-eastern Atlantic). Carbon and nitrogen stable isotope analysis (SIA) and fatty acid analysis (FAA) were conducted on different complementary ecosystem compartments that include suspended particulate organic matter (POM), sedimentary organic matter (SOM), and benthic consumers such as bivalves, large crustaceans and demersal fish. Samples were collected from inshore shallow waters (at ∼1 m in depth) to more than 200 m in depth on the offshore shelf break. Results indicated strong discrepancies in stable isotope (SI) and fatty acid (FA) compositions in the sampled compartments between inshore and offshore areas, although nitrogen SI (δ15N) and FA trends were similar along both transects. Offshore the influence of a permanently stratified area (described previously as a "cold pool") was evident in both transects. The influence of this hydrological structure on benthic trophic functioning (i.e., on the food sources available for

  5. 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

  6. Submarine geomorphology of the Celtic Sea - new observations and hypotheses for the glaciation of a mid-latitude continental shelf

    Science.gov (United States)

    Praeg, Daniel; McCarron, Stephen; Dove, Dayton; Cofaigh, Colm Ó.; Monteys, Xavier; Coxon, Peter; Accettella, Daniella; Cova, Andrea; Facchin, Lorenzo; Romeo, Roberto; Scott, Gill

    2015-04-01

    The southern limit of glaciation of the European continental margin lies in the Celtic Sea, where the full extent and dynamics of the British-Irish Ice Sheet (BIIS) remain in question. This is in part because the broad continental shelf contains no obvious glacial geomorphological features, but is dominated by a system of shelf-crossing sediment ridges, up to 60 m high, 10 km wide and 300 km long, traditionally interpreted as moribund palaeo-tidal sand banks. Ice sheet extent has been constrained by samples of subglacial and glacimarine sediments recovered (in the 1970s) between the ridges, and in places on their flanks, used to propose a tidewater ice margin that advanced to a grounding line on the mid-shelf, overriding a precursor ridge system. New information on the glaciation of the Celtic Sea is available from geophysical and core data acquired during Italian- and Irish-led campaigns in 2009, 2012, and 2014, both from the mid- and outer shelf. On the mid-shelf, multibeam seabed imagery of a 25 x 100 km area reveal a distinctive rectilinear network of en echelon ridge segments giving way laterally and longitudinally to transverse ribs. Seismic correlation to glacigenic sediments previously cored on a ridge flank (at core site 49/-09/44) indicates the ribs to be composed in part of glacimarine sediments, above a till reflection that can be traced across the ridge crest. No change in seabed morphology is observed across the proposed grounding line. On the outer shelf, new cores of glacigenic sediments were obtained from the flank of a shelf-crossing ridge, and provide evidence of ice sheet advance to the shelf edge, 150 km beyond the proposed grounding line. The cores from outer Cockburn Bank contain facies interpreted to record subglacial deformation and glacimarine deposition from turbid meltwater plumes during withdrawal of a tidewater ice sheet margin from the shelf edge by 24,265 ± 195 cal BP. These sediments are inferred to form part of a sheet of

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

    Energy Technology Data Exchange (ETDEWEB)

    Tesi, Tommaso, E-mail: tommaso.tesi@bo.ismar.cnr.it; Miserocchi, Stefano; Langone, Leonardo [ISMAR-CNR, Sede di Bologna - Geologia Marina (Italy); Boni, Laurita; Guerrini, Franca [Universita di Bologna, Laboratorio di Biologia e Fisiologia Algale, Sc. Ambientali (Italy)

    2006-12-15

    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.

  8. 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...

  9. 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.

    , if detailed exploration is done. Several gaps exist inthe data on sea level changes during the Late Quaternary. Shelf edge exchange processes are to be studied in understanding the organic carbon distribution. Attention should be directed in solving...

  10. The Geoclutter Experiment 2001: Remote acoustic imaging of sub-bottom and seafloor geomorphology in continental shelf waters

    Science.gov (United States)

    Makris, Nicholas C.; Ratilal, Purnima; Lai, Yisan; Symonds, Deanelle T.; Ruhlmann, Lilimar A.; Scheer, Edward K.

    2002-11-01

    In the Geoclutter experiment of April-May 2001, an active sonar system was used to remotely and rapidly image geomorphology over wide areas in continental shelf waters by long-range echo sounding. The bistatic system, deployed in the strataform area south of Long Island, imaged extensive networks of buried river channels and inclined subseafloor strata over tens of kilometers in near real time. Bathymetric relief in the strataform area is extremely benign. The vast majority of features imaged apparently correspond to sub-bottom geomorphology that sound waves reach after tunneling as well as propagating through the overlying sediment. Returns from buried river channels were often found to be as discrete and strong as those from calibrated targets placed in the water column. Since buried river channels are expected to be ubiquitous in continental shelf environments, sub-seafloor geomorphology will play a major role in producing ''false alarms'' or clutter in long-range sonar systems that search for submerged objects such as underwater vehicles or marine mammals. Wave guide scattering and propagation are inherent to this new remote sensing technology because source signals are transmitted over hundreds of water-column depths in range to image sub-seafloor and seafloor geomorphology.

  11. Seabed morphology along the rocky shore of the Barlavento Coast, southern Portuguese continental shelf

    Science.gov (United States)

    Correia, Ricardo; Lavoie, Caroline; Pinheiro, Luis; Magalhães, Vitor; Moura, Delminda; Bennazzouz, Omar; Sena, Clara; Silva, Paulo; Gabriel, Selma; Horta, João; Abreu, Tiago; Mota, António

    2014-05-01

    The coastal area between Galé and Olhos de Água, in the southernmost coast of the Algarve (Portugal) is characterized by shore platforms and sandy beaches where the carbonate rocky cliffs are undergoing a dramatic recession (Marques, 2008; Nunes et al., 2009). Such crenulated coast plays an important morphological control on alongshore drift. In order to understand the sedimentation patterns in this area and characterize the seabed morphology and subsurface geology, a detailed sidescan sonar (100 and 400 kHz) and high-resolution seismic (Chirp Sonar, 05-12 kHz) survey was carried out, complemented with sediment sampling, along the rocky shore of the Barlavento Coast, southern Portuguese continental shelf, in the scope of the EROS project. The acquired data concentrate in two main areas: Olhos de Água and Galé. The sidescan sonar data were processed and analyzed using the integrated Triton perspective software and the mosaics were gridded at a cell size of 0.5 m. 27 seabed sediment grab samples were used to ground-truth the sidescan mosaics and produce a semi-quantitative seabed classification map. The seismic data were processed using the SPW and RadExPro softwares. Preliminary results show that the seafloor of the area Galé (2.25 km2) is characterized by: (1) a field of ripples that occurs on the flat portions and in the deeper part of the study area between 10 and 18 m depth; these ripples are symmetric, 3-400 m long and have wavelengths up to 2.5 m; most of the ripples can be classified as straight or sinuous in phase, and they are generally sub-parallel to the slope with a NW-SE trending; (2) bedrock outcrops that are present from the coastline until 12 m water depth; and (3) anthropogenic features associated to small scale fishing activities, observed at the border between fine sand with high concentration of shells and low concentration. In the Olhos de Água area (3.1 km2) the seafloor is generally characterized by (1) asymmetrical E-W trending

  12. Evidences of continental groundwater inputs to the shelf zone in Albardão, RS, Brazil

    Directory of Open Access Journals (Sweden)

    Karina Kammer Attisano

    2008-09-01

    Full Text Available The southern coastal region of Brazil is highly productive and many of its oceanographic processes are still poorly understood due to a great number of forces, such as the continental input from the Plata River and Patos Lagoon, several distinct oceanic water masses, and a complex contribution from groundwater. The shelf near Albardão is highly rich in dissolved nutrients, particularly in the coastal zone. The narrow sandy barrier that separates the ocean from Mangueira Lagoon has led us to wonder about the possibility of groundwater, and if it might play a role in the productivity of the surrounding area. In order to test this hypothesis, nutrient data from Mirim and Mangueira Lagoons and from Albardão were collected during a rainy period. The present work shows the need to include groundwater transport from Mangueira Lagoon to the coastal zone as one of the main sources for the productivity in that region. However, for such phenomenon to be quantified and better understood, it becomes necessary to use natural isotopes as tracers of the underground input.A região sul do Brasil é uma área altamente produtiva, cujos processos oceanográficos ainda são pouco compreendidos devido ao grande número de forçantes, tais como aportes continentais do Rio da Prata, Lagoa dos Patos, diferentes massas de água oceânicas e a complexa contribuição da água subterrânea. A plataforma da região do Albardão é extremamente rica em nutrientes dissolvidos, especialmente na zona costeira. O estreito cordão arenoso que separa a região do Albardão da Lagoa Mangueira levou-nos a questionar a possibilidade do transporte de água subterrânea e se este poderia contribuir de forma expressiva na produtividade dessa região. Para testar essa hipótese, associamos dados de nutrientes das Lagoas Mirim e Mangueira a dados inéditos da plataforma da região do Albardão, todos em período de alta precipitação. Este trabalho demonstra a necessidade de incluir o

  13. 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.

    2015-12-01

    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.

  14. Changes in water clarity in response to river discharges on the Great Barrier Reef continental shelf: 2002-2013

    Science.gov (United States)

    Fabricius, K. E.; Logan, M.; Weeks, S. J.; Lewis, S. E.; Brodie, J.

    2016-05-01

    Water clarity is a key factor for the health of marine ecosystems. The Australian Great Barrier Reef (GBR) is located on a continental shelf, with >35 major seasonal rivers discharging into this 344,000 km2 tropical to subtropical ecosystem. This work investigates how river discharges affect water clarity in different zones along and across the GBR. For each day over 11 years (2002-2013) we calculated 'photic depth' as a proxy measure of water clarity (calibrated to be equivalent to Secchi depth), for each 1 km2 pixel from MODIS-Aqua remote sensing data. Long-term and seasonal changes in photic depth were related to the daily discharge volumes of the nearest rivers, after statistically removing the effects of waves and tides on photic depth. The relationships between photic depths and rivers differed across and along the GBR. They typically declined from the coastal to offshore zones, and were strongest in proximity to rivers in agriculturally modified catchments. In most southern inner zones, photic depth declined consistently throughout the 11-year observation period; such long-term trend was not observed offshore nor in the northern regions. Averaged across the GBR, photic depths declined to 47% of local maximum values soon after the onset of river floods, and recovery to 95% of maximum values took on average 6 months (range: 150-260 days). The river effects were strongest at latitude 14.5°-19.0°S, where river loads are high and the continental shelf is narrow. Here, even offshore zones showed a >40% seasonal decline in photic depth, and 17-24% reductions in annual mean photic depth in years with large river nutrients and sediment loads. Our methodology is based on freely available data and tools and may be applied to other shelf systems, providing valuable insights in support of ecosystem management.

  15. 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.

    Global tidal solutions are sometimes inaccurate in coastal regions. This is particularly true in some regions of the northern Indian Ocean, which are characterized by wide continental shelves and large tidal ranges. We show that these global...

  16. A note on the deflection of a baroclinic current by a continental shelf

    Science.gov (United States)

    Hsueh, Y.; Zhong, Liejun

    2003-05-01

    The deflection, at a step-shelf fronted coast, of a constant potential vorticity current in a reduced-gravity, inviscid model ocean is studied theoretically. The step shelf, with a depth smaller than the reservoir depth, forces the uplifting of the approaching current and causes water column foreshortening, leading to relative vorticity generation that enhances current deflection to the right (facing the coast). As a consequence, in comparison to the case of a vertical wall coast, the proportion of the transport to the right is increased. For normal incidence for a shelf-depth/reservoir-depth ratio of 0.3 and shelf width to deformation radius ratio of 1.5, more than 90% of the approaching current transport goes to the right and less than 10% to the left. In addition, the (barotropic) dynamic pressure at the coast is low to the right and high to the left (with the highest pressure at the stagnation point). In the vertical wall case, the wall pressures on the flank are equal. For oblique incidence from the left, the deflection to the left is drastically reduced. In fact, there is practically no steady-state flow diverted to the left (less than 2%) when the approach angle is greater than 60° to the left of normal. In the vertical wall case, the same angle would have to be 90° for the flow to the left to vanish, namely only when the approach current is parallel to the coast to the right.

  17. Continental Shelf Embayments of the Eastern Margin of the Philippines; Lamon Bay Stratification & Circulation

    Science.gov (United States)

    2014-09-30

    circulation, stratification and the Shelf-Slope interaction within Lamon Bay of the eastern margin of the Philippines, marking the ’ birth ’ of the...blue ship track) and 24 April - 13 May 2012 (green track). The 2011 CTD stations are shown as blue stars for the 2011 cruise, and as green discs for

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

    Digital Repository Service at National Institute of Oceanography (India)

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

    the observed time-series of water level collected during November- December 2005, from four tide gauge stations distributed along the southwest shelf of India. The tidal amplitudes showed a general decrease from north to south. Harmonic analysis of the tidal...

  19. Evidence of microplastic ingestion in the shark Galeus melastomus Rafinesque, 1810 in the continental shelf off the western Mediterranean Sea.

    Science.gov (United States)

    Alomar, Carme; Deudero, Salud

    2017-04-01

    Microplastic (microplastic ingestion. Results have shown that 16.80% of the specimens had ingested a mean value of 0.34 ± 0.07 microplastics/individual. Stomach fullness index ranged from 0.86 to 38.89% and regression analyses showed that fuller stomachs contained more microplastics. A higher quantity of filament type microplastics were identified compared to granular or hard plastic type. No significant differences were given between ingestion values of two locations over the continental shelf providing further evidence of the ubiquitous distribution of microplastics. The findings in this study reflect the availability of this man made contaminant to marine species in seafloor habitats. Based on results from this study, data on microplastic ingestion could be used to study trends in the amount and composition of litter ingested by marine animals in accordance with descriptor 10 of the Marine Strategy Framework Directive.

  20. Hydro-acoustic remote sensing of benthic biological communities on the shallow South East Australian continental shelf

    Science.gov (United States)

    Rattray, Alex; Ierodiaconou, Daniel; Laurenson, Laurie; Burq, Shoaib; Reston, Marcus

    2009-09-01

    Information regarding the composition and extent of benthic habitats on the South East Australian continental shelf is limited. In this habitat mapping study, multibeam echosounder (MBES) data are integrated with precisely geo-referenced video ground-truth data to quantify benthic biotic communities at Cape Nelson, Victoria, Australia. Using an automated decision tree classification approach, 5 representative biotic groups defined from video analysis were related to hydro-acoustically derived variables in the Cape Nelson survey area. Using a combination of multibeam bathymetry, backscatter and derivative products produced highest overall accuracy (87%) and kappa statistic (0.83). This study demonstrates that decision tree classifiers are capable of integrating variable data types for mapping distributions of benthic biological assemblages, which are important in maintaining biodiversity and other system services in the marine environment.

  1. High-resolution geophysical data from the Inner Continental Shelf: South of Martha's Vineyard and north of Nantucket, Massachusetts

    Science.gov (United States)

    Ackerman, Seth D.; Brothers, Laura L.; Foster, David S.; Andrews, Brian D.; Baldwin, Wayne E.; Schwab, William C.

    2016-10-28

    The U.S. Geological Survey and the Massachusetts Office of Coastal Zone Management have cooperated to map approximately 185 square kilometers of the inner continental shelf south of Martha’s Vineyard and north of Nantucket, Massachusetts. This report contains geophysical data collected by the U.S. Geological Survey during a survey in 2013. The geophysical data include (1) swath bathymetry collected by using interferometric sonar, (2) acoustic backscatter from the interferometric sonar, and (3) seismic-reflection profiles from a chirp subbottom profiler. These spatial data support research on the Quaternary evolution of coastal Massachusetts, the influence of sea-level change and sediment supply on coastal evolution, and efforts to understand the type, distribution, and quality of subtidal marine habitats in the coastal ocean of Massachusetts.

  2. Approaches to quantifying long-term continental shelf sediment transport with an example from the Northern California STRESS mid-shelf site

    Science.gov (United States)

    Harris, Courtney K.; Wiberg, Patricia L.

    1997-09-01

    Modeling shelf sediment transport rates and bed reworking depths is problematic when the wave and current forcing conditions are not precisely known, as is usually the case when long-term sedimentation patterns are of interest. Two approaches to modeling sediment transport under such circumstances are considered. The first relies on measured or simulated time series of flow conditions to drive model calculations. The second approach uses as model input probability distribution functions of bottom boundary layer flow conditions developed from wave and current measurements. Sediment transport rates, frequency of bed resuspension by waves and currents, and bed reworking calculated using the two methods are compared at the mid-shelf STRESS (Sediment TRansport on Shelves and Slopes) site on the northern California continental shelf. Current, wave and resuspension measurements at the site are used to generate model inputs and test model results. An 11-year record of bottom wave orbital velocity, calculated from surface wave spectra measured by the National Data Buoy Center (NDBC) Buoy 46013 and verified against bottom tripod measurements, is used to characterize the frequency and duration of wave-driven transport events and to estimate the joint probability distribution of wave orbital velocity and period. A 109-day record of hourly current measurements 10 m above bottom is used to estimate the probability distribution of bottom boundary layer current velocity at this site and to develop an auto-regressive model to simulate current velocities for times when direct measurements of currents are not available. Frequency of transport, the maximum volume of suspended sediment, and average flux calculated using measured wave and simulated current time series agree well with values calculated using measured time series. A probabilistic approach is more amenable to calculations over time scales longer than existing wave records, but it tends to underestimate net transport

  3. 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

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

    Directory of Open Access Journals (Sweden)

    F. Briceño Zuluaga

    2015-07-01

    Full Text Available 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.

  5. Palaeoshorelines on the Australian continental shelf: Morphology, sea-level relationship and applications to environmental management and archaeology

    Science.gov (United States)

    Brooke, Brendan P.; Nichol, Scott L.; Huang, Zhi; Beaman, Robin J.

    2017-02-01

    Palaeoshorelines that lie submerged on stable continental shelves are relict coastal depositional and erosional structures formed during periods of lower sea level. An analysis of the well-dated Late Quaternary (0-128 ka) sea-level record indicates that the most persistent (modal) lower sea levels were at 30 - 40 m below present, which occurred between 97 and 116 ka and at approximately 85 ka and 10 ka. A secondary modal position was at 70-90 m that occurred mostly during a period of fluctuating sea level between 30 and 60 ka, as well as at around 87 ka (70 - 80 m only) and 12-15 ka. For the tectonically stable Australian continental shelf, we show that a range of shorelines formed at each of these sea level modal positions and their morphology and degree of preservation depends on composition (carbonate vs siliciclastic) and oceanographic setting (wave, tide and wind energy). These ancient coasts record a range of oceanographic and geological regimes that existed during relatively long periods of lower sea level and provide a guide to the general depth zones in which similar features likely occur on other shelves globally. Australian palaeoshorelines represent distinctive benthic habitats that strongly influence the distribution of biodiversity across the shelf. Accurate mapping of these features provides a robust geospatial framework for investigations of marine species distributions and environmental change monitoring. These data also enable the better targeting of relict coastal areas that potentially include sand resources and sites of human occupation during periods of lower sea level.

  6. Observed internal tides and near-inertial waves on the continental shelf and slope off Jaigarh, central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Subeesh, M.P.; Unnikrishnan, A

    The characteristics of internal tides (ITs) and near-inertial waves (NIWs) on the continental shelf and slope off Jaigarh (17degreeN), central west coast of India were studied. Eight-month (March–October) long Acoustic Doppler Current Profiler (ADCP...

  7. Applying the basin model: Assessing habitat suitability of young-of-the-year demersal fishes on the New York Bight continental shelf

    Science.gov (United States)

    Sullivan, Mark C.; Cowen, Robert K.; Able, Kenneth W.; Fahay, Michael P.

    2006-09-01

    The extent to which young-of-the-year (YOY) fish habitats become saturated with new recruits has remained relatively unevaluated for temperate, demersal, continental shelf fishes. MacCall's [1990. Dynamic Geography of Marine Fish Populations. Washington Sea Grant Program, University of Washington Press, Seattle, Washington] basin model was used as a framework for examining the dynamics of an assemblage of recently settled fishes in relation to available microhabitat on the New York Bight continental shelf (USA). For four abundant species (three flatfish, one merlucciid hake), density-specific patterns of microhabitat selection, spatial dispersion and overall cross-shelf habitat use were investigated using a research submersible over three cross-shelf transects during the late summer settlement season. Typically, recruits that saturated YOY habitats (>1 ind/m 2) were randomly distributed within underwater transects and formed weak associations with specific microhabitats. At lower densities (ecologically important substrates (i.e. Limanda ferruginea, sand wave crests/low shell hash). For Citharichthys arctifrons, clumping appeared to increase with complexity of the habitat. Several less-abundant species (i.e. Urophycis chuss, Tautogolabrus adspersus) formed tight associations with rare habitat features and may consequently encounter the greatest bottleneck for space during the benthic/pelagic transition. Although restricted by the scale of observation, these results begin to elucidate the mechanisms by which habitat quality and quantity moderate recruitment on the continental shelf.

  8. Ocean Circulation and Dynamics on the West Antarctic Peninsula Continental Shelf

    Science.gov (United States)

    2007-09-01

    Upwelling-favorable winds force roughly the opposite circulation. The cyclonic circulation on the trough helps advect blobs of salty, warm and...roughly the opposite circulation. The cyclonic circulation on the trough helps advect blobs of salty, warm and nutrient-rich water across the shelf...of Warm Events .................... 116 4.5 Circulation Associated with the Warm Events ................ 117 4.5.1 Eddies Advected Pass a Mooring

  9. 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.

    . Microstructural studies of limestones by SEM indicate that phosphate occurs as (a) brown infillings in boring/septal cavities of corals, (b) trapped material between algal laminations and (c) cement in pelletal limestones. Phosphate is in the form of ovoids... is associated with siliciclastic material. It appears that abundant terrigenous flux was transported to the shelf at about 8300 yr B.P. resulted in the demise of corals and favoured the growth of crustose coralline algae for short duration. This flux also...

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

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, Mark J. [Center for Energy Studies, Louisiana State University, Energy Coast and Environment Building, Nicholson Extension Drive, Baton Rouge, LA 70803 (United States)

    2009-11-15

    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)

  11. Late Pleistocene to Holocene sedimentation and hydrocarbon seeps on the continental shelf of a steep, tectonically active margin, southern California, USA

    Science.gov (United States)

    Draut, Amy E.; Hart, Patrick E.; Lorenson, T.D.; Ryan, Holly F.; Wong, Florence L.; Sliter, Ray W.; Conrad, James E.

    2009-01-01

    Small, steep, uplifting coastal watersheds are prolific sediment producers that contribute significantly to the global marine sediment budget. This study illustrates how sedimentation evolves in one such system where the continental shelf is largely sediment-starved, with most terrestrial sediment bypassing the shelf in favor of deposition in deeper basins. The Santa Barbara-Ventura coast of southern California, USA, is considered a classic area for the study of active tectonics and of Tertiary and Quaternary climatic evolution, interpretations of which depend upon an understanding of sedimentation patterns. High-resolution seismic-reflection data over >570 km2 of this shelf show that sediment production is concentrated in a few drainage basins, with the Ventura and Santa Clara River deltas containing most of the upper Pleistocene to Holocene sediment on the shelf. Away from those deltas, the major factor controlling shelf sedimentation is the interaction of wave energy with coastline geometry. Depocenters containing sediment 5-20 m thick exist opposite broad coastal embayments, whereas relict material (bedrock below a regional unconformity) is exposed at the sea floor in areas of the shelf opposite coastal headlands. Locally, natural hydrocarbon seeps interact with sediment deposition either to produce elevated tar-and-sediment mounds or as gas plumes that hinder sediment settling. As much as 80% of fluvial sediment delivered by the Ventura and Santa Clara Rivers is transported off the shelf (some into the Santa Barbara Basin and some into the Santa Monica Basin via Hueneme Canyon), leaving a shelf with relatively little recent sediment accumulation. Understanding factors that control large-scale sediment dispersal along a rapidly uplifting coast that produces substantial quantities of sediment has implications for interpreting the ancient stratigraphic record of active and transform continental margins, and for inferring the distribution of hydrocarbon resources

  12. Geologic influence on groundwater salinity drives large seawater circulation through the continental shelf

    Science.gov (United States)

    Michael, Holly A.; Scott, Kaileigh C.; Koneshloo, Mohammad; Yu, Xuan; Khan, Mahfuzur R.; Li, Katie

    2016-10-01

    Observations of offshore freshened groundwater and saline groundwater discharge along continental shelves have important implications for water resources, ecosystem function, and the composition of the ocean, but they cannot be explained by basic theory. We show that these independent observations are linked and result from processes that drive variable-density groundwater flow through the spatial heterogeneity that is ubiquitous in geologic formations. We use lithologic data to develop geostatistical models that mimic the architecture of coastal aquifers. Simulation of groundwater flow and salt transport through these random realizations shows that heterogeneity produces spatially complex subsurface salinity distributions that extend tens of kilometers offshore, even at steady state. The associated density gradients drive high saline groundwater circulation rates that cannot be predicted by equivalent homogeneous models. Results suggest that these phenomena may be common along continental shelves, potentially altering estimates of ocean chemical budgets and impacting coastal water management for future generations.

  13. Modeling Cape- and Ridge-Associated Marine Sand Deposits; A Focus on the U.S. Atlantic Continental Shelf

    Science.gov (United States)

    Bliss, James D.; Williams, S. Jeffress; Bolm, Karen S.

    2009-01-01

    Cape- and ridge-associated marine sand deposits, which accumulate on storm-dominated continental shelves that are undergoing Holocene marine transgression, are particularly notable in a segment of the U.S. Atlantic Continental Shelf that extends southward from the east tip of Long Island, N.Y., and eastward from Cape May at the south end of the New Jersey shoreline. These sand deposits commonly contain sand suitable for shore protection in the form of beach nourishment. Increasing demand for marine sand raises questions about both short- and long-term potential supply and the sustainability of beach nourishment with the prospects of accelerating sea-level rise and increasing storm activity. To address these important issues, quantitative assessments of the volume of marine sand resources are needed. Currently, the U.S. Geological Survey is undertaking these assessments through its national Marine Aggregates and Resources Program (URL http://woodshole.er.usgs.gov/project-pages/aggregates/). In this chapter, we present a hypothetical example of a quantitative assessment of cape-and ridge-associated marine sand deposits in the study area, using proven tools of mineral-resource assessment. Applying these tools requires new models that summarize essential data on the quantity and quality of these deposits. Two representative types of model are descriptive models, which consist of a narrative that allows for a consistent recognition of cape-and ridge-associated marine sand deposits, and quantitative models, which consist of empirical statistical distributions that describe significant deposit characteristics, such as volume and grain-size distribution. Variables of the marine sand deposits considered for quantitative modeling in this study include area, thickness, mean grain size, grain sorting, volume, proportion of sand-dominated facies, and spatial density, of which spatial density is particularly helpful in estimating the number of undiscovered deposits within an

  14. Subsurface precambrian ridge on the continental shelf of western India between Coondapoor and Kasaragod

    Digital Repository Service at National Institute of Oceanography (India)

    Subrahmanyam, V.; Rao, M.G.; SubbaRaju, L.V.

    -positions of India which are sheared by the ENE-WSW fault F1 since its breakup from Africa. The interpreted (perhaps Precambrian), are of the same age or models are shown in Fig. 8. predates the fault F1. The reactivation of some of ~0 > > Z 3o' 73* 3d 7~ 31....N. and Indra Mohan, 1976. A technical report on integrated geophysical studies in the Koyana hydro-electric is similar to the reported basement ridges on the project area of Maharashtra state, India. western shelf of Africa (Belmonte et al., 1965), Belmonte...

  15. Circulation and exchange at the continental shelf and slope, SEEP-II

    Energy Technology Data Exchange (ETDEWEB)

    Houghton, R.W.; Ou, Hsien-Wang.

    1990-01-01

    This project is a component of the SEEP-2 program to study shelf-slope exchange in the southern Middle Atlantic bight (MBA). It represents the physical oceanographic portion of the SEEP-2 research at Lamont-Doherty Geological Observatory (L-DGO). Since the work consists of two parts: data analysis and theoretical modeling, this report will be divided into two parts to describe the progress of each activity. It covers work performed during the time interval March to December 1990 and is a sequel to the report submitted in February 1990. 25 figs.

  16. 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.

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

    Science.gov (United States)

    2005-01-01

    banda de baixa salinidade formou-se desde o estu•.rio atW 30"N na plataforma continental sul brasileira. 0 efeito de ventos de sudoeste, que causam...distribuiqdo de baixa salinidade 6 muito mais sensivel A direggo dos ventos do que A descarga fluvial. Ventos de sudoeste sao capazes de advectar o sinai...de baixa salinidade ao longo da costa. JA os ventos de nordeste demonstram ser eficientes na erosgo da pluma, que 6 destacada da costa por deriva de

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

    OpenAIRE

    M. Tapia-Garcia; M. C. Garcia-Abad; A. Carranza-Edwards; F. Vazquez-Gutierrez

    2007-01-01

    Se analizan datos e información de las características fisco-químicas del agua y tipo de sedimentos de la plataforma continental del Golfo de Tehuantepec, México. Los cambios de salinidad, temperatura y oxígeno disuelto varían de acuerdo con las estaciones de lluvias y sequía (en esta última prevalecen fuertes vientos denominados Tehuantepecanos). Las estaciones de muestreo fueron agrupadas (utilizando salinidad, temperatura, pH y tipo de sedimentos) con análisis por conglomerados y análisis ...

  19. 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.

  20. 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.

  1. 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

  2. Biogeography and biodiversity of gastropod molluscs from the eastern Brazilian continental shelf and slope Biogeografía y biodiversidad de moluscos gastrópodos de la plataforma y talud continental brasileño

    Directory of Open Access Journals (Sweden)

    Gabriela Benkendorfer

    2009-01-01

    Full Text Available Biogeographic distributional patterns of gastropods are proposed based on the species' geo-graphic and bathymetric distribution. Samples were collected along the Brazilian continental margin between 18° S and 23° S, at 37 stations with depths from 20 m to 1,330 m. The analysis of the biogeographic distribution patterns confirmed the existence of a transitional zone from tropical to subtropical waters in the area of both the continental shelf and slope, suggesting a relationship with water mass circulation. We observed a high species turnover rate between the shelf and slope. The analysis of gastropod species distribution revealed a similar pattern on the shelf and slope and a large difference between shallow and deep-water faunas.Los patrones de distribución biogeográfica de gastrópodos fueron propuestos basados en la distribución geográfica y batimétrica de las especies. Los muestreos fueron realizados en el margen continental brasileño entre 18°S y 23°S, en 37 estaciones de 20 m a 1.330 m de profundidad. El análisis de los patrones de distribución biogeográfica confirmó la existencia de una zona de transición de aguas tropicales a aguas subtropicales, que se encuentra en la zona de la plataforma continental y también en la zona del talud continental, esto puede sugerir una relación con la circulación de las masas de agua. Se observó una elevada tasa de turnover de las especies entre la plataforma y el talud continental. El análisis de las especies de gastrópodos reveló un patrón similar tanto en la plataforma como en el talud y una gran diferencia entre las faunas de las aguas someras y profundas.

  3. 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.

  4. Styles of neotectonic fault reactivation within a formerly extended continental margin, North West Shelf, Australia

    Science.gov (United States)

    Whitney, Beau B.; Hengesh, James V.; Gillam, Dan

    2016-08-01

    We have investigated the locations and patterns of neotectonic deformation in the Carnarvon basin along the Mesozoic rifted margin of Western Australia to evaluate the characteristics of post-Neogene tectonic reactivation. Geological, geophysical, geotechnical, and bathymetric data demonstrate that preferentially oriented rift-era structures have been reactivated under the current neotectonic stress regime. The most recent pulse of neotectonic reactivation initiated during the Plio-Pleistocene (4.0 to 1.8 million years ago) and is ongoing. Reactivated structures in the region demonstrate a variety of styles of deformation consistent with dextral-transpression. Structural styles include both positive and negative flower structures, restraining and releasing bends, and hourglass structures. Barrow Island lies within a broad kinematic restraining bend that appears to warp the MIS 5e marine terrace on the island. Fold reconstructions of Neogene strata on the Cape Range and Barrow anticlines yield uplift rates consistent with uplift rates determined from folded late Pleistocene units in the Cape region. Although tectonic rates are low compared to interplate settings, evidence for active tectonic deformation precludes this part of the Australian plate from being classified as a Stable Continental Region.

  5. Temporal variations in internal tide multimodal structure on the continental shelf, South China Sea

    Science.gov (United States)

    Gao, Dalu; Jin, Guangzhen; Lü, Xianqing

    2017-01-01

    Temporal variations in multimodal structures of diurnal ( D 1) and semidiurnal ( D 2) internal tides were investigated on the continental slope of the Dongsha Plateau, based on 2-month moored acoustic Doppler current profiler observations. Harmonic analysis indicated that the D 1 components ( K 1 and O 1) dominated the internal tide field. The vertical structure of the K 1 constituent presented a first-mode structure while the M 2 constituent seemed to exhibit a high-mode structure. Amplitude spectra analysis of the current data revealed differences in baroclinic current amplitudes between different water depths. Temporal variations in modal structures ware analyzed, based on the D 1 and D 2 baroclinic tides extracted from the baroclinic velocity field with band-pass filters. Analysis showed that the magnitude of the D 1 internal tide current was much larger than the D 2 current, and temporal variations in the modal structure of the D 1 internal tide occurred on an approximately fortnightly cycle. The EOF analyses revealed temporal transformation of multimodal structures for D 1 and D 2 internal tides. The enhancement of the D 1 internal tide was mainly due to the superposition of K 1 and O 1, according to the temporal variation of coherent kinetic energy.

  6. Modeling the Dynamics and Export of Dissolved Organic Matter in the Northeastern U.S. Continental Shelf

    Science.gov (United States)

    Druon, J.N.; Mannino, A.; Signorini, Sergio R.; McClain, Charles R.; Friedrichs, M.; Wilkin, J.; Fennel, K.

    2009-01-01

    Continental shelves are believed to play a major role in carbon cycling due to their high productivity. Particulate organic carbon (POC) burial has been included in models as a carbon sink, but we show here that seasonally produced dissolved organic carbon (DOC) on the shelf can be exported to the open ocean by horizontal transport at similar rates (1-2 mol C/sq m/yr) in the southern U.S. Mid-Atlantic Bight (MAB). The dissolved organic matter (DOM) model imbedded in a coupled circulation-biogeochemical model reveals a double dynamics: the progressive release of dissolved organic nitrogen (DON) in the upper layer during summer increases the regenerated primary production by 30 to 300%, which, in turns ; enhances the DOC production mainly from phytoplankton exudation in the upper layer and solubilization of particulate organic matter (POM) deeper in the water column. This analysis suggests that DOM is a key element for better representing the ecosystem functioning and organic fluxes in models because DOM (1) is a major organic pool directly related to primary production, (2) decouples partially the carbon and nitrogen cycles (through carbon excess uptake, POM solubilization and DOM mineralization) and (3) is intimately linked to the residence time of water masses for its distribution and export.

  7. Horizontal coherence of low-frequency fixed-path sound in a continental shelf region with internal-wave activity.

    Science.gov (United States)

    Duda, Timothy F; Collis, Jon M; Lin, Ying-Tsong; Newhall, Arthur E; Lynch, James F; DeFerrari, Harry A

    2012-02-01

    Sound at 85 to 450 Hz propagating in approximately 80-m depth water from fixed sources to a joint horizontal/vertical line array (HLA/VLA) is analyzed. The data are from a continental shelf area east of Delaware Bay (USA) populated with tidally generated long- and short-wavelength internal waves. Sound paths are 19 km in the along-shore (along internal-wave crest) direction and 30 km in the cross-shore direction. Spatial statistics of HLA arrivals are computed as functions of beam steering angle and time. These include array gain, horizontally lagged spatial correlation function, and coherent beam power. These quantities vary widely in magnitude, and vary over a broad range of time scales. For example, correlation scale can change rapidly from forty to five wavelengths, and correlation-scale behavior is anisotropic. In addition, the vertical array can be used to predict correlation expected for adiabatic propagation with cylindrical symmetry, forming a benchmark. Observed variations are in concert with internal-wave activity. Temporal variations of three coherence measures, horizontal correlation length, array gain, and ratio of actual correlation length to predicted adiabatic-mode correlation length, are very strong, varying by almost a factor of ten as internal waves pass.

  8. 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.

  9. Behaviour of REEs in a tropical estuary and adjacent continental shelf of southwest coast of India: Evidence from anomalies

    Indian Academy of Sciences (India)

    P M Deepulal; T R Gireesh Kumar; C H Sujatha

    2012-10-01

    The distribution and accumulation of the rare earth elements (REE) in the sediments of the Cochin Estuary and adjacent continental shelf were investigated. The rare earth elements like La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and the heavy metals like Mg, V, Cr, Mn, Fe, Cu, Zn, U, Th were analysed by using standard analytical methods. The Post-Archean Australian Shale composition was used to normalise the rare earth elements. It was found that the sediments were more enriched with the lighter rare earth elements than the heavier ones. The positive correlation between the concentrations of REE, Fe and Mn could explain the precipitation of oxyhydroxides in the study area. The factor analysis and correlation analysis suggest common sources of origin for the REEs. From the Ce-anomalies calculated, it was found that an oxic environment predominates in all stations except the station No. 2. The Eu-anomaly gave an idea that the origin of REEs may be from the feldspar. The parameters like total organic carbon, U/Th ratio, authigenic U, Cu/Zn, V/Cr ratios revealed the oxic environment and thus the depositional behaviour of REEs in the region.

  10. 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.

  11. 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.

  12. Primary production in the tropical continental shelf seas bordering northern Australia

    Science.gov (United States)

    Furnas, Miles J.; Carpenter, Edward J.

    2016-10-01

    Pelagic primary production (14C uptake) was measured 81 times between 1990 and 2013 at sites spanning the broad, shallow Northern Australian Shelf (NAS; 120-145°E) which borders the Australian continent. The mean of all areal production measurements was 1048±109 mg C m-2 d-1 (mean±95% CI). Estimates of areal primary production were correlated with integral upper-euphotic zone chlorophyll stocks (above the 50% and 20% light penetration depths) accessible to ocean color remote sensing and total water column chlorophyll standing crop, but not surface (0-2 m) chlorophyll concentrations. While the NAS is subject to a well characterized monsoonal climate regime (austral summer-NW monsoon -wet: austral winter- SE monsoon -dry), most seasonal differences in means of regional-scale chlorophyll standing crop (11-33 mg Chl m-2 for 12 of 15 season-region combinations) and areal primary production (700-1850 mg C m- day-1 for 12 of 15 season-region combinations) fell within a 3-fold range. Apart from the shallow waters of the Torres Strait and northern Great Barrier Reef, picoplankton (80%. While the range of our post-1990 areal production estimates overlaps the range of production estimates made in NAS waters during 1960-62, the mean of post-1990 estimates is over 2-fold greater. We regard the difference to be due to improvements in production measurement techniques, particularly regarding the reduction of potential metal toxicity and incubations in more realistic light regimes.

  13. Outer continental shelf oil and gas activities in the Gulf of Mexico and their onshore impacts. Gulf of Mexico summary report, October 1984-June 1985

    Energy Technology Data Exchange (ETDEWEB)

    Lynch, C.W.; Risotto, S.P.

    1985-01-01

    This report provide a brief but comprehensive overview of oil and gas activites offshore in the Gulf of Mexico. While the reports focus on the Outer Continental Shelf (OCS) and the onshore impacts of operations in federal waters, information also is included on development in state waters and on how significant national issues affect Gulf Coast States. In addition, this sumary report includes a chapter that considers in detail wetland loss in Louisiana resulting from marshland development by the petroleum and other industries. The northern Gulf of Mexico continues to be a world leader in the production of offshore oil and gas, with a cumulative total of over 6 million barrels of crude oil and 67 trillion cubic feet of natural gas. Between December 1983 and the end of 1984, the number of identified oil and gas fields in the Gulf of Mexico Outer Continental Shelf increased from 572 to 621. The 1983 advent of areawide leasing in the Gulf of Mexico Outer Continental Shelf Region resulted in the leasing of more than 10.5 million acres by the oil. The vast number of tracts industry has leased, but not yet explored, leads to expectations of greater exploration activity in the next 3 to 4 years. The Gulf's offshore pipeline network is the most extensive in the world, totaling over 14,000 miles of pipe on the regions's Outer Continental Shelf. Postproduction facilities in the Gulf region have advanced in technology and flexibility in recent years. Major new discoveries in the Gulf augur well for area refineries and processors, as do plans for west-to-east pipelines bringing crude oil from California and Alaska. (DMC)

  14. First hydroacoustic evidence of marine, active fluid vents in the Naples Bay continental shelf (Southern Italy)

    Science.gov (United States)

    Passaro, Salvatore; Genovese, Simona; Sacchi, Marco; Barra, Marco; Rumolo, Paola; Tamburrino, Stella; Mazzola, Salvatore; Basilone, Gualtiero; Placenti, Francesco; Aronica, Salvatore; Bonanno, Angelo

    2014-09-01

    We present the first results of a multidisciplinary research aimed at the detection and mapping of Active Fluid Vents (AFVs) at the seafloor of the Naples Bay, Italy. This segment of the Campania continental margin is characterised by severe Quaternary extension and intense volcanism at Ischia and Procida islands, the Campi Flegrei and Somma-Vesuvius volcanic complexes. High resolution hydroacoustic profilers were used to identify and localize fluid emission from the seafloor. ROV direct observation showed that each emission centre is generally composed by the coalescence of several emitting points. CTD probes showed that there are no significant gradients in temperature profiles. The results of this study include the detection and mapping of 54 fluid emission points all located in the - 71/- 158 m depth range, and spatially distributed into four main clusters. Three of the described clusters are located along the margin of a complex, toe-shaped seafloor morphology southwest of the Somma-Vesuvius, representing the shallow expression of partly buried, coalesced depositional features (namely, two flank collapses and one pyroclastic flow) associated with the Late Pleistocene activity of the volcano. The fourth AFV cluster was detected at the morphological - high, located about 8 km south of Naples (Banco della Montagna), represented by a field of volcaniclastic diapirs composed of massive pumiceous deposits originated from the Campi Flegrei intruding rising through the latest Quaternary-Holocene marine deposits. Our study suggests that the occurrence of AFV in this area could be genetically linked to the interaction between volcanic related seafloor morphologies and the main, NE striking faults present in the area, i.e. the Magnaghi-Sebeto line and the Vesuvian fault.

  15. 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.

  16. Drifting buoy and other data from drifting platforms in the Bering Sea as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 17 January 1981 to 20 June 1981 (NODC Accession 8200120)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Drifting buoy data was collected from drifting platforms in the Bering Sea by the Flow Research Company as part of the Outer Continental Shelf Environmental...

  17. Intertidal organism and other data from the MONTAGUE in the Gulf of Alaska as part of Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 12 September 1974 to 15 October 1974 (NODC Accession 7600105)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Intertidal organism and other data were collected in the Gulf of Alaska from the MONTAGUE as part of the Outer Continental Shelf Environmental Assessment Program...

  18. Drifting buoy and other data from the Beaufort Sea and other locations as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 03 March 1977 to 05 April 1977 (NODC Accession 7700543)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Drifting buoy data was collected from the Beaufort Sea and other locations by the University of Washington (UW) as part of the Outer Continental Shelf Environmental...

  19. Drifting buoy and other data from the Arctic Ocean and other locations as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 02 November 1975 to 03 June 1976 (NODC Accession 7601626)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Drifting buoy data was collected by the University of Washington - Seattle (UW) as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP)....

  20. Drifting buoy and other data from the Beaufort Sea and other locations as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 04 April 1977 to 03 July 1977 (NODC Accession 7700780)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Drifting buoy data was collected from the Beaufort Sea by the University of Washington (UW) as part of the Outer Continental Shelf Environmental Assessment Program...

  1. 50-meter grid representing the Holocene transgressive surface (in meters) beneath the inner-continental shelf offshore of Fire Island, NY (FI_HTS, UTM Zone 18N, WGS 84, Esri Binary Grid)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The U.S. Geological Survey (USGS) mapped approximately 336 square kilometers of the lower shoreface and inner-continental shelf offshore of Fire Island, New York in...

  2. Marine bird sighting and other data from NOAA Ship DISCOVERER and other platforms as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 1975-06-05 to 1976-08-20 (NODC Accession 7800486)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Marine bird sighting and other data were collected from NOAA Ship DISCOVERER and other platforms. Data were collected as part of the Outer Continental Shelf...

  3. Drifting buoy and other data from the Beaufort Sea as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 05 November 1975 to 01 October 1976 (NODC Accession 7700019)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Drifting buoy and other data was collected from the Beaufort Sea by the University of Washington (UW) as part of the Outer Continental Shelf Environmental Assessment...

  4. Marine bird sighting and other data from the SURVEYOR as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 01 September 1976 to 02 September 1976 (NODC Accession 7800704)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Marine bird sighting and other data were collected from the SURVEYOR as part of Outer Continental Shelf Environmental Assessment Program (OCSEAP). Data were...

  5. Drifting buoy and other data from the Arctic Ocean in support of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 04 June 1976 to 27 November 1976 (NODC Accession 7700205)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Drifting buoy data were collected from the Arctic Ocean by the University of Washington in support of the Outer Continental Shelf Environmental Assessment Program...

  6. Drifting buoy and other data from the Gulf of Alaska as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 21 October 1976 to 11 November 1976 (NODC Accession 7700740)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Drifting buoy data was collected from the Gulf of Alaska by the Atlantic Oceanographic and Meteorological Laboratory (AOML) as part of the Outer Continental Shelf...

  7. Intertidal organism and habitat data from the Gulf of Alaska as part of Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 13 May 1976 to 24 August 1976 (NODC Accession 7700029)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Intertidal organism and habitat data were collected from the Gulf of Alaska as part of Outer Continental Shelf Environmental Assessment Program (OCSEAP). Data were...

  8. Bacteria, carbon dioxide, and methane data from bottle casts in the Cariaco Basin on the continental shelf of Venezuela from the HERMANO GINES from 03 May 2000 to 31 October 2000 (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....

  9. Drifting buoy and other data from the Chukchi Sea as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 27 June 1977 to 07 November 1977 (NODC Accession 7800005)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Drifting buoy data was collected from the Chukchi Sea by the University of Washington (UW) as part of the Outer Continental Shelf Environmental Assessment Program...

  10. Bacteria, carbon dioxide, and methane data from bottle casts in the Cariaco Basin on the continental shelf of Venezuela from the HERMANO GINES from 30 April 2001 to 01 May 2001 (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...

  11. Drifting buoy and other data from the Arctic Ocean and Beaufort Sea as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 04 November 1975 to 01 October 1976 (NODC Accession 7700114)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Drifting buoy data was collected from the Arctic Ocean and Beaufort Sea by the University of Washington (UW) as part of the Outer Continental Shelf Environmental...

  12. 50-meter grid representing the Holocene sediment thickness (in meters) on the inner-continental shelf offshore of Fire Island, NY (FI_HISO, UTM Zone 18N, WGS 84, Esri Binary Grid)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The U.S. Geological Survey (USGS) mapped approximately 336 square kilometers of the lower shoreface and inner-continental shelf offshore of Fire Island, New York in...

  13. Herring spawning and other data from aircraft from the Bering Sea as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 07 May 1977 to 28 October 1978 (NODC Accession 8100538)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Herring spawning and other data were collected from aircraft from the Bering Sea as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP)....

  14. 100-meter grid representing the coastal plain unconformity (in meters) beneath the inner-continental shelf offshore of Fire Island, NY (FI_CPUN, UTM Zone 18N, WGS 84, Esri Binary Grid)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The U.S. Geological Survey (USGS) mapped approximately 336 square kilometers of the lower shoreface and inner-continental shelf offshore of Fire Island, New York in...

  15. Herring spawning and other data from aircraft as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 12 April 1976 to 12 July 1976 (NODC Accession 7601911)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Herring spawning and other data were collected from aircraft as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP). Data were collected...

  16. Herring spawning and other data from aircraft from Bristol Bay and other locations as part of the Outer Continental Shelf Environmental Assessment Program (OCSEAP) from 12 April 1976 to 12 July 1976 (NODC Accession 7601910)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Herring spawning and other data were collected from aircraft from Bristol Bay and other locations as part of the Outer Continental Shelf Environmental Assessment...

  17. Tsunami Detection by High-Frequency Radar Beyond the Continental Shelf

    Science.gov (United States)

    Grilli, Stéphan T.; Grosdidier, Samuel; Guérin, Charles-Antoine

    2016-12-01

    Where coastal tsunami hazard is governed by near-field sources, such as submarine mass failures or meteo-tsunamis, tsunami propagation times may be too small for a detection based on deep or shallow water buoys. To offer sufficient warning time, it has been proposed to implement early warning systems relying on high-frequency (HF) radar remote sensing, that can provide a dense spatial coverage as far offshore as 200-300 km (e.g., for Diginext Ltd.'s Stradivarius radar). Shore-based HF radars have been used to measure nearshore currents (e.g., CODAR SeaSonde® system; http://www.codar.com/), by inverting the Doppler spectral shifts, these cause on ocean waves at the Bragg frequency. Both modeling work and an analysis of radar data following the Tohoku 2011 tsunami, have shown that, given proper detection algorithms, such radars could be used to detect tsunami-induced currents and issue a warning. However, long wave physics is such that tsunami currents will only rise above noise and background currents (i.e., be at least 10-15 cm/s), and become detectable, in fairly shallow water which would limit the direct detection of tsunami currents by HF radar to nearshore areas, unless there is a very wide shallow shelf. Here, we use numerical simulations of both HF radar remote sensing and tsunami propagation to develop and validate a new type of tsunami detection algorithm that does not have these limitations. To simulate the radar backscattered signal, we develop a numerical model including second-order effects in both wind waves and radar signal, with the wave angular frequency being modulated by a time-varying surface current, combining tsunami and background currents. In each "radar cell", the model represents wind waves with random phases and amplitudes extracted from a specified (wind speed dependent) energy density frequency spectrum, and includes effects of random environmental noise and background current; phases, noise, and background current are extracted from

  18. Marine geological and geophysical study of the continental shelf off southern part of Cheju Island, Korea

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chi Won; Kim, Seung Woo; Jang, Jung Hae; Kim, Won Sik; Sin, Won Chul; Min, Gun Hong; Park, Young Soo; Lee, Ho Young; Jin, Jae Hwa; Kim, Sung Pil; Kim, Jung Ki; Park, Hong Soo; Lee, Jae Ho; Park, Suk Whan [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)

    1996-12-01

    This report is a preliminary result of marine geological and geophysical surveys conducted by KIGAM in 1996 obtain data available for mapping Korean continental shelves. The survey area is located off Seoguipo city of Cheju Island, which is the largest volcanic island in Korea. Total of 1,050 line-km of geophysical survey includes echo sounding, side scan sonar survey, 3.5 KHz subbottom profiling, air gun seismic and magnetic surveys. 75 grab samples were collected from grid positions of 4 x 4 miles spacing by using a Smith McIntyre sampler for textural analysis of surface sediments, and 27 sediment cores were raised from the sites determined by interpretation of geophysical data. The survey vessel, R/V Tamhae, was positioned by GPS system. Isobaths shallower than 90 m are parallel to coastline and the sea floor deepens rapidly from coast to the water depth of more than 100 m deep. The sea floor exceeding 90 m in water depth is comparatively smooth. A moat-like topographic low up to ca. 160 m deep occurs between Gapa and Mara Islands, where the tidal currents in the upper layer is stronger than 3.4 knots. The sea floor is largely covered with thin (<20 cm) shell fragment aggregates including lithic pebbles. The content of CaCO{sub 3} in coarse fraction of the surface sediments ranges from 30 % to 100 %, and is relatively higher values in nearshore. According to textural parameters and sedimentary structures, the shallow substratum can be divided into 10 sedimentary facies; 1) massive sandy mud (MSm), 2) laminated sandy mud (MSl), 3) massive muddy sand (SMm), 4) bioturbated muddy sand (SMb), 5) faintly laminated muddy sand (SMf), 6) fining-upward muddy sand (SMfu), 7) massive sand (Sm), 8) fining-upward gravelly sand (GSfu), and 9) disorganized gravelly sand (GSd). The near-surface sediments of the survey area has deposited largely under low energy conditions interrupted by high energy events. Laminated sandy mud (MSl) and bioturbated muddy sand (SMb) reflect the

  19. 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

  20. 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

  1. 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

  2. The stoichiometric ratio during biological removal of inorganic carbon and nutrient in the Mississippi River plume and adjacent continental shelf

    Directory of Open Access Journals (Sweden)

    W.-J. Huang

    2012-02-01

    Full Text Available The stoichiometric ratios of dissolved inorganic carbon (DIC and nutrients during biological removal have been widely assumed to follow the Redfield ratios (especially the C/N ratio in large river plume ecosystems. However, this assumption has not been systematically examined and documented because DIC and nutrients are rarely studied simultaneously in a river plume area, a region in which they can be affected by strong river-ocean mixing as well as intense biological activity. We examined stoichiometric ratios of DIC, total alkalinity (TA, and nutrients (NO3, PO43− and Si(OH4 data during biological removal in the Mississippi River plume and adjacent continental shelf in June 2003 and August 2004 with biological removals defined as the difference between measured values and values predicted on the basis of conservative mixing determined using a multi-endmember mixing model. Despite complex physical and biogeochemical influences, relationships between DIC and nutrients were strongly dependent on salinity range and geographic location, and influenced by biological removal. Lower C/Si and N/Si ratios in one nearshore area were attributed to a potential silicate source induced by water exchange with coastal salt marshes. When net biological uptake was separated from river-ocean mixing and the impact of marshes and bays excluded, stoichiometric ratios of C/N/Si were similar to the Redfield ratios, thus supporting the applicability of the Redfield-type C/N/Si ratios as a principle in river-plume biogeochemical models.

  3. Sediments, structural framework, petroleum potential, environmental conditions, and operational considerations of the United States North Atlantic Outer Continental Shelf

    Science.gov (United States)

    ,

    1975-01-01

    The area designated for possible oil and gas lease sale as modified from BLM memorandum 3310 #42 (722) and referred to therein as the North Atlantic Outer Continental Shelf (OCS) contains about 58,300 sq km of shelf beneath water depths of less than 200 m and lies chiefly within the Georges Bank basin. The oldest sediments drilled or dredged on the bordering Continental Slope are sandstone, clay, and silt of Upper Cretaceous age. In Upper Cretaceous exposures, on Marthas Vineyard and nearby New England islands, the predominant lithology appears to be clay. About 125 km northeast of the eastern tip of Georges Bank, the Shell B-93 well penetrated clays and silts of Upper and Lower Cretaceous age above dense Jurassic carbonate rocks which overlie a basement of lower Paleozoic slate, schist, quartzite, and granite. Structurally, the Georges Bank basin is a westerly trending trough which opens to the west-southwest. Post-Paleozoic sediments are more than 8 km thick in parts of the basin. Major structural features appear to be directly related to basement structures. Local anticlines, probably caused by differential compaction over basement flexures and horst blocks or by later uplift along basement faults are reflected principally in Lower Cretaceous and older sediments, though some of these features continue upward to within 0.7 of a second (about 650 m) of the seafloor. Tertiary deposits in the Georges Bank basin are probably up to a kilometre thick and are made up of poorly consolidated sand, silt, and clay. The Cretaceous section is inferred to be up to 3.5 km thick and to be mainly clastics -- shale, siltstone, calcareous shale, changing to limestone in the lowest part of the system. Jurassic rocks in the deepest part of the basin appear to be about 3.6 to 4.0 km thick and probably consist mainly of dense carbonates. Potential source rocks in the Georges Bank basin may include organic-rich Cretaceous shale and carbonaceous Jurassic limestone. By analogy with the

  4. 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.

  5. Observed internal tides and near-inertial waves on the continental shelf and slope off Jaigarh, central west coast of India

    Science.gov (United States)

    Subeesh, M. P.; Unnikrishnan, A. S.

    2016-05-01

    The characteristics of internal tides (ITs) and near-inertial waves (NIWs) on the continental shelf and slope off Jaigarh (17∘N), central west coast of India were studied. Eight-month (March-October) long Acoustic Doppler Current Profiler (ADCP) measurements made in the year 2008 were used in the present study. Analysis of sea surface heights from satellite altimeter data, where the tracks of the satellites are oriented nearly in the direction of the semimajor axis of barotropic tides, reveals the presence of diurnal and semidiurnal internal tides with surface amplitudes of about 2 cm. Baroclinic current spectra of horizontal velocities show peaks in IT frequencies of M2, S2, K1 and O1 and in inertial frequency (f). The observed current spectra show higher energies than those in Garrett-Munk reference spectra by about 2-3 times. Based on the estimates of "critical topography" (where the topographic slope is equal to the slope of IT) and computed barotropic body force (Baines, 1982), the shelf-edge, mid-slope and deep part of the slope region are found to be the possible generation sites of internal tides in the region. Over the period of observation, the IT on the slope is found to be energetic, with a strong IT during March to mid-April (pre-monsoon period). Whereas, on the shelf, IT is weak during the pre-monsoon and found to be strong in the southwest monsoon. The available hydrographic data and model simulated hydrography suggest that this difference is linked with the stratification changes on the shelf and slope during these seasons, where the stratification is found to be weak on the shelf and strong on the slope during pre-monsoon. Strong low-mode NIW is observed on the shelf associated with the storm events while the NIW is found to be less energetic on the slope.

  6. 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.

    developed shelf edge reefs occur on almost all the tracks [ 131 between Ratnagiri and Mormugao, implying some continuity along this 200 km K.H. Vera et al./Marine Geology 134 (1996) I4S-162 Table 1 Salient features of the shelf edge reefs observed... to a subsidence of several meters. This is well possible since the Konkan Coast is believed to be subsiding (Bruckner, 1989). The initial topography might 158 K.H. Vera et aLlMarine Geology 134 (1996) 145-162 Table 3 River discharge along the west...

  7. 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.

  8. 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

  9. 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.

  10. Tectonic and eustatic controls of late quaternary shelf sedimentation along the Central California (Santa Cruz) continental margin: high-resolution seismic stratigraphic evidence

    Science.gov (United States)

    Mullins, Henry T.; Nagel, David K.; Dominguez, Laura L.

    1985-07-01

    A high-resolution "uniboom", seismic stratigraphic investigation of a portion of the central California continental shelf has demonstrated that depositional patterns and sequences are controlled largely by an interplay of glacioeustatic sea-level fluctuations superimposed on local tectonics. Wrench tectonics, associated with active right-lateral shear along the San Gregorio fault zone, and the Pigeon Point Basement High control the location, distribution and overall geometry of depositional sequences via en echelon folding and differential subsidence. Areas of relatively thick and thin late Quaternary sediments conform in large part with structures produced during wrenching. Glacioeustatic sea-level oscillations have also shaped depositional patterns and sequences. Correlation of our seismic stratigraphic data with a southern California continental margin sea-level curve, suggests that during the last glacial maximum, approximately 18,000 yrs ago, a relative lowstand resulted in the erosion of a distinct unconformity upon which late Quaternary sediments have accumulated. A rapid rise of sea level to a relative stillstand, approximately 12,000 yrs ago, produced a concave-up, marine terrace profile across the mid-shelf, that has since been infilled with as much as 22 m of Holocene clastic sediments. A relative drop of sea level, approximately 11,000 yrs ago, allowed sediments to build seaward as a series of prograding clinoforms that form the basal sequences of the late Quaternary sediment fill. The succeeding Holocene transgression partially eroded the top of this earlier regressive sequence, and has now established a typical, wave-graded shelf along which sediments fine in a seaward direction to water depths of 90-100 m. At greater shelf water depths, surface sediments coarsen and appear to be relicts of previous relative sea-level lowstands. The presence of now submerged and buried marine terraces along both the central and southern California continental margins

  11. Executive order no. 1101 of 18. November 2005. Executive order concerning the continental shelf; Bekedtgoerelse no. 1101 af 18. november 2005. Bekendtgoerelse om lov om kontinentalsoklen

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-11-18

    The Danish continental shelf's natural resources belong to the Danish state and can only be explored or exploited by other parties through license. In this law natural resources mean: 1) the sea bed or the sea bed's underground minerals and other non-living occurrences, and 2) living organisms, which, when they are ready to be cached, are either stationary on or under the sea bed or incapable of moving without continuous contact with the sea bed or the underground. (BA)

  12. Maps showing bathymetry and modern sediment thickness on the inner continental shelf offshore of Fire Island, New York, pre-Hurricane Sandy

    Science.gov (United States)

    Schwab, William C.; Denny, Jane F.; Baldwin, Wayne E.

    2014-01-01

    The U.S. Geological Survey mapped approximately 336 square kilometers of the lower shoreface and inner continental shelf offshore of Fire Island, New York, in 2011 by using interferometric sonar and high-resolution chirp seismic-reflection systems. This report presents maps of bathymetry, acoustic backscatter, the coastal plain unconformity, the Holocene marine transgressive surface, and modern sediment thickness. These spatial data support research on the Quaternary evolution of the Fire Island coastal system and provide baseline information for research on coastal processes along southern Long Island.

  13. The São Vicente earthquake of 2008 April and seismicity in the continental shelf off SE Brazil: further evidence for flexural stresses

    Science.gov (United States)

    Assumpção, M.; Dourado, J. C.; Ribotta, L. C.; Mohriak, W. U.; Dias, Fábio L.; Barbosa, J. R.

    2011-12-01

    The continental margin and shelf of most stable intraplate regions tend to be relatively more seismically active than the continental interior. In the southeast continental margin of Brazil, a seismic zone extends from Rio Grande do Sul to Espírito Santo, with seismic activity occurring mainly along the continental slope and suggesting a close relationship with flexural stresses caused by the weight of the sediments. In this region, earthquakes with magnitudes larger than 5 mb occur every 20-25 yr, on average. The focal mechanism solutions of previous earthquakes in this zone indicated reverse faulting on planes dipping approximately 45° with horizontal P-axes. The recent 5.2 mb earthquake of 2008 April 23 occurred 125 km south of São Vicente and was well recorded by many stations in SE Brazil, as well as at teleseismic distances in North America and Africa. Its focal depth was 17 km, locating the hypocentre in the lower crust. A well-determined focal mechanism solution shows one vertical nodal plane and one subhorizontal nodal plane. The P- and T-axes exhibit large dips, which were confirmed by a regional moment tensor inversion. This unusual orientation of the fault mechanism can be attributed to a rotation of the principal stress directions in the lower crust caused by flexural effects due to the load of recent sedimentation.

  14. Bathymetry and acoustic backscatter of the mid and outer continental shelf, head of De Soto Canyon, northeastern Gulf of Mexico: data, images, and GIS

    Science.gov (United States)

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

    2003-01-01

    The mid to outer continental shelf off Mississippi-Alabama and off northwest Florida were the focus of U.S. 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 Ludwig and Walton (1957). The reefs off Mississippi and Alabama were initially described in water depths of 60 to 120 m (Ludwig 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 area known as the "Head of De Soto Canyon" is the large unmapped region between the 2000 and 2001 mapped areas. It was unknown 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 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, personal commun., 2002) is of interest because of the potential benthic habitats they may represent. In the summer of 2002, the USGS, in cooperation with Minerals Management Service (MMS), the University of New Hampshire, and the University of New Brunswick, conducted a MBES survey of the Head of De Soto Canyon Region connecting the 2000 and 2001 mapped regions.

  15. Wind-driven mixing causes a reduction in the strength of the continental shelf carbon pump in the Chukchi Sea (Invited)

    Science.gov (United States)

    Hauri, C.

    2013-12-01

    Dynamic and complex physical and biological processes drive the carbonate system chemistry of the Chukchi Sea. The inflow of nutrient-rich Pacific water through the Bering Straight and sustained periods of solar radiation in summer turn this polar shelf into one of the most productive ecosystems in the world. High rates of primary production (~ 470 g C m-2 y-1) and low pelagic grazing rates draw down pCO2 at the surface and support large fluxes of organic carbon to a rich benthic ecosystem. Much of this carbon is remineralized, leading to elevated pCO2 in bottom and subsurface waters, which are thought to be isolated from the atmosphere by strong stratification. Subsequent shelf to basin transport of remineralized carbon and organic matter into the interior Arctic Ocean are believed to support a globally important CO2 sink, as well as maintain high pCO2 levels in bottom waters along their circulation-driven northward journey. Here, I document a new mechanism of carbon cycling in the Chukchi Sea that substantially reduces the net strength of this globally significant carbon sink. Surface pCO2 measurements and wind analysis suggest that annually occurring storm-induced mixing events during autumn months disrupt water column stratification and mix remineralized carbon from subsurface waters to the surface, leading to strong outgassing of CO2 to the atmosphere. This newly observed physical driver weakens the estimated strength of the continental shelf carbon pump in the Chukchi Sea from an uptake of 38 Tg C y-1 to 18-27 Tg C y-1 and revises our knowledge of the dynamics of carbon cycling on this polar shelf. An improved understanding of the distribution and transport of carbon on the shelf is crucial to elucidate how the Chukchi Sea will respond to ongoing ocean acidification and climate change.

  16. CHIRP seismic reflection study of falling-stage (forced regressive) sediment wedges on the New Jersey outer continental shelf

    Science.gov (United States)

    Santra, M.; Goff, J.; Ron, S.; Austin, J.

    2007-12-01

    High-resolution (1-12 kHz), deep-towed and hull-mounted CHIRP seismic data were collected on the New Jersey outer shelf in 2001, 2002 and 2006 as part of Office of Naval Research-funded projects. These data have imaged two well-developed, offlapping sedimentary wedges (named outer-shelf wedge and deep-shelf wedge) that are now postulated to have developed on the falling-stage limb of the last glacial cycle, during some time prior to the Last Glacial Maximum (20-22 kyrs BP). These wedges formed atop the high-amplitude, regional R horizon, a complex erosional unconformity that formed about 40,000 years ago. The outer shelf wedge is also characterized in part by an enigmatic, erose boundary separating layered horizons below from a mostly transparent section above. New Jersey shelf wedges appear analogous to forced-regressive units imaged on the Rhone shelf edge, as well as Eocene sections documented from seismic-scale outcrops on Spitsbergen Island. These examples can reach thicknesses up to 100 m on the shelf edge and uppermost slope, but usually thin rapidly downslope. Such wedges represent one of two documented mechanisms involving sand transport across a shelf margin into deeper water settings, the other being a canyonized shelf-edge. Our study will includes analysis of the CHIRP data and, if available, additional ground truth provided by short cores collected in summer 2007 at numerous intra-wedge stratigraphic horizons. Our goals are to understand the external and internal geometry of the wedges and sediment pathways across the paleo-shelf. These data should allow us to characterize margin segments that build during sea-level fall by slope-apron accretion rather than by the formation of channel-levee complexes. The literature is heavily weighted by the latter and their associated canyon systems, but information on shelf-edge attached slope aprons and how they contribute to deep-water sedimentation, and in particular the delivery of clean sands to slope settings

  17. 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.

  18. Seabed habitat mapping employing single and multi-beam backscatter data: A case study from the western continental shelf of India

    Science.gov (United States)

    Haris, K.; Chakraborty, Bishwajit; Ingole, Baban; Menezes, Andrew; Srivastava, Ratan

    2012-10-01

    Acoustic backscatter from multi-beam echo-sounder (MBES) and dual-frequency single-beam echo-sounding systems (SBES) operable at 95 kHz and 33/210 kHz, respectively, were used to study the distribution of sediment texture and benthic macro-fauna along the central part of the western continental shelf of India (off Goa). To characterize the continental shelf seafloor, single-beam and multi-beam backscatter signals were acquired along with grab sediment samples. The relationships between processed acoustic backscatter strength, grain size, and benthic macro-fauna abundance were demonstrated employing clustering technique (PCA) and Geographic Information System (GIS) based mapping. The clustering analysis delineated that the backscatter values at three frequencies are strongly correlated with both substrate type and faunal functional groups. The preferences of deposit feeders (soft body benthic macro-fauna) for the fine-sediment regions and filter feeders (hard body benthic macro-fauna) for coarse sediment regions were linked to the variations in sediment granulometry as well as backscatter strengths in the study area. This study further demonstrates the utility of high frequency backscatter data employing echo-sounding systems towards the interpretation of seafloor sediments and benthic habitat characteristics across large areas of seafloor.

  19. 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.

  20. An estimation of nutrient fluxes to the East China Sea continental shelf from the Taiwan Strait and Kuroshio subsurface waters in summer

    Institute of Scientific and Technical Information of China (English)

    LI Hongmei; SHI Xiaoyong; WANG Hao; HAN Xiurong

    2014-01-01

    According to historical mean ocean current data through the field observations of the Taiwan Ocean Re-search Institute during 1991-2005 and survey data of nutrients on the continental shelf of the East China Sea (ECS) in the summer of 2006, nutrient fluxes from the Taiwan Strait and Kuroshio subsurface waters are estimated using a grid interpolation method, which both are the sources of the Taiwan Warm Current. The nutrient fluxes of the two water masses are also compared. The results show that phosphate (PO4-P), silicate (SiO3-Si) and nitrate (NO3-N) fluxes to the ECS continental shelf from the Kuroshio upwelling water are slightly higher than those from the Taiwan Strait water in the summer of 2006. In contrast, owing to its lower velocity, the nutrient flux density (i.e., nutrient fluxes divided by the area of the specific section) of the Ku-roshio subsurface water is lower than that of the Taiwan Strait water. In addition, the Taiwan Warm Current deep water, which is mainly constituted by the Kuroshio subsurface water, might directly reach the areas of high-frequency harmful alga blooms in the ECS.

  1. Distribution and relation of total bacteria, active bacteria, bacterivory, and volume of organic detritus in Atlantic continental shelf waters off Cape Hatteras NC, USA

    Science.gov (United States)

    Sherr, Evelyn B.; Sherr, Barry F.; Verity, Peter G.

    During the Ocean Margins Program, we obtained data on the abundances of bacterioplankton and heterotrophic flagellates, and on rates of bacterivory, across the mid-Atlantic continental shelf off Cape Hatteras, NC, during four spring and summer cruises from 1993 to 1996. Bacterial and grazing parameters were compared for inner, middle, and outer shelf regions. In 1996, we sampled during two seasons: early spring (March) and mid-summer (July), and in addition determined the fractions of in situ bacterioplankton that had visible nucleoids (NV cells), or that had highly active electron transport systems (ETS), i.e. that were positive for reduction of the fluorogenic formazan compound, 5 cyano-2,3 ditolyl tetrazolium chloride (CTC+ cells), as well as the volumetric concentration of organic detrital particles. Detrital volumes and abundances of bacterioplankton and of heterotrophic flagellates, varied by an order of magnitude, and decreased from inshore to offshore shelf regions. In 1996, bacterial abundances and percentages of CTC+ cells were higher across the shelf during the early spring bloom season (March) compared to the post-bloom season (July). In March 1996, percentages of bacterial cells with visible nucleoids varied between 20% and 70%, but showed little change across the shelf; while fractions of total bacteria with highly active ETS were lower and more variable (1-16% CTC+ cells), and on average were twice as high in the inner shelf region compared to the rest of the shelf. Percentages of CTC+ cells were also higher for particle-associated bacteria. There was a strong positive relationship between percent CTC+ cells and volume of organic detrital particles. However, % CTC+ cells and detrital volume were not consistently related to either bulk particulate organic carbon or chlorophyll. Bacterivory, assessed via rate of ingestion of fluorescently labeled bacteria, could remove 2-9% (4-18% accounting for motile cells) of total bacterial stocks per day. If

  2. Early Pleistocene to Holocene glacial activity along the southern Alaska continental shelf inferred from the sedimentary record in the northern Gulf of Alaska - preliminary results

    Science.gov (United States)

    Forwick, M.; Cowan, E. A.; Bahlburg, H.; Childress, L. B.; Jaeger, J. M.; Moy, C. M.; Müller, J.; Ribeiro, F.; Ridgway, K. D.; Gulick, S. P.; Worthington, L. L.; Reece, R.

    2013-12-01

    Preliminary analyses of the lithology at Site U1418 (IODP Expedition 341), located on the proximal Surveyor Fan, provide evidence of continuous presence of tidewater glaciers on the southern Alaska continental shelf for more than c. 1.2 Ma, as well as evidence of prolonged presence of grounded ice at the shelf break and/or the initiation of ice streams. The lowermost lithostratigraphic unit (Unit IV) of the 941 m long record is composed of heavily deformed sediments that are interpreted to be the top of the recently discovered Surveyor mass-transport deposit. Unit III contains mostly laminated mud with thin interbeds of sand, silt and clast-rich muddy diamict with rip-up clasts. A few lonestones of granule and pebble size are present. Massive and laminated mud with scattered lonestones, as well as interbedded intervals of clast-poor diamict (clasts of granule and pebble size) compose Unit II. Unit I contains massive mud with interbedded silt laminae and sand beds. Most silt laminae have the same color as the matrix, but some are lighter. Diatom oozes and graded sand beds occur infrequently and lonestones are present below 3 m. The dominance of mud suggests that sedimentation at Site U1418 was strongly influenced by suspension settling from turbid meltwater plumes emanating into the Gulf of Alaska during the past c. 1.2 Ma. Laminated intervals may reflect temporal variations in meltwater runoff from a single sediment source and/or supply from several sources during the deposition of Units II and III. Lonestones and clasts of granule and pebble size are regarded to be mostly iceberg-rafted debris, indicating that tidewater glaciers have been present on the continental shelf for most of the time since the onset of the deposition of Unit III. Diamicts in Unit II most probably reflect periods of enhanced ice rafting and/or reduced meltwater runoff. Minor silt and sand beds provide evidence of occasional sediment reworking during the deposition of Units II and III. The

  3. Lithology, monsoon and sea-surface current control on provenance, dispersal and deposition of sediments over the Andaman continental shelf

    Directory of Open Access Journals (Sweden)

    Karri Damodararao

    2016-07-01

    Full Text Available Sediments deposited on the Northern and Eastern Andaman Shelf along with a few sediments from the Irrawaddy and the Salween Rivers are studied for their elemental, Sr and Nd concentrations and their isotope composition to identify their sources, 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 such as ophiolites and ultrabasic rocks in the Irrawaddy drainage and over Indo – Burman – Arakan (IBA ranges as their dominant source. 87Sr/86Sr ratios in sediments of the Northern and Eastern Andaman Shelf range between 0.712245 and 0.742183 whereas, εNd varies from -6.29 to -17.25. Sediments around Mergui have the highest 87Sr/86Sr and the lowest εNd values. Sr and Nd isotope composition of these sediments along with that in the potential sources suggest four major sources of these sediments to the Andaman Shelf, (i the Irrawaddy River, (ii the Salween River, (iii Rivers draining the IBA ranges and (vi Rivers draining the Western/Central granitic ranges of the Southern Myanmar and Western Thailand such as the Tavoy and the Tanintharyi Rivers. Erosion in the catchment is controlled by the precipitation and topography. Intensely focused precipitation over the higher relief of the western slopes of the IBA and western/central granitic ranges causes higher erosion over this mountainous region, supplying huge sediments through the Kaladan, Irrawaddy, Salween, and the Tanintharyi Rivers to the western Myanmar Shelf, Northern, and Eastern Andaman Shelves respectively. The majority of the sediments produced in the drainage are delivered to the shelf during the south-west monsoon which is dispersed eastward by sea-surface circulation from the mouth of the Irrawaddy Rivers towards the Gulf of Martaban and further southward. The Andaman Shelf receives very little

  4. Gulf of Mexico outer shelf/slope research consortium corehole in Main Pass 303, Louisiana continental shelf: Integrated biostratigraphic, lithostratigraphic, isotopic investigation of highstand and transgressive system tracts

    Energy Technology Data Exchange (ETDEWEB)

    Fillon, R.H. (Texaco, Inc., New Orleans, LA (United States)); Kohl, B. (Chevron, USA, Inc., New Orleans, LA (United States)); Roberts, H.H. (Louisiana State Univ., Baton Rouge (United States))

    1991-03-01

    Investigation of a 300 ft continuously cored section through an outer shelf delta, including coarse fraction analysis, X-radiography, and a gamma ray log reveal an upward succession consisting of shale greater than carbonate-rich shale, which is greater than silty shale with fine sandy laminae, which is greater than bedded, cross laminated fine to medium sand, which is greater than shale with terrigenous organic matter, which is greater than massive, medium to coarse sand, which is greater than carbonate-rich shale. Paleo sea-level estimates based on benthic foraminifera indicate an upward inner shelf which is greater than outer neritic, which is greater than marginal marine, which is greater than outer neritic transition. Planktonic biostratigraphy and isotope data are consistent with a last interglacial age for the lower, and a Holocene age for the upper, high sea-level stands. Multiple data sets define a maximum flooding surface (MFS) near the base of the high interglacial sea-level interval, and another MFS within the upper carbonate-rich shale. The interval extending upward from the interglacial MFS encompasses condensed, limestone/nodular section that may represent a significant portion of interglacial time. The fine to medium sand overlying the interglacial contains a record of declining sea levels, declining planktonic foraminiferal abundance, and increasing terrigenous sand content documenting a progradational high-stand system tract bounded above by a ravinement surface or type 1 (para) sequence boundary which is evident in X-radiographs.

  5. The MORENA Project: Shelf-ocean exchanges and transport processes along the continental margin in the European coastal upwelling region

    Energy Technology Data Exchange (ETDEWEB)

    Fiuza, A.F.G. [Univ. de Lisboa (Portugal). Inst. de Oceanografia; Perez, F. [Inst. Investigaciones Marinas, Vigo (Spain); Johnson, J. [Univ. East Anglia (United Kingdom)] [and others

    1994-12-31

    The MORENA Project (Multidisciplinary Oceanographic Research in the Eastern Boundary of the North Atlantic) is sponsored by the CEC MAST-2 Programme and has as general objective to measure, understand and model shelf-ocean exchange in a typical coastal upwelling region of the eastern boundary layer of the subtropical ocean. This is being attained through a multidisciplinary approach aimed at the quantitative understanding of the physical, chemical and biological processes involved in the transfer of matter (including salt, particulates, nutrients, organic compounds, biomass), momentum and energy across and along the shelf, the shelf break and the slope, in the Iberian region of the European Atlantic. MORENA has the following components: Observations, Modelling and Combined Analysis.

  6. Development and application of a new comprehensive image-based classification scheme for coastal and benthic environments along the southeast Florida continental shelf

    Science.gov (United States)

    Makowski, Christopher

    The coastal (terrestrial) and benthic environments along the southeast Florida continental shelf show a unique biophysical succession of marine features from a highly urbanized, developed coastal region in the north (i.e. northern Miami-Dade County) to a protective marine sanctuary in the southeast (i.e. Florida Keys National Marine Sanctuary). However, the establishment of a standard bio-geomorphological classification scheme for this area of coastal and benthic environments is lacking. The purpose of this study was to test the hypothesis and answer the research question of whether new parameters of integrating geomorphological components with dominant biological covers could be developed and applied across multiple remote sensing platforms for an innovative way to identify, interpret, and classify diverse coastal and benthic environments along the southeast Florida continental shelf. An ordered manageable hierarchical classification scheme was developed to incorporate the categories of Physiographic Realm, Morphodynamic Zone, Geoform, Landform, Dominant Surface Sediment, and Dominant Biological Cover. Six different remote sensing platforms (i.e. five multi-spectral satellite image sensors and one high-resolution aerial orthoimagery) were acquired, delineated according to the new classification scheme, and compared to determine optimal formats for classifying the study area. Cognitive digital classification at a nominal scale of 1:6000 proved to be more accurate than autoclassification programs and therefore used to differentiate coastal marine environments based on spectral reflectance characteristics, such as color, tone, saturation, pattern, and texture of the seafloor topology. In addition, attribute tables were created in conjugation with interpretations to quantify and compare the spatial relationships between classificatory units. IKONOS-2 satellite imagery was determined to be the optimal platform for applying the hierarchical classification scheme

  7. The western continental shelf of India: A hotspot of anaerobic biogeochemical transformations including production of nitrous oxide

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, H.; Naqvi, S.W.A

    - and it impinges upon a much larger area of the continental margin than do the ODZs of other oceans.? he major portion of the Arabian Sea ODZ lies beyond the continental shelves in the northeastern and central regions.? ertical profiles of N2O here contain two... maxima sandwiching a minimum, and since the upper N2O maximumis located barely a few tens of metres beneath the sea surface it sustains large efflux of N2O to the atmosphere.?n addition to the perennial open- ocean ODZ, reducing conditions also develop...

  8. A taxonomic guide to the brittle-stars (Echinodermata, Ophiuroidea) from the State of Paraíba continental shelf, Northeastern Brazil

    Science.gov (United States)

    Gondim, Anne I.; Alonso, Carmen; Dias, Thelma L. P.; Manso, Cynthia L. C.; Christoffersen, Martin L.

    2013-01-01

    Abstract We provide the first annotated checklist of ophiuroids from the continental shelf of the State of Paraíba, northeastern Brazil. Identification keys and taxonomic diagnoses for 23 species, belonging to 14 genera and 8 families, are provided. The material is deposited in the Invertebrate Collection Paulo Young, at the Federal University of Paraíba. Ophiopsila hartmeyeri represents the first record for the northeastern region of Brazil, while Ophiolepis impressa, Ophiolepis paucispina, Amphiura stimpsoni, Amphiodia riisei, Ophiactis quinqueradia, Ophiocoma wendtii and Ophionereis olivaceae are new records for the State of Paraíba. The number of species known for the state was increased from 16 to 23, representing approximately 17% of the species known for Brazil and 54% of the species known for northeastern Brazil. The recorded fauna has a large geographical and bathymetrical distribution. PMID:23794923

  9. Applicability of NASA contract quality management and failure mode effect analysis procedures to the USGS Outer Continental Shelf oil and gas lease management program

    Science.gov (United States)

    Dyer, M. K.; Little, D. G.; Hoard, E. G.; Taylor, A. C.; Campbell, R.

    1972-01-01

    An approach that might be used for determining the applicability of NASA management techniques to benefit almost any type of down-to-earth enterprise is presented. A study was made to determine the following: (1) the practicality of adopting NASA contractual quality management techniques to the U.S. Geological Survey Outer Continental Shelf lease management function; (2) the applicability of failure mode effects analysis to the drilling, production, and delivery systems in use offshore; (3) the impact on industrial offshore operations and onshore management operations required to apply recommended NASA techniques; and (4) the probable changes required in laws or regulations in order to implement recommendations. Several management activities that have been applied to space programs are identified, and their institution for improved management of offshore and onshore oil and gas operations is recommended.

  10. A taxonomic guide to the brittle-stars (Echinodermata, Ophiuroidea from the State of Paraíba continental shelf, Northeastern Brazil

    Directory of Open Access Journals (Sweden)

    Anne Gondim

    2013-06-01

    Full Text Available We provide the first annotated checklist of ophiuroids from the continental shelf of the State of Paraíba, northeastern Brazil. Identification keys and taxonomic diagnoses for 23 species, belonging to 14 genera and 8 families, are provided. The material is deposited in the Invertebrate Collection Paulo Young, at the Federal University of Paraíba. Ophiopsila hartmeyeri represents the first record for the northeastern region of Brazil, while Ophiolepis impressa, O. paucispina, Amphiura stimpsoni, Amphiodia riisei, Ophiactis quinqueradia, Ophiocoma wendtii and Ophionereis olivaceae are new records for the State of Paraíba. The number of species known for the state was increased from 16 to 23, representing approximately 17% of the species known for Brazil and 54% of the species known for northeastern Brazil. The recorded fauna has a large geographical and bathymetrical distribution.

  11. Sedimentary hydrocarbons and sterols in a South Atlantic estuarine/shallow continental shelf transitional environment under oil terminal and grain port influences.

    Science.gov (United States)

    Bet, Rafael; Bícego, Marcia C; Martins, César C

    2015-06-15

    Sterols and hydrocarbons were determined in the surface sediments from the transitional environment between Paranaguá Bay and the shallow continental shelf in the South Atlantic to assess the sources of organic matter (OM) and the contamination status of an area exposed to multiple anthropogenic inputs. Total aliphatic hydrocarbon concentrations were less than 10μgg(-1), which is typical of unpolluted sediments, and related to recent inputs from higher terrestrial plants. Total polycyclic aromatic hydrocarbon ranged from

  12. 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.

  13. 77 FR 47877 - Potential Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore Maine...

    Science.gov (United States)

    2012-08-10

    ... Bureau of Ocean Energy Management Potential Commercial Leasing for Wind Power on the Outer Continental... noncompetitive leasing processes are outlined in 30 CFR 585, subpart B. Determination of Competitive Interest and Leasing Process After the publication of this announcement, BOEM will evaluate indications of...

  14. 78 FR 760 - Potential Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore New...

    Science.gov (United States)

    2013-01-04

    ... Bureau of Ocean Energy Management Potential Commercial Leasing for Wind Power on the Outer Continental... Act (NEPA). BOEM's competitive and noncompetitive leasing processes are described in 30 CFR part 585, subpart B. Determination of Competitive Interest and Leasing Process After the publication of...

  15. Net sea-air CO2 fluxes and modelled pCO2 in the southwestern subtropical Atlantic continental shelf during spring 2010 and summer 2011

    Science.gov (United States)

    Ito, Rosane Gonçalves; Garcia, Carlos Alberto Eiras; Tavano, Virginia Maria

    2016-05-01

    Sea-air CO2 fluxes over continental shelves vary substantially in time on both seasonal and sub-seasonal scales, driven primarily by variations in surface pCO2 due to several oceanic mechanisms. Furthermore, coastal zones have not been appropriately considered in global estimates of sea-air CO2 fluxes, despite their importance to ecology and to productivity. In this work, we aimed to improve our understanding of the role played by shelf waters in controlling sea-air CO2 fluxes by investigating the southwestern Atlantic Ocean (21-35°S) region, where physical, chemical and biological measurements were made on board the Brazilian R. V. Cruzeiro do Sul during late spring 2010 and early summer 2011. Features such as discharge from the La Plata River, intrusions of tropical waters on the outer shelf due to meandering and flow instabilities of the Brazil Current, and coastal upwelling in the Santa Marta Grande Cape and São Tomé Cape were detected by both in situ measurements and ocean colour and thermal satellite imagery. Overall, shelf waters in the study area were a source of CO2 to the atmosphere, with an average of 1.2 mmol CO2 m-2 day-1 for the late spring and 11.2 mmol CO2 m-2 day-1 for the early summer cruises. The spatial variability in ocean pCO2 was associated with surface ocean properties (temperature, salinity and chlorophyll-a concentration) in both the slope and shelf waters. Empirical algorithms for predicting temperature-normalized surface ocean pCO2 as a function of surface ocean properties were shown to perform well in both shelf and slope waters, except (a) within cyclonic eddies produced by baroclinic instability of the Brazil Current as detected by satellite SST imagery and (b) in coastal upwelling regions. In these regions, surface ocean pCO2 values were higher as a result of upwelled CO2-enriched subsurface waters. Finally, a pCO2 algorithm based on both sea surface temperature and surface chlorophyll-a was developed that enabled the spatial

  16. Changes in C37 alkenones flux on the eastern continental shelf of the Bering Sea: the record of Emiliania huxleyi bloom over the past 100 years

    Science.gov (United States)

    Harada, N.; Sato, M.; Okazaki, Y.; Oguri, K.; Tadai, O.; Saito, S.; Konno, S.; Jordan, R. W.; Katsuki, K.; Shin, K.; Narita, H.

    2008-12-01

    Flourishes of coccolithophores can be detected by ocean color imagery with data from the satellite-borne Sea-viewing Wide Field-of-view sensor SeaWiFs that was launched in 1997. Thus, temporally and spatially large-scale blooms of Emiliania huxleyi (E. huxleyi) have been distinguished annually in the eastern continental shelf of the Bering Sea since 1997. In 1997, a combination of atmospheric mechanisms produced summer weather anomalies such as calm winds, clear skies, and warm air temperature over the Bering Sea and the weather anomalies caused depletion of the subpycnocline nutrient reservoir (Napp and Hunt, 2001). After depletion of nitrate and silicate, a sustained (more than 4-month-long) bloom of E. huxleyi was observed (Stockwell et al., 2001). Because of the speed and magnitude with which parts of the Bering Sea ecosystem responded to changes in atmospheric factors (Napp and Hunt, 2001) and because a bloom of the coccolithophorid, Coccolithus pelagicus has also been detected in the northeastern Atlantic Ocean off Iceland every year since 1997 (Ostermann, 2001), the appearance of an E. huxleyi bloom in the Bering Sea could be related to atmospherically forced decadal oscillations or global factors. We have investigated spatial expansion and temporal development of E. huxleyi bloom on the continental shelf in the Bering Sea by using a biomarker of E. huxleyi, C37 alkenones flux recorded in the sediments during the past 100 years. As a result, the E. huxleyi bloom had been prominent since 1970"fs at latest during the last 100 years. In this presentation, we will discuss the relationship between E. huxleyi bloom and activity of Aleutian low, and also changes in diatom assemblages. References Napp and Hunt, 2001, Fish Oceanogr., 10, 61-68. Ostermann, 2001, WHOI annual report, pp.17-18. Stockwell et al., 2001, Fish Oceanogr., 10, 99-116.

  17. The role of estuarine discharges on the biogeochemical characteristics of the nearby continental shelf ecosystem. The Guadalquivir-Gulf of Cadiz case study

    Science.gov (United States)

    Guerreiro, Catarina; Macías, Diego; Peliz, Alvaro; Prieto, Laura; Ruiz, Javier

    2013-04-01

    The hydrodynamics and biogeochemical conditions of the Gulf of Cadiz (SW Iberian peninsula) is strongly influenced by the input of fresh, warm and nutrient-rich water from the main estuary in the region, the Guadalquivir River. This sea-river interaction favors the generation of surface retention structures that encompasses highly productive waters throughout the year constituting and ideal place for fish spawning and nursery. The biological productivity of the Gulf and its high fisheries yields are, thus, heavily forced by the Guadalquivir River discharges which are conditioned by the freshwater inputs from the upstream sections of the river and by the tidal mixing dynamics in the lower reaches of the estuary. In this work we use a coupled hydrological-biogeochemical 3D model of the Gulf of Cadiz, Strait of Gibraltar and Alboran Sea (a regional application of the Regional Ocean Model System) connected to a virtual estuary representing the Guadalquivir River. With this coupled model we quantify the relative importance of each process (freshwater discharges and tidal mixing) for creating the special conditions of the nearby continental shelf. We found that freshwater input is only relevant during fall and winter when precipitation are important in the river catchment area. Tidal mixing, on the other hand, is more constant throughout the entire year and provides a nutrient input to the marine ecosystem of the same order of magnitude as the freshwater runoff. We also run the model with and without the river input and quantify, for the first time, the exact role of this external forcing on the biogeochemical conditions of the continental shelf ecosystem.

  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. Earthquake-related soft-sediment deformation structures in Palaeogene on the continental shelf of the East China Sea

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Earthquake,as disastrous events in geological history,can be recorded as soft-sediment deformation.In the Palaeogene of the East China Sea shelf,the soft-sediment deformation related to earthquake event is recognized as seismic micro-fractures,micro-corrugated laminations,liquefied veins,'vibrated liquefied layers',deformed cross laminations and convolute laminations,load structures,flame structures,brecciation,slump structures and seismodisconformity.There exists a lateral continuum,the wide spatial distribution and the local vertical continuous sequences of seismites including slump,liquefaction and brecciation.In the Palaeogene of East China Sea shelf,where typical soft-sediment deformation structures were developed,clastic deposits of tidal-flat,delta and river facies are the main background deposits of Middle-Upper Eocene Pinghu Formation and Oligocene Huagang Formation.This succession also records diagnostic marks of event deposits and basinal tectonic activities in the form of seismites.

  20. The carbon dioxide system on the Mississippi River-dominated continental shelf in the northern Gulf of Mexico: 1. Distribution and air-sea CO2 flux.

    Science.gov (United States)

    Huang, Wei-Jen; Cai, Wei-Jun; Wang, Yongchen; Lohrenz, Steven E; Murrell, Michael C

    2015-03-01

    River-dominated continental shelf environments are active sites of air-sea CO2 exchange. We conducted 13 cruises in the northern Gulf of Mexico, a region strongly influenced by fresh water and nutrients delivered from the Mississippi and Atchafalaya River system. The sea surface partial pressure of carbon dioxide (pCO2) was measured, and the air-sea CO2 flux was calculated. Results show that CO2 exchange exhibited a distinct seasonality: the study area was a net sink of atmospheric CO2 during spring and early summer, and it was neutral or a weak source of CO2 to the atmosphere during midsummer, fall, and winter. Along the salinity gradient, across the shelf, the sea surface shifted from a source of CO2 in low-salinity zones (0≤S<17) to a strong CO2 sink in the middle-to-high-salinity zones (17≤S<33), and finally was a near-neutral state in the high-salinity areas (33≤S<35) and in the open gulf (S≥35). High pCO2 values were only observed in narrow regions near freshwater sources, and the distribution of undersaturated pCO2 generally reflected the influence of freshwater inputs along the shelf. Systematic analyses of pCO2 variation demonstrated the importance of riverine nitrogen export; that is, riverine nitrogen-enhanced biological removal, along with mixing processes, dominated pCO2 variation along the salinity gradient. In addition, extreme or unusual weather events were observed to alter the alongshore pCO2 distribution and to affect regional air-sea CO2 flux estimates. Overall, the study region acted as a net CO2 sink of 0.96 ± 3.7 mol m(-2) yr(-1) (1.15 ± 4.4 Tg C yr(-1)).

  1. Impacts of Colonial Deforestation on Sediment Organic Carbon Fluxes and Budget Using Black Carbon Chronology: Waiapu Continental Shelf, New Zealand

    Science.gov (United States)

    Wadman, H. M.; Canuel, E. A.; Bauer, J. E.; McNinch, J. E.

    2009-12-01

    Small, mountainous rivers deliver a disproportionate amount of sediment and associated organic matter to coastal regions globally. The Waiapu River, North Island, New Zealand, is characterized by one of the highest sediment yields on earth, providing a model system for studying episodic delivery and preservation of sedimentary organic matter in an energetic, aggradational setting. Hyperpycnal plumes provide the primary mode of sediment delivery, depositing fine-grained sediment as flood layers on the inner shelf. Severe erosion following colonial-era (~1890-1920) slash and burn deforestation increased the sediment yield to the shelf 4- to 5-fold relative to previous levels. Colonial catchment-wide burning also produced black carbon (BC), which may be used to establish chronological control in the heterogeneous inner shelf sediments that are not easily dateable using traditional techniques. While recent work indicates that these inner shelf flood layers sequester ~16-34% of the total fine-grained sediment budget, comparable to the amount preserved on the mid-outer shelf, little is understood about the organic matter associated with these inner shelf sediments. High-resolution seismic reflection data were used to select four representative cores to characterize total sedimentary BC, total organic carbon (TOC) and total nitrogen (TN) sequestered in the inner shelf fine-grained sediments. Soot and graphitic BC (SGBC) was quantified using chemo-thermal oxidation (CTO-375), while coarse-grained BC (CGBC) was quantified using traditional point-counting methodologies. SGBC weight percentages ranged from ~0.01-0.07, and peaked at ~150cm depth in all four cores. This interval corresponds to peak abundance of CGBC as well. The ~150cm interval is interpreted to represent the height of colonial slash and burn deforestation, and is further supported by fining-upward sequences in all of the cores as well as by multiple 14C dates. Overall, SGBC represented an average of 29% (range

  2. The extent of ocean acidification on aragonite saturation state along the Washington-Oregon continental shelf margin in late summer 2012

    Science.gov (United States)

    Feely, R. A.; Alin, S. R.; Hales, B. R.; Juranek, L.; Greeley, D.

    2012-12-01

    The Washington-Oregon continental shelf region is exposed to conditions of low aragonite saturation state during the late spring/early summer upwelling season. However, the extent of its evolution in late summer/early fall has been largely unknown. Along this continental margin, ocean acidification, upwelling, biological productivity, and respiration processes in subsurface waters are major contributors to the variability in dissolved inorganic carbon (DIC), pH and aragonite saturation state. The persistence of water with aragonite saturation state Washington and Oregon has been previously identified and could have profound ecological consequences for benthic and pelagic calcifying organisms such as mussels, oysters, abalone, echinoderms, and pteropods. In the late summer of 2012 we studied the extent of acidification conditions employing shipboard cruises and profiling gliders. We conducted several large-scale chemical and hydrographic surveys of the region in order to better understand the interrelationships between these natural and human-induced processes and their effects on aragonite saturation. We will compare the results of these new surveys with our previous work in 2011 and 2007.

  3. Paleomagnetism of sedimentary cores from the Ross Sea outer shelf and continental slope (PNRA-ROSSLOPE II Project)

    Science.gov (United States)

    Macrì, Patrizia; Sagnotti, Leonardo; Caricchi, Chiara; Colizza, Ester

    2016-04-01

    We carried out a paleomagnetic and rock magnetic study of 4 gravity cores sampled in the Ross Sea continental slope of the area to the east of Pennell-Iselin banks. The cores (RS14-C1, C2, C3 and ANTA99-C20) consist of hemipelagic fine-grained (silty-clays) sediments with an IRD component. Rock magnetic and paleomagnetic measurements were carried out at 1-cm spacing on u-channel samples. The data indicate that the cored sediments carry a well-defined characteristic remanent magnetization (ChRM) and have a valuable potential to reconstruct dynamics and amplitude of the geomagnetic field variation at high southern latitudes (ca. 75°S) during the Holocene and the late Pleistocene. The paleomagnetic and rock magnetic data are integrated in a multidisciplinary context which includes previous geological, geophysical, oceanographic and morpho-bathimetric data obtained in the same area in the frame of the PNRA/ROSSLOPE (Past and present sedimentary dynamic in the ROSS Sea: a multidisciplinary approach to study the continental slope) Project. The main aim of the project is to investigate the relation between present and past water mass circulation and to provide a basis for paleoceanographic reconstructions and for the development of a depositional model of the modern processes active along the continental slope.

  4. 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.

  5. Submerged sand ridges on the western continental shelf off Bombay, India: Evidence for Late Pleistocene Holocene sea-level changes

    Digital Repository Service at National Institute of Oceanography (India)

    Wagle, B.G.; Veerayya, M.

    -lagoonal-like depressions. Some rounded/smooth ridges appear to be moribund while others have undergone reworking as indicated by superimposed bedforms/sand waves and reefs. Ridges also occurred on the inner shelf where they were either eroded during the Holocene.... broad&i places uneven 7 and shore-side steep; 2 either side lagoon with reefs. often shoreside steep with depressions on the crest; either side lagoon with 2-5 m reefs. e min: 75 min: 4 min: 2.8 Sym R/SR P P max: 85...

  6. Differential responses of seabirds to inter-annual environmental change in the continental shelf and oceanic habitats of southeastern Bering Sea

    Directory of Open Access Journals (Sweden)

    T. Yamamoto

    2015-11-01

    Full Text Available 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

  7. 北冰洋大陆架划界现状%THE DELIMITATION OF THE CONTINENTAL SHELF IN THE ARCTIC OCEAN

    Institute of Scientific and Technical Information of China (English)

    李学杰; 姚永坚; 李刚; 杨楚鹏; 吴峧歧; 张亚玲

    2014-01-01

    北冰洋面积约1300×104 km2,周边国家对200 M(海里)大陆架及专属经济区的划界现状及对200 M外大陆架的诉求,对于我们参与北极科考具有十分重要的参考意义。大陆架与专属经济区的划界,美国与苏联已签署协定,美国国会已批准,但前苏联和俄罗斯未批准,这直接导致两国的海域争议不断。俄罗斯与挪威也已签署协议。美国与加拿大之间未签署协议,争议区超过7000 M2。丹麦与加拿大已签署协议,完成划界,但存在汉斯岛的主权争议。挪威与丹麦及挪威与冰岛已完成划界。根据《联合国海洋法公约》第76条规定,北冰洋周边国家拥有确定北冰洋200 M外大陆架的权利。俄罗斯和挪威已提交200 M外大陆架划界方案,挪威对南森海盆西部的划界方案已得到大陆架界限委员会原则同意,但俄罗斯方案仍有很大的争议。作为《斯瓦尔巴条约》的签署国,斯瓦尔巴协定区,我们有权进入;因美国没有签署《联合国海洋法公约》,阿拉斯加北部大陆架及200 M外的楚科奇海台,都是我们进行科考的选择。此外,也可以通过国际合作,参与不同海域的科考和研究。%The Arctic Ocean covers an area of about 1 300 ×104 km2 .It is important that researchers involved in scientif-ic expeditions to the Arctic are aware of the delimitation of the continental shelf and the 200 nautical mile ( M) ex-clusive economic zone (EEZ).The United States and the former Soviet Union have signed a treaty on the delimita-tion of the continental shelf and the EEZ .The treaty has been ratified by the American Congress , but not by the former Soviet Union , which has led to an ongoing dispute over maritime ownership rights between the two countries . Norway and Russia have also signed a delimitation treaty .Maritime boundaries between Canada and the United States remain unresolved , with an area of more than 7

  8. 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

  9. 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 J.; Storlazzi, Curt D.; Cheriton, Olivia M.

    2016-06-01

    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 variability

  10. 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

  11. Is Submarine Groundwater Discharge a Gas Hydrate Formation Mechanism on the Circum-Arctic Shelf?

    Science.gov (United States)

    Frederick, J. M.; Buffett, B. A.

    2015-12-01

    Methane hydrate is an ice-like solid that can sequester large quantities of methane gas in marine sediments along most continental margins where thermodynamic conditions permit its formation. Along the circum-Arctic shelf, relict permafrost-associated methane hydrate deposits formed when non-glaciated portions of the shelf experienced subaerial exposure during ocean transgressions. Gas hydrate stability and the permeability of circum-Arctic shelf sediments to gas migration is closely linked with relict submarine permafrost. Heat flow observations on the Alaskan North Slope and Canadian Beaufort Shelf suggest the movement of groundwater offshore, but direct observations of groundwater flow do not exist. Submarine discharge, an offshore flow of fresh, terrestrial groundwater, can affect the temperature and salinity field in shelf sediments, and may be an important factor in submarine permafrost and gas hydrate evolution on the Arctic continental shelf. Submarine groundwater discharge may also enhance the transport of organic matter for methanogenesis within marine sediments. Because it is buoyancy-driven, the velocity field contains regions with a vertical (upward) component as groundwater flows offshore. This combination of factors makes submarine groundwater discharge a potential mechanism controlling permafrost-associated gas hydrate evolution on the Arctic continental shelf. In this study, we quantitatively investigate the feasibility of submarine groundwater discharge as a control on permafrost-associated gas hydrate formation on the Arctic continental shelf, using the Canadian Beaufort Shelf as an example. We have developed a shelf-scale, two-dimensional numerical model based on the finite volume method for two-phase flow of pore fluid and methane gas within Arctic shelf sediments. The model tracks the evolution of the pressure, temperature, salinity, methane gas, methane hydrate, and permafrost fields given imposed boundary conditions, with latent heat of

  12. Patterns and Dynamics of Rifting on Passive Continental Margin from Shelf to Slope of the Northern South China Sea:Evidence from 3D Analogue Modeling

    Institute of Scientific and Technical Information of China (English)

    Sun Zhen; Zhou Di; Wu Shimin; Zhong Zhihong; Myra Keep; Jiang Jianqun; Fan Hao

    2009-01-01

    Affected by thermal perturbation due to mantle uprising,the rheological structure of the lithosphere could be modified,which could lead to different rifting patterns from shelf to slope in a passive continental margin.From the observed deformation style on the northern South China Sea and analogue modeling experiments,we find that the rift zone located on the shelf is characterized by half grabens or simple grabens controlled mainly by long faults with large vertical offset,supposed to be formed with normal lithasphere extension.On the slope,where the lithosphere is very hot due to mantle upwelling and heating,composite grabens composed of symmetric grabens developed.The boundary and inner faults are all short with small vertical offset.Between the zones with very hot and normal lithosphere,composite half grnbens composed of half grabens or asymmetric grabens formed,whose boundary faults are long with large vertical offset,while the inner faults are relatively short.Along with the thickness decrease of the brittle upper crust due to high temperature,the deformation becomes more sensitive to the shape of a pre-existing weakness zone and shows orientation variation along strike.When there was a bend in the pre-existing weakness zone,and the basal plate was pulled by a clockwise rotating stress,the strongest deformation always occurs along the middle segment and at the transition area from the middle to the eastern segments,which contributes to a hotter lithosphere in the middle segment,where the Baiyun (白云) sag formed.

  13. Sedimentary record of postglacial variability in near-bottom currents, sediment supply and ice rafting on the continental shelf off SW Spitsbergen

    Science.gov (United States)

    Sternal, B.; Szczuciński, W.; Forwick, M.; ZajÄ czkowski, M.; Lorenc, S.; Vorren, T. O.

    2012-04-01

    The continental shelf off the west coast of southern Spitsbergen is influenced by the northward-flowing water masses (warmer and more saline Atlantic Water carried by the West Spitsbergen Current and colder, fresher Arctic Water carried by the East Spitsbergen Current), as well as ice rafting. The present study was conducted to identify the influence of these factors on the sedimentary environment and to decipher temporal variations in the intensity of bottom currents, ice rafting off and glacial activity on southwestern Spitsbergen during the past 14,000 years. The study is based on a multiproxy analyses of one gravity core from the outer continental shelf (148 m water depth) in decadal to centennial resolution. Age control was obtained on a basis of ten AMS 14C dates along with 210Pb and 137Cs datings. To infer the style of sedimentation and the sediment supply the core was measured for magnetic susceptibility, X-rayed, analysed for grain-size distribution of bulk sediment and for coarse sand fraction components. The assessment of ice rafting intensity was based on coarse sand fraction counting (IRD), whereas to assume the type of ice rafting, whether by icebergs or sea ice, the analysis of quartz grains roundness was performed. Moreover, relative velocity of bottom currents was estimated by grain-size analysis of sortable silt fraction. We distinguish seven intervals: c. 14,000 - 12,600 cal yr BP - Bølling/Allerød (unit 1); 12,600 - 11,500 cal yr BP - Younger Dryas (unit 2) and 11,500 cal yr BP to present - Holocene (units 3 - 7). The smallest mean sortable silt values, reflecting relatively low bottom current velocity, occurred from the Bølling/Allerød to the early Younger Dryas and after ~0.5 cal ka BP. Increased velocities were inferred for the early Holocene as well as period between 8.8 - 7.8 cal yr BP. The IRD was present throughout the entire record indicating continuous supply of a material delivered from ice rafting, with variable dominance of

  14. 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

  15. High-Resolution Chirp and Mini-Sparker Seismic-Reflection Data From the Southern California Continental Shelf - Gaviota to Mugu Canyon

    Science.gov (United States)

    Sliter, Ray W.; Triezenberg, Peter J.; Hart, Patrick E.; Draut, Amy E.; Normark, William R.; Conrad, James E.

    2008-01-01

    The U.S. Geological Survey (USGS) collected high-resolution shallow seismic-reflection data in September, 2007, and June-July, 2008, from the continental shelf offshore of southern California between Gaviota and Mugu Canyon, in support of the California's State Waters Mapping Program. Data were acquired using SIG 2mille mini-sparker and Edgetech chirp 512 instruments aboard the R/V Zephyr (Sept. 2007) and R/V Parke Snavely (June-July 2008). The survey area spanned approximately 120 km of coastline, and included shore-perpendicular transects spaced 1.0-1.5 km apart that extended offshore to at least the 3-mile limit of State waters, in water depths ranging from 10 m near shore to 300 m near the offshore extent of Mugu and Hueneme submarine canyons. Subbottom acoustic penetration spanned tens to several hundred meters, variable by location. This report includes maps of the surveyed transects, linked to Google Earth software, as well as digital data files showing images of each transect in SEG-Y, JPEG, and TIFF formats. The images of sediment deposits, tectonic structure, and natural-gas seeps collected during this study provide geologic information that is essential to coastal zone and resource management at Federal, State and local levels, as well as to future research on the sedimentary, tectonic, and climatic record of southern California.

  16. 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.

  17. Spatial distribution of metal accumulation areas on the continental shelf of the Basque Country (Bay of Biscay): A GIS-based approach

    Science.gov (United States)

    Legorburu, Irati; Galparsoro, Ibon; Larreta, Joana; Rodríguez, José Germán; Borja, Ángel

    2013-12-01

    Recent environmental legislation, worldwide, aims to restore and protect the quality of the marine environment. Within this context, in order to maintain the good functioning of marine ecosystems, sediment pollution monitoring is becoming increasingly important. Hence, for this contribution, the spatial distribution of Cd, Fe, Hg, Mn, Ni and Pb accumulation areas were determined, for the sediments of the Basque continental shelf. Statistically-assisted Geographical Information System (GIS)-mapping techniques were used, in order to infer the processes responsible for such accumulations. Differences in contaminant entrance pathways were observed between sectors. However, hydrodynamic conditions favored the rapid dispersal of contaminants and their stable distribution. The methodology used resulted in a suitable approach for identifying contaminant distribution patterns, which could be used in environmental assessment processes. Nevertheless, an important knowledge gap on the distribution of contaminants in offshore sediments was identified. Extensions of actual monitoring programs are suggested, in order to improve the information available for identifying the behavior and process-drivers for contaminants in offshore systems. This would permit the achievement of a more complete approach, to understand the effects of land-derived contaminants, on offshore systems.

  18. Depositional and erosional coastal processes during the late postglacial sea-level rise: An example from the central Tyrrhenian continental shelf (Italy)

    Energy Technology Data Exchange (ETDEWEB)

    Tortora, P. [Univ. degli Studi di Roma La Sapienza (Italy). Dept. di Scienze della Terra

    1996-03-01

    A transgressive systems tract (TST) deposit on the inner continental shelf of the south Tuscany region (central Tyrrhenian Sea, Italy) formed during the last postglacial sea-level rise. Its small-scale stratigraphy has been detailed using high-resolution seismic profiles, gravity cores, and grab samples. The TST deposit overlies a lowstand unconformity, shows a tabular geometry, and comprises three internal architectures of beach facies. Because the lateral distribution of these vertical successions is not random, but parallel to the coast, each architecture represents an individual sedimentary stage during sea-level rise. However, all architectures were formed via shoreface retreat in response to the landward migration of a beach complex over the unconformity. During this migration the beach system was characterized by a source diastem located in the surf zone and by two sediment dispersal systems. One moved the eroded sand over the flat back-barrier palustrine area by storm washover, while the other transported part of this sand to the lower shoreface, forming a reworked sand sheet above the older and inactive source diastem (ravinement surface). The TST architectures originated from a transgressive succession of beach facies, differentiated according to the intensity of shoreface retreat. Architecture A represents a low preservation potential of the original beach complex, Architecture B relatively high preservation, and Architecture C no preservation. The intensity of erosion and the consequent preservation potential were totally controlled by antecedent topography.

  19. Mercury status of the Amazon Continental Shelf: Guiana dolphins (Sotalia guianensis, Van Benédén 1864) as a bioindicator.

    Science.gov (United States)

    de Moura, Jailson Fulgencio; Emin-Lima, Renata; Hacon, Sandra S; Vega, Claudia Maribel; de Campos, Reinaldo Calixto; Siciliano, Salvatore

    2012-08-01

    Total mercury (Hg) was analyzed in muscle tissue of 27 accidentally captured Guiana dolphins (Sotalia guianensis) in order to evaluate Hg contamination levels present in the Amazon Continental Shelf, in Amapá state, North Brazil. The samples showed a mean concentration of 0.4 ± 0.16 μg/g wet weight (ww), ranging from 0.07 to 0.79 μg/g ww. As observed in several other cetacean species, Hg concentrations presented positive correlations to body length, related to the capacity to bioaccumulate this element throughout life. Hg concentrations were not significantly different between males (mean = 0.38 μg/g ww; n = 15) and females (mean = 0.42 μg/g ww; n = 12). Concentrations were low when compared to results of studies carried out with small cetaceans in the Northern Hemisphere, and with some previous studies in the south-eastern region of Brazil. In contrast with high Hg concentrations normally detected in river dolphin samples from Amazon River tributaries, our results suggest that the Amazon coast contains low levels of Hg in bioavailable form.

  20. 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.

  1. 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

  2. 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)

  3. The Roles of Advection and In Situ Growth in Determining the Dynamics of Continental Shelf Zooplankton: High Frequency Measurements of Zooplankton Biomass Coupled with Measurements of Secondary Productivity in the Middle Atlantic Bight

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Sharon L.

    1999-03-26

    Evaluation of the role of continental margins in planetary carbon cycles can be approached in various ways, with the extremes being knowledge generated either by large-scale studies of a few basic characteristics of the carbon cycle of shelves worldwide (comparative approach) or by temporally intensive studies of a few sites selected to typify contrasting processes. Mechanisms of cross-shelf transfer, for example, are presently of great interest and within the US there are at least four differing continental shelf environments in which cross-shelf processes are driven by storms (southern Bering Sea, northeastern US), by jets and eddies (northern California coast), by freshwater runoff (Bering Sea, Gulf of Mexico), and by frontal meanders and filaments of the Gulf Stream (southeastern US). Because the type and magnitude of the physical forcing, and its variability on an annual scale, are fundamental to the response of the carbon cycle, investigation of each of these shelves would offer insight useful to predictive global understanding of the carbon cycle on continental shelves.

  4. 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...

  5. Outer Continental Shelf Grids, This is an ESRI SDE feature class that depicts less than parcel size Landuse designations for use in maqpping the Rock County Township Land Use Development Plans., Published in 2006, Rock County Planning, Economic, and Community Development Agency.

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This Outer Continental Shelf Grids dataset as of 2006. It is described as 'This is an ESRI SDE feature class that depicts less than parcel size Landuse designations...

  6. 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...

  7. 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...

  8. 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

  9. Determining how the pelagic ecosystem over the continental shelf of the Bay of Biscay (NE Atlantic) functions: An approach using mesozooplankton enzyme activities as descriptors

    Science.gov (United States)

    Bergeron, Jean-Pierre; Delmas, Daniel; Koueta, Noussithé

    2009-04-01

    A fisheries research cruise conducted in 2000 offered a first opportunity to take simultaneous measurements of the activities of three enzymes in mesozooplankton samples collected at a regional scale over the continental shelf of the Bay of Biscay in the NE Atlantic, with the aim of characterizing main aspects of the functioning of the biotic environment of small pelagic fish populations. The activity of the digestive endopeptidase trypsin was selected to characterize the assimilation rate of proteins, whereas pyruvate kinase (PK) was chosen as an indicator of carbohydrate assimilation and aspartate transcarbamylase (ATC) provided an overall assessment of mesozooplankton productivity. The Bay of Biscay region is subject to various strong physical driving forces that directly affect the primary structure of the pelagic food web. On our cruise, the phytoplankton biomass distribution reflected these different physical influences: diatoms dominated the nutrient-enriched coastal water; picoplankton dominated the northern-central part where nutrients were depleted; and nanoplankton were abundant at the shelf break where internal waves provided an input of nutrients. These and other results (on bacteria, particulate organic carbon distribution, among others) illustrate the differences that exist in the microbial food webs of different sectors of the bay. The living matter produced was characterized by the quality and quantity of the smallest prey items that were available to higher trophic levels. Variations in mesozooplankton enzyme activities may agree well not only with classically expected results, but also present unexpected special features: high ATC specific activities were measured around the mouth of the Gironde, in the nutrient-rich desalted water of the plume, but surprisingly not in front of the Loire river. PK specific activities reflected preponderantly the balance between phytoplankton cells sizes and the related bacterial abundance resulting from nutrient

  10. Sediment movement and dispersal patterns on the Grand Banks continental shelf and slope were tied to the dynamics of the Laurentide ice-sheet margin

    Science.gov (United States)

    Rashid, H.; MacKillop, K.; Piper, D.; Vermooten, M.; Higgins, J.; Marche, B.; Langer, K.; Brockway, B.; Spicer, H. E.; Webb, M. D.; Fournier, E.

    2015-12-01

    The expansion and contraction of the late Pleistocene Laurentide ice-sheet (LIS) was the crucial determining factor for the geomorphic features and shelf and slope sediment mobility on the eastern Canadian continental margin, with abundant mass-transport deposits (MTDs) seaward of ice margins on the upper slope. Here, we report for the first time sediment failure and mass-transport deposits from the central Grand Banks slope in the Salar and Carson petroleum basins. High-resolution seismic profiles and multibeam bathymetry show numerous sediment failure scarps in 500-1600 m water depth. There is no evidence for an ice margin on the upper slope younger than MIS 6. Centimeter-scale X-ray fluorescence analysis (XRF), grain size, and oxygen isotope data from piston cores constrain sediment processes over the past 46 ka. Geotechnical measurements including Atterberg limit tests, vane shear measurements and triaxial and multi-stage isotropic consolidation tests allowed us to assess the instability on the continental margin. Cores with continuous undisturbed stratigraphy in contourite silty muds show normal downcore increase in bulk density and undrained peak shear strength. Heinrich (H) layers are identifiable by a marked increase in the bulk density, high Ca (ppm), increase in iceberg-rafted debris and lighter δ18O in the polar planktonic foram Neogloboquadrina pachyderma (sinistral): with a few C-14 dates they provide a robust chronology. There is no evidence for significant supply of sediment from the Grand Banks at the last-glacial maximum. Mass-transport deposits (MTD) are marked by variability in the bulk density, undrained shear strength and little variation in bulk density or Ca (ppm) values. The MTD are older than 46 ka on the central Grand Banks slope, whereas younger MTDs are present in southern Flemish Pass. Factor of safety calculations suggest the slope is statically stable up to gradients of 10°, but more intervals of silty mud may fail during earthquake

  11. 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

  12. The influence of surface low-salinity waters and cold subsurface water masses on picoplankton and ultraplankton distribution in the continental shelf off Rio de Janeiro, SE Brazil

    Science.gov (United States)

    Moser, G. A. O.; Castro, N. O.; Takanohashi, R. A.; Fernandes, A. M.; Pollery, R. C. G.; Tenenbaum, D. R.; Varela-Guerra, J.; Barrera-Alba, J. J.; Ciotti, A. M.

    2016-06-01

    The smallest phytoplankton groups named picoplankton and ultraplankton can be responsible for about 50-80% of the primary production rates in oligotrophic waters, due to their high surface/volume ratios that enables them for competitive growth rates relative to bigger cells under low light and low nutrient availability. The role of picoplankton and ultraplankton in coastal dynamic regions is less clear. This work relates the spatial distribution of autotrophic and heterotrophic components of these communities to the different properties of the water masses in the Southeastern Brazilian Continental Shelf, generally considered oligotrophic. Picoplankton and ultraplankton communities were related to nutrients present in the subsurface South Atlantic Central Water and waters with salinities below 35.5 originated from different estuarine systems. The enhance of autotrophs were also associated with a near shore feature related to topographic effects of São Sebastião Island to the local currents, first reported in this article. A core of higher chlorophyll a concentration, associated with the northeastward current flow at approximately 21 m depth below the surface, was identified as a dome-like shape. This core dissipated in the subsequent days suggesting that the flow towards NE was no longer a permanent feature two days after its observation. Locally enhancement of the contribution of picoplanktonic and ultraplanktonic autotrophs was observed in the surface and at the deep chlorophyll maximum depth associated with the chlorophyll core. Heterotrophs were more abundant inside and at the mouth of Guanabara Bay as well as inside Sepetiba Bay where light levels were low.

  13. 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.

  14. Over 100-year sedimentary record of polycyclic aromatic hydrocarbons (PAHs) and organochlorine compounds (OCs) in the continental shelf of the East China Sea.

    Science.gov (United States)

    Cai, Yizhi; Wang, Xinhong; Wu, Yuling; Li, Yongyu; Ya, Miaolei

    2016-12-01

    Historical records of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were analyzed in two dated sediment cores (DH05 and DH11) collected from the continental shelf of the East China Sea (ECS) to investigate the influence of anthropogenic activities on marine sediment over the past century. The concentrations and fluxes of 15 PAHs were in the range of 28.6-96.5 ng g(-1) and 7.6-35.2 ng cm(-2) yr(-1) in DH05 (1920s-2009), 18.8-76.4 ng g(-1) and 13.9-30.9 ng cm(-2) yr(-1) in DH11 (1860s-2009). The sedimentary records of PAHs in the two cores generally reflected the economic development and energy consumption change in China. Identification of sources suggested that PAHs in ECS were predominantly from petrogenic origin and various combustion sources. A change of source from low- and moderate-temperature combustion to high-temperature combustion process was observed. Although a production ban of technical HCH and DDT was imposed in China in 1983, their sedimentary fluxes display increasing trends or strong rebounds from 1980s to 1990s as recorded in the core profiles. High proportions of DDD + DDE and γ-HCH suggested those OCPs mainly derived from early residuals. Temporal trends of PCBs presented relative high levels from 1970s to 1980s and high proportions of PCB congeners with 3-6 chlorines atoms indicated industrial sources.

  15. 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).

  16. 76 FR 58273 - Agency Information Collection Activities; Proposed Collection; Comment Request; Outer Continental...

    Science.gov (United States)

    2011-09-20

    ... AGENCY Agency Information Collection Activities; Proposed Collection; Comment Request; Outer Continental... Collection Activities; Proposed Collection; Comment Request; Outer Continental Shelf Air Regulations; EPA ICR... all outer continental shelf (OCS) sources except those located in the Gulf of Mexico west of...

  17. Swell Across the Continental Shelf

    Science.gov (United States)

    2001-09-01

    linear wave theory, such as the heave, pitch, and roll of a floating platform (Longuet-Higgins, Cartwright & Smith, 1963; Long, 1980), or pressure p and...horizontal velocity components u and v. A ‘cloverleaf’ curvature buoy ( Cartwright & Smith, 1964), was designed to provide more Fourier components, but...wave ripples was first investigated in the laboratory by Darwin (1883) using a rotating bath. He noted the important role of the vortices generated in

  18. Distribuição de mercúrio total em sedimentos da plataforma continental Amazônica: Brasil Distribution of total mercury in sediments from Amazon continental shelf: Brazil

    Directory of Open Access Journals (Sweden)

    Gilmar W. Siqueira

    2012-06-01

    Full Text Available Este estudo foi desenvolvido na Plataforma Continental do Amazonas (PCA com o objetivo de determinar os níveis de Hg total no sedimento de fundo, e assim contribuir como matriz ambiental indicadora para o plano geral de gerenciamento costeiro na região norte do Brasil. Foram amostrados 20 pontos entre maio e junho dos anos de 1999 a 2002, 2005 e 2007. Os resultados indicam não haver evidências de atividades antrópicas relacionadas à contaminação de mercúrio na região. Os teores encontrados variaram entre 0,047 e 0,166 mg kg-1 com média 0,085±0,026 mg kg-1, estando dentro do intervalo de "background" referido para os rios amazônicos não contaminados, que é de 0,05 a 0,28 mg kg-1. As concentrações de Hg no sedimento, especialmente no sedimento lamoso, mostraram uma estreita dependência com os teores de argila (material fino e matéria orgânica, corroborando mecanismos geoquímicos importantes na dinâmica do metal. A maior adsorção do mercúrio pode estar associada ao aumento dos teores de compostos (óxidos e hidróxidos de ferro, alumínio, manganês e os minerais primários e secundários formadores das rochas da bacia de drenagem amazônica.This study was developed at the Amazon Continental Shelf aims to determine the levels of total mercury in the sediment bottom, and them to contribute as environmental matrix for the general plan of coastal monitoring in the North Region of the Brazil. Twenty sampling sites between May and June from 1999 to 2002, 2005 and 2007 were analyzed. The results indicate there is not evidence of anthropic activities associated to the contamination by mercury in the region. The levels of total mercury founded range between 0.047 and 0.166 mg kg-1 with average of 0.085±0,026 mg kg-1. The results are inside of the background interval determined to not contaminated or not polluted Amazon Rivers, which the interval ranges from 0.05 to 0.28 mg kg-1. The mercury concentrations in the sediment bottom

  19. 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

  20. Imaging continental shelf shallow stratigraphy by using different high-resolution seismic sources: an example from the Calabro-Tyrrhenian margin (Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Eleonora Martorelli

    2010-01-01

    Full Text Available High-resolution seismic reflection profiles of the Calabro-Tyrrhenian continental shelf were collected using different seismic sources (Sub-Bottom Profiler, Uniboom, Sparker 0.5-1-4.5 kJ. Noticeable differences and results were obtained both from a geophysical and geological-interpretative point of view. The availability of different sources permitted the definition of the most suitable seismostratigraphic characterization in terms of resolution, penetration and acoustic facies. Very high resolution stratigraphy was defined through profiles produced by different seismic systems used in parallel. This permitted the application of sequence-stratigraphy concepts with the reconstruction of a thick postglacial depositional sequence, formed by a transgressive and a high-stand systems tract. The thickness distribution of postglacial deposits reveals that the main depocenter (55-65 m is located offshore of the Coastal Range, along a stretch of coast supplied by several small and seasonal streams ("fiumare" and characterized by the lack of a coastal plain. This suggests the greater efficiency of sediment supply and bypass in this area relatively to sectors located offshore of the main rivers. The transgressive systems tract, usually thin or nearly absent, is particularly well developed (up to 33 m and is composed of up to three parasequences with a retrogradational stacking pattern. The high-stand systems tract, up to 30 m thick, is made up of two parasequences and has a quite regular geometry and acoustic facies.Perfis de reflexão sísmica de alta resolução da plataforma continental tirreniana de Calabro foram obtidos utilizando-se recursos sísmicos diversos (Perfilador de Sub-superfície, Uniboom, Sparker 0.5-1-4.5 kJ. Diferenças evidentes foram encontradas sob o ponto de vista geofísico e geológico-interpretativo. A disponibilidade de diferentes fontes permitiu a definição de uma caracterização sismo-estratigráfica mais acurada em termos

  1. 南极地区大陆架划界引发的法律制度碰撞%CONFLICTS OF LEGAL SYSTEMS INDUCED BY THE DELIMITATION OF THE CONTINENTAL SHELF IN THE ANTARCTIC REGION

    Institute of Scientific and Technical Information of China (English)

    朱瑛; 薛桂芳; 李金蓉

    2011-01-01

    自《南极条约》1961年生效以来,南极地区一直处于以《南极条约》为核心的南极条约体系的约束之下.1982年《联合国海洋法公约》(以下简称《公约》)建立了大陆架制度,要求沿海国应在批准《公约》生效10年内完成200海里以外大陆架外部界限的划定①.1994年《公约》生效后,澳大利亚、挪威、阿根廷和英国在提交各国200海里以外大陆架外部界限划界案时,先后对60°S以南地区的外大陆架提出主张要求.通过解读南极洲领土主张国提交的外大陆架划界案和有关大陆架外部界限的初步信息,跟踪研究大陆架界限委员会审议的有关南极地区的划界案案例,分析沿海国在南极地区的大陆架划界主张的法律依据,进而深入剖析南极条约体系和《公约》两种法律制度在南极地区的矛盾与冲突,并探讨南极地区法律制度的发展走向.%The Antarctic has been under the restriction of Antarctic Treaty System, which includes Antarctic Treaty as its core agreement and other related agreements, since Antarctic Treaty took effect in 1961. Nevertheless, the 1982 U-nited Nations Convention on the Law of Sea (UNCLOS, hereafter referred to as the Convention) established the legal regime for the continental shelf and requested a study into the coastal state of the shelf to complete the delineation of the outer limits of the shelf beyond 200 nautical miles within 10 years of the ratification of the convention. Since the Convention entered into force in 1994, Australia, Norway, Argentina and the United Kingdom have successively and individually claimed their sovereign rights over the continental shelves in the south of 60°S, namely the Antarctic region. With such background, the paper assesses the continental-shelf submissions and preliminary information provided by seven countries claiming territorial sovereignty or sovereign rights to the Antarctic region, and reviews the

  2. 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

  3. An Alaskan legend

    Science.gov (United States)

    Mann, H.; Blodgett, R.B.

    2009-01-01

    Jack Lee is a prominent personality, an Alaskan individualist and a skeptic worthy of remembrance if for no other reason than being inextricably associated with the catastrophic Katmai eruption in 1912. Jack remains a provocative reminder of Alaska's pre-1958 drilling and was quite possibly the earliest observer (excepting natives and possibly Russians) of the oil seeps in the area now encompassed by the Becharof National Wildlife Refuge. His observation of the impressive live oil seeps in the Ugashik and Becharof Lakes area, and his subsequent involvement in the early drilling entirely consumed his future interests. He is a firm believer that individualism and suspicion are powerful tools when forced to reconsider alternatives to readily accepted interpretations of modern exploration results. His individualism and sometimes annoying, but thought-provoking skepticism remains useful in any field where clich??s provide safe guards from new concepts.

  4. Sedimentology and chronology of the advance and retreat of the last British-Irish Ice Sheet on the continental shelf west of Ireland

    Science.gov (United States)

    Peters, Jared L.; Benetti, Sara; Dunlop, Paul; Ó Cofaigh, Colm; Moreton, Steven G.; Wheeler, Andrew J.; Clark, Christopher D.

    2016-05-01

    The last British-Irish Ice Sheet (BIIS) had extensive marine-terminating margins and was drained by multiple large ice streams and is thus a useful analogue for marine-based areas of modern ice sheets. However, despite recent advances from investigating the offshore record of the BIIS, the dynamic history of its marine margins, which would have been sensitive to external forcing(s), remain inadequately understood. This study is the first reconstruction of the retreat dynamics and chronology of the western, marine-terminating, margin of the last (Late Midlandian) BIIS. Analyses of shelf geomorphology and core sedimentology and chronology enable a reconstruction of the Late Midlandian history of the BIIS west of Ireland, from initial advance to final retreat onshore. Five AMS radiocarbon dates from marine cores constrain the timing of retreat and associated readvances during deglaciation. The BIIS advanced without streaming or surging, depositing a bed of highly consolidated subglacial traction till, and reached to within ˜20 km of the shelf break by ˜24,000 Cal BP. Ice margin retreat was likely preceded by thinning, grounding zone retreat and ice shelf formation on the outer shelf by ˜22,000 Cal BP. This ice shelf persisted for ≤2500 years, while retreating at a minimum rate of ˜24 m/yr and buttressing a >150-km long, 20-km wide, bathymetrically-controlled grounding zone. A large (˜150 km long), arcuate, flat-topped grounding-zone wedge, termed here the Galway Lobe Grounding-Zone Wedge (GLGZW), was deposited below this ice shelf and records a significant stillstand in BIIS retreat. Geomorphic relationships indicate that the BIIS experienced continued thinning during its retreat across the shelf, which led to increased topographic influence on its flow dynamics following ice shelf break up and grounding zone retreat past the GLGZW. At this stage of retreat the western BIIS was comprised of several discrete, asynchronous lobes that underwent several readvances

  5. Dynamics of the carbonate system in a large continental shelf system under the influence of both a river plume and coastal upwelling

    Science.gov (United States)

    Cao, Zhimian; Dai, Minhan; Zheng, Nan; Wang, Deli; Li, Qian; Zhai, Weidong; Meng, Feifei; Gan, Jianping

    2011-06-01

    We examined the dynamics of the carbonate system in a complex mixing scheme with enhanced biological consumption modulated by both a river plume and summer coastal upwelling in a large shelf system, the northern South China Sea (NSCS) shelf. The plume waters originated from a large flooding upstream the Pearl River, and extended from the mouth of the Pearl River estuary to the middle shelf and were characterized by low dissolved inorganic carbon (DIC) and total alkalinity (TAlk), and a high aragonite saturation state (Ωarag). In contrast, the upwelled water occupying the nearshore area was distinguished by high DIC and TAlk and a low Ωarag. While the dynamics of the carbonate system were largely shaped by physical mixing through plume and upwelling processes between the plume water, the offshore subsurface water and the offshore surface water, biological consumption of DIC was observable in both the river plume and the coastal upwelling areas and contributed to the elevated Ωarag during their pathway. Correlations between salinity normalized TAlk and DIC indicated that organic carbon production rather than biocalcification exclusively induced the DIC removal. By using a three end-member mixing model, we estimated the net community productivity in the plume water and the upwelled water to be 36 ± 19 mmol C m-2 d-1 and 23 ± 26 mmol C m-2 d-1, respectively. With the combination of stoichiometric relationship analysis of the carbonate system and applying the three end-member mixing model, we successfully differentiated semiquantitatively the biologically mediated DIC variations from its overall mixing control. We also attempted to link this natural process to the carbonate saturation on the NSCS shelf, contending that at present natural factors associated with the river plume and the coastal upwelling largely modulate the dynamics of the carbonate system on the NSCS shelf, whereas anthropogenic stressors such as ocean acidification currently play a relatively

  6. 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

  7. 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.

  8. Impact of the Deepwater Horizon Oil Spill on the Changes in the Seasonal Average Concentrations of Nickel, Vanadium, and Lead in Bottom Sediment Retrieved from the Outer Continental Shelf, Gulf of Mexico

    Science.gov (United States)

    Steffy, D. A.; Nichols, A.; Morgan, J.; Gibbs, R.

    2013-12-01

    Sediment samples were collected during the fall of 2010 and 2011from across the Gulf of Mexico outer continental shelf (OCS). A Tukey range test was used to compare samples between the relict sand deposits of the northern Gulf OCS to the relict carbonate sediments off of western Florida OCS. Tests indicate that nickel, vanadium, and lead are significantly higher (p < 0.05) in the seasonal average concentrations in the relict sand deposits closer to the Deepwater Horizon Well. These metals also significantly decreased (p < 0.05) from 2010 to 2011 in each region. These changes can be explained by the presence of a new source for these metals in the crude oil released from the Deepwater Horizon Oil Spill during the spring of 2010. Chromium and thallium did not vary seasonally or between the two areas of the OCS being investigated.

  9. 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

  10. 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. ?? 1990.

  11. 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...

  12. Seabed habitat mapping employing single and multi-beam backscatter data: A case study from the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Haris, K.; Chakraborty, B.; Ingole, B.S.; Menezes, A.A.A.; Srivastava, R.

    wet sieving. The size distribution (<62 µm) of the mud fraction was measured with a Malvern laser particle size analyzer (MASTERSIZER 2000). Since it was difficult to maintain uniform suspension of sandy material within the laser particle analyzer..., the size distribution of the sand fraction was determined using standard dry sieving method (Folk, 1968). The shelf sediments also frequently contain shelly material, which have to be sieved prior to measurement by laser diffraction. The mean grain size...

  13. Submarine slides and influencing factors in the continental shelf break area of the Pearl River Mouth Basin%珠江口盆地陆架坡折带海底滑坡及其影响因素

    Institute of Scientific and Technical Information of China (English)

    王磊; 吴时国; 李清平; 王大伟

    2016-01-01

    As oil and gas exploration have gradually advanced to the deep ocean,submarine slides have drawn increasing concern in the study of deep-water deposition processes. To understand the role of slope failures in shelf-break evolution, in this study, we combined geomorphological analysis and seismic interpretation based on newly acquired 2D/3D seismic data. Based on our results, we identified multiple Neogene submarine slides occurring in the continental shelf break area of the Pearl River Mouth Basin and delineated their distributions. This newly understood geological mode indicates that the combined action of relative sea-level change and fluid flow may trigger these slope failures, which were initiated and retrograded upwards from submarine canyon headward erosion, and terminated in the continental shelf break area.%为了解海底滑坡在陆架坡折演化过程中所起的作用并分析影响海底滑坡发育的因素,以最新采集的二维和三维地震资料为基础,综合运用了地貌分析和地震解释技术,通过对滑坡的地貌形态特征及地震响应特征进行详细刻画,在珠江口盆地陆架坡折带新近纪地层中识别出多处海底滑坡,明确了其分布范围并建立了滑坡发育的地质模式。分析认为,珠江口盆地相对海平面变化和流体活动的综合作用是导致研究区海底不稳定的主要因素。海底滑坡发源于海底峡谷的朔源侵蚀,向上陆坡扩展并终止于陆架坡折带。

  14. 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.

  15. 北极地区200海里外大陆架划界法律问题研究%ANALYSIS OF THE LEGAL ISSUES OF DELIMITING THE OUTER LIMITS OF THE ARCTIC CONTINENTAL SHELF BEYOND 200 NAUTICAL MILES

    Institute of Scientific and Technical Information of China (English)

    吴迪

    2011-01-01

    随着北极冰盖的融化,开采北极蕴藏丰富的石油、矿产资源越来越具有现实可行性,北极地区200海里外大陆架划界问题日益成为各国关注的热点.分析北极地区200海里外大陆架划界的国际法基础、主要法律问题以及学界对解决该问题的建议,认为200海里外大陆架划界不可能通过某一特定程序一次性解决,而是现有国际法框架内各国共同参与、区分不同阶段、依次解决多个问题的综合过程.北极地区200海里外大陆架问题不仅仅是地区事务,也同非北极国家切身利益息息相关.中国应当加强该问题的研究,以期作出积极、适当的反应.%As the Arctic ice cap is melting rapidly, it will be technically possible in the near future for Arctic coastal countries ( Russia, Denmark, Norway, Canada and the United States) to exploit the natural resources hidden in the Arctic region. The delimitation of the continental shelf in the Arctic will be a complicated procedure because of a number of factors; the geological structure of the Arctic continental shelf; the non-legally binding recommendation of the Commission on the limits of the Continental Shelf; the defects in the UNCLOS dispute settlement mechanism; and the fragile Arctic environment system. This article will focus largely on treaty law, legal issues, and a settlement model of the delimitation of the Arctic outer continental shelf. Arctic outer continental shelf issues are not only regional affairs, but are also closely related to China' s vital interests. To ensure China s sustainable and stable economic development, we should pay greater attention to legal rights regarding the natural resources of the sea. China is expected to influence the final settlement of the Arctic outer continental shelf via active and stable legal methods to safeguard its own legitimate interests.

  16. A facies distribution model controlled by a tectonically inherited sea bottom topography in the carbonate rimmed shelf of the Upper Tithonian-Valanginian Southern Tethyan continental margin (NW Sicily, Italy)

    Science.gov (United States)

    Basilone, Luca; Sulli, Attilio

    2016-08-01

    The Upper Tithonian-Valanginian shallow-water carbonates outcropping in the Palermo Mts (NW Sicily) consist of several facies associations reflecting different depositional environments of a carbonate rimmed shelf, pertaining to the Southern Tethyan continental margin. The reconstructed depositional model, based on the sedimentological features, cyclic facies arrangement and biota distribution, shows that a wide protected lagoon, dominated by algae, molluscs and scattered patch reefs, was bordered landward by a tidal flat, where stromatolitic algal mats were cyclically subaerial exposed, and seaward by a marine sand belt and reef complex. Oolitic packstone-grainstone lithofacies, cyclically subjected to subaerial exposure, suggests the occurrence of a barrier island, located nearly to the lagoonal carbonate shoreline, allowing the development of narrow embayments with restricted circulation. In the outer platform, the oolitic lithofacies of the marine sand belt pass landward into the protected lagoon, where washover oolite sands occur, and seaward into a high-energy zone (back-reef apron) gradually merging in the reef complex. In the latter, coral framestone occupied the inner sector (reef flat), while the facies association dominated by boundstone with Ellipsactinia sp. developed in the outer sectors (reef wall), adjacent to the fore-reef and upper slope environments. Stratigraphic evidence, associated with the recognized facies associations, helped to reconstruct the geo-tectonic setting of the carbonate platform, where the distribution of the depositional facies along the shelf and their extension were influenced by the tectonically-inherited sea bottom topography. In a regime of extensional tectonics, localized and thin succession of high-energy prograding oolite sand belt depositional facies occupied structural highs (footwall uplift), while the largely diffused and thick low energy aggrading peritidal-to-lagoonal depositional facies developed in subsiding

  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. RV Ocean Surveyor cruise O1-02-GM: bathymetry and acoustic backscatter of selected areas of the outer continental shelf, northwestern Gulf of Mexico; June 8, through June 28, 2002; Iberia, LA to Iberia, LA

    Science.gov (United States)

    Beaudoin, Jonathan D.; Gardner, James V.; Clarke, John E. Hughes

    2002-01-01

    Following the publication of high-resolution multibeam echosounder (MBES) images and data of the Flower Gardens area of the northwest Gulf of Mexico outer continental shelf (Gardner et al., 1998), the Flower Gardens Banks National Marine Sanctuary (FGBNMS) and the Minerals Management Service (MMS) have been interested in additional MBES data in the area. A coalition of FGBNMS, MMS, and the US Geological Survey (USGS) was formed to map additional areas of interest in the northwestern Gulf of Mexico in 2002. The areas were chosen by personnel of the FGBNMS and the choice of MBES was made by the USGS. MMS and FGBNMS funded the mapping and the USGS organized the ship and multibeam systems through a Cooperative Agreement between the USGS and the University of New Brunswick. The University of New Brunswick (UNB) contracted the RV Ocean Surveyor and the EM1000 MBES system from C&C Technologies, Inc., Lafayette, LA. C&C personnel oversaw data collection whereas UNB personnel conducted the cruise and processed all the data. USGS personnel were responsible for the overall cruise including the final data processing and digital map products.

  19. 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)

  20. 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.

  1. Abundance and distribution of Arctic cod (Boreogadus saida) and other pelagic fishes over the U.S. Continental Shelf of the Northern Bering and Chukchi Seas

    Science.gov (United States)

    De Robertis, Alex; Taylor, Kevin; Wilson, Christopher D.; Farley, Edward V.

    2017-01-01

    We conducted acoustic-trawl (AT) surveys of the northern Bering and Chukchi Seas during ice-free periods in 2012 and 2013. The mixed species assemblages in the study area required refinement of standard AT survey methods, and adjustment of trawl catches for the effects of trawl selectivity. Sensitivity analyses indicate that the AT abundance estimates are relatively robust to the assumptions of the analysis. These surveys indicate that midwater fishes are dominated by age-0 Arctic cod (Boreogadus saida), age-0 saffron cod (Eleginus gracilis), capelin (Mallotus villosus), and Pacific herring (Clupea pallasii). In both years, age-0 Arctic cod were distributed principally ≥69.5 °N, age-0 saffron cod were abundant in coastal areas between 66.5 and 69.5 °N, and Pacific herring were distributed south of 67 °N. These three fishes exhibited consistent associations with temperature, salinity and bottom depth: e.g., age-0 Arctic cod were abundant at lower mean water column temperatures than saffron cod. In contrast, capelin were distributed throughout the study area, and were not consistently associated with environmental measures. There was a geographic trend in body length, with smaller Arctic cod, saffron cod and capelin in northern areas, but smaller herring in the south. Arctic cod, saffron cod, herring and capelin were all >2 times more abundant in 2013 than 2012. Sizeable populations of age-0 Arctic cod were observed in the northern Chukchi Sea, which suggests that this area is an important nursery ground. However, relatively few older Arctic cod were observed in this and other surveys of the area, which suggests that either overwinter mortality of age-0 Arctic cod is high, and/or these fish are not retained on the Chukchi shelf.

  2. 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)

  3. 78 FR 33897 - Atlantic Wind Lease Sale 2 (ATLW2) Commercial Leasing for Wind Power on the Outer Continental...

    Science.gov (United States)

    2013-06-05

    ... for Wind Power on the Outer Continental Shelf Offshore Rhode Island and Massachusetts-- Final Sale...) Commercial Leasing for Wind Power on the Outer Continental Shelf Offshore Rhode Island and Massachusetts... for Commercial Leasing for Wind Power on the Outer Continental Shelf Offshore Rhode Island...

  4. 75 FR 16830 - Geological and Geophysical Exploration (G&G) on the Mid- and South Atlantic Outer Continental...

    Science.gov (United States)

    2010-04-02

    ... Outer Continental Shelf (OCS) AGENCY: Minerals Management Service, Interior. ACTION: Reopening of... Outer Continental Shelf Lands Act (OCSLA, as amended; 43 U.S.C. 1331-1356, (2007)) and its implementing... Leasing Oil and Natural Gas Resources: Outer Continental Shelf (see...

  5. 东海内陆架表层沉积物中黑碳的分布及来源%Distribution and Source of Black Carbon in the Surface Sediments of the Inner Continental Shelf of the East China Sea

    Institute of Scientific and Technical Information of China (English)

    黄亮; 张国森; 吴莹; 张经

    2012-01-01

    This paper studied the contents of black carbon(BC) in the surface sediments of the inner continental shelf of the East China Sea,focusing on the distribution,influence factors and source of BC in different areas.In addition,the BC contents were compared with those in suspended particulate matter(SPM) derived from Xuliujing in the Yangtze River estuary.The results showed that the average BC content in SPM of Xuliujing was 1.68±0.51 mg/g,and the content in the dry season was higher than that in the flood season,which is related with seasonal change of combustion.The distribution of BC in the surface sediments of the inner continental shelf of the East China Sea was characterized by regional difference.The BC contents in nearshore varied over a narrow range and were negatively related with size,and lower than those in SPM of Xuliujing,which showed that BC came from river input and was dominated by soot in this area,and partial small-sized BC was not completely deposited.The BC contents in the east of 123°E were extensively high and positively correlated with size,indicating that BC was dominated by graphitic black carbon.Moreover,the BC/TOC values range from 0.11 to 0.55 in the sediments,so we should not ignore the difference in distribution and species from one area to another,when investigating the carbon cycle in this area.%对东海内陆架表层沉积物中黑碳含量进行了分析,探讨了黑碳在东海内陆架不同区域的分布特征、影响因素及来源,并与长江口徐六径悬浮颗粒物中的黑碳进行了对比。结果显示,长江口徐六径悬浮颗粒物中黑碳的含量平均为1.68±0.51mg/g,且枯季浓度要高于洪季,这反映了燃烧活动的季节变化。黑碳在东海内陆架表层沉积物的分布具有明显的区域特征,近岸区域沉积物中的黑碳含量接近,且与粒径成负相关,并低于徐六径悬浮颗粒物中黑碳的含量,说明来自长江输入的黑碳主要以烟炱为主,并且

  6. Distribuição da fauna de peixes demersais e ecologia dos Sciaenidae da plataforma continental brasileira, entre as latitudes 29º21'S (Tôrres e 33º41'S (Chuí Distribution of demersal fish fauna and ecology of Sciaenidae on the Brazilian continental shelf from 29º21'S (Torres to 33º44'S (Chuí

    Directory of Open Access Journals (Sweden)

    Gelso Vazzoler

    1975-01-01

    Full Text Available This paper deals with a study on Brazilian south coast continental shelf demersal fish fauna distribution and Sciaenidae ecology, comprising the latitudes between Torres (29º21'S -49º44'W and Chuí (33º41'S - 53º27'W. The data on oceanographic as well as on ichthyological variables were obtained from six cruises planned to cover all seasons during the period from April 1968 to March 1969. The variation of the physical conditions of the bottom water layer is studied covering temperature, salinity, dissolved oxygen and type of bottom. The demersal fish families distribution is presented according to its frequencies of occurrence and its particular abundance. As Sciaenidae family shows to be the most important predominant group each species is studied in detail with reference to its distribution and relative abundance, as well as its spatial and temporal variations according to the abiotic environment. Relationship between Sciaenidae species is also discussed concerning feeding habits and the Cole coefficient of inter-specific association is estimated for pairs of species.

  7. Provenance of Holocene sediment on the Chukchi-Alaskan margin based on combined diffuse spectral reflectance and quantitative X-Ray Diffraction analysis

    Science.gov (United States)

    Ortiz, J.D.; Polyak, L.; Grebmeier, J.M.; Darby, D.; Eberl, D.D.; Naidu, S.; Nof, D.

    2009-01-01

    Sediment clay and silt mineral assemblages provide an excellent means of assessing the provenance of fine-grained Arctic sediment especially when a unique mineral assemblage can be tied to specific source areas. The diffuse spectral reflectance (DSR) first derivative measurements and quantitative X-Ray Diffraction (qXRD) on a high-resolution sediment core from the continental slope north of Alaska constrain the sediment mineralogy. DSR results are augmented by measurements on several adjacent cores and compared to surface sediment samples from the northern Alaskan shelf and slope. Using Principal Component Analysis (PCA), we infer that the three leading DSR modes relate to mixtures of smectite + dolomite, illite + goethite, and chlorite + muscovite. This interpretation is consistent with the down core qXRD results. While the smectite + dolomite, and illite + goethite factors show increased variability down core, the chlorite + muscovite factor had highest positive loadings in the middle Holocene, between ca. 6.0 and 3.6??ka. Because the most likely source of the chlorite + muscovite suite in this vicinity lies in the North Pacific, we argue that the oscillations in chlorite + muscovite values likely reflect an increase in the inflow of Pacific water to the Arctic through the Bering Strait. The time interval of this event is associated in other parts of the globe with a non-linear response of the climate system to the decrease in insolation, which may be related to changes in water exchange between the Pacific and Arctic Ocean. ?? 2009 Elsevier B.V.

  8. Value of Alaskan wetlands for waterfowl: Draft

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Few studies have focused specifically on use of Alaskan wetlands by waterfowl and only two of these have been published. However, substantial information on the...

  9. West Florida shelf upwelling: Origins and pathways

    Science.gov (United States)

    Weisberg, Robert H.; Zheng, Lianyuan; Liu, Yonggang

    2016-08-01

    Often described as oligotrophic, the west Florida continental shelf supports abundant fisheries, experiences blooms of the harmful alga, Karenia brevis, and exhibits subsurface chlorophyll maxima evident in shipboard and glider surveys. Renewal of inorganic nutrients by the upwelling of deeper ocean water onto the shelf may account for this, but what are the origins and pathways by which such new water may broach the shelf break and advance toward the shoreline? We address these questions via numerical model simulations of pseudo-Lagrangian, isopycnic water parcel trajectories. Focus is on 2010, when the west Florida shelf was subjected to an anomalously protracted period of upwelling caused by Gulf of Mexico Loop Current interactions with the shelf slope. Origins and pathways are determined by integrating trajectories over successive 45 day intervals, beginning from different locations along the shelf break and at various locations and depths along the shelf slope. Waters upwelling across the shelf break are found to originate from relatively shallow depths along the shelf slope. Even for the anomalous 2010 year, much of this upwelling occurs from about 150 m and above, although waters may broach the shelf break from 300 m depth, particularly in the Florida Panhandle. Such interannual renewal of west Florida shelf waters appears to have profound effects on west Florida shelf ecology.

  10. 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

  11. Acoustic Clutter in Continental Shelf Environments

    Science.gov (United States)

    2008-09-30

    submitted to Science. 2. S. Jagannathan, D. Symonds, I. Bertsatos, T. Chen, M. Andrews,Z. Gong, N. Donabed, H. T. Nia, A. Tan, L. Ngor, R. Nero , J.M...W. Nero , J. M. Jech, N.C. Makris and P. Ratilal, “Atlantic Herring Low Frequency Target Strength and Abundance Estimation:OAWRS 2006 Experiment in...the Array Invariant Technique,” to be submitted to J. Acoust. Soc. Am. 13. N.C. Makris, P.Ratilal, D. Symonds, S. Jagannathan, S. Lee and R.W. Nero

  12. Outer Continental Shelf Active Renewable Energy Leases

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — Active renewable energy leasing areas on the Atlantic OCS - currently Cape Wind offshore Cape Cod Massachusetts, Rhode Island / Massachusetts (RIMA), Delaware,...

  13. 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

  14. 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.

  15. Ice-shelf – ocean interactions at Fimbul Ice Shelf, Antarctica from oxygen isotope ratio measurements

    Directory of Open Access Journals (Sweden)

    K. W. Nicholls

    2008-03-01

    Full Text Available Melt water from the floating ice shelves at the margins of the southeastern Weddell Sea makes a significant contribution to the fresh water budget of the region. In February 2005 a multi-institution team conducted an oceanographic campaign at Fimbul Ice Shelf on the Greenwich Meridian as part of the Autosub Under Ice programme. This included a mission of the autonomous submarine Autosub 25 km into the cavity beneath Fimbul Ice Shelf, and a number of ship-based hydrographic sections on the continental shelf and adjacent to the ice shelf front. The measurements reveal two significant sources of glacial melt water at Fimbul Ice Shelf: the main cavity under the ice shelf and an ice tongue, Trolltunga, that protrudes from the main ice front and out over the continental slope into deep water. Glacial melt water is concentrated in a 200 m thick Ice Shelf Water (ISW layer below the base of the ice shelf at 150–200 m, with a maximum glacial melt concentration of up to 1.16%. Some glacial melt is found throughout the water column, and much of this is from sources other than Fimbul Ice Shelf. However, at least 0.2% of the water in the ISW layer cannot be accounted for by other processes and must have been contributed by the ice shelf. Just downstream of Fimbul Ice Shelf we observe locally created ISW mixing out across the continental slope. The ISW formed here is much less dense than that formed in the southwest Weddell Sea, and will ultimately contribute a freshening (and reduction in δ18O to the upper 100–150 m of the water column in the southeast Weddell Sea.

  16. Ice-shelf – ocean interactions at Fimbul Ice Shelf, Antarctica from oxygen isotope ratio measurements

    Directory of Open Access Journals (Sweden)

    K. W. Nicholls

    2007-09-01

    Full Text Available Melt water from the floating ice shelves at the margins of the southeastern Weddell Sea makes a significant contribution to the fresh water budget of the region. In February 2005 a multi-institution team conducted an oceanographic campaign at Fimbul Ice Shelf on the Greenwich Meridian as part of the Autosub Under Ice programme. This included a mission of the autonomous submarine Autosub 25 km into the cavity beneath Fimbul Ice Shelf, and a number of ship-based hydrographic sections on the continental shelf and adjacent to the ice shelf front. The measurements reveal two significant sources of glacial melt water at Fimbul Ice Shelf: the main cavity under the ice shelf and an ice tongue that protrudes from the main ice front and out over the continental slope into deep water. Glacial melt water is concentrated in a 200 m thick Ice Shelf Water (ISW layer below the base of the ice shelf at 150–200 m, with a maximum glacial melt concentration of up to 1.16%. Some glacial melt is found throughout the water column, and much of this is from sources other than Fimbul Ice Shelf. However, at least 0.2% of the water in the ISW layer cannot be accounted for by other processes and must have been contributed by the ice shelf. Just downstream of Fimbul Ice Shelf we observe locally created ISW mixing out across the continental slope. The ISW formed here is much less dense than that formed in the southwest Weddell Sea, and will ultimately contribute a freshening (and reduction in δ18O to the upper 100–150 m of the water column in the southeast Weddell Sea.

  17. 南海北部大陆架琼东南盆地西南部新近纪沟鞭藻类%NEOGENE DINOFLAGELLATES FROM THE SOUTHWESTERN QIONG DONGNAN BASIN IN THE NORTH CONTINENTAL SHELF OF THE SOUTH CHINA SEA

    Institute of Scientific and Technical Information of China (English)

    何承全; 祝幼华; 麦文

    2005-01-01

    首次报道的低纬度晚第三纪(新近纪)丰富多样的海相沟鞭藻类,产自南海北部大陆架琼东南盆地西南部的两钻孔(主要是Ya21-1-2井,少量为Ya21-1-1井),经鉴定达40余种.文中仅对其中的31种4亚种进行了照相和对15种2亚种和1新种 (Impletosphaeridium capillare sp. nov.)在我国进行了首次描述;在新近系建立2个沟鞭藻组合:即 Hystrichosphaeropsis obscura组合(下部)和Reticulatosphaera actinocoronata-Polysphaeridium zoharyi组合(上部),并讨论了它们的组合特征及其地质时代,认为其下部的组合时代为中新世,上部的组合时代为上新世.%Rich and varied dinoflagellate cysts dealt with in this paper are obtained from the Neogene subsurface sediments of two offshore wells (mainly from well Ya21-1-2 with a depth of 1827.77-4562.79m, but a few from well Ya21-1-1 with a depth of 2413.98-3703.87m) drilled in the southwestern Qiong Dongnan(or Southeast) Basin, the North Continental Shelf of the South China Sea. More than fourty species belonging to 20 genera of dinoflagellates, Granodiscus granulatus of acritarchs, Pterospermella spp. of chlorophytes, and microforaminifer linings have been identified from well Ya21-1-2, of which 31 species of dinoflagellates are only illustrated and described in this work, including one new species, Impletosphaeridium capillare sp. nov. Two dinoflagellate assemblages have been recognized from the Neogene sediments of well Ya21-1-2 which are as follows in ascending order. 1. Hystrichosphaeropsis obscura Assemblage (at a depth of 3727.65-4562.79m) is marked by the latest occurrences of several species including Cordosphaeridium cantharellus, Bosedinia granulata, Hystrichosphaeropsis obscura and by the presence of Edwardsiella sexispinosa, Selenopemphix crenata and Impletosphaeridium capillare sp. nov. In the assemblage Hystrichokolpoma rigaudiae, H. denticulatum, Lingulodinium machaerophorum, Operculodinium centrocarpum, Polysphaeridium

  18. Spatial distribution of bivalve mollusc assemblages in the upwelling ecosystem of the continental shelf of Cabo Frio, Rio de Janeiro, Brazil Distribuição espacial das associações de moluscos bivalves na plataforma continental do ecossistema da ressurgência de Cabo Frio, Rio de Janeiro, Brasil

    Directory of Open Access Journals (Sweden)

    Abilio Soares-Gomes

    2005-03-01

    Full Text Available Bivalve mollusks of the continental shelf of Cabo Frio upwelling ecosystem were sampled monthly from February 1986 to February 1987 along a 30 to 60 m depth gradient. Mactra petiti Orbigny, 1846, and Tellina gibber Ihering, 1907 were constant species in 30 m; Nucula puelcha Orbigny, 1846, Adrana patagonica Orbigny, 1846, T. petitiana, T. gibber, and Corbula patagonica Orbigny, 1846 in 45 m; and N. puelcha, T. gibber, C. patagonica, and C. caribaea in 60 m. The number of rare species was similar along the depth gradient, ranging from six to ten species. The number of common species was higher in 60 m than in 30 m. Some species showed a continuous distribution but changed the frequency and abundance along the bathymetric gradient. The mean density was higher in 45-60 m than in 30 m, ranging from 15.6 ind.m-2, in 30 m, to 68.1 ind.m-2, in 60 m. There was no seasonal change in density nor in the taxocene structure during the studied period. On the other hand, the bivalve assemblage was spatially structured along the depth gradient, showing consistent changes from 30 to 60 m depths. Diversity and richness also follow this distribution pattern.Os moluscos bivalves da plataforma continental do ecossistema da ressurgência do Cabo Frio foram amostrados mensalmente de fevereiro de 1986 a fevereiro de 1987, entre 30 a 60 m de profundidade. Mactra petiti e Tellina gibber Ihering, 1907 foram espécies constantes a 30 m; Nucula puelcha Orbigny, 1846, Adrana patagonica Orbigny, 1846, T. petitiana, T. gibber e Corbula patagonica Orbigny, 1846 a 45 m; e N. puelcha, T. gibber, C. patagonica e C. caribaea a 60 m. O número de espécies raras foi similar nas diferentes profundidades, variando entre seis a dez espécies. O número de espécies comuns foi maior a 60 m que a 30 m. Algumas espécies apresentaram distribuição contínua porém, com variação na freqüência e abundância ao longo do gradiente batimétrico. A densidde média foi maior a 45-60 m do que

  19. Long-term climate patterns in Alaskan surface temperature and precipitation and their biological consequences

    Science.gov (United States)

    Simpson, James J.; Hufford, Gary L.; Fleming, Michael D.; Berg, Jared S.; Ashton, J.B.

    2002-01-01

    Mean monthly climate maps of Alaskan surface temperature and precipitation produced by the parameter-elevation regression on independent slopes model (PRISM) were analyzed. Alaska is divided into interior and coastal zones with consistent but different climatic variability separated by a transition region; it has maximum interannual variability but low long-term mean variability. Pacific decadal oscillation (PDO)- and El Nin??o southern oscillation (ENSO)-type events influence Alaska surface temperatures weakly (1-2 ??C) statewide. PDO has a stronger influence than ENSO on precipitation but its influence is largely localized to coastal central Alaska. The strongest influence of Arctic oscillation (AO) occurs in northern and interior Alaskan precipitation. Four major ecosystems are defined. A major eco-transition zone occurs between the interior boreal forest and the coastal rainforest. Variability in insolation, surface temperature, precipitation, continentality, and seasonal changes in storm track direction explain the mapped ecosystems. Lack of westward expansion of the interior boreal forest into the western shrub tundra is influenced by the coastal marine boundary layer (enhanced cloud cover, reduced insolation, cooler surface and soil temperatures). In this context, the marine boundary layer acts in an analogous fashion to the orographic features which form the natural boundaries of other Alaskan ecosystems. Variability in precipitation may play a secondary role.

  20. Alaskan North Slope petroleum systems

    Science.gov (United States)

    Magoon, L.B.; Lillis, P.G.; Bird, K.J.; Lampe, C.; Peters, K.E.

    2003-01-01

    Six North Slope petroleum systems are identified, described, and mapped using oil-to-oil and oil-to-source rock correlations, pods of active source rock, and overburden rock packages. To map these systems, we assumed that: a) petroleum source rocks contain 3.2 wt. % organic carbon (TOC); b) immature oil-prone source rocks have hydrogen indices (HI) >300 (mg HC/gm TOC); c) the top and bottom of the petroleum (oil plus gas) window occur at vitrinite reflectance values of 0.6 and 1.0% Ro, respectively; and d) most hydrocarbons are expelled within the petroleum window. The six petroleum systems we have identified and mapped are: a) a southern system involving the Kuna-Lisburne source rock unit that was active during the Late Jurassic and Early Cretaceous; b) two western systems involving source rock in the Kingak-Blankenship, and GRZ-lower Torok source rock units that were active during the Albian; and c) three eastern systems involving the Shublik-Otuk, Hue Shale and Canning source rock units that were active during the Cenozoic. The GRZ-lower Torok in the west is correlative with the Hue Shale to the east. Four overburden rock packages controlled the time of expulsion and gross geometry of migration paths: a) a southern package of Early Cretaceous and older rocks structurally-thickened by early Brooks Range thrusting; b) a western package of Early Cretaceous rocks that filled the western part of the foreland basin; c) an eastern package of Late Cretaceous and Paleogene rocks that filled the eastern part of the foreland basin; and d) an offshore deltaic package of Neogene rocks deposited by the Colville, Canning, and Mackenzie rivers. This petroleum system poster is part of a series of Northern Alaska posters on modeling. The poster in this session by Saltus and Bird present gridded maps for the greater Northern Alaskan onshore and offshore that are used in the 3D modeling poster by Lampe and others. Posters on source rock units are by Keller and Bird as well as

  1. New Jersey shallow shelf

    DEFF Research Database (Denmark)

    Expedition 313 Scientists; Bjerrum, Christian J.

    2009-01-01

    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...... to sea level change. We drilled at three locations in 35 m of water 45–67 km offshore, targeting the topsets, foresets, and toesets of several clinoforms at 180–750 m core depth below seafloor (CSF-A). Seismic correlations to previously drilled holes on the continental slope and extrapolations of depths...... successions to as many as 16 surfaces and/or sequence-bounding unconformities mapped in the regional seismic grid. Eight lithologic units are recognized that contain important physical and biofacies indicators of paleobathymetry. Reliable zonations of multiple fossil groups, Sr isotopic ages measured...

  2. M sub(2) tidal currents on the shelf off Goa, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Shenoi, S.S.C.; Gouveia, A.D.; Shetye, S.R.

    the continental shelf and the adjacent slope has influenced the amplitude of internal tidal currents. The bottom slope switches from being supercritical to subcritical in the shelf break region during May and remains subcritical all over the shelf and the slope...

  3. 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.

  4. Seasonal variation of upwelling in the Alaskan Beaufort Sea: Impact of sea ice cover

    Science.gov (United States)

    Schulze, Lena M.; Pickart, Robert S.

    2012-06-01

    Data from a mooring array deployed from August 2002 to September 2004 are used to characterize differences in upwelling near the shelf break in the Alaskan Beaufort Sea due to varying sea ice conditions. The record is divided into three ice seasons: open water, partial ice, and full ice. The basic response is the same in each of the seasons. Roughly 8 h after the onset of easterly winds the shelf break jet reverses, followed approximately 10 h later by upwelling of saltier water which is cold near the shelf break (Pacific Winter Water) and warm at depth (Atlantic Water). The secondary circulation at the outer shelf is, to first order, consistent with a two-dimensional Ekman balance of offshore flow in the upper layer and onshore flow at depth. There are, however, important seasonal differences in the upwelling. Overall the response is strongest in the partial ice season and weakest in the full ice season. It is believed that these differences are dictated by the degree to which wind stress is transmitted through the pack-ice, as the strength of the wind-forcing was comparable over the three seasons. An EOF-based upwelling index is constructed using information about the primary flow, secondary flow, and hydrography. The ability to predict upwelling using the wind record alone is explored, which demonstrates that 90% of easterly wind events exceeding 9.5 m s-1 drive significant upwelling. During certain periods the ice cover on the shelf became landfast, which altered the upwelling and circulation patterns near the shelf break.

  5. Core descriptions, core photographs, physical property logs and surface textural data of sediment cores recovered from the continental shelf of the Monterey Bay National Marine Sanctuary during the research cruises M-1-95-MB, P-2-95-MB, and P-1-97-MB

    Science.gov (United States)

    Orzech, Kevin M.; Dahl, Wendy E.; Edwards, Brian D.

    2001-01-01

    In response to the 1992 creation of the Monterey Bay National Marine Sanctuary (MBNMS), the United States Geological Survey (USGS) initiated a multiyear investigation of the Sanctuary continental margin. As part of the investigative effort, this report summarizes the shipboard procedures, subsequent laboratory analyses, and data results from three seafloor sampling cruises conducted on the continental shelf between Monterey peninsula, CA and San Francisco, CA. The cruises were conducted in 1995 aboard the NOAA Ship McArthur (M-1-95-MB) and in 1995 and 1997 aboard the R/V Point Sur (P-2-95-MB and P-1-97-MB). Scientists and representatives from the Environmental Protection Agency (EPA), the National Oceanic and Atmospheric Administration (NOAA), the California Department of Fish and Game (CDFG), the University of California Santa Cruz (UCSC), and the San Jose State University Moss Landing Marine Laboratory (SJSU-MLML) supported the research effort. In this report we present sediment descriptions, sediment textural data, physical property logs, station metadata, and photographs of subcores from a total of three hundred and eighty four sample stations. At these sites either a box corer, MultiCore™r, grab sampler or a combination of these sampling devices were used to collect the sea floor sediments. The report is presented in an interactive web-based format with each mapped core station linked to the corresponding description and photo, and to a spreadsheet of surface texture and other sampling data.

  6. Alaskan Haida Stories of Language Growth and Regeneration

    Science.gov (United States)

    Breinig, Jeane

    2006-01-01

    In this article, the author talks about the decline of fluent Alaskan Haida speakers. She features her mother's story as an example of why the Haida language is "on the brink." English language fluency as a tool for Indigenous survival is common to Native peoples, as is the desire to see languages flourish again. Alaskan Haidas…

  7. Sufentanil citrate immobilization of Alaskan moose calves.

    Science.gov (United States)

    Kreeger, Terry J; Kellie, Kalin A

    2012-10-01

    Free-ranging Alaskan moose calves (Alces alces gigas) were immobilized with 0.12 mg/kg sufentanil (S; n=16), 0.12 mg/kg sufentanil plus 0.27 mg/kg xylazine (SX; n=11), or 0.007 mg/kg carfentanil plus 0.36 mg/kg xylazine (CX; n=13). Immobilants were antagonized with 1.2 mg/kg naltrexone (S) or 1.2 mg/kg naltrexone plus 2.4 mg/kg tolazoline (SX, CX). There were no differences in induction (P ≥ 0.29) or processing (P ≥ 0.44) times between groups. Moose given either S or SX had significantly shorter recovery times than moose given CX (P=0.001) and recovery times from S were shorter than from SX (P=0.02). Oxygen saturation values for all groups averaged 85 ± 8%, but were significantly higher (P=0.048) for CX (89 ± 7%) than for S (82 ± 8%). Based on these data, sufentanil at 0.1 mg/kg or sufentanil at 0.1 mg/kg plus xylazine at 0.25 mg/kg could provide effective remote immobilization for Alaskan moose calves and could be substituted for carfentanil or thiafentanil should the need arise.

  8. Shelf-sea ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Walsh, J J

    1980-01-01

    An analysis of the food chain dynamics of the Oregon, Alaskan, and New York shelves is made with respect to differences in physical forcing of these ecosystems. The world's shelves are 10% of the area of the ocean, yield 99% of the world's fish catch, and may be a major sink in the global CO/sub 2/ budget.

  9. Surface Wave Processes on the Shelf and Beach

    Science.gov (United States)

    2016-06-07

    surface wave information on the continental shelf and beach to estimate sea state, and to provide input for models of currents, sediment transport, radar...interactions in operational wave prediction models • determine the effects of wave nonlinearity and directional spreading on sea surface statistics...Surface Wave Processes On The Shelf And Beach Thomas H. C. Herbers Department of Oceanography, Code OC/He Naval Postgraduate School Monterey

  10. Carbon cycle uncertainty in the Alaskan Arctic

    Directory of Open Access Journals (Sweden)

    J. B. Fisher

    2014-02-01

    Full Text Available Climate change is leading to a disproportionately large warming in the high northern latitudes, but the magnitude and sign of the future carbon balance of the Arctic are highly uncertain. Using 40 terrestrial biosphere models for Alaska, we provide a baseline of terrestrial carbon cycle structural and parametric uncertainty, defined as the multi-model standard deviation (σ against the mean (x for each quantity. Mean annual uncertainty (σ/x was largest for net ecosystem exchange (NEE (−0.01± 0.19 kg C m−2 yr−1, then net primary production (NPP (0.14 ± 0.33 kg C m−2 yr−1, autotrophic respiration (Ra (0.09 ± 0.20 kg C m−2 yr−1, gross primary production (GPP (0.22 ± 0.50 kg C m−2 yr−1, ecosystem respiration (Re (0.23 ± 0.38 kg C m−2 yr−1, CH4 flux (2.52 ± 4.02 g CH4 m−2 yr−1, heterotrophic respiration (Rh (0.14 ± 0.20 kg C m−2 yr−1, and soil carbon (14.0± 9.2 kg C m−2. The spatial patterns in regional carbon stocks and fluxes varied widely with some models showing NEE for Alaska as a strong carbon sink, others as a strong carbon source, while still others as carbon neutral. Additionally, a feedback (i.e., sensitivity analysis was conducted of 20th century NEE to CO2 fertilization (β and climate (γ, which showed that uncertainty in γ was 2x larger than that of β, with neither indicating that the Alaskan Arctic is shifting towards a certain net carbon sink or source. Finally, AmeriFlux data are used at two sites in the Alaskan Arctic to evaluate the regional patterns; observed seasonal NEE was captured within multi-model uncertainty. This assessment of carbon cycle uncertainties may be used as a baseline for the improvement of experimental and modeling activities, as well as a reference for future trajectories in carbon cycling with climate change in the Alaskan Arctic.

  11. 南海西北部陆架区沿岸流和上升流对中华哲水蚤分布的影响%Effects of coastal current and upwelling on the distributions of Calanus sinicus on the northwest continental shelf of the South China Sea

    Institute of Scientific and Technical Information of China (English)

    尹健强; 黄良民; 李开枝; 练树民; 李超伦; 张建林

    2013-01-01

    Calanus sinicus is a planktonic copepod with wide geographical distribution on the continental shelf of the northwest Pacific It plays an important role in marine system. Four cruises were conducted from July 2006 to October 2007 in order to understand the seasonal and horizontal variations with the influences of monsoon, ocean cur-rent and temperature on its distributions on the northwest continental shelf of the South China Sea. The diel vertical migration (DVM) of C. sinicus was studied at one station located in the southeast of Hainan Island during summer. The results showed that the distribution of C. sinicus abundance varied seasonally and regionally. The mean of C. sinicus abundance was high with 23. 30±77. 78 ind. /m3 in spring, and decreased to 13. 74 + 45.10 ind. /m3 in summer. It disappeared in autumn and did not enter into the study area during the investigated period in winter. The surveyed area was divided into three sub-regions in order to further analyze the regional difference, including the east inshore waters of Leizhou Peninsula, the east inshore waters of Hainan Island and and the offshore waters from Leizhou Peninsula to Hainan Island. The average abundance of C. sinicus within the inshore waters of Leizhou Peninsula was reached to be 115. 63 (±145. 93) and 68. 12 (±84. 00) ind/m3 in spring and summer, respectively, which was higher than those of the inshore Hainan Island and the offshore from Leizhou Peninsula to Hainan Island. The behavior of C. sinicus DVM was not found in the upwelling area in summer. C. sinicus seemed to be mostly habited in the bottom layer in order to avoid the damage of high temperature in the surface layer. The study area is the seasonal distribution zone of C. sinicus. Our findings suggested that C. sinicus was transported from the East China Sea to the northwest continental shelf of South China Sea by the Guangdong Coastal Current, which was driven by the northeast monsoon in winter and spring. The presence of a

  12. Sediments on the Shelf off Southern New England (GARRISON66 shapefile)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The sediments and geomorphology of a portion of the northeastern continental shelf between Hudson Canyon and Georges Bank have been investigated. Wave-cut terraces...

  13. Phosphate geochemistry, mineralization processes, and Thioploca distribution in shelf sediments off central Chile

    DEFF Research Database (Denmark)

    Holmkvist, Lars; Arning, Esther T.; Küster-Heins, Kathrin

    2010-01-01

    mineralization, and occurrence of dense communities of the filamentous sulfur bacteria, Thioploca spp., on the continental shelf off central Chile during the austral summer when high phytoplankton productivity and anoxic bottom water prevailed. Freshly deposited phytodetritus stimulated extremely high sulfate...

  14. Development of Alaskan gas hydrate resources

    Energy Technology Data Exchange (ETDEWEB)

    Kamath, V.A.; Sharma, G.D.; Patil, S.L.

    1991-06-01

    The research undertaken in this project pertains to study of various techniques for production of natural gas from Alaskan gas hydrates such as, depressurization, injection of hot water, steam, brine, methanol and ethylene glycol solutions through experimental investigation of decomposition characteristics of hydrate cores. An experimental study has been conducted to measure the effective gas permeability changes as hydrates form in the sandpack and the results have been used to determine the reduction in the effective gas permeability of the sandpack as a function of hydrate saturation. A user friendly, interactive, menu-driven, numerical difference simulator has been developed to model the dissociation of natural gas hydrates in porous media with variable thermal properties. A numerical, finite element simulator has been developed to model the dissociation of hydrates during hot water injection process.

  15. No barrier to emergence of bathyal king crabs on the Antarctic shelf

    DEFF Research Database (Denmark)

    Aronson, Richard B.; Smith, Kathryn E.; Vos, Stephanie C.

    2015-01-01

    Significance For tens of millions of years, cold conditions have excluded shell-crushing fish and crustaceans from the continental shelf surrounding Antarctica. Rapid warming is now allowing predatory crustaceans to return. Our study of the continental slope off the western Antarctic Peninsula sh...... at 400–550 m. A cold-water barrier above 200 m could be breached within the next few decades. Emergence of king crabs on the shelf could have catastrophic consequences for the unique seafloor communities of Antarctica....

  16. Quaternary phosphorites from the continental margin off Chennai, southeast India: Analogs of ancient phosphate stromatolites

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.; Rao, K.M.; Raju, D.S.N.

    the continental supply and degradation of organic matter associated with benthic microbial communities. The phosphate stratiform stromatolites thus formed were subsequently reworked into a shelf-margin depression and resulted in the occurrence of condensed...

  17. Constraints on Methane Distribution from Acoustic Profiles of Shallow Sediments Across the Alaska Shelf

    Science.gov (United States)

    Wood, W. T.; Hart, P. E.; Greinert, J.; de Batist, M. A.; Rose, K.; Coffin, R. B.

    2009-12-01

    In September of 2009 the U. S. Naval Research Laboratory, U. S. Dept of Energy, and Royal Netherlands Institute for Sea Research conducted piston coring, acoustic profiling, and water sampling on the Alaskan Arctic shelf from the U. S. Coast Guard icebreaker Polar Sea, as part of the MITAS (Methane In The Arctic Shelf) project. The overall project objective is to determine the role of methane in arctic shelf processes by determining the source, distribution, and concentration of shallow (0-30m methane accumulations as well as active and potential methane seeps along selected transects across and along the Alaskan Beaufort Sea shelf. The specific objective of the acoustic program is to delineate gas (methane) by mapping bubble release into the water column (flare detection), and free gas indications as acoustic blanking and gas fronts in the sediment. The data consist of 3.5 kHz, 12 kHz profiles acquired using hull-mounted transducers on the Polar Sea, in conjunction with 3.5 kHz sub-bottom profiler and 180 kHz multi-beam data acquired from the Polar Sea's ASB (Arctic Service Boat). Acoustic profiles and images, as well as preliminary interpretations are discussed in the presentation.

  18. Western Ross Sea continental slope gravity currents

    Science.gov (United States)

    Gordon, Arnold L.; Orsi, Alejandro H.; Muench, Robin; Huber, Bruce A.; Zambianchi, Enrico; Visbeck, Martin

    2009-06-01

    Antarctic Bottom Water of the world ocean is derived from dense Shelf Water that is carried downslope by gravity currents at specific sites along the Antarctic margins. Data gathered by the AnSlope and CLIMA programs reveal the presence of energetic gravity currents that are formed over the western continental slope of the Ross Sea when High Salinity Shelf Water exits the shelf through Drygalski Trough. Joides Trough, immediately to the east, offers an additional escape route for less saline Shelf Water, while the Glomar Challenger Trough still farther east is a major pathway for export of the once supercooled low-salinity Ice Shelf Water that forms under the Ross Ice Shelf. The Drygalski Trough gravity currents increase in thickness from ˜100 to ˜400 m on proceeding downslope from ˜600 m (the shelf break) to 1200 m (upper slope) sea floor depth, while turning sharply to the west in response to the Coriolis force during their descent. The mean current pathway trends ˜35° downslope from isobaths. Benthic-layer current and thickness are correlated with the bottom water salinity, which exerts the primary control over the benthic-layer density. A 1-year time series of bottom-water current and hydrographic properties obtained on the slope near the 1000 m isobath indicates episodic pulses of Shelf Water export through Drygalski Trough. These cold (34.75) pulses correlate with strong downslope bottom flow. Extreme examples occurred during austral summer/fall 2003, comprising concentrated High Salinity Shelf Water (-1.9 °C; 34.79) and approaching 1.5 m s -1 at descent angles as large as ˜60° relative to the isobaths. Such events were most common during November-May, consistent with a northward shift in position of the dense Shelf Water during austral summer. The coldest, saltiest bottom water was measured from mid-April to mid-May 2003. The summer/fall export of High Salinity Shelf Water observed in 2004 was less than that seen in 2003. This difference, if real

  19. 墨西哥湾盆地陆棚区油气田数量与储量规模的分形分析%Fractals of Oil and Gas Field Reserve Distribution in Outer Continental Shelf (OCS), Gulf of Mexico Basin

    Institute of Scientific and Technical Information of China (English)

    鞠玮; 侯贵廷; 肖芳锋

    2011-01-01

    On the basis of dividing the size of proved oil and gas fields in the outer continental shelf (OCS) of Gulf of Mexico Basin, the authors applied the fractal theory to the study of the relationship between the number of oil and gas fields and their sizes, and discussed the meaning of fractal dimension D. The fractal dimension D is a reflection of the exploratory development level, the larger the fractal dimension D is, the more mature the exploration is. The fractal method is a good way to analyze the size-distribution of oil and gas fields, to decide the exploration degree and to predict the reserve distribution of oil and gas fields.%在对墨西哥湾盆地陆棚区已探明油气田储量规模划分的基础上,应用分形理论对油气田数量与储量规模之间的分形关系进行了研究,讨论了油气田储量规模分布的分数维值D的含义。油气田储量规模分布的分数维值D反映了油气田的勘探开发程度,勘探开发程度越高,分数维值D越大;勘探开发程度越低,分数维值D越小。利用分形方法可以较好地分析油气田储量规模与数量之间的关系,评判油气田勘探开发的程度。预测未来发现油气田的数量及其储量规模。

  20. Downslope flow across the Ross Sea shelf break (Antarctica)

    Science.gov (United States)

    Bergamasco, A.; Budillon, G.; Carniel, S.; Defendi, V.; Meloni, R.; Paschini, E.; Sclavo, M.; Spezie, G.

    2003-12-01

    The analysis of some high-resolution hydrological data sets acquired during the 1997, 1998, 2001 and 2003 austral summers across the Ross Sea continental shelf break are here presented. The main focus of these cruises carried out in the framework of the Italian National Antarctic Program was the investigation of the downslope flow of the dense waters originated inside the Ross Sea. Such dense waters, flow near the bottom and, reaching the continental shelf break, ventilate the deep ocean. Two Antarctic continental shelf mechanisms can originate dense and deep waters. The former mechanism involves the formation, along the Victoria Land coasts, of a dense and saline water mass, the High Salinity Shelf Water (HSSW). The HSSW formation is linked to the rejection of salt into the water column as sea ice freezes, especially during winter, in the polynya areas, where the ice is continuously pushed offshore by the strong katabatic winds. The latter one is responsible of the formation of a supercold water mass, the Ice Shelf Water (ISW). The salt supplied by the HSSW recirculated below the Ross Ice Shelf, the latent heat of melting and the heat sink provided by the Ross Ice Shelf give rise to plumes of ISW, characterized by temperatures below the sea-surface freezing point. The dense shelf waters migrate to the continental shelf-break, spill over the shelf edge and descend the continental slope as a shelf-break gravity current, subject to friction and possibly enhanced by topographic channelling. Friction, in particular, breaks the constraint of potential vorticity conservation, counteracting the geostrophic tendency for along slope flow. The density-driven downslope motion or cascading entrains ambient water, namely the lower layer of the CDW, reaches a depth where density is the same and spreads off-slope. In fact, the cascading event is inhibited by friction without entrainment. The downslope processes are important for the ocean and climate system because they play a

  1. Relação dos peixes coletados nos limites da plataforma continental e nas montanhas submarinas Vitória, Trindade e Martin Vaz, durante a campanha oceanográfica MD-55 Brasil List of fishes collected at the continental shelf limits Vitória, Trinidade and Martin Vaz seamounts during the MD-55 Brazil oceanographic campaign

    Directory of Open Access Journals (Sweden)

    José V. Andreata

    1995-09-01

    Full Text Available The result of an agreement between Universidade Santa Ursula, Rio de Janeiro and the Museum of Natural History of Paris, was the oceanographic campaign MD-55 Brasil which took place between May 6th and June 2nd of 1987, aboard the R/V "Marion Dufresne" of the Terres Australes et Antartique Françaises (TAAF. Samples were collected between latitudes 23º36'40"S and 18º49'S. Ichthyofauna sampled was relatively low, and comprised of just one family of Chondrichthyes (three species and 50 families of Osteichthyes (104 species. Zenion hololepsis (Goode & Bean, 1895 (Zeniodontidae is recorded for the first time from the western South Atlantic, as well as is extended the geographic limits for Myrophis frio Jordan & Davis. 1892 (Ophichthidae and Prionotus nudigula Ginshurg, 1950 (Triglidae. Even though relatively not very representative, the species collected from the seamount chain Vitoria/Trindade and Martin Vay suggest being identical to those which occur along the Brazilian continental platform.

  2. Gravity and structure of the continental margins of southwestern Mexico and northwestern Guatemala

    Science.gov (United States)

    Couch, Richard; Woodcock, Stephen

    1981-03-01

    Geophysical measurements over the eastern end of the Tehuantepec Ridge and adjacent continental margins of southern Mexico and northern Guatemala indicate that the ridge is a fracture zone and that it marks the boundary between two different subduction provinces. A positive free-air gravity anomaly which extends northwestward along the outer continental shelf of Guatemala curves abruptly landward in the Gulf of Tehuantepec. The positive shelf anomaly is on trend with the positive anomaly of the Nicoya Peninsula, Costa Rica, and suggests that rocks genetically related to Cretaceous rocks of the Nicoya Complex extend northwestward along the continental shelf to the Gulf of Tehuantepec. A crustal and subcrustal cross section of the continental margin of Guatemala, constrained by gravity, magnetic, and seismic refraction data, indicates that the rock strata causing the outer shelf gravity high dip landward, consistent with imbricate thrusting of the oceanic crust beneath and into the continental margin. A model crustal cross section of the continental margin of southern Mexico, north of the Tehuantepec Ridge, shows a markedly different margin structure with a relatively small amount of continental accretion and a continental crustal block extending to within approximately 25 km of the trench axis.

  3. Statistical Aspects of Ice Gouging on the Alaskan Shelf of the Beaufort Sea,

    Science.gov (United States)

    1983-09-01

    Another characteristic of’ tile d 0 data, whjich 0. t -, arid 0.2-rn s alues, %%ere decleted from the satir - might be anticipated fronm our earlier...Northi America, Sea O.C. Reed and .1.Sater , I ds. 1. Arlington, pp. 113-161. \\ irginia : A-rct ic Inlstilute of North A-merica, pp. Ko% acs, A. and l

  4. Ocean processes at the Antarctic continental slope.

    Science.gov (United States)

    Heywood, Karen J; Schmidtko, Sunke; Heuzé, Céline; Kaiser, Jan; Jickells, Timothy D; Queste, Bastien Y; Stevens, David P; Wadley, Martin; Thompson, Andrew F; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K; Smith, Walker

    2014-07-13

    The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean-atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An iron-cycling model embedded in an eddy-permitting ocean model reveals the importance of sedimentary iron in fertilizing parts of the Southern Ocean. Ocean gliders play a key role in improving our ability to observe and understand these small-scale processes at the continental shelf break. The Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project deployed three Seagliders for up to two months in early 2012 to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. The glider data resolve small-scale exchange processes across the shelf-break front (the Antarctic Slope Front) and the front's biogeochemical signature. GENTOO demonstrated the capability of ocean gliders to play a key role in a future multi-disciplinary Southern Ocean observing system.

  5. A continuous seismic section across the continental slope off Ireland

    NARCIS (Netherlands)

    Lagaay, R.A.; Collette, B.J.

    1967-01-01

    Continuous seismic reflection data show that there are no unconsolidated sediments on the outer part of the Irish continental shelf west of Donegal Bay and on the upper part of the slope. Both the “basement” and the sediment cover on the lower part of the slope are heavily intersected, presumably by

  6. Global multi-scale segmentation of continental and coastal waters from the watersheds to the continental margins

    Directory of Open Access Journals (Sweden)

    G. G. Laruelle

    2013-05-01

    Full Text Available Past characterizations of the land–ocean continuum were constructed either from a continental perspective through an analysis of watershed river basin properties (COSCATs: COastal Segmentation and related CATchments or from an oceanic perspective, through a regionalization of the proximal and distal continental margins (LMEs: large marine ecosystems. Here, we present a global-scale coastal segmentation, composed of three consistent levels, that includes the whole aquatic continuum with its riverine, estuarine and shelf sea components. Our work delineates comprehensive ensembles by harmonizing previous segmentations and typologies in order to retain the most important physical characteristics of both the land and shelf areas. The proposed multi-scale segmentation results in a distribution of global exorheic watersheds, estuaries and continental shelf seas among 45 major zones (MARCATS: MARgins and CATchments Segmentation and 149 sub-units (COSCATs. Geographic and hydrologic parameters such as the surface area, volume and freshwater residence time are calculated for each coastal unit as well as different hypsometric profiles. Our analysis provides detailed insights into the distributions of coastal and continental shelf areas and how they connect with incoming riverine fluxes. The segmentation is also used to re-evaluate the global estuarine CO2 flux at the air–water interface combining global and regional average emission rates derived from local studies.

  7. Global multi-scale segmentation of continental and coastal waters from the watersheds to the continental margins

    Directory of Open Access Journals (Sweden)

    G. G. Laruelle

    2012-10-01

    Full Text Available The complex coastline of the Earth is over 400 000 km long and about 40% of the world's population lives within 100 km of the sea. Past characterizations of the global coastline were constructed either from a continental perspective through an analysis of watershed river basin properties (COSCAT: Coastal Segmentation and related CATchments or from an oceanic perspective, through a regionalization of the proximal and distal continental margins (LME: Large Marine Ecosystems. Here, we present a global-scale coastal segmentation, composed of three consistent levels, that includes the whole aquatic continuum with its riverine, estuarine and shelf sea components. Our work delineates comprehensive ensembles which retain the most important physical characteristics of both the land and shelf areas. The proposed multi-scale segmentation results in a distribution of global exorheic watersheds, estuaries and continental shelf seas among 45 major zones (MARCATS: MARgins and CATchments Segmentation and 149 sub-units (COSCATS. Geographic and hydrologic parameters such as the surface area, volume and fresh water residence time are calculated for each coastal unit as well as different hypsometric profiles. Our analysis provides detailed insights into the distributions of coastal and continental shelf areas and how they connect with incoming riverine fluxes. These results can be used for regional analyses and combined with various typologies for upscaling and biogeochemical budgets. In addition, the three levels segmentation can be used for application in Earth System analysis.

  8. Global multi-scale segmentation of continental and coastal waters from the watersheds to the continental margins

    KAUST Repository

    Laruelle, G. G.

    2013-05-29

    Past characterizations of the land-ocean continuum were constructed either from a continental perspective through an analysis of watershed river basin properties (COSCATs: COastal Segmentation and related CATchments) or from an oceanic perspective, through a regionalization of the proximal and distal continental margins (LMEs: large marine ecosystems). Here, we present a global-scale coastal segmentation, composed of three consistent levels, that includes the whole aquatic continuum with its riverine, estuarine and shelf sea components. Our work delineates comprehensive ensembles by harmonizing previous segmentations and typologies in order to retain the most important physical characteristics of both the land and shelf areas. The proposed multi-scale segmentation results in a distribution of global exorheic watersheds, estuaries and continental shelf seas among 45 major zones (MARCATS: MARgins and CATchments Segmentation) and 149 sub-units (COSCATs). Geographic and hydrologic parameters such as the surface area, volume and freshwater residence time are calculated for each coastal unit as well as different hypsometric profiles. Our analysis provides detailed insights into the distributions of coastal and continental shelf areas and how they connect with incoming riverine fluxes. The segmentation is also used to re-evaluate the global estuarine CO2 flux at the air-water interface combining global and regional average emission rates derived from local studies. © 2013 Author(s).

  9. Global multi-scale segmentation of continental and coastal waters from the watersheds to the continental margins

    KAUST Repository

    Laruelle, G. G.

    2012-10-04

    Past characterizations of the land–ocean continuum were constructed either from a continental perspective through an analysis of watershed river basin properties (COSCATs: COastal Segmentation and related CATchments) or from an oceanic perspective, through a regionalization of the proximal and distal continental margins (LMEs: large marine ecosystems). Here, we present a global-scale coastal segmentation, composed of three consistent levels, that includes the whole aquatic continuum with its riverine, estuarine and shelf sea components. Our work delineates comprehensive ensembles by harmonizing previous segmentations and typologies in order to retain the most important physical characteristics of both the land and shelf areas. The proposed multi-scale segmentation results in a distribution of global exorheic watersheds, estuaries and continental shelf seas among 45 major zones (MARCATS: MARgins and CATchments Segmentation) and 149 sub-units (COSCATs). Geographic and hydrologic parameters such as the surface area, volume and freshwater residence time are calculated for each coastal unit as well as different hypsometric pro- files. Our analysis provides detailed insights into the distributions of coastal and continental shelf areas and how they connect with incoming riverine fluxes. The segmentation is also used to re-evaluate the global estuarine CO2 flux at the air–water interface combining global and regional average emission rates derived from local studies.

  10. Effects of the Oil Spill on Alaskan Education.

    Science.gov (United States)

    Oldaker, Lawrence Lee

    Oil-industry-produced revenues, help finance Alaskan state and local governmental services including education. Capital losses incurred by the Exxon Corporation and by commerical fisheries as a consequence of the Exxon Valdez oil spill caused an economic recession, the result being diminished financing for a number of governmental programs and…

  11. STARS (Secondary Training for Alaskan Rural Students): Mathematics. Draft Copy.

    Science.gov (United States)

    Griffin, Ned; Ostrom, Robert

    STARS (Secondary Training for Alaskan Rural Students) materials resulted from extensive rewriting of the Vocational Adult Secondary Training (VAST) materials produced by the British Columbia Department of Education, after those materials had been used with the 9th and 10th graders on Kodiak Island. Revision was done by teachers who had been using…

  12. Continental Divide Trail

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — This shapefile was created to show the proximity of the Continental Divide to the Continental Divide National Scenic Trail in New Mexico. This work was done as part...

  13. Large Centrophorus (Chondrichthyes, Squaliformes) of the Belgian Neogene continental shelf

    NARCIS (Netherlands)

    Schutter, de P.J.; Wijnker, E.

    2012-01-01

    A number of isolated teeth of gulper sharks (genus Centrophorus Müller & Henle, 1837) have been recovered from Neogene sands in the Antwerp area, marking the first occurrence of the genus Centrophorus in the fossil record of Belgium and the North Sea Basin. The precise stratigraphic origin of th

  14. Outer Continental Shelf Official Protraction Diagrams - Alaska Region NAD 83

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Official Protraction Diagram (OPD) outlines in ESRI shapefile format. At lower latitudes (0-48 degrees) OPDs are 1 degree in latitude by 2...

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

    Digital Repository Service at National Institute of Oceanography (India)

    Chakraborty, B.; Pathak, D.

    designed and interfaced with the 12kHz echosounder installed onboard ORV Sagar Kanya. The reflection coefficients including attenuation at the seawater/bottom interface are computed in the three different sediment areas based on the sediment mean grain size...

  16. Outer Continental Shelf Official Protraction Diagrams - Atlantic Region NAD 83

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Official Protraction Diagram (OPD) outlines in ESRI shapefile format. Atlantic Region OPDs are approximately 2 degrees wide by one degree...

  17. 26 CFR 1.638-1 - Continental Shelf areas.

    Science.gov (United States)

    2010-04-01

    ... resources) for the right to explore for or exploit natural resources does not constitute a tax. (c) Scope... the seabed or subsoil), fish or other animal or plant life. (e) Rights under international law. Nothing in this section shall prejudice or affect the freedoms of the high seas and other rights...

  18. Environmental conditions on the Norwegian continental shelf Barents sea

    Energy Technology Data Exchange (ETDEWEB)

    Bjerke, P.L.; Torsethaugen, K.

    1989-05-01

    Environmental data from the Barents Sea are presented. These data include data from measurements of waves, wind, current, water level and temperature, hindcast data for waves and wind and information on sea ice and icing. The data are synthesized for use in design and operational planning. An overview of the instrumentation used and rutine data analysis performed is given. Mathematical and statistical methods are used in the data analysis and presentation are discussed. 81 refs., 120 figs., 50 tabs. (Author).

  19. Outer Continental Shelf Lease Blocks - Atlantic Region NAD83

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains OCS block outlines in ArcGIS shape file format for the BOEM Atlantic Region. OCS blocks are used to define small geographic areas within an...

  20. Current measurements over the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

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

    100 m. The nature of flows are describEd. by means of visual display, linear regression and spectral analysis. The flows are a result of the superimposition of oscillations of wide-ranging frequencies over a weak mean flow. The mean flow was towards...