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Sample records for continental shelf final

  1. Outer Continental Shelf environmental assessment program. Final reports of principal investigators. Volume 33

    SciTech Connect

    Not Available

    1985-07-01

    This ccompilation of five final reports deals with the distribution and dynamics of heavy metals in Alaskan Shelf environments; characterization of organic matter in sediments; distribution of trace elements in bottom sediment of the Northern Bering Sea; aspects of size distributions, clay mineralogy, and geochemistry of sediments of the Beaufort Sea and adjacent deltas; and the natural distribution and dynamics of hydrocarbons on the Alaskan continental shelf.

  2. 77 FR 3771 - Notice of Issuance of Final Outer Continental Shelf Air Permit for Shell Offshore, Inc.

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-25

    ... From the Federal Register Online via the Government Publishing Office ENVIRONMENTAL PROTECTION AGENCY Notice of Issuance of Final Outer Continental Shelf Air Permit for Shell Offshore, Inc. AGENCY... on November 30, 2011, EPA issued a final Outer Continental Shelf (OCS) air permit for Shell...

  3. 76 FR 48861 - Notice of Issuance of Final Outer Continental Shelf Air Permit for Anadarko Petroleum Corporation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-09

    ... From the Federal Register Online via the Government Publishing Office ] ENVIRONMENTAL PROTECTION AGENCY Notice of Issuance of Final Outer Continental Shelf Air Permit for Anadarko Petroleum Corporation... announce that on June 15, 2011, EPA issued a final Outer Continental Shelf (OCS) air permit for...

  4. Assessment of the US Outer Continental Shelf Environmental Studies Program. 4. Lessons and opportunities. Final report

    SciTech Connect

    Not Available

    1993-01-01

    The report is the last report in a series of six reports prepared by the NRC Committee to Review the Outer Continental Shelf Environmental Studies Program. The committee's conclusions and recommendations in this final report are based on its analyses of published documents and those provided by MMS; on the briefings it has received; on its earlier reports; and on its own deliberations.

  5. Circulation and exchange processes over the continental shelf and slope. Final report

    SciTech Connect

    Csanady, G.T.

    1988-12-31

    The theme of the work during the past triennium has been the SEEP experiment, data interpretation and modeling related to the goals of the experiment, and was characterized by increasing cooperation with colleagues from other disciplines. The theoretical contributions dealt with shelf-slope interaction, the dynamics and climatology of currents over the continental slope, and the behavior of fate of organic particles. Observational papers discussed various exchange mechanisms at the shelf edge, with special attention to particle exchange, and the quiescence of currents over the mid continental slope which is presumably responsible for the accumulation of organic particles.

  6. 77 FR 41448 - Notice of Availability of the Proposed Final Five Year Outer Continental Shelf (OCS) Oil and Gas...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-13

    ... Bureau of Ocean Energy Management Notice of Availability of the Proposed Final Five Year Outer Continental Shelf (OCS) Oil and Gas Leasing Program for 2012-2017 AGENCY: Bureau of Ocean Energy Management... proposal in the required statutory preparation process for a new program to succeed the current...

  7. Outer continental shelf environmental-assessment program. Final reports of principal investigators. Volume 68

    SciTech Connect

    Not Available

    1990-08-01

    The contents of this study include the following: biological reconnaissance of Boulder Island Shoal in western Camden Bay, Beaufort Sea, Alaska; the Chukchi Sea continental shelf: benthos-environmental interactions; ecological assessment of sublittoral plant communities in the northern Gulf of Alaska; and ecology of unconsolidated beaches in Lower Cook Inlet.

  8. Outer Continental shelf environmental assessment program. Final reports of principal investigators. Volume 51

    SciTech Connect

    Not Available

    1986-12-01

    The following are repoted: research to determine the accumulation of organic constituents and heavy metals from petroleum-impacted sediments by marine detritivores of the Alaskan outer continental shelf; Suspended particulate matter distribution, transport, and physical characteristics in the north Aleutian Shelf and St. George Basin lease areas; The production and dispersion of dissolved methane in southeastern Bering Sea; Oil spill vulnerability, coastal morphology, and sedimentation of outer Kenai Peninsula and Montague Island; Circulation and water masses in the Gulf of Alaska; Coastal oceanography of the northeastern Gulf of Alaska.

  9. Outer Continental Shelf environmental assessment program. Final reports of principal investigators. Volume 38

    SciTech Connect

    Not Available

    1986-04-01

    This final report of a study of the environmental characterization of the North Aleutian Shelf nearshore region includes: characterization, processes, and vulnerability to development; and annotated bibliography and keyword index.

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

    SciTech Connect

    Not Available

    1991-01-01

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

  11. Outer Continental Shelf environmental assessment program. Final reports of principal investigators. Volume 54

    SciTech Connect

    Not Available

    1987-02-01

    Contents include: Distribution, abundance, community structure, and trophic relationships of the benthos of the northeastern Gulf of Alaska from Yakutat Bay to Cross Sound; Habitat requirements and expected distribution of Alaska coral; A survey for spawning forage fish on the east side of the Kodiak Archipelago by air and boat during spring and summer 1979; Seasonal composition and abundance of juvenile and adult marine finfish and crab species in the nearshore zone of Kodiak Island's eastside during April 1978 through March 1979; Ecology and behavior of southern hemisphere shearwaters (Genus Puffinus) when over the outer continental shelf of the Gulf of Alaska and Bering Sea during the Northern summer (1975-1976).

  12. Outer Continental Shelf environmental assessment program. Final reports of principal investigators. Volume 34

    SciTech Connect

    Not Available

    1985-08-01

    The report is a compilation of three final reports dealing with geologic processes and hazards of the Beaufort and Chukchi Sea Shelf and coastal regions: Beaufort and Chukchi, seacoast permafrost studies; and the environmental geology and geomorphology of the Barrier Island-lagoon system along the Beaufort Sea coastal plain from Prudhoe Bay to the Colville River. Fifteen oversized maps are included.

  13. Coordination: Southeast continental shelf studies

    SciTech Connect

    Menzel, D.W.

    1989-01-26

    The objective of this investigation is to obtain model descriptions of the flow modifications in the Southeast Atlantic continental shelf due to Gulf Stream fluctuations and topographic effects. 2 refs., 4 figs.

  14. Harpacticoida (crustacea: copepoda) from the California continental shelf. Final report, September 1990-October 1995

    SciTech Connect

    Montagna, P.A.; Burgess, R.; Fiers, F.

    1995-10-01

    Specimens of new Harpacticoida species were obtained during the California Outer Continental Shelf (OCS), Phase II, Monitoring Program (CAMP) between November 1986 and May 1989. The CAMP project was a multidisciplinary study to detect and evaluate the long-term biological impacts of continental shelf oil drilling and production. The study was centered around a proposed platform site named Julius, which was never put into service. Samples were collected in the Santa Maria Basin on a regional scale (10-20 km). Harpacticoids are the second most abundant meiofaunal taxa in the Santa Maria Basin. Harpacticoids have been intensively studied in the Atlantic OCS. However, Pacific studies are limited to collections made in shallow water. There are a great number of undescribed species in the CAMP samples taken from the Santa Maria Basin. The present study is rather limited in scope and only touches on some of the dominate species found. It contains full taxonomic descriptions of six species, a pictorial key of 18 dominant species, and drawings of 42 other unknown species.

  15. Outer Continental Shelf environmental assessment program. Final reports of principal investigators. Volume 46

    SciTech Connect

    Not Available

    1986-07-01

    Contents include: Source, composition, and flux of organic detritus in lower Cook Inlet; Lower Cook Inlet meroplankton; Seasonal population density distribution of copepods, euphausiids, amphipods, and other holoplankton on the Kodiak Shelf.

  16. Outer Continental Shelf environmental assessment program. Final reports of principal investigators. Volume 73

    SciTech Connect

    Not Available

    1991-05-01

    The volume contains information on the following: Subsea permafrost: probing, thermal regime, and data analyses, 1975-81 and a geographic based information management system for permafrost prediction in the Beaufort and Chukchi seas. Part I contains: Submarine permafrost on the Alaskan shelf and a geographic based information management system for permafrost prediction in the Beaufort and Chukchi seas. Part II contains: Submarine permafrost on the Arctic shelf of Eurasia and the development of the Arctic in the Pleistocene. Each paper is in reference to offshore drilling of oil and gas.

  17. Outer Continental Shelf environmental assessment program. Final reports of principal investigators. Volume 69

    SciTech Connect

    Not Available

    1990-09-01

    This article includes the following: trace contaminants in surface sediment of the northern Bering Sea: a statistical review; trace contaminants in the greater St. George Basin: a statistical review; mercury in Alaska marine surface sediments: a review of the regional data; and natural distribution and environmental background of trace heavy metals in Alaskan shelf and estuarine areas.

  18. Coordination: southeast continental shelf studies. Progress report

    SciTech Connect

    Menzel, D.W.

    1981-02-01

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

  19. Outer Continental Shelf Environmental Assessment Program. Final reports of principal investigators. Volume 67

    SciTech Connect

    Not Available

    1990-07-01

    The contents of this study include the following: distribution, abundance, and biology of blue king and Korean hair crabs around the Pribilof Islands; distribution, abundance, and diversity of the epifaunal benthic organisms in Alitak and Ugak bays, Kodiak Island, Alaska; distribution and abundance of some epibenthic invertebrates of the northeastern Gulf of Alaska with notes on the feeding biology of selected species; reproductive success in Dungeness crab (Cancer magister) during long-term exposures to oil-contaminated sediments; and distribution and abundance of decapod larvae of the Kodiak shelf.

  20. 26 CFR 1.638-1 - Continental Shelf areas.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 7 2012-04-01 2012-04-01 false Continental Shelf areas. 1.638-1 Section 1.638-1...) INCOME TAXES (CONTINUED) Continental Shelf Areas § 1.638-1 Continental Shelf areas. (a) General rule. For.... The terms Continental Shelf of the United States and Continental Shelf of a possession of the...

  1. 26 CFR 1.638-1 - Continental Shelf areas.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 7 2011-04-01 2009-04-01 true Continental Shelf areas. 1.638-1 Section 1.638-1...) INCOME TAXES (CONTINUED) Continental Shelf Areas § 1.638-1 Continental Shelf areas. (a) General rule. For.... The terms Continental Shelf of the United States and Continental Shelf of a possession of the...

  2. 26 CFR 1.638-1 - Continental Shelf areas.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 7 2013-04-01 2013-04-01 false Continental Shelf areas. 1.638-1 Section 1.638-1...) INCOME TAXES (CONTINUED) Continental Shelf Areas § 1.638-1 Continental Shelf areas. (a) General rule. For.... The terms Continental Shelf of the United States and Continental Shelf of a possession of the...

  3. 26 CFR 1.638-1 - Continental Shelf areas.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 7 2010-04-01 2010-04-01 true Continental Shelf areas. 1.638-1 Section 1.638-1...) INCOME TAXES (CONTINUED) Continental Shelf Areas § 1.638-1 Continental Shelf areas. (a) General rule. For.... The terms Continental Shelf of the United States and Continental Shelf of a possession of the...

  4. 26 CFR 1.638-1 - Continental Shelf areas.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 7 2014-04-01 2013-04-01 true Continental Shelf areas. 1.638-1 Section 1.638-1...) INCOME TAXES (CONTINUED) Continental Shelf Areas § 1.638-1 Continental Shelf areas. (a) General rule. For.... The terms Continental Shelf of the United States and Continental Shelf of a possession of the...

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

    SciTech Connect

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

    1991-09-01

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

  6. Outer Continental Shelf environmental-assessment program: final reports of principal investigators. Volume 25

    SciTech Connect

    Not Available

    1984-10-01

    This compilation of includes final reports on the following subjects: ice edge ecosystems, primary productivity, nutrient cycling and organic matter transfer; analysis of Harrison Bay zooplankton samples; Beaufort Sea plankton studies, winter-spring studies in Stefansson Sound and off Narwhal Island; foodweb and nutrient dynamics in nearshore Beaufort Sea waters.

  7. 75 FR 61512 - Outer Continental Shelf Official Protraction Diagrams

    Federal Register 2010, 2011, 2012, 2013, 2014

    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,...

  8. Outer Continental Shelf environmental assesment program. Final reports of principal investigators. volume 37

    SciTech Connect

    Not Available

    1986-03-01

    A compilation of seven final reports dealing with seal/sea lion and walrus surveys of the Navarin Basin; potential impacts of man-made noise on ringed seals; modern populations, migrations, demography, trophics, and historical status of the Pacific Walrus; distribution of marine mammals in the coastal zone of the eastern Chukchi Sea during summer and autumn; and early spring distribution, density and abundance of the Pacific Walrus in 1976.

  9. Environmental assessment of the Alaskan Continental Shelf. Final reports of principal investigators. Volume 11. Biological studies

    SciTech Connect

    Not Available

    1981-07-01

    This volume of final reports includes the following: Toxicity of Oil-Well Drilling Muds to Alaska Larval Shrimp and Crabs; Trophic Relationships Among Ice-Inhabiting Phocid Seals and Functionally Related Marine Mammals in the Chukchi Sea; Trophic Relationships Among Ice-Inhabiting Phocid Seals and Functionally Related Marine Mammals in the Bering Sea; Ecological Studies in the Bering Strait Region; and The Relationships of Marine Mammal Distributions, Densities and Activities to Sea Ice Conditions.

  10. Environmental assessment of the Alaskan continental shelf. Final reports of principal investigators. Volume 19

    SciTech Connect

    Not Available

    1983-12-01

    This is a compilation of 7 final reports on the following subjects: selected annotated references on marine mammals of Alaska, trophic relationships among ice-inhabiting phocid seals in the Chukchi Sea, biology of the harbor seal in the Gulf of Alaska, natural history and ecology of the bearded seal, measurements and localization of underwater sounds from the Prudhoe Bay region, March 1981; population, assessment, ecology, and trophic relationships of Steller sea lions in the Gulf of Alaska; harvest of Pacific walruses by the pelagic whaling industry 1848-1914.

  11. Shelf export of particulates/transport in continental margin waters. Final report

    SciTech Connect

    Pietrafesa, L.J.

    1995-07-01

    During the present funding period, research activities at NCSU have been directed towards: publishing the results of SEEP-I; publishing further results from NCSU`s South Atlantic Bight studies; designing and constructing four cages which house the 3 NCSU and 1 BNL RD-Acoustic Doppler Current Profilers used successfully in SEEP-II, calibrating all current meters, transmissometers, thermister chains and conductivity pressure and temperature sensors for SEEP-II phases 2 and 3; determining the temporal and spatial scales of physical processes observed during phase 1 of SEEP-II in preparation for finalizing the mooring positions and sampling intervals for SEEP-II; shipping all NCSU gear to the URI and ODU; and successful deployment of NCSU SEEP-II, phases 1 and 2 moorings.

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

    SciTech Connect

    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.

  13. 76 FR 2254 - Notice of Arrival on the Outer Continental Shelf

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-13

    ... Arrival (NOA) on the Outer Continental Shelf in the Federal Register (74 FR 29439). We received two sets... established on March 4, 1982, as part of a final rule entitled, Outer Continental Shelf Activities (47 FR 9366... SECURITY Coast Guard 33 CFR Part 146 RIN 1625-AB28 Notice of Arrival on the Outer Continental Shelf...

  14. 77 FR 57572 - Notice of Arrival on the Outer Continental Shelf

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-18

    ... of Arrival (NOA) on the Outer Continental Shelf (OCS) final rule [Docket No. USCG-2008-1088] (76 FR... SECURITY Coast Guard Notice of Arrival on the Outer Continental Shelf AGENCY: Coast Guard, DHS. ACTION... Continental Shelf (OCS). The Coast Guard NOA-OCS program currently requires NOA information for those...

  15. 76 FR 2919 - Outer Continental Shelf Official Protraction Diagram and Supplemental Official Outer Continental...

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  16. Freshwater peat on the continental shelf

    USGS Publications Warehouse

    Emery, K.O.; Wigley, R.L.; Bartlett, A.S.; Rubin, M.; Barghoorn, E.S.

    1967-01-01

    Freshwater peats from the continental shelf off northeastern United States contain the same general pollen sequence as peats from ponds that are above sea level and that are of comparable radiocarbon ages. These peats indicate that during glacial times of low sea level terrestrial vegetation covered the region that is now the continental shelf in an unbroken extension from the adjacent land areas to the north and west.

  17. Freshwater peat on the continental shelf.

    PubMed

    Emery, K O; Wigley, R L; Bartlett, A S; Rubin, M; Barghoorn, E S

    1967-12-01

    Freshwater peats from the continental shelf off northeastern United States contain the same general pollen sequence as peats from ponds that are above sea level and that are of comparable radiocarbon ages. These peats indicate that during glacial times of low sea level terrestrial vegetation covered the region that is now the continental shelf in an unbroken extension from the adjacent land areas to the north and west. PMID:17801856

  18. Circulation on the continental shelf between 87 deg W and 90 deg W with data appendix. Final report, volume 1

    SciTech Connect

    Eleuterius, C.K.; Criss, G.A.

    1994-08-01

    Knowledge of the circulation of waters over the continental shelf and slope between 87 deg W and 90 deg W longitude is essential for judicious management of the region`s living and mineral resources and related industrial activities. This region, an integral part of the Fertile Fisheries Crescent, has been in a state of on-going development by the oil and gas industry for over four decades. The increase in activities of all types on the shelf, e.g., offshore oil and gas, maritime commerce, and fisheries, with the inherent risks each imposes on the environment, underscores the need for better knowledge of the region`s hydrodynamics, biology, chemistry, and geology. Prior to planning and initiating any further physical oceanography studies which require taking additional measurements in this region, the authors believe it prudent to first extract whatever relevant information remains in existing data. This effort entailed the laborious recovery of oceanographic data at the Gulf Coast Research Laboratory, which was in a number of disparate forms and formats.

  19. 49 CFR 192.10 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Outer continental shelf pipelines. 192.10 Section... shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf (as defined in the Outer Continental Shelf Lands Act; 43 U.S.C. 1331) must identify on all their respective pipelines...

  20. 49 CFR 192.10 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Outer continental shelf pipelines. 192.10 Section... shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf (as defined in the Outer Continental Shelf Lands Act; 43 U.S.C. 1331) must identify on all their respective pipelines...

  1. 49 CFR 192.10 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Outer continental shelf pipelines. 192.10 Section... shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf (as defined in the Outer Continental Shelf Lands Act; 43 U.S.C. 1331) must identify on all their respective pipelines...

  2. 49 CFR 192.10 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false Outer continental shelf pipelines. 192.10 Section... shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf (as defined in the Outer Continental Shelf Lands Act; 43 U.S.C. 1331) must identify on all their respective pipelines...

  3. 49 CFR 192.10 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Outer continental shelf pipelines. 192.10 Section... shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf (as defined in the Outer Continental Shelf Lands Act; 43 U.S.C. 1331) must identify on all their respective pipelines...

  4. Coordination: southeast continental shelf studies. Progress report

    SciTech Connect

    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.

  5. Oil-spill risk analysis: Cook inlet outer continental shelf lease sale 149. Volume 1. The analysis. Final report

    SciTech Connect

    Johnson, W.R.; Marshall, C.F.; Anderson, C.M.; Lear, E.M.

    1994-08-01

    This report summarizes results of an oil-spill risk analysis (OSRA) conducted for the proposed lower Cook Inlet Outer Continental Shelf (OCS) Lease Sale 149. The objective of this analysis was to estimate relative oil-spill risks associated with oil and gas production from the leasing alternatives proposed for the lease sale. The Minerals Management Service (MMS) will consider the analysis in the environmental impact statement (EIS) prepared for the lease sale. The analysis for proposed OCS Lease Sale 149 was conducted in three parts corresponding to different aspects of the overall problem. The first part dealt with the probability of oil-spill occurrence. The second dealt with trajectories of oil spills from potential spill sites to various environmental resources or land segments. The third part combined the results of the first two parts to give estimates of the overall oil-spill risk if there is oil production as a result of the lease sale. To aid the analysis, conditional risk contour maps of seasonal conditional probabilities of spill contact were generated for each environmental resource or land segment in the study area (see vol. 2).

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

    SciTech Connect

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

    1992-02-01

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

  7. Coordination: Southeast Continental Shelf studies. Progress report

    SciTech Connect

    Menzel, D.W.

    1981-02-01

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

  8. Elephant teeth from the atlantic continental shelf

    USGS Publications Warehouse

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

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-16

    ... PIONEER at Walker Ridge 249, Outer Continental Shelf FPSO, Gulf of Mexico in the Federal Register (74 FR... Continental Shelf FPSO, Gulf of Mexico AGENCY: Coast Guard, DHS. ACTION: Final rule. SUMMARY: The Coast Guard... (FPSO) system, at Walker Ridge 249 in the Outer Continental Shelf. The purpose of the safety zone is...

  10. 77 FR 5529 - Commercial Lease of Submerged Lands for Renewable Energy Development on the Outer Continental Shelf

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  11. 49 CFR 195.9 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 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

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-08

    ... Minerals Management Service Outer Continental Shelf Civil Penalties AGENCY: Minerals Management Service.... SUMMARY: The Outer Continental Shelf Lands Act requires the MMS to review the maximum daily civil penalty assessment for violations of regulations governing oil and gas operations in the Outer Continental Shelf...

  13. 49 CFR 195.9 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 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...

  14. 49 CFR 195.9 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 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...

  15. 49 CFR 195.9 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 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...

  16. 49 CFR 195.9 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2010 CFR

    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...

  17. Modeling the dynamics of continental shelf carbon.

    PubMed

    Hofmann, Eileen E; Cahill, Bronwyn; Fennel, Katja; Friedrichs, Marjorie A M; Hyde, Kimberly; Lee, Cindy; Mannino, Antonio; Najjar, Raymond G; O'Reilly, John E; Wilkin, John; Xue, Jianhong

    2011-01-01

    Continental margin systems are important contributors to global nutrient and carbon budgets. Effort is needed to quantify this contribution and how it will be modified under changing patterns of climate and land use. Coupled models will be used to provide projections of future states of continental margin systems. Thus, it is appropriate to consider the limitations that impede the development of realistic models. Here, we provide an overview of the current state of modeling carbon cycling on continental margins as well as the processes and issues that provide the next challenges to such models. Our overview is done within the context of a coupled circulation-biogeochemical model developed for the northeastern North American continental shelf region. Particular choices of forcing and initial fields and process parameterizations are used to illustrate the consequences for simulated distributions, as revealed by comparisons to observations using quantitative statistical metrics. PMID:21329200

  18. Transport and transfer rates in the waters of the continental shelf and slope: SEEP. Final report, May 1, 1987--December 31, 1993

    SciTech Connect

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

    1993-12-31

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

  19. Iceberg scouring on the Norwegian continental shelf

    SciTech Connect

    Lien, R.

    1983-05-01

    This paper is a condensed version of parts of a Dr. ing. thesis to be presented during 1983. The first part of the paper deals with the regional distribution of iceberg scouring on the Norwegian continental shelf, and some general aspects related to it. The second part deals with iceberg scouring as a local phenomenon and its relation to the sea floor topography, sediment distribution, and geological and geotechnical properties of the sediments.

  20. 76 FR 1389 - Outer Continental Shelf Air Regulations Consistency Update for California

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-10

    ... 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... FR 63774), and the preamble to the final rule promulgated September 4, 1992 (57 FR 40792) for...

  1. 76 FR 7518 - Outer Continental Shelf Air Regulations Consistency Update for Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    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... 5, 1991 (56 FR 63774), and the preamble to the final rule promulgated September 4, 1992 (57 FR...

  2. 75 FR 9780 - Technical Amendment to the Outer Continental Shelf Air Regulations Consistency Update; Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-04

    ... AGENCY 40 CFR Part 55 Technical Amendment to the Outer Continental Shelf Air Regulations Consistency... Outer Continental Shelf Air Regulations for Alaska. DATES: Effective on March 22, 2010. FOR FURTHER... Information This Notice is to provide a technical correction to the final regulation published at 75 FR...

  3. 75 FR 3392 - Outer Continental Shelf Air Regulations Consistency Update for Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    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... FR 63774), and the preamble to the final rule promulgated September 4, 1992 (57 FR 40792) for...

  4. Circulation and exchange at the continental shelf and slope SEEP-2. Final report, May 1, 1989--December 31, 1991

    SciTech Connect

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

    1991-12-31

    This project was a component of the SEEP-II program. It contributed to the instrumentation of the SEEP-II moored array to the processing and analysis of the time-series data of water temperature and currents, and to a theoretical modeling study of the circulation on the continental margin. We are responsible for nearly half of the current meters and thermistor chains that were deployed in the SEEP-II moored array on the continental margin off the Delmarva peninsula. Data tapes derived from three deployments of the instruments in this array were processed. A second component of this project was a theoretical study of the interaction of the Gulf Stream with the continental margin north of Cape Hatteras. The model shows how the topographic influence on the local vorticity balance leads to back-folding filaments of Gulf Stream water and to the Slope Sea gyre circulation.

  5. LINKAGE BETWEEN PRODUCTION AND RESPIRATION ON THE LOUISIANA CONTINENTAL SHELF.

    EPA Science Inventory

    Abstract for presentation. Original title, "PRIMARY PRODUCTION, BACTERIOPLANKTON PRODUCTION, AND COMMUNITY RESPIRATION IN STRATIFIED WATERS OF THE NORTHERN GULF OF MEXICO CONTINENTAL SHELF: LINKAGE TO HYPOXIA."

  6. Oil-spill risk analysis: Central and western Gulf of Mexico Outer Continental Shelf Lease Sales 142 and 143. Final report

    SciTech Connect

    Price, J.M.; Lear, E.M.

    1992-03-01

    The Federal Government has proposed to offer Outer Continental Shelf lands in the Gulf of Mexico for oil and gas leasing. Because oil spills may occur from activities associated with offshore oil production, the Minerals Management Service conducts a formal risk assessment. In evaluating the significance of accidental oil spills, it is important to remember that the occurrence of such spills is fundamentally probabilistic. The effects of oil spills that could occur during oil and gas production must be considered. The report summarizes results of an oil spill risk analysis conducted for the proposed Gulf of Mexico Outer Continental Shelf Lease Sales 142 and 143. The objective of the analysis was to estimate relative risks associated with oil and gas production for the proposed lease sales.

  7. Oil-spill risk analysis: Central and Western Gulf of Mexico (Proposed Lease Sales 123 and 125) Outer Continental Shelf. Final report

    SciTech Connect

    Hannon, L.J.; Lear, E.M.

    1990-06-01

    The Federal Government has proposed to offer Outer Continental Shelf lands in the Central and Western Gulf of Mexico for oil and gas leasing. Oil spills are a major concern associated with offshore oil production. In evaluating the significance of accidental oil spills, it is important to remember that the occurrence of such spills is fundamentally probabilistic. The effects of oil spills that could occur during oil and gas production must be considered. The report summarizes results of and oil spill risk analysis conducted for the proposed Gulf of Mexico Outer Continental Shelf Lease Sales 123 125. The objective of the analysis was to estimate relative risks associated with oil and gas production for the proposed lease sales.

  8. Impacts of Outer Continental Shelf (OCS) development on recreation and tourism. Volume 2. Final report and case studies

    SciTech Connect

    Not Available

    1987-04-01

    The final report for the project is comprised of five volumes. The volume presents the study conclusions, summarizes the methodology used (more detail is found in Volume 3), discusses four case study applications of the model, and contains profiles of coastal communities in an Appendix.

  9. 76 FR 54787 - Outer Continental Shelf Official Protraction Diagram, Lease Maps, and Supplemental Official Outer...

    Federal Register 2010, 2011, 2012, 2013, 2014

    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,...

  10. Sonography of a glaciated continental shelf

    NASA Astrophysics Data System (ADS)

    Loncarevic, B. D.; Courtney, R. C.; Fader, G. B. J.; Giles, P. S.; Piper, D. J. W.; Costello, G.; Hughes Clarke, J. E.; Stea, R. R.

    1994-08-01

    Sonographs of the inner continental shelf off Halifax, Nova Scotia, show a large part of the inner shelf area consisting of exposed bedrock in which the inferred sequence of structural events is clearer than the record on land. Ribbed moraines overlie eroded drumlins and provide new information on the deglaciation history. Morphologic features allow a precise definition of the maximum postglacial lowstand of sealevel at -65 to -70 m. A 1000 km2 area in eastern Canada was surveyed with a multibeam sounder EM100, manufactured by Simrad of Norway. A 100% coverage of the sea floor was achieved with 50 to 100 m track spacing, and position control was achieved using the differential global positioning system (DGPS) with an accuracy of 1-2 m. Data were corrected for ship motion, gridded at a 10 m spacing, and displayed as obliquely illuminated relief image. The sonograph revealed characteristics of the sea bed in detail for the interpretation of bedrock and surficial structures and processes. The bathymetric images may be more useful for geologic mapping than air photographs and satellite images on nearby land, where vegetation commonly obscures the geologic features.

  11. Oceanology of the antarctic continental shelf: Volume 43

    SciTech Connect

    Jacobs, S.S.

    1985-01-01

    This book discusses the seas of the deep continental shelf, which play an important climatic role in sea ice production, deep ocean ventilation and wastage of the Antarctic ice sheet. This volume includes analyses of measurements taken from ships and satellites, and from sea ice and glacial ice. High resolution profiling equipment, long term bottom-moored instruments, continuous remote sensors, geochemical tracers and computer models have provided the basis for new insights into the continental shelf circulation. Color plates and an accompanying GEBCO Circum-Antarctic map effectively portray the continental shelf in relation to the glaciated continent, the sea ice and the surrounding Southern Ocean.

  12. Petroleum potential of northern Australian Continental Shelf

    SciTech Connect

    Smith, M.R.; Ross, J.G.

    1986-11-01

    A study of the publicly available data from the offshore northern Australian continental shelf has shown that three prospective sedimentary sequences are present. A Cenozoic basin possibly containing Miocene reefal carbonates exists in the west part of the region, a structurally distinct Mesozoic basin containing thick sandstone intervals underlies the Cenozoic, and a thick paleozoic basin, possibly containing Devonian reefs and younger Paleozoic sandstone intervals, lies southeast of the Aru Archipelago and east of a north-northeast-trending ridge located along the eastern edges of the Aru and Timor Troughs. Paleozoic sediments also underlie the Mesozoic west of this ridge. The cenozoic and Mesozoic basins and the western Paleozoic subbasin are separated by major sequence boundaries. All the basins present hydrocarbon potential to a greater or lesser extent. The Mesozoic basin will probably be the prime target for exploration over the next few years, but secondary objectives in Cenozoic and Paleozoic sediments should not be ignored. The numerous different play types identified in this study, the positive signs from exploration in the early 1970s, the recent neighboring discoveries, and improvements in seismic data quality provide an incentive for oil companies to conduct detailed exploration of the area. 7 figures.

  13. Outer Continental Shelf Oil and Gas Leasing/Production Program

    SciTech Connect

    Not Available

    1988-01-01

    This annual report on the Outer Continental Shelf (OCS) Oil and Gas Leasing and Production program summarizes receipts and expenditures, and includes information on OCS safety violations as reported by the US Coast Guard. 3 figs., 12 tabs.

  14. Manganese, Iron, and sulfur cycling in Louisiana continental shelf sediments

    EPA Science Inventory

    Sulfate reduction is considered the primary pathway for organic carbon remineralization on the northern Gulf of Mexico Louisiana continental shelf (LCS) where bottom waters are seasonally hypoxic, yet limited information is available on the importance of iron and manganese cyclin...

  15. Phytoplankton Communities in Louisiana coastal waters and the continental shelf

    EPA Science Inventory

    Louisiana coastal waters and the adjacent continental shelf receive large freshwater and nutrient inputs from the Mississippi and Atchafalaya Rivers, creating favorable conditions for increased phytoplankton productivity. To examine inshore-offshore patterns in phytoplankton comm...

  16. Oil-spill risk analysis: Cook inlet outer continental shelf lease sale 149. Volume 2: Conditional risk contour maps of seasonal conditional probabilities. Final report

    SciTech Connect

    Johnson, W.R.; Marshall, C.F.; Anderson, C.M.; Lear, E.M.

    1994-08-01

    The Federal Government has proposed to offer Outer Continental Shelf (OCS) lands in Cook Inlet for oil and gas leasing. Because oil spills may occur from activities associated with offshore oil production, the Minerals Management Service conducts a formal risk assessment. In evaluating the significance of accidental oil spills, it is important to remember that the occurrence of such spills is fundamentally probabilistic. The effects of oil spills that could occur during oil and gas production must be considered. This report summarizes results of an oil-spill risk analysis conducted for the proposed Cook Inlet OCS Lease Sale 149. The objective of this analysis was to estimate relative risks associated with oil and gas production for the proposed lease sale. To aid the analysis, conditional risk contour maps of seasonal conditional probabilities of spill contact were generated for each environmental resource or land segment in the study area. This aspect is discussed in this volume of the two volume report.

  17. Beaufort Sea monitoring program: analysis of trace metals and hydrocarbons from Outer Continental Shelf (OCS) activities. Final report, 1983-1986

    SciTech Connect

    Boehm, P.D.; Crecelius, E.; Steinhauer, W.; Steinhauer, M.; Tuckfield, C.

    1986-08-13

    An environmental-monitoring program, designed to detect and quantify long-term changes in sediment and tissue concentrations of metals and hydrocarbons potentially due to oil and gas exploration and development on the U.S. Beaufort Sea continental shelf, was initiated in 1984. In Year-1 of the three-year study, a series of benthic stations was established in the nearshore area between Barter Island and Cape Halkett. In Year-2 of the study, areal coverage of the Study Area was increased to 39 marine stations and 10 shoreline and river stations. Analysis of six replicate sediment samples for trace metals, and saturated and aromatic hydrocarbons revealed a wide range of concentrations. Both trace metal and hydrocarbon analyses of bivalve and crustacean tissues indicated concentrations differences between species but no apparent relationship between animal body burdens and sediment concentrations.

  18. Sediment metabolism on the Louisiana continental shelf - Eldridge

    EPA Science Inventory

    Rates of aerobic and anaerobic sediment metabolism were measured on the Louisiana Continental Shelf during 5 cruises in 2006 and 2007. On each cruise, 3-4 stations were occupied in regions of the shelf that experience summer bottom-water hypoxia. Net DIC, O2, N2, and nutrient f...

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

    USGS Publications Warehouse

    ten Brink, U.S.; Schneider, Christopher

    1995-01-01

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

  20. Crescentic dunes on the inner continental shelf off northern California

    USGS Publications Warehouse

    Cacchione, D.A.; Field, M.E.; Drake, D.E.; Tate, G.B.

    1987-01-01

    These dunes appear to be migrating obliquely to the regional shelf gradient; a preferred offshore direction of tranpsort is indicated by the extended southern wings of many dunes. Over longer time periods (decades), the seaward transport of fine to medium sand in the crescentic dunes is probably an important way by which sand escapes the shallow part of the continental shelf in this region and mixes with the muddy deposits of the central shelf. -from Authors

  1. Macrofaunal production along the UK continental shelf

    NASA Astrophysics Data System (ADS)

    Bolam, S. G.; Barrio-Frojan, C. R. S.; Eggleton, J. D.

    2010-10-01

    Estimates of secondary production ( P/ B ratio and total production) by macrobenthic communities across the UK continental shelf are presented. Values for individual sampling stations varied from 0.21 to 4.1 y - 1 for community P/ B and 3.1 to 897.2 kJ m - 2 y - 1 for total production. Such data fills an important gap pertaining to our understanding of the spatial variation in production estimates for this region. Benthic production estimates varied primarily at small (inter-station) scales (24 nm), although larger-scale differences were observed. In general, the highest production estimates were exhibited by benthic communities in Cardigan Bay (Irish Sea) and East English Channel, while the lowest estimates were observed for the mid- and northern North Sea areas. The former were typified by shallow, gravelly areas of seabed which exhibit high bed tidal stress and do not thermally stratify during the summer months. On average, annelids contribute an overwhelming majority of the total production with different regions varying in the relative contributions from other phyla such as molluscs, crustaceans and echinoderms. Spatial heterogeneity of sediment granulometric variables occurred primarily between stations while those of other variables (e.g., depth, stratification, and tidal bed stress) were more regional. Although a large proportion of the spatial variation in secondary production estimates was not explained by environmental characteristics, the data indicate that such relationships are scale-dependent. Average bed temperature was a significant factor in creating some of the observed differences at large spatial scales. The possible reasons why a larger proportion of the variation in production estimates was not explained by the present study are presented.

  2. In search of the Malaysian Extended Continental Shelf

    NASA Astrophysics Data System (ADS)

    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. Seals map bathymetry of the Antarctic continental shelf

    NASA Astrophysics Data System (ADS)

    Padman, Laurie; Costa, Daniel P.; Bolmer, S. Thompson; Goebel, Michael E.; Huckstadt, Luis A.; Jenkins, Adrian; McDonald, Birgitte I.; Shoosmith, Deborah R.

    2010-11-01

    We demonstrate the first use of marine mammal dive-depth data to improve maps of bathymetry in poorly sampled regions of the continental shelf. A group of 57 instrumented elephant seals made on the order of 2 × 105 dives over and near the continental shelf on the western side of the Antarctic Peninsula during five seasons, 2005-2009. Maximum dive depth exceeded 2000 m. For dives made near existing ship tracks with measured water depths H<700 m, ˜30% of dive depths were to the seabed, consistent with expected benthic foraging behavior. By identifying the deepest of multiple dives within small areas as a dive to the seabed, we have developed a map of seal-derived bathymetry. Our map fills in several regions for which trackline data are sparse, significantly improving delineation of troughs crossing the continental shelf of the southern Bellingshausen Sea.

  4. Circulation and exchange processes over the continental shelf and slope

    SciTech Connect

    Csanady, G.T.

    1988-01-01

    The theme of the work during the past triennium has been the SEEP experiment, data interpretation and modeling related to the goals of the experiment, and was characterized by increasing cooperation with colleagues from other disciplines. The theoretical contributions dealt with shelf-slope interaction, the dynamics and climatology of currents over the continental slope, and the behavior of fate of organic particles. Observational papers discussed various exchange mechanisms at the shelf edge, with special attention to particle exchange, and the quiescence of currents over the mid continental slope which is presumably responsible for the accumulation of organic particles.

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

    SciTech Connect

    Not Available

    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.

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

    SciTech Connect

    Not Available

    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.

  7. 78 FR 14917 - Outer Continental Shelf Air Regulations Consistency Update for California

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-08

    ...EPA is finalizing the update of the Outer Continental Shelf (``OCS'') Air Regulations proposed in the Federal Register on October 9, 2012. Requirements applying to OCS sources located within 25 miles of States' seaward boundaries must be updated periodically to remain consistent with the requirements of the corresponding onshore area (``COA''), as mandated by the Clean Air Act, as amended in......

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  9. Outer Continental Shelf Environmental Assessment Program: comprehensive bibliography, January 1988

    SciTech Connect

    Not Available

    1988-01-01

    The bibliography lists reports from investigators of the Alaska Outer Continental Shelf Environmental Assessment Program. Some non-program documents are also included. More than 3600 entries are sorted by author and citation number. Cross-references are available by Alaska region, discipline and research unit number.

  10. Microbial Communities in Sediments across the Louisiana Continental Shelf

    EPA Science Inventory

    The Louisiana continental Shelf (LCS) is a dynamic system that receives discharges from two large rivers. It has a stratified water column that is mixed by winter storms, hypoxic bottom water from spring to fall, and a muddy seafloor with highly mixed surficial sediments. Spatia...

  11. Coastal zone and Continental Shelf conflict resolution: improving ocean use and resource dispute management

    SciTech Connect

    Nyhart, J.D.; Harding, E.T.

    1985-11-01

    Contents include: An overview of coastal zone and continental shelf conflicts; Experience in coastal zone management conflict; Future coastal zone conflicts; Outer continental shelf conflicts; Georges Bank and Gulf of Maine; and Future considerations.

  12. 77 FR 15382 - Outer Continental Shelf Scientific Committee; Notice of Renewal

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  13. 76 FR 43230 - Outer Continental Shelf Air Regulations Consistency Update for Virginia

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  14. 75 FR 10809 - Outer Continental Shelf (OCS) Scientific Committee-Notice of Renewal

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  15. Down-welling circulation of the northwest European continental shelf: A driving mechanism for the continental shelf carbon pump

    NASA Astrophysics Data System (ADS)

    Holt, Jason; Wakelin, Sarah; Huthnance, John

    2009-07-01

    Annually integrated measurements of pCO2 have demonstrated that seasonally stratified regions of temperate shelf seas can be an important sink of atmospheric CO2. A key process to support this sink is the transport of carbon from shelf seas to below the permanent pycnocline of the deep ocean. Using a hydrodynamic model simulation of the northwest European Continental shelf, we find that both the large scale circulation and frictional processes support the off-shelf transport of carbon sufficiently quickly to remove ˜40% of the carbon sequestered by one growing season before the onset of the next. This transport is highly heterogeneous, with some regions being only weakly flushed. Only 52% of this exported carbon is transported below the permanent pycnocline, hence the shelf sea and open ocean carbon cycles are intrinsically coupled.

  16. Geochemistry of sediments of the western Canadian continental shelf

    NASA Astrophysics Data System (ADS)

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

    1991-08-01

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

  17. 78 FR 4167 - Commercial Wind Lease Issuance on the Atlantic Outer Continental Shelf Offshore Delaware

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-18

    ... Bureau of Ocean Energy Management Commercial Wind Lease Issuance on the Atlantic Outer Continental Shelf... Availability of a Commercial Lease of Submerged Lands for Renewable Energy on the Outer Continental Shelf... (Bluewater) for an area of the Outer Continental Shelf (OCS) offshore Delaware. The purpose of this notice...

  18. 26 CFR 1.1402(a)-12 - Continental shelf and certain possessions of the United States.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 12 2012-04-01 2012-04-01 false Continental shelf and certain possessions of... Income § 1.1402(a)-12 Continental shelf and certain possessions of the United States. (a) Certain... amounts are excluded from gross income under section 931. (b) Continental shelf. For the definition of...

  19. 26 CFR 1.1402(a)-12 - Continental shelf and certain possessions of the United States.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 12 2014-04-01 2014-04-01 false Continental shelf and certain possessions of... Income § 1.1402(a)-12 Continental shelf and certain possessions of the United States. (a) Certain... amounts are excluded from gross income under section 931. (b) Continental shelf. For the definition of...

  20. 26 CFR 301.9001 - Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 18 2013-04-01 2013-04-01 false Statutory provisions; Outer Continental Shelf... Rules Application of Internal Revenue Laws § 301.9001 Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978. Section 302 of the Outer Continental Shelf Lands Act Amendments of...

  1. 26 CFR 1.1402(a)-12 - Continental shelf and certain possessions of the United States.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 12 2010-04-01 2010-04-01 false Continental shelf and certain possessions of....1402(a)-12 Continental shelf and certain possessions of the United States. (a) Certain possessions. For... from gross income under section 931. (b) Continental shelf. For the definition of the term...

  2. 26 CFR 301.9001 - Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 18 2010-04-01 2010-04-01 false Statutory provisions; Outer Continental Shelf... Rules Application of Internal Revenue Laws § 301.9001 Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978. Section 302 of the Outer Continental Shelf Lands Act Amendments of...

  3. 26 CFR 301.9001 - Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 18 2012-04-01 2012-04-01 false Statutory provisions; Outer Continental Shelf... Rules Application of Internal Revenue Laws § 301.9001 Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978. Section 302 of the Outer Continental Shelf Lands Act Amendments of...

  4. 26 CFR 1.1402(a)-12 - Continental shelf and certain possessions of the United States.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 12 2013-04-01 2013-04-01 false Continental shelf and certain possessions of... Income § 1.1402(a)-12 Continental shelf and certain possessions of the United States. (a) Certain... amounts are excluded from gross income under section 931. (b) Continental shelf. For the definition of...

  5. 26 CFR 301.9001 - Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 18 2011-04-01 2011-04-01 false Statutory provisions; Outer Continental Shelf... Rules Application of Internal Revenue Laws § 301.9001 Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978. Section 302 of the Outer Continental Shelf Lands Act Amendments of...

  6. 26 CFR 301.9001 - Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 18 2014-04-01 2014-04-01 false Statutory provisions; Outer Continental Shelf... Rules Application of Internal Revenue Laws § 301.9001 Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978. Section 302 of the Outer Continental Shelf Lands Act Amendments of...

  7. 26 CFR 1.1402(a)-12 - Continental shelf and certain possessions of the United States.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 12 2011-04-01 2011-04-01 false Continental shelf and certain possessions of... Income § 1.1402(a)-12 Continental shelf and certain possessions of the United States. (a) Certain... amounts are excluded from gross income under section 931. (b) Continental shelf. For the definition of...

  8. 75 FR 18404 - Safety Zone; FRONTIER DISCOVERER, Outer Continental Shelf Drillship, Chukchi and Beaufort Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-12

    ... Continental Shelf Drillship, Chukchi and Beaufort Sea, Alaska'' in the Federal Register (75 FR 803). The NPRM... various prospects located in the Chukchi and Beaufort Sea Outer Continental Shelf, Alaska, during the 2010... off the northern coast in the Beaufort Sea Outer Continental Shelf, Alaska, during the 2010...

  9. 76 FR 79705 - Information Collection Activities: Operations in the Outer Continental Shelf for Minerals Other...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-22

    ... the Outer Continental Shelf for Minerals Other than Oil, Gas, and Sulphur; Submitted for Office of..., ``Operations in the Outer Continental Shelf for Minerals Other than Oil, Gas, and Sulphur''. DATES: Submit... Continental Shelf for Minerals other than Oil, Gas, and Sulphur. OMB Control Number: 1014-NEW. Abstract:...

  10. 77 FR 15118 - Information Collection Activities: Operations in the Outer Continental Shelf for Minerals Other...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-14

    ... Continental Shelf for Minerals Other Than Oil, Gas, and Sulphur; Submitted for Office of Management and Budget... Continental Shelf for Minerals Other than Oil, Gas, and Sulphur. This notice also provides the public a second... 282, Operations in the Outer Continental Shelf for Minerals Other than Oil, Gas, and Sulphur....

  11. Heat flow of the Norwegian continental shelf

    NASA Astrophysics Data System (ADS)

    Pascal, Christophe

    2015-04-01

    Terrestrial heat flow influences a large collection of geological processes. Its determination is a requirement to assess the economic potential of deep sedimentary basins. Published heat flow calculations from e.g. major oil provinces are however seldom. Robust heat flow determinations in drillholes require logging of undisturbed temperatures and intensive sampling of core material for petrophysical measurements. Temperature logging in exploration drillholes is traditionally conducted during drill breaks or shortly after drilling, resulting in temperatures severely disturbed by mud circulation and coring is restricted to selected intervals. Alternatively, test temperatures, information from electric logs and lithological descriptions of drill cuttings can be used to overcome these limitations. The present contribution introduces new heat flow determinations based on 63 exploration drillholes from the Norwegian North Sea, the Mid Norway Margin and the Barents Shelf. Our analyses are based on released DST temperatures, precise lithological descriptions of drill cuttings, previously measured rock matrix thermal conductivities and established porosity laws. Our results suggest median heat flow values of 64 mW/m2, 65 mW/m2 and 72 mW/m2 for the North Sea, the Mid Norway Margin (mainly the Trøndelag Platform) and the SW Barents Shelf respectively. The Barents Shelf shows significantly high heat flow, suggesting lateral transfer of heat from the mantle of the adjacent young ocean. In detail, heat flow increases by ~ 10 mW/m2 from the southern Norwegian North Sea towards the Mid Norway Margin. This result appears to be in very good agreement with seismic tomographic studies suggesting northward thinning of the underlying mantle lithosphere. Our results together with published marine heat flow data from the Mid Norway Margin suggest a gradual decrease in heat flow levels from both the North Sea and the Trøndelag Platform towards the centres of the deep Møre and V

  12. Continental shelf waves on the Alborán sea

    NASA Astrophysics Data System (ADS)

    Serrano, M. A.; Díez-Minguito, M.; Ortega-Sánchez, M.; Losada, M. A.

    2015-12-01

    The existence of free continental shelf waves in the Western Mediterranean Sea is studied using a statistical approach. Hourly mean sea level at six locations extended along the northern and southern coast of the Alborán Sea were analyzed by standard correlation and spectral analysis techniques for two periods of 91 and 92 days, respectively. The mean sea level was adjusted for the effect of atmospheric pressure according to the hydrostatic approximation. The wind-coherent response of sea level was removed by calculating the transfer function between the input alongshore wind stress and the output adjusted sea level. The cross-correlation analyses indicate time lags that are consistent with the hypothesis of the propagation of the free shelf waves predicted by the continental shelf wave theory. The presence of a westward-travelling signal on the NCS and a west-to-east travelling signal on the SCS of the Alborán Sea is confirmed. The cross spectra between residual sea level at the six locations show significant coherence at long periods. For these periods, the phase difference spectra show that the directions of propagation of the free waves are consistent with the interpretation of the cross correlation analysis. There is evidence of a seasonal variation in the phase speed of the waves, which may be related to variations in the speeds of currents in the Alborán Sea. The observations suggest the presence of continental shelf waves on both coasts of the Alborán Sea.

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

    NASA Astrophysics Data System (ADS)

    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. Structure and development of the southern Moroccan continental shelf

    USGS Publications Warehouse

    Dillon, William P.

    1974-01-01

    The structure of the continental shelf off southern Morocco was studied by means of 2,100 km of seismic reflection profiles, magnetic and bathymetric surveys, and dredge samples. The research area lies off four geologic divisions adjacent to the coast: the Atlas Mountains; the Souss Trough; the Anti-Atlas Mountains; and the Aaiun Basin. The continental shelf, along with the western Atlas Mountains, the western Souss Trough, and the entire Aaiun Basin, has subsided along a normal fault-flexure system. This system runs along the shore at the Anti-Atlas Mountains, and cuts off this cratonic block from the shelf subsidence. The shelf is narrow and characterized by out-building off the Anti-Atlas range, whereas it is broader and characterized by upbuilding to the north and south. Deposition was essentially continuous at least from Early Cretaceous through Eocene time. Published work suggests that the last cycle of sedimentation began during Permian rifting. After Eocene time, most sediments carried to the shelf must have bypassed it and gone to construct the slope and rise or to the deep sea. Tertiary orogenies caused extensive folding of Mesozoic and early Tertiary deposits off the Atlas Mountains. ?? 1974.

  15. Heat Flow of the Norwegian Continental Shelf

    NASA Astrophysics Data System (ADS)

    Pascal, C.

    2015-12-01

    Terrestrial heat flow determination is of prime interest for oil industry because it impacts directly maturation histories and economic potential of oil fields. Published systematic heat flow determinations from major oil provinces are however seldom. Robust heat flow determinations in drillholes require logging of undisturbed temperatures and intensive sampling of core material for petrophysical measurements. Temperature logging in exploration drillholes is traditionally conducted during drill breaks or shortly after drilling, resulting in temperatures severely disturbed by mud circulation and coring is restricted to selected intervals. Alternatively, test temperatures, information from electric logs and lithological descriptions of drill cuttings can be used to overcome these limitations. The present contribution introduces new heat flow determinations based on 63 exploration drillholes from the Norwegian North Sea, the Mid Norway Margin and the Barents Shelf. Our analyses are based on released DST temperatures, precise lithological descriptions of drill cuttings, previously measured rock matrix thermal conductivities and established porosity laws. For the sake of comparison, we carefully review previous heat flow studies carried out both onshore and offshore Norway. Our results suggest median heat flow values of 64 mW/m2, 65 mW/m2 and 72 mW/m2 for the North Sea, the Mid Norway Margin (mainly the Trøndelag Platform) and the SW Barents Shelf respectively. In detail, heat flow increases by ~ 10 mW/m2 from the southern Norwegian North Sea towards the Mid Norway Margin. This result appears to be in very good agreement with seismic tomographic studies suggesting northward thinning of the underlying mantle lithosphere. Our results together with published marine heat flow data from the Mid Norway Margin suggest a gradual decrease in heat flow levels from both the North Sea and the Trøndelag Platform towards the centres of the deep Møre and Vøring basins. This latter

  16. Modelisation of Circulation On The French Guiana Continental Shelf

    NASA Astrophysics Data System (ADS)

    Chevalier, C.; Dekeyser, I.; Ramamonjiarisoa, A.; Baklouti, M.; van Nieuwerberg, V.

    The continental shelf which extends more over than 1000 km to the north-west of the mouth of the Amazon river is an usual oceanographic environment : the entire area is influenced by fresh water flowing from the Amazon. The current on the shelf inter- acts with the strong, shallow Guiana Current along the outer shelf area. The prevailing trade winds across the area impose surface stresses. The tidal influence is also signif- icant with a diminishing amplitude from the Amazon to the north. This combination results in a persistent long-shore current flowing north-westward in the shallow wa- ter along the shore. In particular on French Guiana continental shelf, the combination of significant stratification, great coastal current just out of the shelf, influence of the wind and strong tidal component presents an interesting process for study. The purpose of this study is to look into the circulation that develops under these interacting forces. For that, we develop a numerical model of the circulation on the French Guiana shelf. Nowadays, in the bibliography, it seems to be the first numerical study on this area. This work is included in the Programme National dSEnvironnement Côtier (PNEC) in French Guiana. Simulations described the coastal currents, the salinity and temperature evolution on the shelf under the influence of rivers discharging in the shelf and the effect of north- eastward wind on the circulation. The current is parallel to the coast and the highest velocities are in the middle of the shelf, the maximum intensity is located at the surface and reached speed of 1m/s. The fresh water discharged by rivers extends alongshore near the coast, to about 30m-isobath, whereas the fresh water coming from the Ama- zon spreads out essentially in the middle of the shelf. The halocline is situated few meters (between 2 and 5 m) under the surface, with a lower salinity at the south-east boundary which is 20 and which is 25 at the north-west boundary, whereas, the

  17. Fisheries and oil development on the continental shelf

    SciTech Connect

    Benner, C.S.; Middleton, R.W.

    1991-01-01

    The title of this volume is misleading because it has not clearly defined the geographic limits of the continental shelf. However, a glance at the Contents makes it clear that the contributions to this symposium are restricted to some shelf areas of the continental USA and especially to the Beaufort Sea off the north coast of Alaska. These papers were derived from presentations at the 119th annual meeting of the American Fisheries Society held in Anchorage, Alaska, in 1989. An awareness of the geographic scope of this symposium helps to put its contents into better focus. It is apparent that a broad coverage of fisheries, oil development, and its probable consequences from a global or even North American perspective is not provided. With the exception of the first 38 pages covering a broad range of topics, the remaining 134 pages are devoted exclusively to the Beaufort Sea.

  18. Comparison of marine productivity among Outer Continental Shelf planning areas

    SciTech Connect

    Darnell, R.M.

    1991-04-01

    Continental Shelf Associates was contracted to update and expand an earlier work on a comparison of primary productivity among Outer Continental Shelf (OCS) planning areas. The update consists of four general objectives. This report addresses the fourth objective, the potential to use measures of marine secondary productivity in determining relative rankings of the OCS planning area. Ideally, comparisons of secondary productivity among diverse geographic areas would take an ecosystem perspective. However, there is not enough ecosystem-level understanding to allow a comparison on that basis. The report focuses on individual species and group of species. Zooplankton and benthic communities represent major portions of the marine ecosystems and would be the preferred subjects for comparative studies. At this time comparisons of secondary productivity among planning areas would be difficult with existing databases. It is unlikely this situation will improve in the near future.

  19. Carbon Dynamics on the Louisiana Continental Shelf and Cross-Shelf Feeding of Hypoxia

    EPA Science Inventory

    Large-scale hypoxia regularly develops during the summer on the Louisiana continental shelf. Traditionally, hypoxia has been linked to the vast winter and spring nutrient inputs from the Mississippi River and its distributary, the Atchafalaya River. However, recent studies indica...

  20. Facies analysis of Nile delta continental shelf sediments off Egypt

    NASA Astrophysics Data System (ADS)

    Frihy, Omran E.; Gamai, Ibrahim H.

    This study evaluates the texture and coarse fraction composition of 108 bottom samples from the Nile delta continental shelf. In total 19 petrological variables were considered for each of the samples, and Q-mode factor analysis of the textural and mineralogical variables yielded 4 factors (facies groups): Facies I. Fine and very fine sands, light minerals, heavy minerals and 'glauconite', extending from the shoreline to the inner shelf and decreasing away from the shoreline. Facies II. Silty sand rich in biogenic components occupies the entire outer shelf and its contiguous lower terraces. Facies III. Mud (silt plus clay), mica and 'glauconite', covering the middle shelf and the upper terraces. Facies IV. Fine to coarse-grained sediments and 'glauconite', locally distributed along the coast off lake ldku, Burullus headland, and Damietta promontory and El Gamil. The configuration patterns of facies I (delta-front), facies III (prodelta) and facies IV (distributary mouth bar or progradational coastal sand) help identify delta lobes related to former distributary branches of the Nile river (Canopic, Saitic, Sebennitic, Atribic and Mendisian). The 4 facies-forming shelf sediments have resulted from sediment dynamics, sea-level fluctuation and differences in sediment input and provenance.

  1. The deglaciation history of the mid-Norwegian continental shelf

    NASA Astrophysics Data System (ADS)

    Haflidason, Haflidi; Bøyum, Eivind; Oline Hjelstuen, Berit

    2013-04-01

    The present knowledge on the last deglaciation of the mid-Norwegian continental shelf is still largely based on works from the late 1970's to early 1980's and improved by re-dating shell rich events using the AMS technology in the late 1990´s. These new dating results offered a new chronological framework for the two youngest till units identified in the outer shelf setting of the Mid-Norwegian shelf area using a regional grid of sparker lines. These till units were found to have been deposited around 15000 and 13500 14C BP. The results showed that the Mid-Norwegian shelf ice partly reached the shelf edge as late as ca. 13000 14C BP. Dating from the nearest coastal area show that most of the shelf area had been deglaciated in less than 1000 years. New high-resolution seismic technology, applying the TOPAS parametric echosounder system, the multibeam and the Olex data bathymetric data combined with new AMS dated gravity cores have in the recent year made it possible to approach the deglaciation history in a more detailed way than previously available. The results show that the last glacial maximum ice sheet retreated from the outer shelf area around 15200 14C. The ice sheet readvanced around 14500 14C and created a large end moraine complex and a new minor readvance is interpreted to have occurred around 13700 14C BP before a rapid retreat to the coastal areas during the Bølling period. The two dated ice sheet readvances have occurred within the period of the cold regional climatic event Heinrich 1.

  2. 76 FR 63654 - Outer Continental Shelf Official Protraction Diagram, Lease Maps, and Supplemental Official Outer...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-13

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

  3. Depositional history of Louisiana-Mississippi outer continental shelf

    USGS Publications Warehouse

    Kindinger, J.L.; Miller, R.J.; Stelting, C.E.

    1982-01-01

    A geological study was undertaken in 1981 in the Louisiana-Mississippi outer continental shelf for the Bureau of Land Management. The study included a high-resolution seismic reflection survey, surficial sediment sampling and surface current drifter sampling. Approximately 7100 sq km of the Louisiana-Mississippi shelf and upper slope were surveyed. The sea floor of the entire area is relatively smooth except for occasional areas of uplift produced by diapiric intrusion along the upper slope. Characteristics of the topography and subsurface shelf sediments are the result of depositional sequences due to delta outbuilding over transgressive sediments with intervening periods of erosion during low sea level stands. Little evidence of structural deformation such as faults, diapirs, and shallow gas is present on the shelf and only a few minor faults and scarps are found on the slope. Minisparker seismic records in combination with air gun (40 and 5 cu in) and 3.5-kHz subbottom profile records reveal that seven major stages of shelf development have occurred since the middle Pleistocene. The shelf development has been controlled by the rise and fall of sea level. These stages are defined by four major unconformities, several depositions of transgressive sediments, sequences of river channeling and progradational delta deposits. Surficial sediment sample and seismic records indicate tat the last major depositional event was the progradation of the St. Bernard Delta lobe. This delta lobe covered the northwestern and central regions. Surficial sediments in most of the study area are the product of the reworking of the San Bernard Delta lobe and previous progradations.

  4. Southeastern U.S.A. Continental Shelf Respiratory Rates Revisited

    NASA Technical Reports Server (NTRS)

    Sheldon, Joan E.; Griffith, Peter C.; Peters Francesc; Sheldon, Wade M., Jr.; Blanton, Jackson O.; Amft, Julie; Pomeroy, Lawrence R.

    2010-01-01

    Respiratory rates on the U. S. southeastern continental shelf have been estimated several times by different investigators, most recently by Jiang et al. (Biogeochemistry 98:101-113, 2010) who report lower mean rates thanwere found in earlier work and attribute the differences to analytical error in all methods used in earlier studies. The differences are, instead, attributable to the differences in the geographical scope of the studies. The lower estimates of regional organic carbon flux of Jiang et al. (Biogeochemistry 98:101-113, 2010) are a consequence of their extrapolation of data from a small portion of the shelf to the entire South Atlantic Bight. This comment examines the methodologies used as well as the variability of respiratory rates in this region over space and time.

  5. Bryozoans from rio grande do sul continental shelf, southern Brazil.

    PubMed

    Ramalho, Laís V; Calliari, Lauro

    2015-01-01

    The continental shelf of Rio Grande do Sul (RS) is predominantly composed of unconsolidated sediments with a few hard substrates represented principally by beachrock. In this area there are elongate deposits of shell gravel material which are interpreted as indicators of the palaeo-shorelines. These Pleistocene deposits are overlapped by Holocene sediments (Recent), but are exposed during erosive events caused by extra-tropical cyclones, which provide the mixture of both sediments mainly during autumn and winter. The few studies on bryozoans made in this area previously recorded seven species, one fossil and the other six from Recent fluvial and marine environments. The aim of the present study was to describe the eight most abundant bryozoan species that occur in the inner RS shelf. Of these, four are new records for RS State (Arachnopusia aff. pusae, Hippomonavella brasiliensis, Turbicellepora pourtalesi, and Lifuella gorgonensis), and the other four are new to science (Chaperia taylori, Micropora nodimagna, Cellaria riograndensis, and Exochella moyani). PMID:25947873

  6. Structure of the continental shelf west of San Francisco, California

    USGS Publications Warehouse

    Cooper, Alan K.

    1973-01-01

    The continental shelf west of San Francisco, California is divided into two structural provinces along the offshore extension of the Seal Cove fault, the Farallon and Golden Gate platforms. The Farallon platform lies west of the Seal Cove fault and is characterized by a thick sequence of Tertiary sediments with a maximum thickness of 3.5 km. These sediments are bounded at the edge of the continental shelf by a ridge of Cretaceous granitic rock which crops out at the Farallon Islands. The granitic basement is vertically displaced along the eastern flank of the granitic ridge and along two high angle reverse faults located near Point Reyes. The Point Reyes fault trends east-west and has possibly offset the granitic basement 1500 meters since late Pliocene time. Two northwest trending anticlines lie south of the Point Reyes fault. The eastern boundary of the Tertiary basin is delineated by a structural high composed of deformed basin sediments. This structural high is truncated at the Seal Cove fault. On the Golden Gate platform, the San Andreas fault zone is marked by a near surface graben, showing a maximum vertical displacement of 20 meters, and by a wider linear depression observed to a depth of 700 meters. The Pilarcitos fault continues offshore and joins the San Andreas fault south of Bolinas. The development of the present Tertiary basin under the continental shelf commenced in late Miocene time with. the initial uplift of the Farallon ridge and the compression of the eastern basin margin. Strike-slip faulting on the seal Cove fault in Pliocene time truncated middle Tertiary sediments at the fault and thus formed a distinct structural boundary between the Farallon and Golden Gate platforms. Surface extensional features observed within the San Andreas fault zone are suggestive of strike-slip faulting in late Tertiary time. The compressional high angle reverse faulting at Point Reyes occurred during the late Pliocene orogenic period of the California Coast Ranges.

  7. Continental shelf benthos off Otago Peninsula, New Zealand

    NASA Astrophysics Data System (ADS)

    Probert, P. Keith; Wilson, John B.

    1984-09-01

    Benthic macrofauna of the continental shelf off Otago Peninsula, south-eastern New Zealand (45°51'S, 170°52'E) was surveyed by dredge sampling during 1973-1975. Numerical classification (Canberra metric coefficient and flexible sorting) was used to produce site groups and species groups, and three major benthic communities were recognised: a shallow-water (14-25 m) fauna inhabiting well-sorted fine sand, a mid-shelf fauna (concentrated in the depth range 50-76 m) associated with sediments containing the greatest proportions of gravel and siltclay, and a predominantly sand-bottom fauna occurring mainly on the outer shelf (87-150 m). All station groups were dominated numerically by polychaetes (mean of 36·6-56% of individuals) with Mollusca (13·8-25%) or Crustacea (12·1-19·4%) the next most abundant group. The inshore sand fauna was the most distinct, characteristic elements being the trochid gastropod Antisolarium egenum, an amphipod of the genus Hippomedon and dense patches of the spionid polychaete Spiophanes bombyx. Diagnostic species of the mid-shelf mixed sediments were Lepidonotus jacksoni, Psammolyce antipoda, Lumbrineris brevicirra and Phyllamphicteis foliata (Polychaeta), Terenochiton otagoensis, Micrelenchus caelatus caelatus, Maoricolpus roseus roseus and Zegalerus tenuis (Mollusca), Ampelisca chiltoni (Amphipoda) and Amphipholis squamata (Ophiuroidea). Outer shelf sand stations were faunally less distinct, but among the more characteristic species were Euthalenessa fimbriata, Sigalion sp. and Euchone sp. (Polychaeta) and Gari stangeri (Bivalvia). Several abundant species were widely distributed among station groups, notably Nephtys macroura, Lumbrineris magalhaensis, Phyllochaetopterus socialis and Owenia fusiformis (Polychaeta) and Nucula nitidula and Tawera spissa (Bivalvia). Free-living lunulitiform Bryozoa of the genus Otionella were a characteristic component of inner and outer shelf sand faunas, and their inshore penetration probably marks

  8. Surficial sediments on the western Canadian continental shelf

    NASA Astrophysics Data System (ADS)

    Bornhold, Brian D.; Barrie, J. Vaughn

    1991-08-01

    The active continental margin off western Canada is characterized in the south by convergence between the Explorer and Juan de Fuca Plates and the America Plate, and in the north by transform fault motion between the Pacific and America Plates along the Queen Charlotte Fault. Except in some of the deepest troughs and basins shelf sediments are dominated by immature lithic arenites reflecting this tectonic setting. The Vancouver Island shelf is from 5 to 75 km wide and displays complex topography on the inner shelf and a relatively featureless mid- and outer shelf. An exception is the area off southwestern Vancouver Island where large basins bounded by morainal deposits extend more than two-thirds of the distance across the shelf. The shelf edge varies from 180 to 225 m depth and is indented by numerous canyons. Nearshore sediments consist mainly of gravels and boulders and become finer offshore such that muds are slowly accumulating in depths greater than 100 m. Off northwestern Vancouver Island calcareous sediments are abundant with carbonate values often exceeding 75%. High wave and current energies and efficient sediment trapping in coastal fiords have resulted in low rates of accumulation. Olive, glauconitic, Holocene muds and muddy sands are generally less than 0.3 m thick and accumulate only on the outer shelf over an extensive stiff, gray, glaciomarine sandy mud. Queen Charlotte Sound exhibits three broad, shallow, glacially scoured troughs, filled mainly with clayey silts and fine sands and separated by sand and gravel covered banks. Hecate Strait, between the Queen Charlotte Islands and the mainland, consists of a prominent southward-opening trough along the east side of the Strait bounded by Dogfish and Laskeek Banks on the west adjacent to Graham and Moresby Islands, respectively. The trough below 200 m is filled by silts. The banks are covered by discontinuous sands and gravels of variable calcareous content. The bank edges often display megaripples and

  9. Sources and Distribution of Organic Matter in Sediments of the Louisiana Continental Shelf

    EPA Science Inventory

    Both riverine and marine sources of organic matter (OM) contribute to sediment organic pools, and either source can contribute significantly to sediment accumulation, burial, and remineralization rates on river dominated continental shelf systems. For the Louisiana continental sh...

  10. 77 FR 10707 - Safety Zone; NOBLE DISCOVERER, Outer Continental Shelf Drillship, Chukchi and Beaufort Seas, Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-23

    ... SECURITY Coast Guard 33 CFR Part 147 RIN 1625-AA00 Safety Zone; NOBLE DISCOVERER, Outer Continental Shelf... prospects located in the Chukchi and Beaufort Seas Outer Continental Shelf, Alaska, from 12:01 a.m. on July... Federal Register (73 FR 3316). Public Meeting The Coast Guard does not plan to hold a public meeting....

  11. 78 FR 27427 - Outer Continental Shelf (OCS) Geological and Geophysical Exploration Activities in the Gulf of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-10

    ... Bureau of Ocean Energy Management Outer Continental Shelf (OCS) Geological and Geophysical Exploration... ] Geological and Geophysical Exploration for Mineral Resources on the Gulf of Mexico Outer Continental Shelf... activities in GOM waters. It will also provide information for future decisions regarding Outer...

  12. 76 FR 29156 - Outer Continental Shelf Air Regulations Consistency Update for California

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-20

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for California AGENCY... Continental Shelf (``OCS'') Air Regulations proposed in the Federal Register on January 10, 2011. Requirements... Comment III. EPA Action IV. Statutory and Executive Order Reviews I. Background On January 10, 2011 (76...

  13. 75 FR 3387 - Outer Continental Shelf Air Regulations Consistency Update for Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-21

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Alaska AGENCY... Continental Shelf (``OCS'') Air Regulations proposed in the Federal Register on March 3, 2009. Requirements... reader may refer to the Notice of Proposed Rulemaking, December 5, 1991 (56 FR 63774), and the...

  14. 77 FR 27480 - Outer Continental Shelf Scientific Committee; Announcement of Plenary Session

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  15. 78 FR 64243 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    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... from bidding with any entity in any of the other following groups at Outer Continental Shelf oil...

  16. 78 FR 25100 - Outer Continental Shelf Scientific Committee; Announcement of Plenary Session

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  17. 75 FR 803 - Safety Zone; FRONTIER DISCOVERER, Outer Continental Shelf Drillship, Chukchi and Beaufort Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-06

    ... the Chukchi and Beaufort Sea Outer Continental Shelf, Alaska, from 12:01 a.m. on July 1, 2010 through..., 2008 issue of the Federal Register (73 FR 3316). Public Meeting We do not now plan to hold a public... Continental Shelf, Alaska. Shell Exploration & Production Company has five proposed drill sites within...

  18. 75 FR 51968 - Outer Continental Shelf Air Regulations Consistency Update for Massachusetts

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  19. 76 FR 37274 - Outer Continental Shelf Air Regulations Consistency Update for Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-27

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Alaska AGENCY... of the Outer Continental Shelf (``OCS'') Air Regulations proposed in the Federal Register on February... refer to the Notice of Proposed Rulemaking, December 5, 1991 (56 FR 63774), and the preamble to...

  20. 76 FR 15898 - Outer Continental Shelf Air Regulations; Consistency Update for California

    Federal Register 2010, 2011, 2012, 2013, 2014

    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... onshore requirements. \\1\\ See Notice of Proposed Rulemaking, December 5, 1991 (56 FR 63774), and...

  1. 78 FR 33859 - Outer Continental Shelf (OCS) Geological and Geophysical Exploration Activities in the Gulf of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-05

    ... Bureau of Ocean Energy Management Outer Continental Shelf (OCS) Geological and Geophysical Exploration.... SUMMARY: On May 10, 2013, BOEM published a document in the Federal Register (78 FR 27427) entitled ``Outer Continental Shelf Geological and Geophysical Exploration Activities in the Gulf of Mexico.'' This...

  2. 76 FR 28449 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-17

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) Notice on Outer Continental Shelf... with any entity in any other of the following groups at Outer Continental Shelf oil and gas lease...

  3. 76 FR 43185 - Outer Continental Shelf Air Regulations Consistency Update for Virginia

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...'' subject to review by the Office of Management and Budget under Executive Order 12866 (58 FR 51735,...

  4. 76 FR 67759 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    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... from bidding with any entity in any other of the following groups at Outer Continental Shelf oil...

  5. 78 FR 27430 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    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... from bidding with any entity in any of the other following groups at Outer Continental Shelf oil...

  6. 76 FR 4129 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-24

    ... 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... any entity in any other of the following groups at Outer Continental Shelf oil and gas lease sales...

  7. 77 FR 24980 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    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... from bidding with any entity in any other of the following groups at Outer Continental Shelf oil...

  8. 75 FR 24966 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  9. 77 FR 64826 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  10. 77 FR 50855 - Oil and Gas and Sulphur Operations on the Outer Continental Shelf-Increased Safety Measures for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-22

    ... Energy Management, Regulation, and Enforcement (BOEMRE) published the Interim Final Rule (75 FR 63346... 14, 2010 (75 FR 63346). The IFR was effective immediately, with a 60-day comment period. On October 1... Part 250 Oil and Gas and Sulphur Operations on the Outer Continental Shelf-- Increased Safety...

  11. 78 FR 62660 - Outer Continental Shelf (OCS), Gulf of Mexico (GOM), Oil and Gas Lease Sales Eastern Planning...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-22

    ... Bureau of Ocean Energy Management Outer Continental Shelf (OCS), Gulf of Mexico (GOM), Oil and Gas Lease Sales Eastern Planning Area (EPA) Lease Sales 225 and 226 AGENCY: Bureau of Ocean Energy Management... (42 U.S.C. 4321 et seq.) (NEPA), BOEM has prepared a Final EIS on oil and gas lease sales...

  12. 77 FR 2991 - Gulf of Mexico (GOM), Outer Continental Shelf (OCS), Central Planning Area (CPA), Oil and Gas...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-20

    ... Bureau of Ocean Energy Management Gulf of Mexico (GOM), Outer Continental Shelf (OCS), Central Planning... Management (BOEM), Interior. ACTION: Notice of Availability (NOA) of a Final Supplemental Environmental... Management, Gulf of Mexico OCS Region, 1201 Elmwood Park Boulevard (MS 5410), New Orleans, Louisiana...

  13. 77 FR 40081 - Gulf of Mexico, Outer Continental Shelf (OCS), Western Planning Area (WPA) and Central Planning...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-06

    ... Bureau of Ocean Energy Management Gulf of Mexico, Outer Continental Shelf (OCS), Western Planning Area... Energy Management (BOEM), Interior. ACTION: Notice of availability (NOA) of the Multisale Final...-ROM copy of the Multisale FEIS, you may contact the Bureau of Ocean Energy Management, Gulf of...

  14. 75 FR 63345 - Oil and Gas and Sulphur Operations in the Outer Continental Shelf-Increased Safety Measures for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-14

    ...This interim final rule implements certain safety measures recommended in the report entitled, ``Increased Safety Measures for Energy Development on the Outer Continental Shelf'' (Safety Measures Report), dated May 27, 2010. The President directed the Department of the Interior to develop the Safety Measures Report to identify measures necessary to improve the safety of oil and gas exploration......

  15. 78 FR 1759 - Notice of Approval of Clean Air Act Outer Continental Shelf Minor Source/Title V Minor Permit...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-09

    ...This notice announces that EPA Region 10 has issued a final decision granting Shell Offshore Inc.'s (``Shell'') request for minor modifications of Clean Air Act Outer Continental Shelf (``OCS'') Minor Source/Title V Permit No. R10OCS03000 (``permits''). The permits authorize air emissions associated with Shell's operation of the Kulluk Conical Drilling Unit (``Kulluk'') in the Beaufort Sea to......

  16. 77 FR 27054 - Notice of Approval of Clean Air Act Outer Continental Shelf Permits Issued to Shell Offshore, Inc...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-08

    ...This notice announces that EPA Region 10 has issued a final permit decision granting a Clean Air Act Outer Continental Shelf (OCS) permit to construct and Title V air quality operating permit to Shell Offshore, Inc. (``Shell'') for operation of the Kulluk conical drilling unit in the Beaufort Sea off the north coast of...

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

    SciTech Connect

    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.

  18. Habitat Specialization in Tropical Continental Shelf Demersal Fish Assemblages

    PubMed Central

    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

  19. Cathodoluminescent bimineralic ooids from Pleistocene of Florida continental shelf

    SciTech Connect

    Major, R.P.; Halley, R.B.; Lukas, K.J.

    1987-05-01

    A bored and encrusted late Pleistocene ooid grainstone was recovered from the sea floor at a depth of approximately 40 m on the continental shelf of eastern Florida. Ooid cortices are dominantly bimineralic, consisting generally of inner layers of radial magnesian calcite and outer layers of tangential aragonite. The transition from radial to tangential cortex layers occurs at an approximate diameter of 0.30 to 0.35 mm. Ooid nuclei are predominantly rounded cryptocrystalline grains, although quartz grains and a variety of skeletal grains also occur as nuclei. Ooids were partially cemented by blocky calcite, followed by partial infilling of interparticle porosity by micrite and subsequently by sparse acicular cement. The radial cortex layers and some ooid nuclei are brightly cathodoluminescent, whereas the tangential cortex layers, micrite matrix, acicular cement, and the bulk of blocky calcite cement are nonluminescent. Some blocky calcite cement has a thin outer cathodoluminescent zone. Electron microprobe analyses indicate that radial layers contain approximately 10 mole % MgCO/sub 3/ and tangential layers generally contain 10,000 to 11,000 ppm strontium. The manganese content of radial layers ranges as high as 250 ppm, whereas the manganese content of tangential layers is generally below the detection limit of approximately 100 ppm. Iron content varies over a wide range. Scanning electron microscope analysis indicates no microdolomites. They assume manganese is the principal cathodoluminescent activator. Although there is some uncertainty concerning the partition coefficient for manganese into magnesian calcite and the influence of kinetic effects at varying rates of precipitation is poorly understood, they favor the interpretation that these cathodoluminescent magnesian calcite cortex layers have undergone diagenetic alteration in sea water of the Florida continental shelf.

  20. Anomalous topography on the continental shelf around Hudson Canyon

    USGS Publications Warehouse

    Knebel, H. J.

    1979-01-01

    Recent seismic-reflection data show that the topography on the Continental Shelf around Hudson Canyon is composed of a series of depressions having variable spacings (< 100 m to 2 km), depths (1-10 m), outlines, and bottom configurations that give the sea floor an anomalous "jagged" appearance in profile. The acoustic and sedimentary characteristics, the proximity to relict shores, and the areal distribution indicate that this rough topography is an erosional surface formed on Upper Pleistocene silty sands about 13,000 to 15,000 years ago by processes related to Hudson Canyon. The pronounced southward extension of the surface, in particular, may reflect a former increase in the longshore-current erosion capacity caused by the loss of sediments over the canyon. Modern erosion or nondeposition of sediments has prevented the ubiquitous sand sheet on the Middle Atlantic shelf from covering the surface. The "anomalous" topography may, in fact, be characteristic of areas near other submarine canyons that interrupt or have interrupted the longshore drift of sediments. ?? 1979.

  1. Analysis of the petroleum resources of the Norwegian Continental Shelf

    SciTech Connect

    Flertoft, I.P.; Kvadsheim, E.; Kalheim, J.E.

    1995-08-01

    The 1995 analysis of the petroleum resources of Norway is based on a play analysis. The input to the 1995 analysis is updated and refined compared with the analysis of 1993. The analysis makes a major distinction between unconfirmed play models and plays confirmed by discoveries. The unconfirmed plays have a higher risk and a greater range of uncertainty in the resource estimates compared to the confirmed plays. The effect of the unconfirmed plays on the estimates within different exploration areas is discussed. The unconfirmed play models are an important aspect of the exploration in the new exploration areas north of 62{degrees}N. The total estimate for the Norwegian Shelf is well within the estimate given in the 1993 analysis, but there are some adjustments in the relative importance of the different exploration provinces. Much emphasis is placed on incorporating historical exploration data and statistics to calibrate the play models. This includes rate of success and field size distributions of the individual play models and exploration provinces. Major confirmed plays in the North Sea have a rate of success of about 30% and show a good fit to a log normal field size distribution. Based on the log normal distribution it is possible to give prognosis for the size distribution of the undiscovered accumulation. This has made it possible to work out an economic analysis of the profitability of future exploration on the Norwegian Continental Shelf.

  2. Oil-spill risk analysis: Gulf of Mexico, Outer Continental Shelf (OCS) central and western lease sales, 1998-2002, and gulfwide OCS program, 1998-2036. Final report

    SciTech Connect

    Price, J.M.; Marshall, C.F.; Lear, E.M.

    1997-11-01

    The Federal Government has proposed to offer Outer Continental Shelf lands in the Central and Western Gulf of Mexico for oil and gas leasing during 1998-2002. Because oil spills may occur from activities associated with offshore oil production the Minerals Management Service conducts a formal risk assessment. This report summarizes results of an oil-spill risk analysis conducted for the proposed Central and Western Gulf of Mexico lease sales and te Gulfwide OCS Program, 1998-2036. The objective of this analysis was to estimate relative risks associated with oil and gas production for the proposed lease sales.

  3. Inversion of IceBridge gravity data for continental shelf bathymetry beneath the Larsen ice shelf (Invited)

    NASA Astrophysics Data System (ADS)

    Cochran, J. R.; Bell, R. E.; Frearson, N.; Elieff, S.

    2010-12-01

    Accurate bathymetry beneath large ice shelves is crucial for developing models of the ocean circulation in the large sub-ice cavities and for effectively deploying moorings to monitor changing conditions. Improved models and observations should improve our understanding of how these large ice shelves collapse. A grid of free-air gravity data collected during the IceBridge 2009 Antarctic campaign over the floating Larsen C ice shelf was utilized to investigate the bathymetry of the underlying continental shelf. Data were collected with a Sander AIRGrav system mounted in a NASA DC-8 aircraft and flown at an altitude of about 500 m above the ice surface. Airborne data were augmented by upward continued marine gravity data from the former Larsen B ice shelf to provide control in an area where the bathymetry is known. Independent control on the geologic structures of the continental shelf was used to constrain the bathymetric inversion. The bathymetry determined by inverting the gravity data generally agrees with the shipboard bathymetry to within ±30 m and with a BAS seismic refraction line at 67°30’S on the ice shelf to 24 m. Simultaneously collected laser altimetry and radar data allow the geometry of the water-filled cavity to be investigated. Depths on the continental shelf beneath the ice shelf estimated from the inversion average about 450-600 m, but vary greatly from less than 300 m to greater than 1000 m. Distinctive localized overdeepenings, 20-30 km wide and reaching 900-1000 m deep are located in the inlets where three to five glaciers converge. Submarine valleys extending seaward from the overdeepened areas coalesce into three broad channels that extend to the seaward limit of the ice shelf and appear to extend to the edge of the continental shelf. The channels generally are at a depth of 550-700 m although the southernmost mapped channel deepens to over 1000 m near the edge of the ice shelf just south of 68°S. These newly imaged channels provide a

  4. 77 FR 74204 - Commercial Leasing for Wind Power on the Outer Continental Shelf Offshore North Carolina-Call for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-13

    ... Bureau of Ocean Energy Management Commercial Leasing for Wind Power on the Outer Continental Shelf... Power on the Outer Continental Shelf, Offshore North Carolina. SUMMARY: BOEM invites the submission of... project on the Outer Continental Shelf (OCS) offshore North Carolina, and to develop the project...

  5. 77 FR 29682 - Gulf of Mexico, Outer Continental Shelf, Central Planning Area, Oil and Gas Lease Sale 216/222

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-18

    ... Bureau of Ocean Energy Management Gulf of Mexico, Outer Continental Shelf, Central Planning Area, Oil and...) for Gulf of Mexico (GOM), Outer Continental Shelf (OCS) Oil and Gas Lease Sale: 2012 Central Planning... of the continental shelf boundary between the United States and Mexico. The CPA lease sale...

  6. 77 FR 38718 - Safety Zone; NOBLE DISCOVERER, Outer Continental Shelf Drillship, Chukchi and/or Beaufort Seas, AK

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-29

    ... SECURITY Coast Guard 33 CFR Part 147 RIN 1625-AA00 Safety Zone; NOBLE DISCOVERER, Outer Continental Shelf... Seas Outer Continental Shelf, Alaska, on or about July 1, 2012 through November 30, 2012. See TABLE 1...; NOBLE DISCOVERER, Outer Continental Shelf Drillship, Chukchi and Beaufort Seas, Alaska'' in the...

  7. 76 FR 38294 - Oil and Gas and Sulphur Operations in the Outer Continental Shelf-Civil Penalties

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-30

    ... and Gas and Sulphur Operations in the Outer Continental Shelf--Civil Penalties AGENCY: Bureau of Ocean... Continental Shelf Lands Act (OCSLA) requires the Bureau of Ocean Energy Management, Regulation and Enforcement...@boemre.gov . SUPPLEMENTARY INFORMATION: Background The goal of BOEMRE's Outer Continental Shelf...

  8. 75 FR 76632 - Oil and Gas and Sulphur Operations in the Outer Continental Shelf-Increased Safety Measures for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-09

    ... and Sulphur Operations in the Outer Continental Shelf--Increased Safety Measures for Energy Development on the Outer Continental Shelf; Correction AGENCY: Bureau of Ocean Energy Management, Regulation... oil and gas exploration and development on the Outer Continental Shelf. This document contains...

  9. 76 FR 55090 - Commercial Lease of Submerged Lands for Renewable Energy Development on the Outer Continental Shelf

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  10. Complex Patterns in Coastal Tsunami Impact Associated with Continental Shelf Topography

    NASA Astrophysics Data System (ADS)

    Gica, E.; Spillane, M. C.; Titov, V. V.

    2008-12-01

    Transoceanic propagation of tsunamis can cause severe impacts to remote coastal infrastructure and communities. Waves generated by submarine earthquakes have an initial dipole anisotropy with lobes normal to the fault line. Further complexity is added to the energy distribution by scattering from seafloor features such as seamounts and escarpments. Finally, as the waves encounter the continental slope and shelf, refraction and interference patterns further modify the waves as they move toward land, resulting in fine scale alongshore structure in the tsunami impact. Presented here are some results emerging from a risk assessment study for the eastern seaboard of the U.S. In addition to events in the eastern Atlantic, such as the Lisbon tsunami of 1755, broad-brush estimates of coastal impacts have identified the Puerto Rico trench as a potential source of damaging tsunamis. We employ a grid resolution of 30 arc-seconds bathymetry that encompasses the entire east coast to model fine- scale details of tsunami dynamics over the shelf for worst case tsunami scenarios. Some case studies, based on the Blake Ridge (extending offshore from Cape Hatteras) and the Hudson Canyon illustrate the importance of such features of the continental shelf and slope in focusing or dispersing tsunami wave energy.

  11. On instability and mixing on the UK Continental Shelf

    NASA Astrophysics Data System (ADS)

    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.

  12. Estimating rocky seafloor extent on the Southern California continental shelf

    USGS Publications Warehouse

    Cochrane, G.R.; Greene, H. Gary

    2009-01-01

    High-resolution sonar data are necessary to map bottom substrate for habitat studies but are lacking over much of the continental shelf. With such data, areas covered by sediment can be distinguished from bedrock areas with an accuracy of ??90%. Without these data, the extent of sediment as thick as 10 m cannot be resolved, and estimates of the extent of rocky seafloor are exaggerated. A study area north of Anacapa Island in Southern California interpreted as a large rocky area after mapping with low-resolution seismic systems was found to have exposed rocky bottom in only 10% of the area when mapped with high-resolution, side-scan sonar. The area of rock was estimated using video-supervised, sonar-image classification of textural derivatives of the data calculated from gray-level co-occurrence matrices. The classification of soft bottom was found to be ??90% accurate using an independent data set, derived from seafloor sampling records. Two general types of rock exposure are observed-sparse linear outcrops of layered sedimentary rocks and more massive, rounded outcrop areas of volcanic rocks. The percentage of exposed rock in volcanic areas exceeded that in sedimentary rock areas by a factor of 5 in the study area north of Anacapa Island. South of Point Arguello, 80% of the shelf seafloor is underlain by sedimentary rock units. The percentage of area that is exposed, rocky-reef habitat may be greater in other areas of coastal seafloor if the bedrock is predominantly volcanic. ?? 2009 The Geological Society of America.

  13. Export and Cycling of Continental Shelf Carbon: A Modeling Study

    NASA Astrophysics Data System (ADS)

    Siedlecki, S.; Archer, D.; Mahadevan, A.

    2004-12-01

    Continental margins play a significant role in the production and burial of organic carbon in the ocean, but these areas are poorly resolved in global circulation models. In this study, a high-resolution three-dimensional, nonhydrostatic idealized coastal model of the eastern United States after Mahadevan and Archer, 2000, 1998, was modified to simulate organic carbon production and export off the shelf. The model assumes a periodic north and south boundary, solid offshore and bottom boundaries, and a shelf-break density front determined by bathymetry. The model uses a free surface and a sigma grid in the vertical. We are in the process of formulating a carbon and nutrient component for this model. The model is initialized with a vertical nutrient profile taken from the open Atlantic Ocean. Mesoscale wind-driven circulation and vertical diffusion bring nutrients to the euphotic zone. Primary production is based on light availability and nutrient concentration. The particles advect with the flow and sink with a specified velocity. Remineralization is first-order in carbon concentration, and produces ammonia. Ammonia is slowly reoxidized to nitrate in subsurface waters, and used for recycled production in the euphotic zone. We are searching for a model of the production, sinking, and interconversion of multiple types of particles, which predicts the observed trends in f-ratio from coastal to pelagic ecosystems. The model is sensitive to sinking velocity, remineralization rate, vertical diffusivity, the uptake rate of nitrate, the uptake rate of ammonia, and the oxidation rate of ammonia to nitrate. Using the steady state solution of the one-dimensional model to initialize the three-dimensional model, we study the effect of vertical and horizontal advection and three-dimensional oceanographic processes on the distribution and export of carbon from the coastal system. We will compare the sensitivities of a box-budget, a one-dimensional diffusional, and the full 3-D

  14. Trophic interactions within the Ross Sea continental shelf ecosystem

    PubMed Central

    Smith, Walker O; Ainley, David G; Cattaneo-Vietti, Riccardo

    2006-01-01

    The continental shelf of the Ross Sea is one of the Antarctic's most intensively studied regions. We review the available data on the region's physical characteristics (currents and ice concentrations) and their spatial variations, as well as components of the neritic food web, including lower and middle levels (phytoplankton, zooplankton, krill, fishes), the upper trophic levels (seals, penguins, pelagic birds, whales) and benthic fauna. A hypothetical food web is presented. Biotic interactions, such as the role of Euphausia crystallorophias and Pleuragramma antarcticum as grazers of lower levels and food for higher trophic levels, are suggested as being critical. The neritic food web contrasts dramatically with others in the Antarctic that appear to be structured around the keystone species Euphausia superba. Similarly, we suggest that benthic–pelagic coupling is stronger in the Ross Sea than in most other Antarctic regions. We also highlight many of the unknowns within the food web, and discuss the impacts of a changing Ross Sea habitat on the ecosystem. PMID:17405209

  15. Continental shelf fish production estimation from CZCS chlorophyll data

    NASA Technical Reports Server (NTRS)

    Iverson, Richard L.

    1989-01-01

    A method for ocean fish production estimation was proposed for development. The method was to use data acquired with the Coastal Zone Color Scanner, and processed into chlorophyll concentrations by the GSFC ocean Sciences Division, in combination with fish production and primary production data acquired from different ocean areas. A linear relation exits between annual fish production and annual phytoplankton carbon production for a wide range of coastal ocean environments. The uses of several existing algorithms which relate primary production to CZCS chlorophyll data as input to the fish production regression model is proposed. A question relating phytoplankton production to CZCS chlorophyll was obtained by Eppley (1984) using chlorophyll data obtained from field samples, equivalent to chlorophyll data obtained from CZCS imagery, and primary production data obtained from ship-board observations on a wide variety of coastal and open ocean environments. This equation was modified with additional data and was successfully tested using CZCS data and field chlorophyll and phytoplankton production data obtained from northeastern North American continental shelf waters and Atlantic open ocean waters. The modified Eppley (1984) relation also estimated phytoplankton annual carbon production in the Sargasso Sea within the confidence limits of a mean value obtained from the Eppley (1984) equation for oceanic waters that provide about 90 percent of total ocean primary production. The modified Eppley production formula applied to CZCS chlorophyll data obtained from several northeastern North American coastal environments gave phytoplankton annual carbon production values similar to the values used in the fish production regression equation.

  16. Observational evidence for tidal straining over a sloping continental shelf

    NASA Astrophysics Data System (ADS)

    Endoh, Takahiro; Yoshikawa, Yutaka; Matsuno, Takeshi; Wakata, Yoshinobu; Lee, Keun-Jong; Umlauf, Lars

    2016-04-01

    Straining of a horizontal density gradient by tidal currents acts to periodically produce and destroy near-bottom stratification, which has been shown to modulate turbulence in the bottom boundary layer (BBL). Previous observations of such periodic variations have been limited to the coastal ocean and estuaries, where horizontal density gradients are maintained by river runoff or differential heating. In the present study, we show evidence for the existence of tidal straining over the continental shelf, outside any regions of freshwater influence, where horizontal density gradients are likely to result from the projection of the interior vertical stratification onto sloping topography. Based on microstructure data obtained in the East China Sea, we demonstrate that the tidal current shear interacting with the cross-isobath density gradient results in semidiurnal switching between unstable and stable stratification in the lower part of the BBL. The cycle of turbulent dissipation is quarter-diurnal, corresponding to the semidiurnal variation of tidal current shear. In addition, a noticeable diurnal modulation in stratification as well as a significant diurnal cycle of turbulent dissipation are observed in the upper part of the BBL, where the time evolution of stratification is dominated by tidal advection, rather than tidal straining.

  17. 77 FR 19321 - Geological and Geophysical Exploration on the Atlantic Outer Continental Shelf (OCS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-30

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Geological and Geophysical Exploration on the Atlantic Outer Continental Shelf (OCS) AGENCY: Bureau of Ocean Energy Management (BOEM), Interior. ACTION: Notice...

  18. 76 FR 23331 - Outer Continental Shelf (OCS) Scientific Committee (SC); Announcement of Plenary Session

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  19. 77 FR 4056 - Outer Continental Shelf (OCS) Scientific Committee (SC); Announcement of Plenary Session

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  20. Phytoplankton Community Structure, Biomass and Diversity on the Louisiana Continental Shelf

    EPA Science Inventory

    Phytoplankton communities on the Louisiana continental shelf (LCS) respond to nutrient loading from the Mississippi and Atchafalaya River Basin (MARB). Enhanced phytoplankton biomass is a source of organic matter contributing to the development of seasonal hypoxia. Samples were ...

  1. Geology of continental shelf, Onslow Bay, North Carolina, as revealed by submarine outcrops ( USA).

    USGS Publications Warehouse

    Blackwelder, B. W.; Macintyre, Ian G.; Pilkey, O.H.

    1982-01-01

    Lithologic and stratigraphic data from rocks dredged from the continental shelf off Onslow Bay, North Carolina, provide surface control for seismic studies of the southeastern United States continental margin and help to explain the distribution of potentially economic phosphate-rich sediments on this shelf. Outcropping Miocene rocks in this area indicate that the region has long been a positive geologic feature and has received relatively little Pliocene and Pleistocene sedimentation. -from Authors

  2. Increased spatial variance accompanies reorganization of two continental shelf ecosystems.

    PubMed

    Litzow, Michael A; Urban, J Daniel; Laurel, Benjamin J

    2008-09-01

    Phase transitions between alternate stable states in marine ecosystems lead to disruptive changes in ecosystem services, especially fisheries productivity. We used trawl survey data spanning phase transitions in the North Pacific (Gulf of Alaska) and the North Atlantic (Scotian Shelf) to test for increases in ecosystem variability that might provide early warning of such transitions. In both time series, elevated spatial variability in a measure of community composition (ratio of cod [Gadus sp.] abundance to prey abundance) accompanied transitions between ecosystem states, and variability was negatively correlated with distance from the ecosystem transition point. In the Gulf of Alaska, where the phase transition was apparently the result of a sudden perturbation (climate regime shift), variance increased one year before the transition in mean state occurred. On the Scotian Shelf, where ecosystem reorganization was the result of persistent overfishing, a significant increase in variance occurred three years before the transition in mean state was detected. However, we could not reject the alternate explanation that increased variance may also have simply been inherent to the final stable state in that ecosystem. Increased variance has been previously observed around transition points in models, but rarely in real ecosystems, and our results demonstrate the possible management value in tracking the variance of key parameters in exploited ecosystems. PMID:18767612

  3. Problem on the United States Continental Shelf - measuring the environmental {open_quotes}effectiveness{close_quotes} of the Outer Continental Shelf Act (OCSA)

    SciTech Connect

    Dubner, B.H.

    1994-12-31

    This article reviews the interplay of environmental standard with oil and gas leasing on the Outer Continental Shelf (OSC) in order to determine if the marine environment is really protected by the interplay of domestic legislation. The 1982 LOS treaty leaves environmental protection to State (domestic) regulation. There is no customary law regarding this type of domestic shelf regulation. The main problem is measuring the {open_quotes}effectiveness{close_quotes} of our domestic shelf legislation. For example, do we simply review effectiveness in terms of controlling operational damage or in terms of environmental injury caused by catastrophic accidents?

  4. Seafloor Rocks and Sediments of the Continental Shelf From Monterey Bay to Point Sur, California

    USGS Publications Warehouse

    Eittreim, Stephen L.; Anima, Roberto J.; Stevenson, Andrew J.; Wong, Florence L.

    2000-01-01

    Introduction Acoustic swath mapping of the greater Monterey Bay area continental shelf from Point Ano Nuevo to Point Sur reveals complex patterns of rock outcrops on the shelf, and coarse sand bodies that occur in distinct depressions on the inner and mid-shelves. This publication portrays the seafloor components in a 36- by 48-inch map sheet at 1:100,000 scale.

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  6. Trinity shoal: a reworked deltaic barrier on Louisiana continental shelf

    SciTech Connect

    Suter, J.R.; Penland, S.; Moslow, T.F.

    1985-02-01

    Abandonment and reworking of deltaic complexes of the Holocene Mississippi River have produced a series of sandy shoals on the muddy Louisiana continental shelf. Trinity shoal, one of these transgressive deposits, is located 30 km offshore of Atchafalaya Bay and the Point Au Fer-March Island shell reefs. Approximately 1000 km of high-resolution uniboom and 3.5 kHz subbottom-profile seismic data, taken in this area in 1983 and 1984, provide the data base for this study. Trinity shoal, associated with the abandoned Maringouin delta complex, is a lunate shore-parallel feature approximately 36 km long and 5-10 km wide. Relief on the shoal ranges from 2 to 3 m, and minimum water depths over the shoal vary from -5 to -2 m. The shoal sand body is from 5 to 7 m thick and is composed largely of parallel to low-angle clinoform reflectors. Several levels of buried fluvial channels, ranging in age from early Wisconsinian to Holocene, are associated with the shoal deposit. The occurrence of channel features within the shoal sand itself suggests the presence of tidal inlets, indicating a possible barrier-island origin for the shoal. The underlying deltaic sediments reach approximately 15 m in thickness and are made up of low-angle clinoform reflectors dipping to the southwest. Distributary, bay-fill, estuarine, and buried oyster-reef deposits can be recognized, making these similar to modern Atchafalaya delta deposits. Continued progradation of the Atchafalaya delta will probably result in burial of the Trinity shoal and Maringouin delta deposits by fine-grained sediments, giving these shoal deposits a high-preservation potential and creating an excellent stratigraphic trap.

  7. Manganese, iron, and sulfur cycling in Louisiana continental shelf sediments

    NASA Astrophysics Data System (ADS)

    Devereux, Richard; Lehrter, John C.; Beddick, David L.; Yates, Diane F.; Jarvis, Brandon M.

    2015-05-01

    Sulfate reduction is considered the primary pathway for organic carbon remineralization on the northern Gulf of Mexico Louisiana continental shelf (LCS) where bottom waters are seasonally hypoxic, yet limited information is available on the importance of iron and manganese cycling in the region. Sedimentary manganese, iron, and sulfur cycling were investigated on the LCS using a combined chemical analysis and sediment diagenesis modeling approach. Three stations situated 320 km across the LCS along the 20 m isobath were sampled up to five times between the spring of 2006 and summer of 2007. Bottom water oxygen levels at the stations ranged from 203 mmol m-3 in spring to 2.5 mmol m-3 in summer. Porewater Mn and Fe2+ concentrations (up to 275 and 300 μmol L-1, respectively), sulfate reduction rates (1.0-8.4 mmol m-2 d-1), and the fraction of total oxalate extracted iron obtained as Fe(II) (0.25-0.52) differed between station and season. Sediments at station Z02 on the eastern LCS, south of Terrebonne Bay, had higher organic matter content and sulfate reduction rates than sediments at Z03, 160 km further west. Sulfate reduction rates were higher in summer than spring at station Z02 but not at Z03 where porewater Mn and Fe concentrations were highest in summer. Porewater Fe2+ concentrations, solid phase oxalate-extractable Fe concentrations, and sediment incubation experiments suggested iron reduction at Z03 may account for 20% or more of organic carbon remineralization. LCS Fe(III) concentrations decreased and sulfate reduction rates increased in model simulations by lowering interfacial dissolved oxygen levels and increasing the rates of organic matter deposited on the sediment surface. Results from this study demonstrate that LCS sedimentary metal oxide cycling may be more important in organic carbon mineralization pathways than previously recognized.

  8. Some Cenozoic hydrocarbon basins on the continental shelf of Vietnam

    SciTech Connect

    Dien, P.T.

    1994-07-01

    The formation of the East Vietnam Sea basins was related to different geodynamic processes. The pre-Oligocene basement consists of igneous, metamorphic, and metasediment complexes. The Cretaceous-Eocene basement formations are formed by convergence of continents after destruction of the Tethys Ocean. Many Jurassic-Eocene fractured magmatic highs of the Cuulong basin basement constitute important reservoirs that are producing good crude oil. The Paleocene-Eocene formations are characterized by intramountain metamolasses, sometimes interbedded volcanic rocks. Interior structures of the Tertiary basins connect with rifted branches of the widened East Vietnam Sea. Bacbo (Song Hong) basin is predominated by alluvial-rhythmic clastics in high-constructive deltas, which developed on the rifting and sagging structures of the continental branch. Petroleum plays are constituted from Type III source rocks, clastic reservoirs, and local caprocks. Cuulong basin represents sagging structures and is predominated by fine clastics, with tidal-lagoonal fine sandstone and shalestone in high-destructive deltas that are rich in Type II source rocks. The association of the pre-Cenozoic fractured basement reservoirs and the Oligocene-Miocene clastic reservoir sequences with the Oligocene source rocks and the good caprocks is frequently met in petroleum plays of this basin. Nan Conson basin was formed from complicated structures that are related to spreading of the oceanic branch. This basin is characterized by Oligocene epicontinental fine clastics and Miocene marine carbonates that are rich in Types I, II, and III organic matter. There are both pre-Cenozoic fractured basement reservoirs, Miocene buildup carbonate reservoir rocks and Oligocene-Miocene clastic reservoir sequences, in this basin. Pliocene-Quaternary sediments are sand and mud carbonates in the shelf facies of the East Vietnam Sea back-arc basin. Their great thickness provides good conditions for maturation and trapping.

  9. Oceanography of the Subtropical Shelf Front Zone in the SW-Atlantic Continental Shelf

    NASA Astrophysics Data System (ADS)

    Muelbert, J. H.; Acha, M.; Berasategui, A.; Bersano, J. G.; Braga, E. S.; Eichler, P.; Garcia, V. M.; Gomez-Erache, M.; Guerrero, R.; Mianzan, H.; Reta, R.; Ramirez, F.

    2005-05-01

    Only physical aspects of the Subtropical Shelf Front (STSF) have been described for the Southwest Atlantic Continental Shelf. The main goal of this paper is to present results of an integrated physical, chemical and biological study at the STSF conducted during the winter of 2003 and summer of 2004. A cross section was established at the historical determined location of the STSF. Nine stations were sampled during the winter cruise and 7 stations during summer. Each section included a series of conductivity-temperature-depth (CTD) stations fitted with dissolved oxygen and turbidity sensors. Selected water samples were filtered and frozen at -20oC for nutrient determination. Samples for chlorophyll were concentrated on filters and these were stored frozen for later processing. Plankton net tows were carried out above and below pycnocline. Surface benthic foraminifera were collected with a bottom snapper. Results revealed that winter was marked by an inner shelf salinity front and the STSF located in the mid-shelf. Inner salinity showed the strong influence of freshwater, with high silicate (71.98 μM), phosphate (2.70 μM), nitrate (1.01 μM), Total Dissolved Nitrogen (22.98 μM) and suspended matter (44.80 mg/L). With distance from the coast and reduction of terrestrial input, subsurface high values of nutrients were associated with SACW upwelling. As a result, chlorophyll a concentration decreased from coastal well-mixed waters, where values up to 3.0 mg.m3 are registered, to offshore waters. Zooplankton abundance and biomass, and ichthyoplankton abundance follows the same trend. Zoo and ichthyoplankton abundance revealed the presence of 3 groups associated to the inner, mid and offshore shelf region. Benthic foraminifera composition suggested that shallow stations are dominated by few large freshwater species, while offshore stations presented smaller forms and higher species diversity. During summer, the halocline extended over the shelf and joined the STSF in

  10. On the difficulty of modeling Circumpolar Deep Water intrusions onto the Amundsen Sea continental shelf

    NASA Astrophysics Data System (ADS)

    Nakayama, Y.; Timmermann, R.; Schröder, M.; Hellmer, H. H.

    2014-12-01

    In the Amundsen Sea, warm Circumpolar Deep Water (CDW) intrudes onto the continental shelf and flows into the ice shelf cavities of the West Antarctic Ice Sheet, resulting in high basal melt rates. However, none of the high resolution global models resolving all the small ice shelves around Antarctica can reproduce a realistic CDW flow onto the Amundsen Sea continental shelf, and previous studies show simulated bottom potential temperature at the Pine Island Ice Shelf front of about -1.8 °C. In this study, using the Finite-Element Sea ice-ice shelf-Ocean Model (FESOM), we reproduce warm CDW intrusions onto the Amundsen Sea continental shelf and realistic melt rates of the ice shelves in West Antarctica. To investigate the importance of horizontal resolution, forcing, horizontal diffusivity, and the effect of grounded icebergs, eight sensitivity experiments are conducted. To simulate the CDW intrusion realistically, a horizontal resolution of about 5 km or smaller is required. The choice of forcing is also important and the cold bias in the NCEP/NCAR reanalysis over the eastern Amundsen Sea prevents warm CDW from intruding onto the continental shelf. On the other hand, the CDW intrusion is not highly sensitive to the strength of horizontal diffusion. The effect of grounded icebergs located off Bear Peninsula is minor, but may act as a buffer to an anomalously cold year.

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

    NASA Astrophysics Data System (ADS)

    Ruiz Etcheverry, L. A.; Saraceno, M.; Piola, A. R.; Strub, P. T.

    2016-04-01

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

  12. Low-frequency currents and continental shelf waves in the southern Weddell Sea

    SciTech Connect

    Middleton, J.H.; Foster, T.D.; Foldvik, A.

    1982-07-01

    The salient features of low-frequency current fluctuations, obtained from an analysis of eight current meter records from the continental shelf and slope of the southern Weddell sea, are compared to baroclinic and barotropic theories. A simple baroclinic theory of internal waves is used successfully to predict high-frequency spectral cutoff values from low-frequency velocity ellipse calculations made from the continental slope mooring data. The success of this theory indicates that the higher spectral energy levels observed over the slope compared to the shelf are probably due to baroclinic motions. A barotropic model of free continental shelf waves proposed by Saint-Guily (1976) is adapted for the local topography and the predictions of the model compared to observations. Coherences and phases between moorings separated by 10 and 160 km in the long-shelf direction provide substantial evidence of the existence of shelf waves as predicted by the theory for periods of 3--60 days and for the lowest three modes. For periods of 3--8 days rotary spectral levels indicate anticlockwise rotating current vectors over the shelf as predicted by theory, but for longer periods current vectors rotate clockwise. It is speculated that fluctuations in along-shelf wind stress drive the shelf waves but that the longer period motions are driven directly by the wind stress.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    SciTech Connect

    Not Available

    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.

  16. Seabed acoustics of a sand ridge on the New Jersey continental shelf.

    PubMed

    Knobles, D P; Wilson, P S; Goff, J A; Cho, S E

    2008-09-01

    Acoustic measurements were made on a sand ridge on the New Jersey continental shelf. Data collected on two L arrays separated by 20 km from a single multi-frequency tow suggest small horizontal environmental variability. Values for the sound speed structure of the seabed are extracted by first applying a geo-acoustic inversion method to broadband and narrowband acoustic data from short-range sources. Then, a parabolic equation algorithm is used to properly include the bathymetry and sub-bottom layering. Finally, the frequency dependence of the seabed attenuation is inferred by optimizing the model fit to long-range transmission loss data in the 50-3000 Hz band. PMID:19045558

  17. Production and remineralization in continental shelf ecosystems: A test of the SEEP hypothesis

    SciTech Connect

    Rowe, G.T.

    1986-09-01

    The hypothesis that continental shelf ecosystems export a major fraction of the carbon produced by the phytoplankton during the spring bloom was tested during the Shelf Edge Exchange Processes (SEEP) experiment off the northeast US coast in 1984. This study, along with a reanalysis of traditional concepts, leads to the conclusion that only a small fraction of continental shelf phytodetritus is exported across a distinct shelf-slope hydrographic frontal system. What is not consumed in the spring is utilized on the shelf during the ensuing stratified season. More open ended ecosystems may export production more readily. The total benthic standing stocks in terms of organic carbon (macrofauna, meiofauna, and bacteria) have been estimated in the SEEP area. Their preponderance on the continental shelf was partial evidence that little organic matter escapes to the upper continental slope. Measurements of the metabolism of the biota allowed calculation of turnover times of organic detritius and the total biota. The turnover time of detritus increased as grain size decreased, suggesting that fine-grained deposits contain mostly refractory, nonreactive compounds, especially on the deep slope. Turnover times of the total biota were about the same in the coarse versus fine-grained shelf deposits, but a far larger fraction of the turnover was attributed to the bacteria in the fine sediments than in the coarse. On average, about 25% of the primary production appeared to be utilized by the aerobic benthos on the continental shelf in the SEEP area. The role of anaerobes at depth in the sediments remains uncertain.

  18. Quaternary seismic stratigraphy and paleoenvironments on the continental shelf of the East China Sea

    NASA Astrophysics Data System (ADS)

    Liu, Zhen-Xia; Berne, Serge; Saito, Yoshiki; Lericolais, G.; Marsset, T.

    2000-08-01

    Paleoenvironments and stratigraphy have been interpreted from 4380 km of seismic profiling collected during a geological and geophysical cruise on the continental shelf of the East China Sea (ECS) undertaken in 1996. The geophysical data are correlated with a borehole situated on the outer shelf obtained by Shanghai Marine Geology Bureau, indicating that six seismic units have been preserved since oxygen-isotope stage 6, including four regressive-transgressive cycles. Seismic units U2, U3+U4+U5, U6, and U7 are interpreted to correspond respectively to oxygen-isotope stages 1, 3, 5, and 6, implying that sediment partitioning and sequence architecture in the ECS have been controlled by glacio-eustasy and global climate changes. Alternating continental and marine strata corresponding to glaciation and interglaciation are well preserved on the outer shelf of the ECS. Most of the cold environment strata, which formed on the outer shelf during oxygen-isotope stages 2 and 4, are too thin to be recognized on SIG 600J because of resolution, but corresponding erosion surfaces exist. Seismic unit U7 is widespread over the shelf, extending to the continental edge and showing little variation in thickness, as the regression was pronounced and lasted a long time. Thus, U7 can be used as a marker layer for correlation of Quaternary strata on the shelf of the ECS. Post-glacial transgression is obvious in the ECS. Marine strata with varied thickness were developed in the shallow sea of the inner shelf, thinning toward the outer shelf. The continental shelf of the ECS has been influenced by Pacific tide-wave systems for a long time, forming tidal sand-ridge sequences, developed during transgressions, corresponding to oxygen-isotope stages 7 (or 9), 5, 3 and 1.

  19. Holocene stratigraphy of the Alabama inner continental shelf: Influence of shelf sand ridges on determining lithofacies architecture

    SciTech Connect

    Davies, D.J.; Parker, S.J. . Energy and Coastal Geology Div.)

    1993-03-01

    Surface and subsurface distribution of lithofacies from Holocene sediments of the AL inner continental shelf was determined from a series of 59 vibracores and associated surface sediment grab sediments. Five Holocene lithofacies composed of 12 discrete microfacies were delineated based on grain size, color, sedimentary structures, shell content, and fabric of samples. These lithofacies include: (1) Graded Shelly Sand Lithofacies; (2) Clean Sand Lithofacies; (3) Dirty Sand Lithofacies; (4) Biogenic Sediment Lithofacies; and (5) Muddy Sediment Lithofacies. These represent four major depositional environments: The Shelf Sand Sheet Environment (lithofacies 1 and 2); the Sand Ridge Environment (lithofacies 1, 2, and 3); the Bay/Lagoon Environment (lithofacies 3, 4 and 5); and the Muddy Shelf Environment (lithofacies 5). East of the Main Pass of Mobile Bay, the seafloor is composed of a clean Shelf Sand Sheet with oblique shelf sand ridges; Clean Sand and Graded Shelly Sand are the dominant surface sediment types. Coarse shell beds that grade up to quartz sand units (total thickness 0.1 to 3+m) interpreted as tempestites comprise most of the upper portion of the ridges. West of the Pass, the muddier lithofacies (3 and 5) dominate surface samples. Microfacies at depth represent the early Holocene transgressive systems tract; these include the Muddy Shelf Depositional Environment and the filled estuaries and bays of the flooded Pleistocene fluvial valleys represented by the Bay/Lagoon Depositional Environment. The AL inner shelf provides an excellent model of the variability of sedimentation mode in time and space during deposition of a transgressive systems tract. Development of the palimpsest sand sheet/ridge complex progressed on the eastern shelf due to shut off of sediment influx, westward longshore currents, and episodic incidence of major hurricanes. On the western shelf a patchy distribution of muddier sediments developed from input of floodwaters from Mobile Bay.

  20. Variations in sediment texture on the northern Monterey Bay National Marine Sanctuary continental shelf

    USGS Publications Warehouse

    Edwards, B.D.

    2002-01-01

    The storm-protected continental shelf of Monterey Bay, part of the Monterey Bay National Marine Sanctuary, north-central California, is subject to abundant, episodic sediment input from fluvial sources. North of Monterey Bay, conditions of reduced sediment supply combined with the exposed nature of the shelf provide an effective laboratory for studying the contrasting effects of storm- versus fluvial-dominated conditions on modern sedimentation. Textural analyses performed on surface sediment samples collected from more than 380 box cores and MultiCores??? document the existence of a clearly defined mud belt occupying the mid-shelf throughout the region. Inshore sands combined with these mid-shelf muds represent deposits from modern sedimentation processes. In Monterey Bay, where episodic fluvial input from winter storms dominates sedimentation, the mid-shelf mud belt extends across the shelf to the shelf break. North of Monterey Bay, where sediment loads are reduced and both oceanographic and storm processes dominate, the mid-shelf mud belt is bordered by relict sediments occupying the outer shelf. In the study area, mass accumulation rates established by radiochemical studies support the contention that storm-induced along-shelf processes result in northward transport of sediment within the mud belt. The continuity of transport, however, is interrupted by topographic highs which are barriers or inhibitors to sediment transport created by wrench-style tectonics associated with the San Andreas fault system.

  1. Source and dispersal of silt on northern Gulf of Mexico Continental Shelf

    SciTech Connect

    Peterson, M.; Mazzullo, J.

    1988-02-01

    The surficial sediment on the continental shelf of the northern Gulf of Mexico is characterized by abundant silty clay which was deposited during the late Pleistocene lowstand and reworked during and after the Holocene transgression. The purposes of this study were to determine the sources of the silt fraction in this surficial sediment by quartz grain roundness and surface texture analysis, and to determine the effects of modern shelf currents upon the distribution of silt.

  2. Water mass circulation on the continental shelf of the Gulf of Cádiz

    NASA Astrophysics Data System (ADS)

    García-Lafuente, Jesús; Delgado, Javier; Criado-Aldeanueva, Francisco; Bruno, Miguel; del Río, Jorge; Miguel Vargas, Juan

    2006-06-01

    Acoustic Doppler Current Profiler data collected during three successive surveys in the Gulf of Cádiz in May-June 2001 have been used to analyse the surface circulation on the continental shelves of the Gulf of Cádiz and how this circulation matches the circulation in the ocean side of the Gulf. The wider and larger eastern continental shelf holds a cyclonic circulation bounded at the south by a shelf-break jet that is identified with the Huelva front. The coastal current that closes the gyre at the north is identified with the warm counterflow mentioned in the literature. Under westerly winds, this counter current recirculates toward the east while recent upwelled water near Cape Santa Maria is advected downstream by the shelf-break jet, leaving the cold signature at the surface that has been identified historically with the Huelva front. Under easterlies, part of the coastal counterflow invades the western continental shelf while the remaining recirculates eastward to close the cyclonic cell. The western continental shelf and slope is occupied by a larger-scale cyclonic eddy that extends into the deep ocean. This eddy has vertical length scale of hundreds of metres and is linked to the general wind forcing in the area. Both cyclonic structures are bounded at the south by a jet that enters in the Gulf of Cádiz moving around the second eddy and eastward to feed the Atlantic inflow through the Strait of Gibraltar.

  3. Cross-shelf and vertical structure of ichthyoplankton assemblages in continental shelf waters of the Southern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Espinosa-Fuentes, M. L.; Flores-Coto, C.

    2004-02-01

    The horizontal and vertical variation of ichthyoplankton assemblages in continental shelf waters of the Southern Gulf of Mexico was studied during an annual cycle (1994-1995) at 22 stations distributed across four transects located off the main fluvio-lagoon systems of the area. Samples were collected from five levels of the water column, from the surface to a depth of 105 m. The Bray-Curtis Dissimilarity Index identified five assemblages: Coastal, Inner Neritic, Outer Neritic, Oceanic and a Transition Group. The main species of each assemblage reflected the habitat, season, and spawning area of adult organisms. The Coastal Assemblage occupied the uppermost water column levels of the most nearshore stations. The Oceanic Assemblage was restricted to the deepest samplings of the stations of the outer shelf and the Neritic Assemblages were located on the continental shelf between the Coastal and Oceanic Assemblages, embracing all the sampling levels in some periods. Variation in composition, location and abundance of larvae in each assemblage was determined by a series of physical processes that act at different temporal and spatial scales, especially the mixing process generated by the wind stress and continental water discharges acting at a mesoscale that influences the distribution of the assemblages along the whole continental shelf as well as a fine scale affecting the composition and vertical distribution of organisms in a more reduced area of just tens of meters in the water column. Canonical Correspondence Analysis revealed that the depth of the sample, the potential energy, and the temperature generated the greatest variability in the system. Vertical and horizontal salinity gradients play a determinant role in delimiting the Coastal and Neritic Assemblages.

  4. An instrument system for long-term sediment transport studies on the continental shelf

    USGS Publications Warehouse

    Butman, Bradford; Folger, David W.

    1979-01-01

    A bottom-mounted instrument system has been designed and built to monitor processes of bottom sediment movement on the continental shelf. The system measures bottom current speed and direction, pressure, temperature, and light transmission and photographs the bottom. The system can be deployed for periods of 2–6 months to monitor intermitent processes of sediment movement such as storms and to assess seasonal variability. Deployments of the system on the U.S. east coast continental shelf show sediment resuspension and changes in bottom microtopography due to surface waves, tidal currents, and storms.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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

  7. Sea ice and oceanic processes on the Ross Sea continental shelf

    NASA Technical Reports Server (NTRS)

    Jacobs, S. S.; Comiso, J. C.

    1989-01-01

    The spatial and temporal variability of Antarctic sea ice concentrations on the Ross Sea continental shelf have been investigated in relation to oceanic and atmospheric forcing. Sea ice data were derived from Nimbus 7 scanning multichannel microwave radiometer (SMMR) brightness temperatures from 1979-1986. Ice cover over the shelf was persistently lower than above the adjacent deep ocean, averaging 86 percent during winter with little month-to-month of interannual variability. The large spring Ross Sea polynya on the western shelf results in a longer period of summer insolation, greater surface layer heat storage, and later ice formation in that region the following autumn.

  8. 77 FR 5039 - Accommodation Service Provided on Vessels Engaged in U.S. Outer Continental Shelf Activities

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-01

    ... SECURITY Coast Guard Accommodation Service Provided on Vessels Engaged in U.S. Outer Continental Shelf... providing accommodation service on the U.S. Outer Continental Shelf. DATES: Comments and related material... Act notice regarding our public dockets in the January 17, 2008, issue of the Federal Register (73...

  9. 77 FR 39164 - Safety Zone; KULLUK, Outer Continental Shelf Mobile Offshore Drilling Unit (MODU), Beaufort Sea, AK

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-02

    ... SECURITY Coast Guard 33 CFR Part 147 RIN 1625-AA00 Safety Zone; KULLUK, Outer Continental Shelf Mobile...; KULLUK, Outer Continental Shelf Mobile Offshore Drilling Unit (MODU), Beaufort Sea, Alaska'' in the Federal Register (77 FR 10711). The NPRM included a 30- day comment period. We received 2...

  10. 76 FR 53481 - Outer Continental Shelf, Alaska OCS Region, Chukchi Sea Planning Area, Oil and Gas Lease Sale 193

    Federal Register 2010, 2011, 2012, 2013, 2014

    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... Continental Shelf (OCS) Oil and Gas Lease Sale 193, Chukchi Sea, Alaska (OCS EIS/EA BOEMRE 2011-041)....

  11. 77 FR 10711 - Safety Zone; KULLUK, Outer Continental Shelf Mobile Offshore Drilling Unit (MODU), Beaufort Sea, AK

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-23

    ... SECURITY Coast Guard 33 CFR Part 147 RIN 1625-AA00 Safety Zone; KULLUK, Outer Continental Shelf Mobile... prospects located in the Beaufort Sea Outer Continental Shelf, Alaska, from 12:01 a.m. on July 1, 2012... Federal Register (73 FR 3316). Public Meeting The Coast Guard does not plan to hold a public meeting....

  12. 76 FR 70156 - Proposed 5-Year Outer Continental Shelf (OCS) Oil and Gas Leasing Program for 2012-2017

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-10

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Proposed 5-Year Outer Continental Shelf (OCS) Oil and Gas Leasing... Continental Shelf Lands Act (OCSLA) specifies a multi-step process of consultation and analysis that must...

  13. 75 FR 72679 - Renewable Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf-Acquire a...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-26

    ... Federal Register on July 9, 2008 (73 FR 39376). The North American Industry Classification System (NAICS... Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf--Acquire a Lease... an Outer Continental Shelf (OCS) renewable energy lease. We are taking this action because...

  14. 76 FR 8962 - Renewable Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf-Acquire a...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-16

    ... published in the Federal Register on July 9, 2008 (73 FR 39376). The North American Industry Classification... Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf--Acquire a Lease... acquisition of an Outer Continental Shelf (OCS) renewable energy lease. We are taking this action because...

  15. 76 FR 40725 - Approval of Outer Continental Shelf (OCS) Permit Issued to Cape Wind Associates, LLC (EPA Permit...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-11

    ... offshore renewable wind energy project in federal waters off the coast of Massachusetts. DATES: Effective... AGENCY Approval of Outer Continental Shelf (OCS) Permit Issued to Cape Wind Associates, LLC (EPA Permit... Outer Continental Shelf (OCS) air permit decision regarding Cape Wind Associates, LLC (Cape Wind)....

  16. Origin and extent of fresh paleowaters on the Atlantic continental shelf, USA

    USGS Publications Warehouse

    Cohen, D.; Person, M.; Wang, P.; Gable, C.W.; Hutchinson, D.; Marksamer, A.; Dugan, B.; Kooi, H.; Groen, K.; Lizarralde, D.; Evans, R.L.; Day-Lewis, F. D.; Lane, J.W., Jr.

    2010-01-01

    While the existence of relatively fresh groundwater sequestered within permeable, porous sediments beneath the Atlantic continental shelf of North and South America has been known for some time, these waters have never been assessed as a potential resource. This fresh water was likely emplaced during Pleistocene sea-level low stands when the shelf was exposed to meteoric recharge and by elevated recharge in areas overrun by the Laurentide ice sheet at high latitudes. To test this hypothesis, we present results from a high-resolution paleohydrologic model of groundwater flow, heat and solute transport, ice sheet loading, and sea level fluctuations for the continental shelf from New Jersey to Maine over the last 2 million years. Our analysis suggests that the presence of fresh to brackish water within shallow Miocene sands more than 100 km offshore of New Jersey was facilitated by discharge of submarine springs along Baltimore and Hudson Canyons where these shallow aquifers crop out. Recharge rates four times modern levels were computed for portions of New England's continental shelf that were overrun by the Laurentide ice sheet during the last glacial maximum. We estimate the volume of emplaced Pleistocene continental shelf fresh water (less than 1 ppt) to be 1300 km3 in New England. We also present estimates of continental shelf fresh water resources for the U.S. Atlantic eastern seaboard (104 km3) and passive margins globally (3 ?? 105 km3). The simulation results support the hypothesis that offshore fresh water is a potentially valuable, albeit nonrenewable resource for coastal megacities faced with growing water shortages. ?? 2009 National Ground Water Association.

  17. Origin and extent of fresh paleowaters on the Atlantic continental shelf, USA.

    PubMed

    Cohen, Denis; Person, Mark; Wang, Peng; Gable, Carl W; Hutchinson, Deborah; Marksamer, Andee; Dugan, Brandon; Kooi, Henk; Groen, Koos; Lizarralde, Daniel; Evans, Robert L; Day-Lewis, Frederick D; Lane, John W

    2010-01-01

    While the existence of relatively fresh groundwater sequestered within permeable, porous sediments beneath the Atlantic continental shelf of North and South America has been known for some time, these waters have never been assessed as a potential resource. This fresh water was likely emplaced during Pleistocene sea-level low stands when the shelf was exposed to meteoric recharge and by elevated recharge in areas overrun by the Laurentide ice sheet at high latitudes. To test this hypothesis, we present results from a high-resolution paleohydrologic model of groundwater flow, heat and solute transport, ice sheet loading, and sea level fluctuations for the continental shelf from New Jersey to Maine over the last 2 million years. Our analysis suggests that the presence of fresh to brackish water within shallow Miocene sands more than 100 km offshore of New Jersey was facilitated by discharge of submarine springs along Baltimore and Hudson Canyons where these shallow aquifers crop out. Recharge rates four times modern levels were computed for portions of New England's continental shelf that were overrun by the Laurentide ice sheet during the last glacial maximum. We estimate the volume of emplaced Pleistocene continental shelf fresh water (less than 1 ppt) to be 1300 km(3) in New England. We also present estimates of continental shelf fresh water resources for the U.S. Atlantic eastern seaboard (10(4) km(3)) and passive margins globally (3 x 10(5) km(3)). The simulation results support the hypothesis that offshore fresh water is a potentially valuable, albeit nonrenewable resource for coastal megacities faced with growing water shortages. PMID:19754848

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

    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.

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

    USGS Publications Warehouse

    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.

  1. Novel decomposition products of chlorophyll- a in continental shelf (Louisiana shelf) sediments: formation and transformation of carotenol chlorin esters

    NASA Astrophysics Data System (ADS)

    Chen, Nianhong; Bianchi, Thomas S.; Bland, John M.

    2003-06-01

    In April 2000, we collected box cores from five stations along a cross-shelf transect on the Louisiana (LA) continental shelf. Novel esters of carotenols and chlorins (carotenoid chlorin esters, CCEs), which are highly specific grazing markers, were identified in surface and deep sediments (>10 cm) from the LA shelf. Chlorophyll- a inventory indicated that CCEs are one of the major decay products of chlorophyll- a in shelf sediments. Abundances of total CCEs (9-18%) in surface sediments along the cross-shelf transect were comparable to the abundance of pheophytin- a, pyropheophytin- a, and total steryl chlorin esters (SCEs). Prior work has identified four CCEs which have dehydrated fucoxanthin/fucoxanthinol as a substitute alcohol of phytol. We report on four newly identified CCEs associated with nondehydrated fuxocanthin/fucoxanthinol esterified to (pyro)pheophorbide- a. These nondehydrated CCEs were generally present in lower concentrations than their dehydrated counterparts, but were detectable by atmospheric pressure chemical ionization (APCI) mass spectrometry coupled with high-performance liquid chromatography (HPLC). We attributed differences between this study and previous work to the time allowed for predepositional decay and grazing processes to occur. The rapid sedimentation of CCEs in the shallow water column (ca. 10 m) on the LA shelf allowed for effective burial of all CCEs compared to the deeper water column regions sampled by previous work. This speculation is supported by the fact that the concentrations of CCEs with nondehydrated fucoxanthin/fucoxanthinol were extremely low in sediments from the site on the outer LA shelf with a deeper (253 m) water column. We also tentatively identified an additional CCE and its isomer as fucoxanthinol didehydrate pyropheophorbide- a ester. We suggest that the formation and transformation of CCEs are primarily controlled by the following three biologically mediated reactions: demethoxycarbonylation, dehydration

  2. 78 FR 48180 - Consolidation of Officer in Charge, Marine Inspection For Outer Continental Shelf Activities...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-07

    ... SECURITY Coast Guard Consolidation of Officer in Charge, Marine Inspection For Outer Continental Shelf Activities; Eighth Coast Guard District AGENCY: Coast Guard, DHS. ACTION: Notice and request for comments. SUMMARY: The Coast Guard is considering establishing a single Officer in Charge, Marine Inspection...

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

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-18

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management North American Datum of 1983 (NAD 83) Outer Continental Shelf (OCS) Provisional Official Protraction Diagram (OPDs) AGENCY: Bureau of Ocean Energy Management (BOEM),...

  4. 78 FR 45965 - Research Lease on the Outer Continental Shelf (OCS) Offshore Virginia, Request for Competitive...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-30

    ... Bureau of Ocean Energy Management Research Lease on the Outer Continental Shelf (OCS) Offshore Virginia... FR 44150-44156). The area identified for potential commercial wind leasing in the PSN was delineated... Environmental Assessment (EA) (76 FR 40926). Among the comments received on the draft EA was a letter...

  5. 76 FR 13205 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    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.... Correction In the Federal Register of February 9, 2011, in FR Doc. 2011-2791, on page 7230, in the...

  6. 76 FR 7230 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    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.... Correction In the Federal Register of January 24, 2011, in FR Doc. 2011-1319, on page 4129, correct...

  7. 75 FR 20859 - Outer Continental Shelf (OCS) Policy Committee; Notice and Agenda for Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-21

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Minerals Management Service Outer Continental Shelf (OCS) Policy Committee; Notice and Agenda for Meeting AGENCY: Minerals Management Service (MMS), Interior. ACTION: Notice of Meeting. SUMMARY: The OCS...

  8. 78 FR 5836 - Adjustment of Service Fees for Outer Continental Shelf Activities

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-28

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Adjustment of Service Fees for Outer Continental Shelf Activities... updated in 2008, with Federal Register Notice 73 FR 49943. BOEM is now adjusting various cost...

  9. The application of Seasat-1 radar altimetry to continental shelf circulation modeling

    NASA Technical Reports Server (NTRS)

    Cornillon, P.; Reed, M.; Spaulding, M.; Swanson, C.

    1980-01-01

    Seasat-1 radar altimetry data have been used to verify a continental shelf circulation model subjected to tidal forcing on the open boundary. The model makes use of the semi-implicit mode of time integration, removing the surface gravity wave time step restriction. Both the altimetry and the model predictions are compared with empirically determined tidal fluctuations and generally good agreement is obtained.

  10. Application of remote sensing to study nearshore circulation. [and the continental shelf

    NASA Technical Reports Server (NTRS)

    Zeigler, J.; Lobecker, R.; Stauble, D.; Welch, C.; Haas, L.; Fang, C. S.

    1974-01-01

    The research to use remote sensing techniques for studying the continental shelf is reported. The studies reported include: (1) nearshore circulation in the vincinity of a natural tidal inlet; (2) identification of indicators of biological activity; (3) remote navigation system for tracking free drifting buoys; (4) experimental design of an estuaring tidal circulation; and (5) Skylab support work.

  11. 76 FR 5189 - BOEMRE Information Collection Activities: 1010-0081, Operations in the Outer Continental Shelf...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-28

    ...To comply with the Paperwork Reduction Act of 1995 (PRA), we are notifying the public that we have submitted to OMB an information collection request (ICR) to renew approval of the paperwork requirements in the regulations under 30 CFR 282, Operations in the Outer Continental Shelf for Minerals Other than Oil, Gas, and Sulphur. This notice also provides the public a second opportunity to......

  12. Reactive Iron and Iron-Reducing Bacteria in Louisiana Continental Shelf Sediments

    EPA Science Inventory

    The Mississippi and Atchafalaya Rivers release sediments containing 15 x 106 t of iron onto the Louisiana continental shelf (LCS) each year. Iron oxides reaching the seafloor may be utilized as electron acceptors by iron-reducing bacteria for organic matter oxidation or become r...

  13. A PROBABILISTIC SURVEY OF FISH TISSUE CONTAMINATION FROM THE CONTINENTAL SHELF OF THE US WEST COAST

    EPA Science Inventory

    A probabilistic survey of environmental condition of the continental shelf of the US West Coast was conducted in 2003 by the US EPA National Coastal Assessment (NCA), with collaboration by the NOAA National Marine Fisheries Service. Metals and organic contaminants were analyzed ...

  14. Nutrient distributions, transports, and budgets on the inner margin of a river-dominated continental shelf

    EPA Science Inventory

    Physical and biogeochemical processes determining the distribution and fate of nutrients delivered by the Mississippi and Atchafalaya rivers to the inner (<50 m depth) Louisiana continental shelf (LCS) were examined using a three-dimensional hydrodynamic model of the LCS and obse...

  15. 76 FR 70156 - Draft Programmatic Environmental Impact Study (PEIS) for Proposed 5-Year Outer Continental Shelf...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-10

    ... Bureau of Ocean Energy Management Draft Programmatic Environmental Impact Study (PEIS) for Proposed 5-Year Outer Continental Shelf (OCS) Oil and Gas Leasing Program for 2012-2017 AGENCY: Bureau of Ocean... FURTHER INFORMATION CONTACT: Bureau of Ocean Energy Management, Headquarters, 381 Elden Street,...

  16. 77 FR 24734 - Outer Continental Shelf (OCS) Renewable Energy Program Leasing for Marine Hydrokinetic Technology...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-25

    ... Bureau of Ocean Energy Management Outer Continental Shelf (OCS) Renewable Energy Program Leasing for... and information on the public session can be found online at: http://www.boem.gov/Renewable-Energy... Renewable Energy Programs, 381 Elden Street, HM 1328, Herndon, Virginia 20170-4817, (703) 787-1340...

  17. Interpretation of graphic data on potential geologic hazards on the southeastern United States Atlantic continental shelf

    USGS Publications Warehouse

    Popenoe, Peter; Butman, Bradford; Paull, Charles K.; Ball, Mahlon M.; Pfirman, Stephanie L.

    1981-01-01

    This report presents and analyzes seismic-survey data and bottom-instrument data as they pertain to a regional assessment of potential geologic hazards and other constraints to petroleum exploration and development on the southeastern United States Continental Shelf (see fig. 1).  

  18. 75 FR 61511 - Intent To Prepare a Supplemental Environmental Impact Statement: Outer Continental Shelf, Alaska...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-05

    ...The Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) is giving notice of its intent to publish a Supplemental Environmental Impact Statement for Outer Continental Shelf (OCS) Oil and Gas Lease Sale 193 in the Chukchi Sea Planning Area, Alaska. This Supplementary EIS will provide new analysis in response to a remand by the United States District Court for the District of......

  19. 75 FR 82055 - Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore Massachusetts...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-29

    ...The Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) invites submissions describing interest in obtaining one or more commercial leases for the construction of a wind energy project(s) on the Outer Continental Shelf (OCS) offshore Massachusetts. BOEMRE will use the responses to this RFI to gauge specific interest in commercial development of OCS wind resources in the area......

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

    SciTech Connect

    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.

  1. 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

    USGS Publications Warehouse

    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.

  2. Source and dispersal of silt on northern Gulf of Mexico continental shelf

    SciTech Connect

    Peterson, M.; Mazzullo, J.

    1988-01-01

    The surficial sediment on the continental shelf of the northern Gulf of Mexico is characterized by abundant silty clay which was deposited during the late Pleistocene lowstand and reworked during and after the Holocene transgression. The purposes of this study were to determine the sources of the silt fraction in this surficial sediment by quartz grain roundness and surface texture analysis, and to determine the effects of modern shelf currents upon the distribution of silt. Areal variations in quartz grain roundness and surface texture define six silt provinces on the northern Gulf of Mexico continental shelf. The Mississippi province is the largest province and stretches from the Chandeleur Islands to Matagorda Bay. It is characterized by a mixture of rounded grains that were derived from the sedimentary rocks of the Gulf coastal plain and the Mid-Continent, and angular, fractured grains that were derived from glacial deposits in the northern United States. A comparison of the areal distribution of these six provinces with the late Pleistocene paleogeography of the continental shelf shows evidence for varying degrees of shore-parallel transport of silt by modern shelf currents.

  3. Tidal energy fluxes and dissipation on the European continental shelf

    NASA Astrophysics Data System (ADS)

    Davies, Alan M.; Kwong, Simon C. M.

    2000-09-01

    The spatial distribution of the energy flux, energy dissipation, current magnitude, and surface elevation amplitude of the major tidal constituents over the northwest European shelf are examined in detail. These distributions are obtained from the harmonic analysis of a 6 month three-dimensional simulation of 28 tidal constituents. The model currents are validated by a comparison of computed tidal harmonics against those derived from a harmonic analysis of up to 278 current time series. A similar comparison is performed for tidal elevations based on 257 tide gauges. Calculations show that for the most significant tidal constituents (e.g., M2, S2 and K2) there is a major energy flux in the deep water along the shelf edge off the northwest of Scotland, with some energy leaking onto the shelf and into the North Sea. A second source of energy is across the shelf edge at the southern end of the Celtic Sea, with this energy flux propagating into the Irish Sea and southern North Sea, where the majority of the energy is dissipation in the shallow regions. Significantly different distributions are found for the diurnal and shallow water constituents, and the spatial distributions of energy flux and dissipation of the various constituents are considered. The accuracy of separating tidal current harmonics using model data of less than a synodic period is examined with reference to the S2 and K2 tide. Calculations suggest that the accuracy of computed currents comparable to those obtained from observations can be obtained from an analysis of a 60 day period compared with the synodic period for S2 and K2 of 182 days, a significant saving in computer time.

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

    NASA Technical Reports Server (NTRS)

    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.

  5. High-magnesium calcite dissolution in tropical continental shelf sediments controlled by ocean acidification.

    PubMed

    Haese, R R; Smith, J; Weber, R; Trafford, J

    2014-01-01

    Increases in atmospheric CO2 cause the oceanic surface water to continuously acidify, which has multiple and profound impacts on coastal and continental shelf environments. Here we present the carbonate mineral composition in surface sediments from a range of continental shelf seabed environments and their current and predicted stability under ocean acidifying conditions. Samples come from the following four tropical Australian regions: (1) Capricorn Reef (southern end of the Great Barrier Reef), (2) the Great Barrier Reef Lagoon, (3) Torres Strait, and (4) the eastern Joseph Bonaparte Gulf. Beyond the near-shore zone, these regions typically have a carbonate content in surface sediments of 80 wt % or more. The abundance of high-magnesium calcites (HMC) dominates over aragonite (Arag) and low-magnesium calcite (LMC) and constitutes between 36% and 50% of all carbonate. HMC, with a magnesium content larger than 8-12 mol %, is more soluble than both Arag and LMC, and the solubility of HMC positively correlates with its magnesium concentration. From the solubility data of Plummer and Mackenzie ( Am. J. Sci. 1974 , 274 , 61 - 83 ), 95% of HMC in the four regions is presently in metastable equilibrium relative to global mean tropical sea surface water. HMC is predicted to become destabilized in the four regions between 2040 and 2080 AD, with typical HMC decline rates between 2% and 5% per year. The range of respective estimated carbonate dissolution rates is expected to exceed current continental shelf carbonate accumulation rates, leading to net dissolution of carbonate during the period of HMC decline. In a geological context, the decline in HMC in tropical continental shelf environments is a global event triggered by reaching below-equilibrium conditions. The characteristic change in carbonate mineral composition in continental shelf sediments will serve as a geological marker for the proposed Anthropocene Epoch. PMID:24972293

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

    SciTech Connect

    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.

  7. Characteristics, generation and mass transport of nonlinear internal waves on the Washington continental shelf

    NASA Astrophysics Data System (ADS)

    Zhang, Shuang; Alford, Matthew H.; Mickett, John B.

    2015-02-01

    As a step toward better understanding the generation of nonlinear internal waves (NLIWs) on continental shelves and the factors determining their morphology, amplitude and propagation, we analyze more than 1500 NLIWs detected on the Washington (WA) continental shelf using four summer/fall time series of temperature and velocity measurements from a surface mooring deployed in 100 m of water. Propagating onshore toward the northeast, these NLIWs take a variety of forms, including internal solitary waves, solitary wave trains and bores. Nearly all are mode-1 depression waves that arrive semidiurnally along with the internal tide. The NLIW energy flux is correlated with the internal tide energy flux but not the local barotropic forcing, implying that the observed NLIWs arise primarily from shoaling remotely generated internal tides rather than local generation. Estimated onshore transport by the waves can equal or exceed offshore Ekman transport, suggesting the waves may play an important role in the mass balance on the continental shelf.

  8. Sources of phytoplankton to the inner continental shelf in the Santa Barbara Channel inferred from cross-shelf gradients in biological, physical and chemical parameters

    NASA Astrophysics Data System (ADS)

    Goodman, Jo; Brzezinski, Mark A.; Halewood, Elisa R.; Carlson, Craig A.

    2012-10-01

    Phytoplankton are a major food resource for filter-feeding organisms occupying intertidal and subtidal habitats of the inner continental shelf. Phytoplankton in these nearshore waters experience different anthropogenic and natural forcing compared to those offshore such that cross-shelf exchange would allow phytoplankton that were produced offshore to serve as a subsidy to inner shelf consumers when phytoplankton production on the shelf is negatively impacted. In the Santa Barbara Channel (SBC) the continental shelf is only a few kilometers wide facilitating exchange with offshore waters. Physical, chemical and biological gradients were examined monthly along a 3-km cross-shelf transect in the SBC from January, 2008 through April, 2009. Chemical and biological distributions followed temporal changes in physical forcing with higher nutrient concentrations and a more intense period of biological production associated with spring upwelling. Chlorophyll was relatively evenly distributed across the shelf during upwelling, but was present at higher concentrations on the inner shelf under stratified conditions. Similarly, cross-shelf gradients in the distribution of dominant phytoplankton genera were weakest during upwelling when blooms of the prymnesiophyte, Phaeocystis, and the diatoms, Eucampia spp. and Thalassiosira spp. occurred across most of the shelf. Upon stratification, blooms were largely confined to the inner shelf within 0.75 km of the shoreline with an initial bloom of the diatom Leptocylindrus spp. followed by Pseudo-nitzschia spp. and series of dinoflagellate blooms with Prorocentrum spp. and Lingulodinium spp. attaining the highest abundances. Phytoplankton taxonomic similarity decreased with increasing distance separating stations along the transect and was inversely related to stratification intensity. The observed distribution patterns and the trends in taxonomic similarity imply that for most of the year consumers within rocky intertidal and subtidal

  9. Sea-ice and surface water circulation, Alaskan continental shelf

    NASA Technical Reports Server (NTRS)

    Wright, F. F.; Sharma, G. D.; Burns, J. J. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Over 1500 water samples from surface and from standard hydrographic depths were collected during June and July 1973 from Bering Sea and Gulf of Alaska. The measurement of temperature, salinity, and productivity indicated that various distinct water masses cover the Bering Sea Shelf. The suspended load in surface waters will be correlated with the ERTS-1 imagery as it becomes available to delineate the surface water circulation. The movement of ice floes in the Bering Strait and Bering Sea indicated that movement of ice varies considerably and may depend on wind stress as well as ocean currents.

  10. Sedimentary environments of inner Continental Shelf, west Florida

    SciTech Connect

    Donoghue, J.F. )

    1989-09-01

    Near-surface sediments of the Appalachia region of the west Florida shelf reflect a fluvial origin with strong evidence of reworking in a moderate-energy shallow marine environment. The inner shelf sediments are moderately sorted, fine quartz sands with only minor amounts of gravel and fines. High-resolution seismic records reveal a continual interplay of fluvial, deltaic, and nearshore environments during sea level fluctuations of the late Quaternary. Subsurface geomorphology includes large fluvial channels, prograding clinoforms, and ridge-and-swale topography. These relict features have been buried during the Holocene beneath a transgressive sand sheet with sediment supplied from mass nearshore shoals. The same source has contributed to the formation of a chain of barrier islands that forms a rim around the modern Apalachicola River delta. Barrier formation began approximately 3,000 years ago. Modern migration rates of the islands are high, in both landward and longshore directions, providing evidence for the rapid rate of transition from one type of sedimentary environment to another. The ample sedimentary supply appears at present to be keeping pace with moderate subsidence and sea level rise.

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

    NASA Technical Reports Server (NTRS)

    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.

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

    PubMed

    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

    2016-01-01

    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. PMID:27575831

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

    PubMed Central

    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

    2016-01-01

    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. PMID:27575831

  14. Upper ocean variability in west Antarctic Peninsula continental shelf waters as measured using instrumented seals

    NASA Astrophysics Data System (ADS)

    Costa, Daniel P.; Klinck, John M.; Hofmann, Eileen E.; Dinniman, Michael S.; Burns, Jennifer M.

    2008-02-01

    Temperature profile data for the west Antarctic Peninsula (WAP) continental shelf waters, collected from freely ranging instrumented seals (crabeater, Lobodon carcinophagus and leopard, Hydrurga leptonyx), were used to demonstrate that these platforms can be used to supplement traditional oceanographic sampling methods to investigate the physical properties of the upper water column. The seal-derived profiles were combined with temperature profiles obtained from ship-based CTD measurements and from a numerical circulation model developed for the WAP to describe changes in temperature structure, heat content, and heat flux in the upper ocean waters of the WAP continental shelf. The seal-derived data documented the fall-to-winter transition of the surface waters and the shelf-wide presence of modified Circumpolar Deep Water (CDW) below 150-200 m on the WAP continental shelf. The heat content of the upper 200 m calculated from the seal-derived temperature profiles ranged between 1000 and 1500 MJ m -2; similar estimates were obtained from simulated temperature distributions. The seal-derived temperature measurements provided broader space and time resolution than was possible using any other currently available oceanographic sampling method. As such, the seal-derived measurements provided a valuable dataset for evaluation of temperature fields obtained from a numerical circulation model.

  15. Wildlife Densities and Habitat Use Across Temporal and Spatial Scales on the Mid-Atlantic Outer Continental Shelf. Final Report to the Department of Energy EERE Wind & Water Power Technologies Office

    SciTech Connect

    Williams, Kathryn A.; Stenhouse, Iain J.; Johnson, Sarah M.; Connelly, Emily E.

    2015-10-01

    The Mid-Atlantic Baseline Studies Project helped address environmental barriers to offshore wind energy development in the mid-Atlantic region by providing regulators, developers, and other stakeholders with comprehensive baseline ecological data and analyses. Project funders and collaborators from a range of academic institutions, non-governmental organizations, federal agencies, foundations, and private companies came together to study bird, sea turtle, and marine mammal distributions, densities, and movements on the mid-Atlantic Outer Continental Shelf between 2012 and 2014. Specific project activities and goals included the following: (1) Conduct standardized surveys to quantify bird, sea turtle, and marine mammal densities seasonally and annually throughout the study region and identify important habitat use or aggregation areas. (2) Develop statistical models to help understand the drivers of wildlife distribution and abundance patterns. (3) Use individual tracking data for several focal bird species to provide information on population connectivity and individual movements that is complementary to survey data. (4) Identify species that are likely to be exposed to offshore wind energy development activities in the mid-Atlantic study area. (5) Develop U.S.-based technological resources and assessment methods for future monitoring efforts, including a comparison of high resolution digital video aerial surveys to boat-based surveys. (6) Help meet data needs associated with National Environmental Policy Act (NEPA), Marine Mammal Protection Act, and Endangered Species Act requirements, by contributing several years of data and analysis towards future Environmental Impact Statements. This report consists of six parts: Project overview (executive summary and Chapters 1-2); Examining wildlife distributions and relative abundance from a digital video aerial survey platform (Chapters 3-6); Examining wildlife distributions and abundance using boat-based surveys

  16. A new bathymetry of the Northeast Greenland continental shelf: Constraints on glacial and other processes

    NASA Astrophysics Data System (ADS)

    Arndt, Jan Erik; Jokat, Wilfried; Dorschel, Boris; Myklebust, Reidun; Dowdeswell, Julian A.; Evans, Jeffrey

    2015-10-01

    A new digital bathymetric model (DBM) for the Northeast Greenland (NEG) continental shelf (74°N-81°N) is presented. The DBM has a grid cell size of 250 m × 250 m and incorporates bathymetric data from 30 multibeam cruises, more than 20 single-beam cruises and first reflector depths from industrial seismic lines. The new DBM substantially improves the bathymetry compared to older models. The DBM not only allows a better delineation of previously known seafloor morphology but, in addition, reveals the presence of previously unmapped morphological features including glacially derived troughs, fjords, grounding-zone wedges, and lateral moraines. These submarine landforms are used to infer the past extent and ice-flow dynamics of the Greenland Ice Sheet during the last full-glacial period of the Quaternary and subsequent ice retreat across the continental shelf. The DBM reveals cross-shelf bathymetric troughs that may enable the inflow of warm Atlantic water masses across the shelf, driving enhanced basal melting of the marine-terminating outlet glaciers draining the ice sheet to the coast in Northeast Greenland. Knolls, sinks, and hummocky seafloor on the middle shelf are also suggested to be related to salt diapirism. North-south-orientated elongate depressions are identified that probably relate to ice-marginal processes in combination with erosion caused by the East Greenland Current. A single guyot-like peak has been discovered and is interpreted to have been produced during a volcanic event approximately 55 Ma ago.

  17. Interpretation of seismic stratigraphy on the Amazon continental shelf

    SciTech Connect

    Alexander, C.R. Jr.; Nittrouer, C.A.; Demaster, D.J.

    1985-01-01

    The stratigraphy of the Amazon subaqueous delta has been examined using high-resolution reflection profiles. 15 piston cores from the Amazon Shelf were used to interpret the significance of the reflectors evident in the seismic profiles. Acoustic reflectors correlate with changes in grain size within cores, and generally represent coarser layers within the muddy deposits of the delta. Measurement of compressional-wave seismic velocity and saturated bulk density demonstrate that the correlation results from changes in acoustic impedance, caused by the grain-size variations. The reflectors reveal two predominant types of seismic stratigraphy: depositional and erosional. The depositional stratigraphy contains reflectors formed by relatively subtle change in grain size. Gently dipping topset and steeply dipping foreset demonstrate upward and seaward progradation of the subaqueous delta. This stratigraphy is truncated by erosional reflectors, which are significantly coarser layers. The erosional reflectors divide the depositional stratigraphy into distinct sets. The prevalence of erosional reflectors is greatest in the topset region near the river mouth, suggesting that sediment in this region, which is rapidly accumulating on 100-year time scales, has been eroded over longer time scales within the Holocene.

  18. Sea, ice and surface water circulation, Alaskan continental shelf

    NASA Technical Reports Server (NTRS)

    Sharma, G. D.; Wright, F. F.; Burns, J. J. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. ERTS-1 imagery has been extremely useful in understanding the tidal water movements in a large estuary such as Cook Inlet. As more imagery obtained during various tidal stages become available it appears that complex and fast changing micro-circulation patterns develop in various regions of Cook Inlet during each advancing and receding tide. More ERTS-1 synoptic imagery is needed to fully understand the effect of the approach of tidal front on the water movements in the various regions through the estuary. The conventional onboard ship data gathered during various cruises although revealed the overall circulation pattern in Cook Inlet but failed to show micro-subgyres which develop in various regions during each tide which are discernible on ther ERTS-1 imagery. Suspended load distribution in the Bering Sea during summer varies significantly. In areas of phytoplankton bloom and at the river mouths the suspended load is higher than the 1 mg/1 which is found over most areas. The influence of major rivers on temperature, salinity, and suspended load in surface water as well as at shallow depth is apparent. On the Bering shelf a strong pycnocline generally at depth 10-20 m is formed by surface fresh water flow which retains sediment in suspension over extended periods.

  19. Macrofaunal production and biological traits: Spatial relationships along the UK continental shelf

    NASA Astrophysics Data System (ADS)

    Bolam, S. G.; Eggleton, J. D.

    2014-04-01

    Biological trait analysis (BTA) is increasingly being employed to improve our understanding of the ecological functioning of marine benthic invertebrate communities. However, changes in trait composition are seldomly compared with concomitant changes in metrics of ecological function. Consequently, inferences regarding the functional implications of any changes are often anecdotal; we currently have a limited understanding of the functional significance of the traits commonly used. In this study, we quantify the relationship between benthic invertebrate trait composition and secondary production estimates using data spanning almost the breadth of the UK continental shelf. Communities described by their composition of 10 traits representing life history, morphology and behaviour showed strong relationships with variations in total secondary production. A much weaker relationship was observed for community productivity (or P:B), a measure of rate of energy turnover. Furthermore, the relationship between total production and multivariate taxonomic community composition was far weaker than that for trait composition. Indeed, the similarities between communities as defined by taxonomy were very different from those depicted by their trait composition. That is, as many studies have demonstrated, taxonomically different communities may display similar trait compositions, and vice versa. Finally, we found that descriptions of community trait composition vary greatly depending on whether abundance or biomass is used as the enumeration weighting method during BTA, and trait assessments based on biomass produced better relations with secondary production than those based on abundance. We discuss the significance of these findings with respect to BTA using marine benthic invertebrates.

  20. Morphology and Dynamics of Subaqueous Dunes in a Tideless Outer Shelf (murcia Continental Shelf, Western Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Durán, R.; Rivera, J.; Guillén, J.; de Cárdenas, E.; Muñoz, A.; Acosta, J.

    2014-12-01

    During the last years, the increasing application of multibeam sonar systems for mapping the seafloor has revealed the occurrence of sedimentary bedforms on the continental shelves worldwide. In addition, repeated multibeam surveys are used to monitor and compare the temporal evolution of such morphologies providing important insights into the sedimentary processes on the continental shelf. In the Murcia continental shelf, Western Mediterranean Sea, a large filed of subaqueous dunes has been observed in the middle and outer shelf. Here, we present a detailed morphologic and sedimentological analysis of these features with the aim to discuss their possible mechanism of formation and assess their potential mobility. The findings are based on swath-bathymetry collected using a SIMRAD EM 710 and EM3000D multibeam echosounders, high-resolution seismic profiles acquired with a TOPAS 018 system and sediment samples. Dunes are widely distributed between 60 and 110 m depth, from the Cope Cape, to the north, to the Águilas submarine canyon head rim, to the south. Dunes range from 18 to 140 m in wavelength and from 0.29 to 1.28 m in height. Dunes have asymmetrical profiles (average asymmetry of 0.065) with the lee slope facing towards the southwest that indicate a net south-westward sediment transport. Seabed samples collected in the crests and troughs of individual dunes show a similar grain-size distribution curve, but differ in the content of fines, which is higher in the trough, whereas the crests are dominated by coarse particles. High resolution seismic profiles reveal the presence of a continuous strong reflector that constitutes the base of the subaqueous dunes and could likely correspond to the Holocene transgressive ravinement surface.Dune migration rates were determined from the net displacement of the crests and troughs positions deduced from repeated multibeam surveys (2003 and 2013). Results indicate that the subaqueous dunes remain stationary or migrate at low

  1. Instabilities in nonlinear internal waves on the Washington continental shelf

    NASA Astrophysics Data System (ADS)

    Zhang, Shuang; Alford, Matthew H.

    2015-07-01

    Previous studies have identified two primary mechanisms (shear instability and convective instability) by which nonlinear internal waves (NLIWs) induce mixing on continental shelves. To determine the relative importance of these and their dependence on background flow conditions, we examine a much longer (6 month) data set from a moored ADCP/thermistor chain with 2 m vertical spacing in which over 600 NLIWs are detected. Turbulent properties of the 318 waves with detectable overturning instabilities are documented using Thorpe scales. The 130 waves detected while an ADCP was functioning are classified based on a Froude number criterion (Fr = uc, where u is velocity in the wave propagation direction, c is the wave phase speed). Of these, 108 waves are identified as shear-instability (Type I; Fr < 1) waves and 22 as convective instability (Type II; Fr > 1). Composites are constructed by averaging in a wave coordinate frame over all waves in each category, showing the mean spatial structure of dissipation and other wave quantities. Turbulence is highest at the sheared interface for Type I waves and throughout the wave core for Type II waves. No relationship between wave instability mechanisms and wave/background parameters such as wave steepness, stratification, or mean flow is found, except that unstable waves tend to be more energetic, demonstrating a need to better understand wave propagation and breaking in complex and variable coastal oceanographic background flows.

  2. The influence of surface waves on water circulation in a mid-Atlantic continental shelf region

    NASA Technical Reports Server (NTRS)

    Whitlock, C. H.; Talay, T. A.

    1974-01-01

    The importance of wave-induced currents in different weather conditions and water depths (18.3 m and 36.6 m) is assessed in a mid-Atlantic continental-shelf region. A review of general circulation conditions is conducted. Factors which perturb the general circulation are examined using analytic techniques and limited experimental data. Actual wind and wave statistics for the region are examined. Relative magnitudes of the various currents are compared on a frequency of annual occurrence basis. Results indicated that wave-induced currents are often the same order of magnitude as other currents in the region and become more important at higher wind and wave conditions. Wind-wave and ocean-swell characteristics are among those parameters which must be monitored for the analytical computation of continental-shelf circulation.

  3. An oilspill risk analysis for the North Atlantic outer continental shelf lease area

    USGS Publications Warehouse

    Smith, Richard Allmon; Slack, James Richard; Davis, Robert K.

    1976-01-01

    The Federal Government has proposed to lease 1,172,795 acres of Outer Continental Shelf (OCS) lands on Georges Bank off the New England Coast for oil and gas development. Estimated recoverable petroleum resources for the proposed 206 tract sale area range from 180 to 650 million barrels. Contingent upon actual discovery of this quantity of oil, production is expected to span a period of about 20 years. An oilspill risk analysis was conducted to determine relative environmental hazards of developing oil in the North Atlantic Outer Continental Shelf lease area. The study analyzed probability of spill occurrence, likely path of pollutants from spills, and locations in space and time of recreational and biological resources likely to be vulnerable. These results are combined to yield estimates of the overall oilspill risk associated with development of the lease area. (Woodard-USGS)

  4. Water exchange between the continental shelf and the cavity beneath Nioghalvfjerdsbræ (79 North Glacier)

    NASA Astrophysics Data System (ADS)

    Wilson, N. J.; Straneo, F.

    2015-09-01

    The mass loss at Nioghalvfjerdsbræ is primarily due to rapid submarine melting. Ocean data obtained from beneath the Nioghalvfjerdsbræ ice tongue show that melting is driven by the presence of warm (1°C) Atlantic Intermediate Water (AIW). A sill prevents AIW from entering the cavity from Dijmphna Sund, requiring that it flow into the cavity via bathymetric channels to the south at a pinned ice front. Comparison of water properties from the cavity, Dijmphna Sund, and the continental shelf support this conclusion. Overturning circulation rates inferred from observed melt rates and cavity stratification suggest an exchange flow between the cavity and the continental shelf of 38mSv, sufficient to flush cavity waters in under 1 year. These results place upper bounds on the timescales of external variability that can be transmitted to the glacier via the ice tongue cavity.

  5. Bottom stress estimates and sand transport on northern California inner continental shelf

    USGS Publications Warehouse

    Cacchione, D.A.; Drake, D.E.; Ferreira, J.T.; Tate, G.B.

    1994-01-01

    Measurements of velocities and light transmission in the bottom boundary layer on the continental shelf off northern California demonstrate the importance of storms in the transport of sediment along the coast and offshore in this region. Time-series estimates of bottom stress obtained from a combined wave-current bottom boundary layer model in which wave and current measurements from the Geoprobe tripod were used as input show high stress values of 10 dynes cm-2 during two distinct storm events in early February and early March, 1991. These stresses induce significant offshore sediment transport, achieving maximum values of about 0.5 g cm-1 s-1. The net transport over the entire measurement period from 30 January 1991 to 13 March 1991 was along the coast toward the north and offshore. This transport pattern explains slow migration of low amplitude, broad crescentic dunes along and across this portion of the inner continental shelf. ?? 1994.

  6. [Circulation and exchange processes on the South Atlantic Bight Continental Shelf]. [Progress summary for 1986

    SciTech Connect

    Not Available

    1986-12-31

    A continuation of the physical oceanography program to investigate circulation and exchange processes on the South Atlantic Bight (SAB) Continental Shelf is proposed. The transport and dispersal of materials entering the inner shelf zone with river discharge is not well understood at present. Climatological data, satellite imagery, and numerical modeling results indicate two removal routes for these nearshore waters: northeast transport and offshore exchange between Cape Fear and Savannah during the spring and summer when maximum run-off and northward winds prevail; and southward transport and offshore exchange near Cape Canaveral during the fall when southward winds prevail. We have conducted interdisciplinary experiments to investigate the transport processes in the inner to outer shelf between Savannah, Georgia and Cape Fear, North Carolina. In addition we propose to continue synthesis and interpretation of current measurements. The analyses will focus on determining the coupling mechanisms of inner shelf and outer shelf waters with special emphasis placed on resolving the modes and rates of shelf water removal.

  7. High Resolution Quaternary Seismic Stratigraphy of the New York Bight Continental Shelf

    USGS Publications Warehouse

    Schwab, William C.; Denny, J.F.; Foster, D.S.; Lotto, L.L.; Allison, M.A.; Uchupi, E.; Swift, B.A.; Danforth, W.W.; Thieler, E.R.; Butman, Bradford

    2003-01-01

    A principal focus for the U.S. Geological Survey (USGS) Coastal and Marine Geology Program (marine.usgs.gov) is regional reconnaissance mapping of inner-continental shelf areas, with initial emphasis on heavily used areas of the sea floor near major population centers. The objectives are to develop a detailed regional synthesis of the sea-floor geology in order to provide information for a wide range of management decisions and to form a basis for further investigations of marine geological processes. In 1995, the USGS, in cooperation with the U.S. Army Corps of Engineers (USACOE), New York District, began to generate reconnaissance maps of the continental shelf seaward of the New York - New Jersey metropolitan area. This mapping encompassed the New York Bight inner-continental shelf, one of the most heavily trafficked and exploited coastal regions in the United States. Contiguous areas of the Hudson Shelf Valley, the largest physiographic feature on this segment of the continental shelf, also were mapped as part of a USGS study of contaminated sediments (Buchholtz ten Brink and others, 1994; 1996). The goal of the reconnaissance mapping was to provide a regional synthesis of the sea-floor geology in the New York Bight area, including: (a) a description of sea-floor morphology; (b) a map of sea-floor sedimentary lithotypes; (c) the geometry and structure of the Cretaceous strata and Quaternary deposits; and (d) the geologic history of the region. Pursuing the course of this mapping effort, we obtained sidescan-sonar images of 100 % of the sea floor in the study area. Initial interpretations of these sidescan data were presented by Schwab and others, (1997a, 1997b, 2000a). High-resolution seismic-reflection profiles collected along each sidescan-sonar line used multiple acoustic sources (e.g., watergun, CHIRP, Geopulse). Multibeam swath-bathymetry data also were obtained for a portion of the study area (Butman and others, 1998;). In this report, we present a series

  8. Benthic foraminifers from the continental shelf and slope of the Gulf of Mexico: An indicator of shelf hypoxia

    USGS Publications Warehouse

    Osterman, L.E.

    2003-01-01

    Benthic foraminifers from 74 core-top sediment samples collected primarily from the continental shelf of the Gulf of Mexico were analyzed to determine a microfaunal indicator for shelf hypoxia to be used in future paleoenvironmental studies. Principal component analysis (PCA) and cluster analysis (CA) of 93 species recognized factors/clusters that were similar to previous investigations of the benthic foraminifers, except that both analyses also identified PCA6/CA6 in the area where hypoxic conditions have been observed. Three low-oxygen-tolerant species, Pseudononion atlanticum, Epistominella vitrea, and Buliminella morgani have high factor loadings in PCA6. The cumulative percentage of three species is defined as the PEB (PEB, Pseudononion, Epistominella, Buliminella) index. The highest PEB values observed in the 74 surface sediment samples occur in the zone of recognized hypoxia on the Louisiana shelf. Values of the PEB index are also elevated along the southern Texas coastline, suggesting that this area may experience periodic hypoxia as well. ?? 2003 Elsevier Ltd. All rights reserved.

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

    SciTech Connect

    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)

  10. Outer continental shelf, Beaufort Sea, oil and gas lease sale 170 (proposed notice of sale)

    SciTech Connect

    1997-12-31

    The Minerals Management Service (MMS) is issuing this proposed Notice of Sale under the Outer Continental Shelf (OCS) Lands Act (43 U.S.C. 1331-1356, as amended) and the regulations issued thereunder (30 CFR Part 256). A `Sale Notice Package,` containing this Notice and several supporting and essential documents referenced in the Notice, is available from the MMS Alaska OCS Regional Office Public Information Unit.

  11. Oil and gas developments in Atlantic Coastal Plain and Outer Continental Shelf in 1985 and 1986

    SciTech Connect

    Amato, R.V.

    1987-10-01

    Drilling activity for 1985 was not reported previously due to the low level of activity. No exploratory drilling took place on the Atlantic outer continental shelf in 1985 or 1986. One shallow well was drilled onshore in Georgia on the Atlantic coastal plan in 1985, and 2 wells were completed in Georgia in 1986. Texaco drilled 6 core holes on the Virginia coastal plain in 1986. 2 tables.

  12. An oilspill risk analysis for the Mid-Atlantic Outer Continental Shelf lease area

    USGS Publications Warehouse

    Smith, Richard Allmon; Slack, James Richard; Davis, Robert K.

    1976-01-01

    An oilspill risk analysis was conducted to determine relative environmental impacts of developing oil in different regions of the Mid-Atlantic Outer Continental Shelf lease area. The study analyzed probability of spills, likely path of pollutants from spills, and locations in space and time of recreational and biological resources likely to be vulnerable. These results are combined to yield estimates of the overall oilspill risk associated with development of the lease area. (Woodard-USGS)

  13. Hydrothermal origin of oil and gas reservoirs in basement rock of the South Vietnam continental shelf

    SciTech Connect

    Dmitriyevskiy, A.N.; Kireyev, F.A.; Bochko, R.A.; Fedorova, T.A. )

    1993-07-01

    Oil-saturated granites, with mineral parageneses typical of hydrothermal metasomatism and leaching haloes, have been found near faults in the crystalline basement of the South Vietnam continental shelf. The presence of native silver, barite, zincian copper, and iron chloride indicates a deep origin for the mineralizing fluids. Hydrothermally altered granites are a new possible type of reservoir and considerably broaden the possibilities of oil and gas exploration. 15 refs., 22 figs., 1 tab.

  14. Megaflutes in a continental shelf setting, Placentia Bay, Newfoundland

    NASA Astrophysics Data System (ADS)

    Shaw, John; Puig, Pere; Han, Guoqi

    2013-05-01

    Megaflutes - erosional scours normally found in deep water on continental slopes - were identified in 1978 on sidescan sonograms and seismic reflection profiles from Placentia Bay on the south coast of Newfoundland, Canada. Data from recent extensive multibeam sonar surveys provide an opportunity to describe the morphology and distribution of the megaflutes in detail, and to consider the formative processes. They occur on the east side of the outer bay, at a depth of ~ 200 m, in a 2-3 km-wide swath that continues to the south into Halibut Channel, over a total distance of ~ 100 km. The megaflutes have been formed by removal of a layer of postglacial mud, exposing underlying glaciomarine sediments and releasing a volume of 4.5 km3. They occur in a range of forms, including single, multiple, and coalescent types, and in some areas at least their inception was related to pre-existing pockmarks. Radiocarbon dates from piston cores are used to demonstrate that megaflute formation post-dated ca. 9 ka. Megaflute formation in Placentia Bay has been attributed to a 'reverse flow' from the tsunami generated by the 1929 Grand Banks earthquake, and this is still the accepted hypothesis. We argue that the return flow from a tsunami did not generate the megaflutes, and suggest instead that they could be formed during south-flowing density currents generated when volumes of cold saline water stored in the deep (> 250 m) basins at the head of Placentia Bay are intermittently displaced and spilled south in a shallow channel at the east side of the bay after intense coastal surface dense water formation events, perhaps during very cold winters.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    PubMed

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

    2013-11-01

    An analytical model derived from normal mode theory for the accumulated effects of range-dependent multiple forward scattering is applied to estimate the temporal coherence of the acoustic field forward propagated through a continental-shelf waveguide containing random three-dimensional internal waves. The modeled coherence time scale of narrow band low-frequency acoustic field fluctuations after propagating through a continental-shelf waveguide is shown to decay with a power-law of range to the -1/2 beyond roughly 1 km, decrease with increasing internal wave energy, to be consistent with measured acoustic coherence time scales. The model should provide a useful prediction of the acoustic coherence time scale as a function of internal wave energy in continental-shelf environments. The acoustic coherence time scale is an important parameter in remote sensing applications because it determines (i) the time window within which standard coherent processing such as matched filtering may be conducted, and (ii) the number of statistically independent fluctuations in a given measurement period that determines the variance reduction possible by stationary averaging. PMID:24180758

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

    EPA Science Inventory

    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

    EPA Science Inventory

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

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-05

    ... Minerals Management Service Gulf of Mexico, Outer Continental Shelf, Western Planning Area, Oil and Gas Lease Sale 215 (2010) Environmental Assessment AGENCY: Minerals Management Service, Interior. ACTION: Notice of availability of an environmental assessment. SUMMARY: The Minerals Management Service (MMS)...

  20. Resuspended sediments can contribute to the establishment and maintenance of hypoxia on the Louisiana continental shelf - Eldridge

    EPA Science Inventory

    Hypoxia occurs during summer on the Louisiana Continental Shelf. We investigated whether resuspension of sediment organic matter and the reduced end products of anaerobic microbial metabolism contributes to the onset and maintenance of hypoxia. The potential oxygen demand due to...

  1. Trace metal distribution in sediments of northern continental shelf of Crete Island, Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Poulos, S. E.; Dounas, C. G.; Alexandrakis, G.; Koulouri, P.; Drakopoulos, P.

    2009-08-01

    The present study investigates the distribution of trace metals (Zn, Hg, Cd, Cu, and Pb), as indicators of pollution, in the surficial offshore shelf sediments along the northern coast of Heraklion Prefecture (Crete, Mediterranean Sea). The concentrations and the spatial distribution of the different trace metals, in relation to the sedimentological characteristics and the water circulation pattern of the entire continental shelf, are associated with human inshore sources of pollutants located along the coastline of the study area. Although the trace metal concentrations measured are higher than the background values, they are not considered to be dangerous to human health, as they are lower than the standard values given by the World Health Organisation, with only a few localised exceptions. Furthermore, results reveal the important role of local hydrodynamism that moves fine-grained material and associated trace metals offshore (seawards to wave breaking zone) and then transports them eastwards by entrapping them in the prevailing offshore shelf-water circulation.

  2. Cetacean high-use habitats of the northeast United States continental shelf

    SciTech Connect

    Kenney, R.D.; Winn, H.E.

    1986-04-01

    Results of the Cetacean and Turtle Assessment Program previously demonstrated at a qualitative level that specific areas of the continental shelf waters off the northeastern US coast consistently showed high-density utilization by several cetacean species. They have quantified, on a multispecies basis and with adjustment for level of survey effort, the intensity of habitat use by whales and dolphins, and defined areas of especially high-intensity utilization. The results demonstrate that the area off the northeast US, which is used most intensively as cetacean habitat, is the western margin of the Gulf of Maine, from the Great South Channel to Stellwagen Bank and Jeffreys Ledge. Secondary high-use areas include the continental shelf edge and the region around the eastern end of Georges Bank. High-use areas for piseivorous cetaceans are concentrated mainly in the western Gulf of Maine and secondarily at mid-shelf east of the Chesapeake region, for planktivores in the western Gulf of Maine and the southwestern and eastern portions of Georges Bank, and for teuthivores in the western Gulf of Maine and the southwestern and eastern portions of Georges Bank, and for teuthivores along the edge of the shelf. In general, habitat use by cetaceans is highest in spring and summer, and lowest in fall and winter.

  3. Controls on water column chemistry of the southern Brazilian continental shelf

    NASA Astrophysics Data System (ADS)

    Niencheski, L. F.; Windom, H. L.; Moore, W. S.

    2014-10-01

    Chemistry of Southern Brazilian Continental Shelf (SBS) waters, between 28.5°S and 34°S, is evaluated in relation to the mixing of thermohaline defined water masses and concomitant water column processes. Data on inorganic nutrient and trace metal (Ba, Cd, Co, Cu, Fe, Mn, U, V and Zn) concentrations and radium isotopic activities from previous reports and recent analyses are presented and discussed with the aim of providing a state of knowledge on processes governing their sources, distribution, transport and fate on the SBS. Nutrients concentrations/distributions on the shelf are controlled mainly by Tropical Water/Subtropical Shelf Water, seasonally modified as a result of summer upwelling in the northern shelf region, and by Plata Plume Water, which is seasonally modified by discharges of submarine groundwater (SGD), the Patos Lagoon and by the greater northern penetration of the Rio de la Plata plume during winter. Radium-226 activity varies little across the shelf. Radium-228 activity, associated dominantly with SGD, decreases conservatively, with respect to salinity, across shelf transects, converging on a typical ocean endmember activity. The low salinity endmember activity, however, depends on the location of the shelf transect controlled by the variability of coastal SGD. Because SGD is so important to the coastal shelf region, 228Ra activity appears to provide a better tracer of water mass interactions than thermohaline characteristics. Using metal-228Ra relationships, sources, transport and fate of trace metals are better constrained enabling the following conclusion: The major source of dissolved Co, Mn and Fe to the shelf is SGD, along the coastal Holocene barrier system, followed by removal as coastal water mixes across the shelf. Cu and Si concentrations are explained as conservative mixtures of three endmembers: SGD, surface freshwater discharge and oceanic. Cd and Zn are largely explained similarly. Vanadium is enriched in coastal waters during

  4. Mixed carbonate-siliciclastic sequence stratigraphy of a Paleogene transition zone continental shelf, southeastern USA

    NASA Astrophysics Data System (ADS)

    Coffey, Brian P.; Fred Read, J.

    2004-04-01

    The sequence stratigraphy and facies of the Paleogene in the subsurface of the Albemarle Basin, North Carolina was defined using 1600 thin sections of plastic impregnated well cuttings from 24 wells, wireline logs, biostratigraphic data, and seismic data. The facies formed in the transition zone between warm subtropical and temperate conditions on a swell-wave dominated, open shelf exposed to major boundary current activity. The shelf has a distinctive seismic profile consisting of a shallow inner shelf, inner-shelf break, deep shelf (depths in excess of 200 m), and the continental slope. The inner shelf was characterized by distinctive quartz sand and sandy mollusk facies inshore, passing seaward into a broad, wave-swept abrasional shelf, and then into storm-influenced bryozoan-echinoderm limestones to depths of several tens of meters. Argillaceous lime mud (marl) deposition was widespread across the deep shelf, extending onto the inner-shelf during major highstands. Sediment thickness trends were controlled by greater differential subsidence of crustal blocks within the Albemarle Basin, which considerably modified but did not obliterate the effects of eustatic sea level changes in this passive margin setting. Five supersequences were identified on seismic and in wells, each consisting of multiple regionally identifiable sequences. The Paleocene supersequence is dominated by widespread marl deposition, reflecting shelf flooding into the Late Paleocene thermal maximum. This warming corresponds with widespread inner-shelf skeletal carbonate deposition from the Late Paleocene through the Middle Eocene. The two Eocene supersequences identified are dominated by bryozoan-echinoderm-rich carbonates that formed a seismically definable sediment buildup 50 km wide by 100 m thick across the deepest inner-shelf during the Lower to early Middle Eocene. Middle to Upper Eocene supersequence highstand sequences indicate increased progradation and greater mixing of shelf

  5. Provenance and distribution of clay minerals in the sediments of the western continental shelf and slope of India

    NASA Astrophysics Data System (ADS)

    Purnachandra Rao, V.; Ramalingeswara Rao, B.

    1995-12-01

    The distribution of clay minerals from 156 surficial sediments of the western continental margin of India, ranging from 17 to 2000 m water depth, indicate that there are three principal sources of sediments. The illite and chlorite-rich assemblage derived from the Indus (Indus Province) is predominant in the continental margin sediments to the north of the Gulf of Kachchh. An assemblage of smectite with minor kaolinite, illite and chlorite, mostly derived from the Deccan Trap basalts (Deccan Trap Province), occurs all along the inner shelf from Saurashtra to Goa. Illite, however, dominates smectite in the outer shelf of Saurashtra and on the continental slope from Saurashtra to Goa. Some samples on the outer shelf of the Gulf of Cambay-Goa show trace contents of all clay minerals, while others from the same region show the dominance of smectite over illite. A smectite and kaolinite-rich assemblage with minor illite, chlorite and gibbsite derived from the Gneissic Province occurs both on the shelf and slope between Goa and Cochin. It appears that the Indus derived sediments are transported onto the continental slope and, to a lesser extent, the outer shelf of western India by a southerly surface current and admix with clays transported from the hinterland. The influence of the Indus borne sediments on the continental slope decreases from north to south and cross shelf transport processes dominate in the southwestern continental margin between Goa and Cochin.

  6. Insights into Diversity and Imputed Metabolic Potential of Bacterial Communities in the Continental Shelf of Agatti Island

    PubMed Central

    Dhar, Sunil Kumar; Jani, Kunal; Apte, Deepak A.; Shouche, Yogesh S.; Sharma, Avinash

    2015-01-01

    Marine microbes play a key role and contribute largely to the global biogeochemical cycles. This study aims to explore microbial diversity from one such ecological hotspot, the continental shelf of Agatti Island. Sediment samples from various depths of the continental shelf were analyzed for bacterial diversity using deep sequencing technology along with the culturable approach. Additionally, imputed metagenomic approach was carried out to understand the functional aspects of microbial community especially for microbial genes important in nutrient uptake, survival and biogeochemical cycling in the marine environment. Using culturable approach, 28 bacterial strains representing 9 genera were isolated from various depths of continental shelf. The microbial community structure throughout the samples was dominated by phylum Proteobacteria and harbored various bacterioplanktons as well. Significant differences were observed in bacterial diversity within a short region of the continental shelf (1–40 meters) i.e. between upper continental shelf samples (UCS) with lesser depths (i.e. 1–20 meters) and lower continental shelf samples (LCS) with greater depths (i.e. 25–40 meters). By using imputed metagenomic approach, this study also discusses several adaptive mechanisms which enable microbes to survive in nutritionally deprived conditions, and also help to understand the influence of nutrition availability on bacterial diversity. PMID:26066038

  7. Compiling Multibeam Sonar data for the U.S. Pacific West Coast Extended Continental Shelf Project

    NASA Astrophysics Data System (ADS)

    Lim, E.; Gardner, J. V.; Henderson, J. F.

    2011-12-01

    The United States Extended Continental Shelf (ECS) Project is a multi-agency collaboration whose goals are to determine and define a potential extension of the U.S. continental shelf beyond 200 nautical miles (nmi). Under international law as reflected in the 1982 United Nations Convention on the Law of the Sea (UNCLOS), every coastal state is entitled to a continental shelf out to 200 nmi (the Exclusive Economic Zone) from its coastal baseline or out to a maritime boundary with another coastal country. The extended continental shelf (ECS) is the area that lies beyond this 200 nm limit where a country could gain sovereign rights to the resources of the seafloor and sub-seafloor. In 2007, the U.S. ECS Task Force designated NOAA's National Geophysical Data Center (NGDC) as the Data Management lead for the U.S. ECS Project and the data stewards and archival location for all data related to this project. The process to determine the outer limits of the ECS requires the collection and analysis of data that describe the depth, shape, and geophysical characteristics of the seafloor and sub-seafloor, as well as the thickness of the underlying sediments. The specific types of data that need to be collected include bathymetric data, seismic profiles, magnetic and gravity data, and other geophysical data. NGDC maintains several global geophysical databases, including bathymetric, seismic and geological data, all critical for supporting ECS analysis. Multibeam bathymetry is a primary dataset used for ECS analysis. Since 2003, the U.S. has collected more than 1.65 million square kilometers of multibeam bathymetric data from 18 cruises. One area where new data has been collected and where the U.S. may have an extended continental shelf is off the U.S. Pacific West Coast. New and old multibeam bathymetry archived at and delivered by NGDC were individually gridded by survey for an area within 48-30 degrees north latitude and -140 and -115 west longitude at a resolution of 210

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

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

    USGS Publications Warehouse

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Maps showing late Pleistocene and Holocene evolution of the South Texas continental shelf

    USGS Publications Warehouse

    Pyle, Carroll A.; Berryhill, Henry L., Jr.; Trippet, Anita R.

    1979-01-01

    Interpretation of acoustical profiles has provided insight into the late Quaternary geologic history of the Continental Shelf off South Texas. (See the geographic index map on sheet 1 for location of the area studied.) The profiles reveal the interplay of tectonism, sedimentation, and cyclic fluctuations of sea level in the building and geologic evolution of the continental terrace. The sequence of sediments studied extends to about 200 meters (m) beneath the sea-floor surface. Four seismic-stratigraphic units underlain by four prominent sound reflectors were identified and mapped. This geologic synthesis, for which the research was funded by the U.S. Bureau of Land Management (BLM), is but one aspect of a coordinated, multidisciplinary environmental study of the South Texas Outer Continental Shelf sponsored by BLM (Berryhill, 1976, 1977). The environmental studies are keyed to the leasing of Federal Outer Continental Shelf (OCS) lands for petroleum exploration and production. Their purpose is to provide the data development of petroleum resources on the OCS, as well as to provide the basis for predicting the impact of oil and gas exploration and production on the marine environment. Of primary concern is the recognition of geologic conditions that might be hazardous to structures placed on the sea floor. Geologic hazards relate directly to the potential for significant movement of the sea floor in the future. Judging sea-floor stability and recognizing geologic features that are potentially hazardous require an understanding of the recent geologic history of the area, which, in turn, entails determining the relative rates and interactions of sedimentation and tectonism through time. In addition to the primary objective, the synthesis provides knowledge about the magnitude and extent of sea-level fluctuations in the western Gulf of Mexico, and it provides a depositional facies model of possible use in appraising the resource potential of the more deeply buried

  12. 75 FR 16833 - Preliminary Revised 5-Year Outer Continental Shelf (OCS) Oil and Gas Leasing Program for 2007-2012

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-02

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Minerals Management Service Preliminary Revised 5-Year Outer Continental Shelf (OCS) Oil and Gas Leasing... original environmental sensitivity analysis relied on only two studies conducted by Continental...

  13. On consistent criteria to delineate the outer limits of the Continental Shelf (or ECS: Extended Continental Shelf) out of the formulae lines

    NASA Astrophysics Data System (ADS)

    Kisimoto, K.; Nishimura, A.

    2013-12-01

    This presentation is to discuss supplemental unambiguous procedural ECS delineating rules to the criteria defined in the 'United Nations Convention on the Law of the Sea' (the Convention) and the 'Scientific and the Technical Guidelines of the Commission on the Limits of the Continental Shelf' (the Guidelines 1999). Both the EEZ and the ECS are the lines of limits of Continental Shelf (Article 76 of the Convention), but the most significant difference between them is that EEZ are defined as continuous envelope lines, on the other hand, ECS are piece-wise segments (shortcuts hereinafter) connected between finite number of points called 'fixed points' and each distance of shortcut should be less than 60 M (the Convention). This difference may be causing seemingly inconsistent results in the recommendations among the coastal states. There are 66 submissions from the coastal states and 18 of them have received their recommendations as of June 24, 2013. Comparing and studying summaries of the recommendations available (http://www.un.org/depts/los/clcs_new/commission_submissions.htm), we recognize some inconsistencies between recommendations. To minimize the inconsistencies we have devised a couple of supplemental rules and its implementation guidance to compose the formulae lines (connecting fixed points) in the last step of defining the ECS. The two rules are: 1) any two fixed points separated less than 60 M can be chosen to create a shortcut, 2) no shortcut line should cross each other. If shortcuts create a closed area which is not self-apparent to be inside or outside of the ECS, then 3) the implementation guidance defines if the either side of the area divided by the shortcuts is inside of the ECS or not by further applying 1)&2) to check if the area is completely covered with shortcuts. We cannot prove the rules and guidance above are unique or the optimal solution for the seeming problem we found, but we solicit sincere discussion on site.

  14. Flux of energy and essential elements through the continental shelf ecosystem. Progress report, June 1, 1982-May 31, 1983

    SciTech Connect

    Pomeroy, L.R.

    1983-01-15

    Methods were perfected for counting protozoans in shelf water and we are working on methods for measuring bacterial production, taking into account the problem of protozoan grazing, which does not seem to have been investigated with respect to bacteria. Samples were collected on transects of the continental shelf on six cruises to improve our seasonal coverage and provide materials for the development of methods. Work on a model of energy flux through continental shelf ecosystems has been completed, and a manuscript will be submitted during the present contract year.

  15. Late Pleistocene and Holocene sedimentary facies on the Ebro continental shelf

    USGS Publications Warehouse

    Diaz, J.; Nelson, C.H.; Barber, J.H., Jr.; Giro, S.

    1990-01-01

    Late Pleistocene-Holocene history of the Ebro continental shelf of northeastern Spain is recorded in two main sedimentary units: (1) a lower, transgressive unit that covers the shelf and is exposed on the outer shelf south of 40??40???N, and (2) an upper, progradational, prodeltaic unit that borders the Ebro Delta and extends southward along the inner shelf. The lower transgressive unit includes a large linear shoal found at a water depth of 90 m and hardground mounds at water depths of 70-80 m. Some patches of earlier Pleistocene prodelta mud remain also, exposed or covered by a thin veneer of transgressive sand on the northern outer shelf. This relict sand sheet is 2-3 m thick and contains 9000-12,500 yr old oyster and other shells at water depths of 78-88 m. The upper prodelta unit covers most of the inner shelf from water depths of 20-80 m and extends from the present Ebro River Delta to an area to the southwest where the unit progressively thins and narrows. Interpretation of high-resolution seismic reflection data shows the following facies occurring progressively offshore: (1) a thick stratified facies with thin progradational "foresets beds", (2) a faintly laminated facies with sparse reflectors of low continuity, and (3) a thin transparent bottomset facies underlain by a prominent flat-lying reflector. Deposition in the northern half of the prodelta began as soon as the shoreline transgressed over the mid-shelf, but progradation of the southern half did not begin until about 1000-3000 yrs after the transgression. A classic deltaic progradational sequence is shown in the Ebro prodelta mud by (1) gradation of seismic facies away from the delta, (2) coarsening-upward sequences near the delta and fining-upward sequences in the distal mud belt deposits, and (3) thin storm-sand layers and shell lags in the nearshore stratified facies. The boundaries of the prodeltaic unit are controlled by increased current speeds on the outer shelf (where the shelf narrows) and

  16. Benthic faunal assemblages and carbon supply along the continental shelf/shelf break-slope off Cape Hatteras, North Carolina

    NASA Astrophysics Data System (ADS)

    Aller, J. Y.; Aller, R. C.; Green, M. A.

    Patterns of benthic faunal abundances, biomass, and productivity were examined in the continental shelf-break/upper-slope and mid-slope region of the Ocean Margins Program study area off Cape Hatteras, NC in July 1994, and July and August 1996. Macrofaunal abundances were comparable to or slightly higher than other shelf-slope locales in the North Atlantic. Similar to previous studies in the region, there were no clear depth (75-900 m) or latitudinal (36°20'N-35°25') trends. Sta. S300 in 300 m had greatest abundances (539,000±38,400 m -2) for individuals >0.3 mm, more than 3 times higher than the average for all stations. Annelids of all sizes dominated numerically, equaling >80% of all macrofauna regardless of size. The majority of infauna were found in the upper 5 cm, but direct visual observations and geochemical evidence from other studies imply a deep-burrowing benthos. Meiofauna (excluding benthic foraminifera) were twice as abundant at shelf-break/upper-slope stations than mid-slope stations, while foraminifera were more abundant at deeper stations. Meiofaunal-sized polychaetes and nematodes were found to at least 7-8 cm below the sediment surface. Bacterial inventories at shelf-break/upper-slope depths were high relative to other shelf regions, but declined precipitously deeper than 500 m. Relative biomass patterns were similar for all stations, highest for macrobenthos and lowest for bacteria. Although densities were high, the contribution of nematodes to benthic biomass was <1%. Macrofaunal biomass averaged 54±47 g C m -2 and ranged from 6 g C m -2 at station N455 to 188 g C m -2 (>0.3 mm) at station S300, while metazoan meiofauna contributed from 0.6 g C m -2 at station N-274 to 11 g C m -2 at M76, averaging 2.2±2.4 g C m -2. Bacterial biomass over the upper 10 cm was ˜4 times higher at shelf-break/upper-slope stations than mid-slope stations, averaging 1.05±1.14 g C m -2 and ranging from 5 g C m -2 at M76 to 0.12 g C m -2 at MLB-679Rb. Benthic

  17. 33 CFR 147.T17-0024 - Safety Zone; NOBLE DISCOVERER, Outer Continental Shelf Drillship, Chukchi and/or Beaufort Seas...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., Outer Continental Shelf Drillship, Chukchi and/or Beaufort Seas, Alaska. 147.T17-0024 Section 147.T17... CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.T17-0024 Safety Zone; NOBLE DISCOVERER, Outer Continental..., June 29, 2012, temporary § 147.T17-0024 was added, effective from July 1, 2012 to Dec. 1, 2012. 33...

  18. Hydrodynamic and Thermohaline Seasonal Structures of Peninsular Malaysia's eastern continental shelf sea

    NASA Astrophysics Data System (ADS)

    Daryabor, Farshid; Tangang, Fredolin; Juneng, Liew

    2010-05-01

    The seasonal ocean circulation and the seasonal thermal structure in Peninsular Malaysia's eastern continental shelf sea were studied numerically using the Regional Ocean Model System (ROMS) with 18-km horizontal resolution and 50 sigma levels conforming to a realistic bottom topography. A 10-year control run was performed using climatological monthly mean wind stresses, restoring-type surface salt, temp and heat, and observational oceanic inflow/outflow at the open boundaries. The seasonally averaged effects of isolated forcing terms are presented and analyzed from the following experiments: 1) heat fluxes effects removed and 2) wind effects removed. This procedure allowed analysis of the contribution of individual parameters to the general hydrology and specific features of the Peninsular Malaysia's eastern continental shelf sea: for example, coastal jets, mesoscale topographic gyres, and countercurrents. The results show that the ROMS model has the capability of simulating seasonal variations of the Peninsular Malaysia's eastern continental shelf sea circulation and thermohaline structure. The simulated Peninsular Malaysia's eastern continental shelf sea surface circulation is generally anticyclonic (cyclonic) during the summer (winter) monsoon period with a strong western boundary current, a mean maximum speed of 0.8 m s-1 (0.5 m s-1), and extending to a depth of around 30 m (40 m). During summer, the western boundary current splits and partially leaves the coast; the bifurcation point is at 40°N in Jun and shifts north to 70°N in July. A mesoscale eddy on the Sunda shelf, the southwest of Natuna Island at (2.50°N, 1060°E) and extending to two mesoscale eddy at (20°N, 1070°E) and (2.50°N, 1090°E) also on the Gulf of Thailand (7.50°N, 1040°E), was also simulated. These eddies are cyclonic (anticyclonic) with maximum swirl velocity of 0.3 m s-1 at the peak of the summer (winter) monsoon. The simulated thermohaline structure for summer and winter are

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

    NASA Astrophysics Data System (ADS)

    Sutherland, David A.; Straneo, Fiammetta; Stenson, Garry B.; Davidson, Fraser J. M.; Hammill, Mike O.; Rosing-Asvid, Aqqalu

    2013-02-01

    Interaction of warm, Atlantic-origin water (AW) and colder, polar origin water (PW) advecting southward in the East Greenland Current (EGC) influences the heat content of water entering Greenland's outlet glacial fjords. Here we use depth and temperature data derived from deep-diving seals to map out water mass variability across the continental shelf and to augment existing bathymetric products. We compare depths derived from the seal dives with the IBCAO Version 3 bathymetric database over the shelf and find differences up to 300 m near several large submarine canyons. In the vertical temperature structure, we find two dominant modes: a cold mode, with the typical AW/PW layering observed in the EGC, and a warm mode, where AW is present throughout the water column. The prevalence of these modes varies seasonally and spatially across the continental shelf, implying distinct AW pathways. In addition, we find that satellite sea surface temperatures (SST) correlate significantly with temperatures in the upper 50 m (R = 0.54), but this correlation decreases with depth (R = 0.22 at 200 m), and becomes insignificant below 250 m. Thus, care must be taken in using SST as a proxy for heat content, as AW mainly resides in these deeper layers. Sample Unit Level Copyright

  20. Monitoring seabird populations in areas of oil and gas development on the Alaskan continental shelf: Foraging distribution and feeding ecology of seabirds at the Diomede Islands, bering strait. Final report

    SciTech Connect

    Piatt, J.F.; Pinchuk, A.; Kitsiskiy, A.; Springer, A.M.; Hatch, S.A.

    1992-10-01

    The distribution of zooplankton and seabirds in relation to oceanography in Bering Strait was investigated July 1-8, 1991. Seabirds were counted at the sea surface on 302 standardized shipboard transects. Zooplankton densities in various depth strata were measured acoustically during 287 seabird transects. Species composition was determined from 65 net-tows at 18 stations. Sea surface salinity and temperature were recorded continuously on transects, and CTD profiles of the water column were obtained at 70 stations. Millions of seabirds, mostly planktivorous Aethial auklets, breed on the Diomede islands in the center of Bering Strait. Three distinct water masses flow north through Bering Strait. East of the Diomedes is the Alaska Coastal Water. Least Auklets and ocean copepods were abundant in stratified Shelf Water and near upwelled Anadyr Water in western Bering Strait. It was concluded that physical processes in Bering Strait determine zooplankton availability to planktivores.

  1. 210Pb balance and implications for particle transport on the continental shelf, U.S. Middle Atlantic Bight

    USGS Publications Warehouse

    Bacon, M.P.; Belastock, Rebecca A.; Bothner, Michael H.

    1994-01-01

    Supply of 210Pb to the continental shelf off the northeastern United States is dominated by the deposition from the atmosphere, the rate of which is reliably known from previously published work. Excess 210Pb inventories in the shelf sediments show accumulations that are nearly in balance with the supply, even in areas of relict sands where it is believed that no net accumulation of sediment presently occurs. The 210Pb distributions in shelf and slope water indicate that the two-way fluid exchange at the shelf-slope front and the net transport in the alongshore flow make comparatively small contributions to the shelf 210Pb budget. The near balance between supply and decay of 210Pb on the shelf implies a limit to the particle export flux. It is concluded that the export of particulate organic carbon does not exceed 60 g m-2 y-1 (???25% of primary production) and is probably lower. The hypothesis is advanced that fine particulate matter introduced to the continental shelf is detained in its transit of the shelf because of bioturbational trapping in the sediment due to benthic animals. Distributions of 210Pb in suspended particulate matter and in the fine fraction of shelf sediments suggest that the average fine particle must undergo several cycles of deposition-bioturbation-resuspension-redeposition and requires a number of decades for its transit and ultimate export from the shelf. Thus, only the most refractory organic matter is likely to be exported. ?? 1994.

  2. Interannual variability of wintertime temperature on the inner continental shelf of the Middle Atlantic Bight

    NASA Astrophysics Data System (ADS)

    Connolly, Thomas P.; Lentz, Steven J.

    2014-09-01

    The shallow depth of the inner continental shelf allows for rapid adjustment of the ocean to air-sea exchange of heat and momentum compared with offshore locations. Observations during 2001-2013 are used to evaluate the contributions of air-sea heat flux and oceanic advection to interannual variability of inner-shelf temperature in the Middle Atlantic Bight. Wintertime processes are important for interpreting regional interannual variability at nearshore locations since winter anomalies account for 69-77% of the variance of the annual anomalies and are correlated over broad along-shelf scales, from New England to North Carolina. At the Martha's Vineyard Coastal Observatory on the 12 m isobath, a heat budget is used to test the hypothesis that interannual differences in winter temperatures are due solely to air-sea heat flux. Bimonthly averages of air-sea heat flux are correlated with temporal changes in temperature, but overestimate the observed wintertime cooling. Velocity and satellite-derived temperature data show that interannual variability in wintertime surface cooling is partially compensated for by alongshore advection of warmer water from the west at this particular location. It is also shown that surface heat flux is a strong function of air-sea temperature difference. Because of this coupling between ocean and air temperatures in shallow water, along-shelf advection can significantly modify the surface heat flux at seasonal and interannual time scales. While along-shelf advection at relatively small (˜100 km) scales can be an important component of the heat budget over the inner shelf, interannual temperature variability is still largely determined by adjustment to large-scale air-temperature anomalies.

  3. Reprocessing and Interpretation of the High Resolution Seismic Data from Northern Marmara Continental Shelf, NW Turkey

    NASA Astrophysics Data System (ADS)

    Nasif, Aslıhan; Dondurur, Derman; Ergintav, Semih; Cifci, Gunay

    2015-04-01

    The Marmara Sea is an inland sea located in the NW of Turkey with a maximum depth of 1270 m, and consists of a 3 major sub-basins. The active dextral North Anatolian Fault (NAF) passes through the basins, which shapes the general morphology and forms the tectonic settlement of the Marmara Sea. The investigations for the Marmara Sea are now important since İstanbul city, which is the most populous and economically the most important city of Turkey, is located just north of the Marmara Sea, quite close to the NAF. In order to define the morphology and structural state of the northern continental shelf of the Marmara Sea, we collected 224 km of multichannel high resolution seismic and 338 km of Chirp subbottom profiler data along the shallow shelf in 2007. A 600 m long, 96 channel digital seismic streamer, and a Generator-Injector (GI) gun was used to obtain high resolution seismic data. The Chirp data was collected a 2.75-6.75 kHz over-the-side-mount transducer system. The data have been processed using a conventional data processing flow. The scope of the present study is to re-process and to interpret the seismic and Chirp data between Silivri and Sarayburnu on the northern Marmara shelf up to 100 m water depth. The active tectonic characteristics of the area, especially its geological connection with the terrestrial area, are investigated using acoustic data. In addition, offshore continuity of the of the Çatalca Fault zone is investigated. The Çatalca Fault enters the shelf along the B. Çekmece Lake and can be tracked in the SSE direction on the seismic data. The seismic data is tied to North Marmara-1 well located on the central part of the shelf area, and distributions and thicknesses of the pre-Miocene sediments are mapped using a jump-correlation to the well information. The seismic data located at the southernmost part of the shelf along the shelf break also indicate the presence of active sediment erosion. Behind the shelf break, the slope inclination

  4. Steric contribution to the long-term sea level variations within the Gulf of Cadiz continental shelf

    NASA Astrophysics Data System (ADS)

    Laiz, Irene; Tejedor, Begoña; Gómez-Enri, Jesús; Aboitiz, Alazne; Villares, Pilar

    2015-04-01

    The response of the long-term coastal sea level variations to the steric contribution has been explored within the Gulf of Cadiz (GoC) for the period 1997-2008 using tide gauge data as well as altimeter-derived sea level anomaly maps (AVISO). In order to remove the atmospheric pressure contribution, tide gauge data were corrected using the inverted barometer (IB) method. The AVISO maps were initially de-corrected using the Dynamic Atmospheric Correction product and then corrected using the same IB method. Steric height (ssh) time series were computed by combining a high resolution climatology (0.1° x 0.1°) with monthly maps of AVHRR sea surface temperature considering a reference depth of 500 m at the open ocean and the bottom depth for shallower areas. In order to evaluate the steric effect on the long-term sea level changes, four types of steric contribution were defined: (1) The ssh values interpolated to the AVISO grid resolution were considered as the local steric effect. (2) The open ocean steric effect was computed by averaging all the steric heights corresponding to grid points located over the 500 m isobath and deeper. (3) The Eastern / Western continental shelf steric contribution was obtained by averaging over those grid points located within each continental shelf. (4) Finally, a basin-wide steric effect was computed by averaging the steric heights all over the GoC. The potential contribution of each of the defined steric effects on the pressure-adjusted sea level was evaluated. The open ocean contribution explained the highest percentage of variance all over the basin with the exception of the western shelf, where the best results were obtained with the local contribution, supporting the idea that the cell of cyclonic circulation found off Cape San Vicente is a local quasi-permanent feature. The fact that the open ocean steric effect explained the highest percentage of variance within the eastern shelf suggested that the deep ocean thermosteric

  5. Beyond hydrography: daily ichthyoplankton variability and short term oceanographic events on the Sydney continental shelf

    NASA Astrophysics Data System (ADS)

    Dempster, Tim; Gibbs, Mark T.; Rissik, David; Suthers, Iain M.

    1997-10-01

    Surface ichthyoplankton concentrations along a shore-normal transect across the Sydney continental shelf and upper slope changed between three replicate nights in January and April of 1994. Over 70 families of fish were recorded, which, during January, included: Myctophidae (49% of individuals), Carangidae (14%), Gonostomatidae (11%) and Pomacentridae (8%); and during April included: Gonorhynchidae (43%), Myctophidae (10%), Berycidae (11%) and Serranidae (6%). Multidimensional scaling analysis identified inshore and offshore communities, which nightly moved between the nearshore and mid-shelf stations. During January no distinct near-surface water masses could be identified from the temperature-salinity data, although the shelf waters were under the influence of forcing by the local wind stress and the East Australian Current. Good agreement between the cross-shore transport in the near-surface layer and the temporal variability of the icthyoplankton was nevertheless found. The sampling during April was performed during a period of relatively steady oceanographic conditions, and two water masses were identified from the hydrographic data. Temporal ichthyoplankton variability at any station was correspondingly less during the April period and stable inshore and offshore communities were identified, that shifted with characteristic water masses. The results presented in this paper demonstrate that the large variance often associated with ichthyoplankton distribution within a similar water mass may be interpreted by the dynamics in cross-shelf flows, which has implications for the selection of control sites used when studying environmental impacts of coastal outfalls.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    USGS Publications Warehouse

    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.

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

    PubMed

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

    2015-01-01

    Since inferring spawning areas from larval distributions in the Sargasso Sea a century ago, the oceanic migration of adult American eels has remained a mystery. No adult eel has ever been observed migrating in the open ocean or in the spawning area. Here, we track movements of maturing eels equipped with pop-up satellite archival tags from the Scotian Shelf (Canada) into the open ocean, with one individual migrating 2,400 km to the northern limit of the spawning site in the Sargasso Sea. The reconstructed routes suggest a migration in two phases: one over the continental shelf and along its edge in shallow waters; the second in deeper waters straight south towards the spawning area. This study is the first direct evidence of adult Anguilla migrating to the Sargasso Sea and represents an important step forward in the understanding of routes and migratory cues. PMID:26505325

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

    SciTech Connect

    Zuniga-Rivero, F.; Keeling, J.A.; Hay-Roe, H.

    1998-11-16

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

  10. Structural cross sections, Plio-Pleistocene Series, southeastern Texas Continental Shelf

    SciTech Connect

    Not Available

    1989-01-01

    The Plio-Pleistocene Series in the western Gulf Coast basin comprises a thick wedge of terrigenous clastic sediment that produces modest volumes of hydrocarbons from offshore leases along the outer shelf and upper slope. Sandstone reservoirs within this wedge have yielded more than 40 million bbl of oil and 2.5 Tcf of gas. They initially contained about 1.6 billion bbl of oil equivalent, or nearly two-thirds of the estimated total recoverable reserves beneath the Texas Outer Continental Shelf. To interpret the structural and stratigraphic framework of the area, the authors used publicly available electric logs, paleontological reports, and published information, in addition to proprietary data released by operators and approximately 2,000 miles of multichannel seismic profiles. In this book biostratigraphic zones of the Plio-Pleistocene Series, locations of major oil and gas fields and trends, and areas of tectonic features and salt structures are included.

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

    PubMed Central

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

    2015-01-01

    Since inferring spawning areas from larval distributions in the Sargasso Sea a century ago, the oceanic migration of adult American eels has remained a mystery. No adult eel has ever been observed migrating in the open ocean or in the spawning area. Here, we track movements of maturing eels equipped with pop-up satellite archival tags from the Scotian Shelf (Canada) into the open ocean, with one individual migrating 2,400 km to the northern limit of the spawning site in the Sargasso Sea. The reconstructed routes suggest a migration in two phases: one over the continental shelf and along its edge in shallow waters; the second in deeper waters straight south towards the spawning area. This study is the first direct evidence of adult Anguilla migrating to the Sargasso Sea and represents an important step forward in the understanding of routes and migratory cues. PMID:26505325

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

    USGS Publications Warehouse

    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

  13. Sequence stratigraphy and continental margin development of the northwestern shelf of the South China Sea

    SciTech Connect

    Chen, P.P.H. ); Zhi Yuong Chen; Qi Min Zhang )

    1993-05-01

    Based on the sequence stratigraphic analyses of the Tertiary in the northwestern continental margin of the South China Sea, this paper summarizes the regional tectonics and their influences on the basin developments and discusses the systems tract distributions through the continental margin growth. The study area is underlain by two Tertiary basins separated by a major basin boundary fault across which two distinctly different basin structural styles developed. The Qiongdongnan basin shows characteristic rift structures and is closely related to the opening of the South China Sea. The Yinggehai basin is filled with thick Neogene monoclines overlying basement without apparent rift structures. The Yinggehai's genesis has been linked to the tectonism along the Red River suture zone. The margin development is characterized by depositional environments of sediment influx constantly exceeding accommodation space. Under these environments, the highstand deltas frequently developed near shelf edges, where vertically stacked shallow water sands of both highstand deltas and lowstand wedges/deltas could produce favorable exploration targets. High rates of sedimentation in the study area allow the identification of fourth-order cyclicity in the Quaternary. Regional sequence stratigraphic correlations suggest that many sequence boundaries appear to be synchronous, but not all boundaries exist in all basins along the eastern and southern continental margins of mainland China. The margin evolved through the repeated development of lowstand fans, lowstand wedges, transgressive systems tracts, and highstand deltas. Prior to the Pliocene, the shelf was sourced both from Vietnam and Hainan Island and, as a result, two shelf margins developed. The southwestern margin stopped growing in the late Miocene, and the northern margin continued to prograde with possible additional sediment inputs through the Red River system in the Quaternary. 29 refs., 22 figs.

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

    PubMed

    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

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

    PubMed Central

    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

  16. Interannual variability in atmospheric CO2 uptake on the northeast U.S. continental shelf

    NASA Astrophysics Data System (ADS)

    Previdi, Michael; Fennel, Katja; Wilkin, John; Haidvogel, Dale

    2009-12-01

    Continental shelf systems are thought to play an important role in the exchange of carbon dioxide (CO2) between the atmosphere and ocean. Currently, our ability to quantify the air-sea flux of CO2 on continental shelves is limited due to large spatial and temporal variability coupled with historically sparse oceanographic measurements (e.g., of surface water pCO2). Here we use the Regional Ocean Modeling System (ROMS) to quantify the air-sea flux of CO2 and its interannual variability on the northeast U.S. continental shelf, which includes the Middle Atlantic Bight (MAB) and Gulf of Maine (GOM). Two years marked by opposite phases of the North Atlantic Oscillation (NAO) are considered in the study. A novel analysis method, second-order Taylor series decomposition, is used to identify the important processes responsible for producing NAO-related changes in the CO2 air-sea flux. On the northeast U.S. shelf, atmospheric CO2 uptake as simulated by ROMS decreases from 2.4 Mt C yr-1 in 1985 (low NAO) to 1.8 Mt C yr-1 in 1990 (high NAO), with most of this decrease (0.5 Mt C yr-1) occurring in the MAB. In the MAB the difference in annual air-sea flux of CO2 is due mainly to changes in near-surface wind speed, while the flux difference in the GOM is controlled primarily by surface water pCO2 (CO2 partial pressure) changes resulting from changes in sea surface temperature and new production. The large magnitude of interannual variability in the air-sea flux of CO2 simulated here suggests the potential for even more significant flux changes in the future as climate change accelerates.

  17. Estimated oil and gas reserves, Gulf of Mexico outer continental shelf and continental slope, December 31, 1982

    USGS Publications Warehouse

    Hewitt, Jack E.; Brooke, Jeff P.; Knipmeyer, John H.

    1983-01-01

    Remaining recoverable reserves of oil* and gas in the Gulf of Mexico Outer Continental Shelf and Continental Slope have been estimated to be about 2.98 billion barrels of oil and 39.8 trillion cubic feet of gas, as of December 31, 1982. These reserves are recoverable from 468 studied fields under the Federal submerged lands off the coasts of Louisiana and Texas. An additional 53 fields, discovered since December 31, 1980, have not been sufficiently developed to permit a reasonably accurate estimate of reserves. Original recoverable reserves are estimated to have been 8.56 billion barrels of oil and 98.1 trillion cubic feet of gas from 484 fields in the same geographic area. Included in this number are 16 fields that are depleted and were abandoned; not included are the 53 insufficiently developed fields. Estimates were made for individual reservoirs in 382 fields and on a field-wide basis for the other 102 fields. *The term 'oil' as used in this report includes crude oil and condensate.

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

    NASA Astrophysics Data System (ADS)

    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

  19. Delineation of Late Quaternary depositional sequences by high-resolution seismic stratigraphy, Louisiana continental shelf

    SciTech Connect

    Suter, J.R.; Berryhill, H.L. Jr.; Penland, S.

    1987-05-01

    Interpretations of over 20,000 line km of single-channel, high-resolution seismic reflection profiles, coupled with nearshore vibracores and logs of industrial platform borings, provide the data base for determining the history and stratigraphy of late Quaternary sea level fluctuations on the Louisiana continental shelf. Regional unconformities, formed by subaerial exposure of the shelf during glacio-eustatic sea level withdrawals and modified by shoreface erosion during ensuing transgression, serve as markers to identify the boundaries of depositional sequences. Unconformities are recognizable on seismic profiles by high-amplitude reflectors as well as discordant relationships between reflectors. Within the upper Quaternary section, six depositional sequences have been recognized. Five of these are related to glacio-eustatic sea level fluctuations, involving sea level fall close to, or beyond, the margin of the continental shelf. Three of these fluctuations culminated in the deposition of shelf margin delta sequences. Extensive fluvial channeling characterizes the regressive phase of these sequences. Transgressive phases are marked by infilling of fluvial channels, flood-plain aggradation, truncation, or deposition of sand sheets, depending upon sediment supply and rate of sea level rise. Sequences 4 and 5 are correlated with the late Wisconsinan glacial stage and Holocene transgression. The upper portion of sequence 5 consists of an early Holocene Mississippi delta complex. Abandonment and transgression of this delta are responsible for the formation of sequence 6. Although these deposits cover a smaller area, this demonstrates that deltaic processes can produce sequences similar to those driven by glacially controlled sea level changes.

  20. The scattering of a continental shelf wave by a semi-infinite barrier located along the outer edge of a step shelf

    NASA Astrophysics Data System (ADS)

    Hsieh, William W.; Buchwald, V. T.

    1984-04-01

    On a step shelf, the scattering of an incident shelf wave by a semi-infinitely long, thin barrier located along the outer edge of the shelf is solved using an approximate Wiener-Hopf technique. Within the flat channel enclosed by the barrier, the incoming energy flux from the first mode shelf wave is essentially all transferred to the zeroth channel mode, which corresponds to the Kelvin wave modified by the rigid lid approximation. Other evanescent modes are excited, but all decay rapidly with distance. The problem is relevant to the diffraction of long period waves by a long thin island, or a chain of islands or coral reefs, which fringe a continental shelf.

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

    NASA Astrophysics Data System (ADS)

    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

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

    PubMed Central

    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

  3. Wave height, peak period, and orbital velocity for the California continental shelf

    USGS Publications Warehouse

    Erikson, Li H.; Storlazzi, Curt D.; Golden, Nadine E.

    2014-01-01

    In this study, bathymetric data compiled as part of the California Seafloor Mapping Program Project and within the 3-NM limit were supplemented with deeper water bathymetric data (NOAA, http://maps.ngdc.noaa.gov/, last downloaded April 2013) and used to populate numerical wave grids for simulation of wave growth and propagation across the continental shelf bordering the California coast. Wave computations were done with the widely used and accepted numerical model SWAN (Ris, 1997; Booij and others, 1999; Ris and others, 1999). SWAN is a third-generation spectral model that simulates wind-wave growth, propagation, refraction, dissipation, and depth-induced breaking.

  4. Derivation of a three dimensional numerical water quality model for estuary and continental shelf application

    NASA Technical Reports Server (NTRS)

    Spaulding, M.

    1973-01-01

    A derivation is given for a three dimensional mass transport equation which is appropriate for numerical modeling of estuary and continental shelf water quality variations for both the time dependent and steady state cases. A finite difference approximation to the derived equation is presented and a solution scheme for the resulting equations outlined. Preliminary results are obtained using the model for the extremely simple problems which have analytical solutions. The numerical model, as presented, will provide a scheme to study water quality problems in coastal waters for both steady state and time dependent cases.

  5. Clay mineral content of continental shelf and river sediments, southern California

    USGS Publications Warehouse

    Hein, James R.; Dowling, Jennifer S.

    2001-01-01

    This report contains data on the clay mineral content of 250 shelf surface-sediment samples from the California Continental Borderland (Tables 1, 2; Figures 1-7), 79 samples with depth in cores from Santa Monica Bay (Table 3; see Table 1 for surface sediment data for those same cores and for core locations), 24 suspended and 13 bottom sediment samples from rivers draining Southern California (Table 4), and six rock samples or composite rock samples from the Palos Verdes Headland (Table 4). This report is designed as the data repository and these data are discussed in a paper by Hein et al. (2001).

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

    PubMed

    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. Benthic oxygen fluxes and sediment properties on the northeastern New Zealand continental shelf

    NASA Astrophysics Data System (ADS)

    Giles, H.; Pilditch, C. A.; Nodder, S. D.; Zeldis, J. R.; Currie, K.

    2007-11-01

    We examined spatial variations in benthic remineralisation (measured as sediment oxygen consumption (SOC)) and sediment properties on the northeastern New Zealand continental shelf and slope to assess the importance of benthic mineralisation in this ecosystem and to provide data for more complete global carbon budgets. SOC measured in dark incubations conducted in early summer ranged from 128 μmol m -2 h -1 at the deepest (360 m) to 1222 μmol m -2 h -1 at the shallowest (4.2 m) site and decreased significantly with water depth ( p<0.001, r2=0.78, SOC=1222.8-456.3×log 10[water depth], n=14 sites). These rates were in the range found on continental shelves elsewhere (64-1750 μmol m -2 h -1, n=30 studies) and had a very similar distribution with water depth. SOC was also measured in light incubations at seven sites (4.2-35 m water depth) to examine the effects of microphytobenthos and accounted for 42-106% of rates measured in the dark. Measurements of near-bed light intensities suggested that microphytobenthos production was not solely regulated by light intensity but evidently influenced by other factors. A two-dimensional PCA ordination of surface sediment properties accounted for 83.3% of the total variance in the data and divided the study area into three clusters that corresponded well to its spatial division into the shallow (<30 m) Firth of Thames, the Hauraki Gulf (30-50 m) and the northern shelf-slope region. In the Firth of Thames sediments were very fine-grained with low CaCO 3 and high total organic matter and pigment content, and low C:N ratios. The northern shelf-slope sediments showed the opposite trends to the Firth of Thames and those in the Hauraki Gulf had mostly intermediate values. Dark SOC was significantly correlated with sediment organic matter, carbon, nitrogen, pigments and silt/clay content ( p<0.05, r=0.55-0.85) but a multiple linear regression revealed that water depth was the only significant predictor. Calculations suggest that

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

    NASA Astrophysics Data System (ADS)

    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. Multichannel seismic depth sections and interval velocities over outer continental shelf and upper continental slope between Cape Hatteras and Cape Cod: rifted margins

    USGS Publications Warehouse

    Grow, John A.; Mattick, Robert E.; Schlee, John S.

    1979-01-01

    Six computer-generated seismic depth sections over the outer continental shelf and upper slope reveal that subhorizontal Lower Cretaceous reflectors continue 20 to 30 km seaward of the present shelf edge. Extensive erosion on the continental slope has occurred primarily during the Tertiary, causing major unconformities and retreat of the shelf edge to its present position. The precise age and number of erosional events is not established, but at least one major erosional event is thought to be Oligocene and related to a marine regression in response to a worldwide eustatic lowering of sea level. Velocities derived from the multichannel data reveal distinctive ranges and lateral trends as functions of sediment age, depth of burial, and distance from the coastline. Seismic units beneath the shelf and slope of inferred Tertiary age range from 1.7 to 2.7 km/sec, increasing with age and depth of burial. Units interpreted as Upper Cretaceous rocks beneath the shelf range from 2.3 to 3.6 km/sec and show a distinct lateral increase across the shelf followed by a decrease beneath the present continental slope. Inferred Lower Cretaceous and Upper Jurassic rocks beneath the shelf increase from 3.7 to 4.8 km/sec from nearshore to offshore and indicate a change in facies from clastic units below the inner shelf to carbonate units beneath the outer shelf and upper continental slope. Both reflection and refraction data suggest that thin, high-velocity limestone units (5.0 km/sec) are present within the Lower Cretaceous and Upper Jurassic units beneath the outermost shelf edge, but that these change lithology or pinch out before reaching the middle shelf. Although lateral changes in velocity across the shelf and local velocity inversions appear, the interval velocities along the length of the margin show excellent continuity between Cape Hatteras and Cape Cod. The high-velocity horizons within the Lower Cretaceous and Upper Jurassic shelf-edge complex indicate the presence of a

  10. On the temporal variation of DOM fluorescence on the southwest Florida continental shelf

    NASA Astrophysics Data System (ADS)

    Mendoza, Wilson G.; Zika, Rod G.

    2014-01-01

    Dissolved organic matter (DOM) plays a crucial role in the nutrient and carbon cycling in the coastal-shelf-ocean boundary. It is a major reservoir of reduced carbon and carries important information on how sea and landscape have been modified. Due to the complexity of the biogeochemical processes in this boundary, its distribution is not well understood. This study evaluated the Excitation Emission Matrix (EEM) fluorescence method combined with Parallel Factorial Analysis (PARAFAC) modeling to resolve DOM fluorescence components, and their distribution from near-shore to off-shore on the southwest (SW) Florida Shelf. The PARAFAC model derived identified five unique DOM components from 272 Excitation and Emission Matrix (EEM) samples measured across the shelf on May and October 2008, and January and April 2009 cruises. These five different fluorophores consisted of two humic-like components that were attributed to natural (component 1: HLC1) and anthropogenic (component 2: HLC2) sources; an unidentified component (component 3); two autochthonous protein components, identified as tryptophan-like (component 4:TLC4); and tyrosine-like (component 5:TLC5) fluorophores. The observed temporal variations of terrestrial and anthropogenic humic-like DOM fluorescent materials were not necessarily dependent on the timing of river runoffs and rainfall frequency on the shelf, but also on other factors (i.e., suspension of sediments in shallow water induced by wind-driven mixing, dilution, hypersalinity conditions). The areal distribution of the resolved terrestrial DOM fluorescence on the mid-shelf indicates evidence of offshore transport of land-derived materials. The evident terrestrial humic-like inputs into the shelf correspond to the increase in the protein-like fluorescence, which was attributed to autochthonous biological degradation. Results from this study demonstrated advances in several aspects of monitoring the temporal distribution of DOM on the continental shelf of

  11. A 3D, finite element model for baroclinic circulation on the Vancouver Island continental shelf

    USGS Publications Warehouse

    Walters, R.A.; Foreman, M.G.G.

    1992-01-01

    This paper describes the development and application of a 3-dimensional model of the barotropic and baroclinic circulation on the continental shelf west of Vancouver Island, Canada. A previous study with a 2D barotropic model and field data revealed that several tidal constituents have a significant baroclinic component (the K1 in particular). Thus we embarked on another study with a 3D model to study the baroclinic effects on the residual and several selected tidal constituents. The 3D model uses a harmonic expansion in time and a finite element discretization in space. All nonlinear terms are retained, including quadratic bottom stress, advection and wave transport (continuity nonlinearity). The equations are solved as a global and a local problem, where the global problem is the solution of the wave equation formulation of the shallow water equations, and the local problem is the solution of the momentum equation for the vertical velocity profile. These equations are coupled to the advection-diffusion equation for density so that density gradient forcing is included in the momentum equations. However, the study presented here describes diagnostic calculations for the baroclinic residual circulation only. The model is sufficiently efficient that it encourages sensitivity testing with a large number of model runs. In this sense, the model is akin to an extension of analytical solutions to the domain of irregular geometry and bottom topography where this parameter space can be explored in some detail. In particular, the consequences of the sigma coordinate system used by the model are explored. Test cases using an idealized representation of the continental shelf, shelf break and shelf slope, lead to an estimation of the velocity errors caused by interpolation errors inherent in the sigma coordinate system. On the basis of these estimates, the computational grid used in the 2D model is found to have inadequate resolution. Thus a new grid is generated with increased

  12. Gas-related sedimentary features from the eastern Canadian continental shelf

    NASA Astrophysics Data System (ADS)

    Fader, Gordon B. J.

    1991-08-01

    The first discovery of pockmarks (gas-escape craters) was in muds of the basins of the central Scotian Shelf off eastern Canada. Since then, pockmarks have been found in many continental shelf environments of the world. They may be used as a hydrocarbon exploration tool and recently their role as foci of intense biological chemosynthetic activity has attracted considerable attention. Pockmarks occur in the Gulf of Maine, Passamaquoddy Bay, eastern Scotian Shelf, Scotian Slope, Laurentian Channel, Gulf of St Lawrence, Halibut Channel and on Labrador Shelf. Their formation in Passamaquoddy Bay may be enhanced through earthquake activity as their greatest density occurs in association with a large fault zone. Pockmarks on Labrador Shelf and in Laurentian Channel may have been formed preferentially as a consequence of disturbance of the seabed by grounded moving icebergs. Pockmarks in Placentia Bay, Newfoundland occur in an area of large megaflutes at the seabed and the pockmarks may have provided an initial seabed roughness for subsequent formation of the megaflutes by a tsunami-generated turbidity current. Subsurface zones of gas-charged Quaternary sediments are often associated with areas of pockmarks. Gas-charged sediments in the nearshore frequently appear as thick Holocene deposits occurring in areas overlying buried channel systems. In the nearshore, biogenic methane is the probable source. In other areas, such as Downing Basin on the Grand Banks of Newfoundland, the gas-charged sediments contain ethane, butane and methane, suggesting a deeper hydrocarbon source. Active gas venting has been observed at the seabed in Downing Basin without the formation of pockmarks. Seabed observations from research submersibles and bottom photography have identified areas of white filamentous bacteria on sandy sediments sometimes associated wtih circular patches of dense benthic communities. Seismic reflection profiles from these areas also indicate the presence of shallow gas

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

    NASA Astrophysics Data System (ADS)

    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

  14. Phytoplankton functional community structure in Argentinian continental shelf determined by HPLC pigment signatures

    NASA Astrophysics Data System (ADS)

    Moreno, D. Vega; Marrero, J. Pérez; Morales, J.; García, C. Llerandi; Úbeda, M. G. Villagarcía; Rueda, M. J.; Llinás, O.

    2012-03-01

    The Patagonian Sea in Argentina is known as an area with high primary production and biodiversity. The complex hydrodynamic environment resulting from the interaction between the Malvinas-Brazil convergence and the waters over the continental shelf and slope enhances the development of high chlorophyll concentrations, especially in frontal and coastal areas. The composition, distribution and variability of several phytoplankton functional types (PFTs) derived from diagnostic pigments were studied in relation to the local hydrographical conditions, using data from a research cruise carried out on board the RV Bio Hesperides at the end of the Summer season (March 2008). Phytoplankton cell size and PFT distributions were found to be highly influenced by the physical and chemical characteristics of the studied environments. Thus large cells, mainly diatoms, were the dominant size fraction in the southern frontal areas, where the SubAntarctic Surface Waters (SASW) from the Malvinas Current meet shelf waters. However, other groups of microphytoplankton (mPF), mainly dinoflagellates, were also detected in the shallow waters zone influenced by the tidal regime near the Valdes Peninsula. Picophytoplankton (pPF) was an important contributor to the floristic composition in the southern frontal zones, while nanophytoplankton (nPF) was dominant in the stations located over the continental slope, and in the oligotrophic area near Mar del Plata. The ratio between photoprotective and photosynthetic pigments (PPC:PSC) and the photoprotection index (PI) indirectly provide information about the environment and its effect on the PFTs composition.

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

    USGS Publications Warehouse

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

    2012-01-01

    Starting in Late Pleistocene time (~19 ka), sea level rise inundated coastal zones worldwide. On some parts of the present-day circum-Arctic continental shelf, this led to flooding and thawing of formerly subaerial permafrost and probable dissociation of associated gas hydrates. Relict permafrost has never been systematically mapped along the 700-km-long U.S. Beaufort Sea continental shelf and is often assumed to extend to ~120 m water depth, the approximate amount of sea level rise since the Late Pleistocene. Here, 5,000 km of multichannel seismic (MCS) data acquired between 1977 and 1992 were examined for high-velocity (>2.3 km s−1) refractions consistent with ice-bearing, coarse-grained sediments. Permafrost refractions were identified along <5% of the tracklines at depths of ~5 to 470 m below the seafloor. The resulting map reveals the minimum extent of subsea ice-bearing permafrost, which does not extend seaward of 30 km offshore or beyond the 20 m isobath.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Achievements of risk-based produced water management on the Norwegian continental shelf (2002-2008).

    PubMed

    Smit, Mathijs G D; Frost, Tone K; Johnsen, Ståle

    2011-10-01

    In 1996, the Norwegian government issued a White Paper requiring the Norwegian oil industry to reach the goal of "zero discharge" for the marine environment by 2005. To achieve this goal, the Norwegian oil and gas industry initiated the Zero Discharge Programme for discharges of produced formation water from the hydrocarbon-containing reservoir, in close communication with regulators. The environmental impact factor (EIF), a risk-based management tool, was developed by the industry to quantify and document the environmental risks from produced water discharges. The EIF represents a volume of recipient water containing concentrations of one or more substances to a level exceeding a generic threshold for ecotoxicological effects. In addition, this tool facilitates the identification and selection of cost-effective risk mitigation measures. The EIF tool has been used by all operators on the Norwegian continental shelf since 2002 to report progress toward the goal of "zero discharge," interpreted as "zero harmful discharges," to the regulators. Even though produced water volumes have increased by approximately 30% between 2002 and 2008 on the Norwegian continental shelf, the total environmental risk from produced water discharges expressed by the summed EIF for all installations has been reduced by approximately 55%. The total amount of oil discharged to the sea has been reduced by 18% over the period 2000 to 2006. The experience from the Zero Discharge Programme shows that a risk-based approach is an excellent working tool to reduce discharges of potential harmful substances from offshore oil and gas installations. PMID:21594986

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

    USGS Publications Warehouse

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

    2009-01-01

    An area of oxygen-depleted bottom- and subsurface-water (hypoxia = dissolved oxygen < 2 mg/L-1) occurs seasonally on the Louisiana Shelf near the Mississippi River. The area of hypoxia, also known as the 'dead zone', forms when spring and early summer freshwater flow from the Mississippi River supplies a large amount of nutrients to the shelf while creating a freshwater lens, or cap, above the shelf water. The excess nutrients cause phytoplankton blooms in the shallow shelf water. After the bloom ceases, the organic material sinks in the water column and uses up oxygen during decomposition. Thus, the subsurface waters become oxygen depleted. The seasonal dead zone exists until a reduction in freshwater flow, or overturning by storms, allows mixing of the water column to 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

  19. Seabed erodibility variations on the Louisiana continental shelf before and after the 2011 Mississippi River flood

    NASA Astrophysics Data System (ADS)

    Xu, K.; Corbett, D. R.; Walsh, J. P.; Young, D.; Briggs, K. B.; Cartwright, G. M.; Friedrichs, C. T.; Harris, C. K.; Mickey, R. C.; Mitra, S.

    2014-08-01

    Erodibility is critical to the sediment resuspension process but has not been measured systematically in large river-dominated muddy continental shelves before. During early summer of 2011, the Mississippi River experienced a major flood event. This flood provided a unique opportunity to examine how shelf seabed erodibility responded to a large river flood, and the ultimate fate of flood deposition is important to geological and biogeochemical processes (e.g., stratal formation, carbon sequestration). A total of 106 sediment cores were collected on the Louisiana shelf during five cruises in 2010 and 2011, and a new dataset was used to evaluate the response of the seabed to the recent conditions. The localized flood deposit was mainly within tens of kilometers of river sources, and little sediment accumulated on the middle Louisiana shelf. Seabed erodibility was measured using a dual-core Gust Erosion Microcosm System. The erodibility of sediment collected in April 2011 exceeded that for August 2010 and August 2011. The springtime increase in erodibility seemed to be related to the recent presence of energetic waves that mobilized the seabed. Erodibility was highest on the inner shelf southwest of Atchafalaya Bay, intermediate on the middle shelf, lowest in the Mississippi Canyon, and highly variable on the Mississippi subaqueous delta. These spatial patterns were influenced by proximity to river sources, flood-deposit thicknesses, intensity of wave-driven bed stresses, and bioturbation. The flood-deposit thickness itself, however, was not sufficient to explain all the spatial variations of erodibility after the peak of the Mississippi flood. Comparing values to published data, the depth-varying erodibility on the Louisiana shelf was close to the "low erodibility" level for the York River of Virginia, and similar to the data collected from Baltimore Harbor in Maryland and the main stem of upper Chesapeake Bay. Our findings promote understanding of the resuspension

  20. Production and turnover of suspended organic detritus in the coastal water of the southeastern continental shelf: Progress report, June 1, 1988--May 31, 1989

    SciTech Connect

    Pomeroy, L.R.

    1988-12-01

    As one of a group cooperative research projects on the southeastern continental shelf, this project is concerned with specific aspects of microbial processes and related phenomena that influence the fate of particulate organic materials naturally produced on the continental shelf. The projects of other grantees encompass the dynamics of the shelf from physical oceanography to biology. The integrated information as a whole will be useful in understanding the potential fate of a variety of energy related pollutants that may be released in continental shelf waters. With a focus on events on the southeastern continental shelf and their boundary conditions (Gulf Stream dynamics; river and estuarine processes), we form an interface between studies of oceanic processes such as GOFS and WOCE, and studies of processes at the land-sea boundary. During this grant year we completed two research cruises on the southeastern continental shelf on R/V Blue Fin, and processed data from previous cruises.

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

    USGS Publications Warehouse

    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

  2. Processes controlling the characteristics of the surficial sand sheet, U.S. Atlantic outer continental shelf

    USGS Publications Warehouse

    Knebel, H. J.

    1981-01-01

    A review of recent data on the velocity of bottom currents, the frequency of bottom-sediment movement, the kinds and amounts of suspended sediments in near-bottom waters, and the acoustic and sedimentary features of subbottom strata indicates that the characteristics of the ubiquitous sand sheet on the Atlantic outer continental shelf of the United States have been controlled by a variety of past and present processes. Although these processes collectively have had a widespread effect on the characteristics of the sand sheet, the relative importance of each process changes geographically. On Georges Bank, late Pleistocene glaciations along with modern tidal currents and the regional circulation pattern have played a dominant role. On the Middle Atlantic shelf, ancestral rivers, former near-shore processes, and modern wind- and wave-generated currents are important factors. On the South Atlantic shelf, the sediments reflect subaerial weathering, erosion or nondeposition over or near hardgrounds, and the production of biogenic carbonate. Other processes such as the movement of water masses, bioturbation, and bottom fishing probably have affected the sediments in all areas. A knowledge of the various factors affecting the sand sheet is fundamental to an understanding of its general geologic history and to the paleoenvironmental interpretation of ancient sand strata. ?? 1981.

  3. Transport and fate of river discharge on the continental shelf of the Southeastern United States

    SciTech Connect

    Blanton, J.O.; Atkinson, L.P.

    1983-05-30

    We have analyzed 8 years of wind and salinity data from a frontal zone in a region of the inner continental shelf off the southeastern United States. The changes in low-salinity water stored in the frontal zone have been parameterized by analyzing the montly rate of change in freshwater content. When the rate of change in freshwater content was negative, we interpreted this as a loss of low-salinity water from the frontal zone. When this parameter was compared with seasonally averaged alongshore wind stress, the rate of loss was independent of the alongshore wind stress magnitude until threshold of about 0.1 dyne cm/sup -2/ was reached. Above the thereshold there was a clear relationship between northward alongshore wind stress and rate of loss freshwater from the inner shelf. Experimental evidence suggests that horizontal currents in the inner-shelf frontal zone have cyclonic shear with increasing depth. When wind stres is northward and offshore, near-surface low-salinity water is transported offshore by Ekman transport while near-bottom high-salinity water is transported shoreward.

  4. Bryozoan faunal composition and community structure from the continental shelf off Cap de Creus (Northwestern Mediterranean)

    NASA Astrophysics Data System (ADS)

    Madurell, T.; Zabala, M.; Dominguez-Carrió, C.; Gili, J. M.

    2013-10-01

    Bryozoan specimens obtained in 2009-2010 from the continental shelf off Cap de Creus (Northwestern Mediterranean) were studied. Samples were collected using a Rauschert sled at depths ranging from 61 to 225 m. Bryozoans were present in all 26 samples examined, although they were only abundant in 20 of them. A total of 113 species of Bryozoa were identified (2 Ctenostomata, 90 Cheilostomata and 21 Cyclostomata), most of them are well known to science, although a few of the species have barely or never been cited in the Mediterranean Sea (Hincksinoflustra octodon, Alderina imbellis, Escharella immersa, Neolagenipora collaris and Escharina johnstoni), or are currently poorly described (Lagenipora lepralioides). The species Palmicellaria aff. aviculifera (sensu Gautier, 1957) is redescribed, for which the new name of Palmiskenea gautieri is proposed. Species richness, abundance and biomass were linked to the availability of suitable substrates. Multivariate analysis in relation to environmental data showed that the spatial distribution of the bryozoan species was related to the sediment type. Samples from areas dominated by silt and sandy sediments showed few or no bryozoans, whereas coarse sands and gravels presented higher diversity, abundance and biomass. Within the depth range studied, the faunistic composition of the bryozoan assemblages was similar for the whole continental shelf off Cap de Creus. The bulk of bryozoans was found near the canyon rim. This is related to the proximity of the submarine canyon and its associated hydrological processes. The high diversity and abundance of the bryozoan community located on the circalittoral and shelf-edge off Cap de Creus reflect the presence of critical habitats that are essential for the design of marine protected areas.

  5. Denitrification in continental shelf sediments has major impact on the oceanic nitrogen budget

    NASA Astrophysics Data System (ADS)

    Christensen, John P.; Murray, James W.; Devol, Allan H.; Codispoti, Louis A.

    1987-06-01

    Denitrification rates in sediments within the oxygen deficient waters off Mexico and from the Gulf of Maine were investigated on the basis of interstitial nutrient profiles. Nitrate fluxes into the sediments were calculated from gradients across the sediment-water interface and vertical molecular diffusion coefficients and averaged 0.151 (Mexico) and 0.0920 (Gulf of Maine) pmol NO-3 cm-2 s-1. These are minimum values, since these gradients may have been underestimated. In the Gulf of Maine, bottom water irrigation by macrobenthos increases the nitrate supply well above this estimate. In addition, only 15-22% of the expected ammonium is present in Gulf of Maine sediments perhaps because of removal by a rapid coupling of nitrification with denitrification. This large apparent loss of the regenerated ammonium appears to be ubiquitous in shelf sediments with oxygenated bottom water. The global denitrification rate in continental shelf sediments was reassessed to be >50 Tg N yr-1 (1 Tg = 1012 g), demonstrating that sediments are an important sink for oceanic nitrogen. Globally, current nitrogen losses from the oceans may exceed inputs by 60-90 Tg N yr-1. Over the glacial-interglacial cycle the global sedimentary denitrification rate probably varied commensurately with the changing continental shelf area. An oscillating oceanic nitrogen budget over these time scales could occur given the sequence of (1) scouring and dumping of terrestrial nitrogen into the oceans during glacial advance, (2) removal of oceanic combined nitrogen to the atmosphere by denitrification following glacial retreat, and (3) reincorporation of this N into terrestrial biomass during the interglacial period.

  6. How well do we know the infaunal biomass of the continental shelf?

    NASA Astrophysics Data System (ADS)

    Powell, Eric N.; Mann, Roger

    2016-03-01

    Benthic infauna comprise a wide range of taxa of varying abundances and sizes, but large infaunal taxa are infrequently recorded in community surveys of the shelf benthos. These larger, but numerically rare, species may contribute disproportionately to biomass, however. We examine the degree to which standard benthic sampling gear and survey design provide an adequate estimate of the biomass of large infauna using the Atlantic surfclam, Spisula solidissima, on the continental shelf off the northeastern coast of the United States as a test organism. We develop a numerical model that simulates standard survey designs, gear types, and sampling densities to evaluate the effectiveness of vertically-dropped sampling gear (e.g., boxcores, grabs) for estimating density of large species. Simulations of randomly distributed clams at a density of 0.5-1 m-2 within an 0.25-km2 domain show that lower sampling densities (1-5 samples per sampling event) resulted in highly inaccurate estimates of clam density with the presence of clams detected in less than 25% of the sampling events. In all cases in which patchiness was present in the simulated clam population, surveys were prone to very large errors (survey availability events) unless a dense (e.g., 100-sample) sampling protocol was imposed. Thus, commercial quantities of surfclams could easily go completely undetected by any standard benthic community survey protocol using vertically-dropped gear. Without recourse to modern high-volume sampling gear capable of sampling many meters at a swath, such as hydraulic dredges, biomass of the continental shelf will be grievously underestimated if large infauna are present even at moderate densities.

  7. Paleoecology of late-glacial terrestrial deposits with in situ conifers from the submerged continental shelf of western canada

    NASA Astrophysics Data System (ADS)

    Lacourse, Terri; Mathewes, Rolf W.; Fedje, Daryl W.

    2003-09-01

    Extensive portions of the continental shelf off the coast of British Columbia were subaerially exposed during Late Wisconsinan deglaciation due to lowering of relative sea level by as much as 150 m. Paleoecological analyses were conducted at two sites on the emergent continental shelf where terrestrial surfaces with in situ conifers are preserved. The woody plant remains confirm that, during the latest period of subaerial exposure, terrestrial vegetation was established on the continental shelf. Microscopic identification of fossil wood, and analyses of pollen and plant macrofossils from the associated paleosols and overlying shallow pond sediments indicate that productive Pinus contorta-dominated communities with abundant Alnus crispa and ferns grew on the shelf adjacent to and on the Queen Charlotte Islands around 12,200 14C yr B.P. Dwarf shrubs including Salix and Empetrum, and herbaceous plants such as Heracleum lanatum and Hippuris vulgaris, were also important components of the shelf vegetation. Near northern Vancouver Island, mixed coniferous forests dominated by Pinus contorta with Picea, Tsuga spp., Alnus spp., and ferns occupied the shelf at 10,500 14C yr B.P.

  8. Hydrographic and particle distributions over the Palos Verdes continental shelf: Spatial, seasonal and daily variability

    USGS Publications Warehouse

    Jones, B.H.; Noble, M.A.; Dickey, T.D.

    2002-01-01

    Moorings and towyo mapping were used to study the temporal and spatial variability of physical processes and suspended particulate material over the continental shelf of the Palos Verdes Peninsula in southwestern Los Angeles, California during the late summer of 1992 and winter of 1992-93. Seasonal evolution of the hydrographic structure is related to seasonal atmospheric forcing. During summer, stratification results from heating of the upper layer. Summer insolation coupled with the stratification results in a slight salinity increase nearsurface due to evaporation. Winter cooling removes much of the upper layer stratification, but winter storms can introduce sufficient quantities of freshwater into the shelf water column again adding stratification through the buoyancy input. Vertical mixing of the low salinity surface water deeper into the water column decreases the sharp nearsurface stratification and reduces the overall salinity of the upper water column. Moored conductivity measurements indicate that the decreased salinity persisted for at least 2 months after a major storm with additional freshwater inputs through the period. Four particulate groups contributed to the suspended particulate load in the water column: phytoplankton, resuspended sediments, and particles in treated sewage effluent were observed in every towyo mapping cruise; terrigenous particles are introduced through runoff from winter rainstorms. Terrigenous suspended particulate material sinks from the water column in <9 days and phytoplankton respond to the stormwater input of buoyancy and nutrients within the same period. The suspended particles near the bottom have spatially patchy distributions, but are always present in hydrographic surveys of the shelf. Temporal variations in these particles do not show a significant tidal response, but they may be maintained in suspension by internal wave and tide processes impinging on the shelf. ?? 2002 Elsevier Science Ltd. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Observations of storm and river flood-driven sediment transport on the northern California continental shelf

    NASA Astrophysics Data System (ADS)

    Ogston, A. S.; Cacchione, D. A.; Sternberg, R. W.; Kineke, G. C.

    2000-12-01

    In the winter of 1996-1997, three bottom-boundary layer tripods were placed in an alongshelf array on the northern California continental shelf off Eureka, CA in 60-65-m water depth. During the observation period, multiple storms and river discharge events occurred, as well as the largest flood on record since 1964. Suspended-sediment concentration at all three sites fluctuated in response to both wave resuspension and advection of river-derived sediments. However, considerable spatial differences in low-frequency currents and suspended-sediment concentration were observed at the three sites. Sediment flux vectors calculated during periods of high suspended-sediment concentration suggest a convergence of sediment flux coincident with the center of recent flood deposits. Suspended-sediment concentrations observed at the two northern tripod sites following the large flood reached magnitudes typical of fluid mud (>10 g/l) in a thin near-bed layer. The net sediment flux during the single three-day event was two orders of magnitude larger than any other event during the winter, and accounted for seven times the flux observed over an entire year (1995-1996). A conceptual model for the advection of sediment to the mid shelf is proposed in which river plume sediments are trapped on the inner shelf either due to a weak front or the rapid input of sediment from a confined plume, and form a thin layer of fluid mud. The fluid mud subsequently is transported seaward due to gravitational forcing. The measured sediment concentration and velocity profiles on the shelf provide strong evidence to support this conclusion.

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

    USGS Publications Warehouse

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

    1978-01-01

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

  12. Metal elements in the bottom sediments of the Changjiang Estuary and its adjacent continental shelf of the East China Sea.

    PubMed

    Cao, Lu; Hong, Gi Hoon; Liu, Sumei

    2015-06-15

    The metal elements (Al, Fe, Mn, Cr, Co, Ni, Cu, Zn, As, Pb and Ca) in the bottom sediment of the Changjiang Estuary and its adjacent continental shelf of the East China Sea were studied to map their spatial distribution and to assess their potential risk to the marine biota. These metal concentrations except Ca were generally higher in the inner shelf and northeastern part, and were found to decrease from the coast to the offshore of the Changjiang Estuary. Sedimentary Ca was most abundant in the outer shelf sediments and decreased in inner shelf. Arsenic (As) appeared to be contaminated due to economic development from 1980s in the inner shelf overall, but the potential ecological risk from the selected metals was low in the coastal sea off the Changjiang. PMID:25869200

  13. Model for the formation of longshore sand ridges on the Continental Shelf: The interaction of internal waves and the bottom topography

    SciTech Connect

    Restrepo, J.M.; Bona, J.L.

    1994-01-05

    Longshore sand ridges are frequently observed to occur on the continental shelf where the overlying ocean is stratified. This study formulates a model for the formation and evolution of three-dimensional longshore sand ridges on the continental shelf. The model is based on the interaction of interfacial, weakly nonlinear waves in a stratified ocean with the sedimentary bottom topography.

  14. Shelf basin exchange along the Siberian continental margin: Modification of Atlantic Water and Lower Halocline Water

    NASA Astrophysics Data System (ADS)

    Bauch, Dorothea; Cherniavskaia, Ekaterina; Timokhov, Leonid

    2016-09-01

    Salinity and stable oxygen isotope (δ18O) evidence shows a modification of Atlantic Water in the Arctic Ocean by a mixture of sea-ice meltwater and meteoric waters along the Barents Sea continental margin. On average no further influence of meteoric waters is detectable within the core of the Atlantic Water east of the Kara Sea as indicated by constant δ18O, while salinity further decreases along the Siberian continental slope. Lower Halocline Waters (LHW) may be divided into different types by Principal Component Analysis. All LHW types show the addition of river water and an influence of sea-ice formation to a varying extent. The geographical distribution of LHW types suggest that the high salinity type of LHW forms in the Barents and Kara seas, while other LHW types are formed either in the northwestern Laptev Sea or from southeastern Kara Sea waters that enter the northwestern Laptev Sea through Vilkitsky Strait. No further modification of LHW is seen in the eastern Laptev Sea but the distribution of LHW-types suggest a bifurcation of LHW at this location, possibly with one branch continuing along the continental margin and a second branch along the Lomonosov Ridge. We see no pronounced distinction between onshore and offshore LHW types, as the LHW components that are found within the halocline over the basin also show a narrow bottom-bound distribution at the continental slope that is consistent with a shelf boundary current as well as a jet of water entering the western Laptev Sea from the Kara Sea through Vilkitsky Strait.

  15. 210Pb balance and implications for particle transport on the continental shelf, U.S. Middle Atlantic Bight

    USGS Publications Warehouse

    Bacon, M.P.; Belastock, Rebecca A.; Bothner, Michael H.

    1994-01-01

    Supply of 210Pb to the continental shelf off the northeastern United States is dominated by the deposition from the atmosphere, the rate of which is reliably known from previously published work. Excess 210Pb inventories in the shelf sediments show accumulations that are nearly in balance with the supply, even in areas of relict sands where it is believed that no net accumulation of sediment presently occurs. The 210Pb distributions in shelf and slope water indicate that the two-way fluid exchange at the shelf-slope front and the net transport in the alongshore flow make comparatively small contributions to the shelf 210Pb budget. The near balance between supply and decay of 210Pb on the shelf implies a limit to the particle export flux. It is concluded that the export of particulate organic carbon does not exceed 60 g m−2 y−1 (∼25% of primary production) and is probably lower. The hypothesis is advanced that fine particulate matter introduced to the continental shelf is detained in its transit of the shelf because of bioturbational trapping in the sediment due to benthic animals. Distributions of 210Pb in suspended particulate matter and in the fine fraction of shelf sediments suggest that the average fine particle must undergo several cycles of deposition-bioturbation-resuspension-redeposition and requires a number of decades for its transit and ultimate export from the shelf. Thus, only the most refractory organic matter is likely to be exported.

  16. Sediment dynamics and post-glacial evolution of the continental shelf around the Blanes submarine canyon head (NW Mediterranean)

    NASA Astrophysics Data System (ADS)

    Durán, Ruth; Canals, Miquel; Lastras, Galderic; Micallef, Aaron; Amblas, David; Pedrosa-Pàmies, Rut; Sanz, José Luis

    2013-11-01

    The Blanes submarine canyon (BC) deeply incises the Catalan continental shelf in the NW Mediterranean Sea. As a consequence of the closeness (only 4 km) of its head to the coastline and the mouth of the Tordera River, the canyon has a direct influence on the shelf dispersal system as it collects large amounts of sediment, mainly during high-energy events. Multibeam bathymetry, backscatter imagery and very-high resolution seismic reflection profiles have allowed characterizing the morphology of the continental shelf around the canyon head, also identifying sediment sources and transport pathways into the canyon. The morphological data have also been used to reconstruct the evolution of the continental shelf during the last sea-level transgression so that the current understanding of shelf-to-canyon sediment exchanges through time could be improved. The continental shelf surrounding the BC consists of both depositional and erosional or non-depositional areas. Depositional areas display prominent sediment bodies, a generally smooth bathymetry and variable backscatter. These include: (i) an area of modern coarse-grained sediment accumulation that comprises the inner shelf; (ii) a modern fine-grained sedimentation area on the middle shelf offshore Tossa de Mar; and (iii) a modern sediment depleted area that covers most of the middle and outer shelf to the west of the canyon head. Erosional and non-depositional areas display a rough topography and high backscatter, and occur primarily to the east of the canyon head, where the arrival of river-fed inputs is very small. In agreement with this pattern, the continental shelf north and west of the canyon head likely is the main source of shelf sediment into the canyon. To the north, a pattern of very high backscatter extends from the coastline to the canyon head, suggesting the remobilization and off-shelf export of fines. Additionally, relict near-shore sand bodies developed over the Barcelona shelf that extend to the canyon

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  19. Bathymetric map of Lydonia Canyon, U.S. Atlantic Outer Continental Shelf

    USGS Publications Warehouse

    Butman, Bradford; Moody, John A.

    1984-01-01

    Lydonia Canyon is one of several large submarine canyons that indent the eastern U.S. Continental Shelf along the southern flank of Georges Bank (Index map).  This bathymetric map of the upper part of Lydonia Canyon (water depths shallower than about 2,00 m) was prepared as part of a study of the physical oceanography and geology of Lydonia Canyon (Butman and others, 1983; Twichell, 1983).  An accurate map of the canyon at a scale of at least 1:50,000 was needed for placement of current-meter morrings, for location of hydrographic and sediment sampling stations, and for interpretation of current-meter and geologic data. The map covers the area from 40°10'N. to 40°40'N. and from 67°28'W. to 67°50'W. 

  20. Temperatures of quartz cementation in Jurassic sandstones from the Norwegian continental shelf -- evidence from fluid inclusions

    SciTech Connect

    Walderhaug, O. )

    1994-04-01

    Recent studies of fluid inclusions in quartz overgrowths have shown quartz cementation to have taken place at temperatures within the range 60--145 C in several sandstones from the North Sea and offshore mid-Norway (Malley et al. 1986; Konnerup-Madsen and Dypvik 1988; Burley et al. 1989; Walderhaug 1990; Ehrenberg 1990; Saigal et al. 1992; Nedkvitne et al. 1993). This study aims at determining whether these results are typical for quartz cementation of sandstones by presenting homogenization temperatures for 274 aqueous and 366 hydrocarbon inclusions in quartz overgrowths from Jurassic reservoir sandstones on the Norwegian continental shelf, and by reviewing previously published fluid-inclusion data. Possible explanations for different ranges of homogenization temperatures in different sandstones are also discussed, and possible sources of quartz cement and the effect of hydrocarbon emplacement on quartz cementation are considered.

  1. Subsurface geology of upper Tertiary and Quaternary deposits, coastal Louisiana and adjacent Continental Shelf

    SciTech Connect

    McFarlan, E. Jr.; Leroy, D.O.

    1988-09-01

    Upper Tertiary and Quaternary deposits thicken seaward from a feather edge on the outcrop in the uplands of southern Louisiana to more than 7000 ft (2134 m) beneath the middle continental shelf. Through a study of cores and cuttings from 100 control wells and electric-log pattern correlations from 350 water and petroleum industry wells with seismic corroboration in the offshore area, these deposits have been divided into six major time-stratigraphic units, four of which correlate to outcropping terraces. This investigation presents a regional stratigraphic framework of the major upper Tertiary and Quaternary units from their updip pinch-outs in and beneath the terraced uplands, into the subsurface, across the coastal plain to the Louisiana offshore area.

  2. Rippled scour depressions on the inner continental shelf off central California

    USGS Publications Warehouse

    Cacchione, David A.; Drake, David E.; Grant, William D.; Tate, George B.

    1984-01-01

    Side-scan sonar records taken during the recent Coastal Ocean Dynamics Experiment (CODE) show elongate, shore-normal tippled depressions of low relief on the inner continental shelf off central California between Bodega Bay and Point Arena. These features extend up to 2 kin from the coast into water depths of up to 65 m. The proposed mechanism for their generation is storm- generated bottom currents associated with coastal downwelling during the late fall and winter which scour the surficial fine-sand sediment and expose the coarser-sand substrate in the depressions. The zones of most intense erosion and the irregular spacing of the features may be controlled by submerged rock ledges and other prominent coastal features. The large straight-crested ripples within the depres- sions (heights to 40 cm; wavelengths to 1.7 m) are probably formed by large-amplitude, long-period surface waves generated by winter storms.

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

    NASA Technical Reports Server (NTRS)

    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.

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

    SciTech Connect

    Not Available

    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.

  5. High-Resolution geophysical data from the inner continental shelf at Vineyard Sound, Massachusetts

    USGS Publications Warehouse

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

    2013-01-01

    The U.S. Geological Survey (USGS) and the Massachusetts Office of Coastal Zone Management (CZM) have mapped approximately 340 square kilometers of the inner continental shelf in Vineyard Sound, Massachusetts, under a cooperative mapping program. The geophysical data collected between 2009 and 2011 by the U.S. Geological Survey as part of this program are published in this report. The data include (1) swath bathymetry from interferometric sonar, (2) acoustic backscatter from sidescan sonar, and (3) seismic-reflection profiles from a chirp subbottom profiler. These data were collected to support research on the influence of sea-level change and sediment supply on coastal evolution and sediment transport processes and to provide baseline seabed characterization information required for management of coastal and offshore resources within the coastal zone of Massachusetts.

  6. Self-advection of density perturbations on a sloping continental shelf

    SciTech Connect

    Ping-Tung Shaw; Csanady, G.T.

    1983-05-01

    Bottom water movement on the continental shelf is modeled by the nonlinear interaction between longshore bottom geostrophic flow and the density field. Bottom geostrophic velocity, subject to linear steady momentum equations with linear bottom friction, can be generated by along-isobath density variations over a sloping bottom. At the same time, the density field is slowly advected by the velocity field. Away from boundary layers, the interplay is governed by Burgers' equation, which shows the formation and self-propulsion of strong density gradients along an isobath. The direction of propagation of a dense water blob is to have shallow water on the right- (left-) hand side facing downstream in the Northern (Southern) Hemisphere. The propagation of a light water blob is opposite to that of a dense water blob.

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

    NASA Astrophysics Data System (ADS)

    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 (

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

    USGS Publications Warehouse

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

    2010-01-01

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

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

    SciTech Connect

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

    1991-10-01

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

  10. Seismic refraction studies on the acoustic basement in the continental shelf of the East Sea, Korea

    SciTech Connect

    Kim, K.Y.; Kim, H.J.; Han, S.J.

    1996-12-31

    Critically refracted seismic waves can be utilized in elucidation of physical properties of a high-impedance acoustic basement, where reflection methods are not effective in general. Quality factor Q was estimated for the high-impedance acoustic basement in the continental shelf of the East Sea, Korea. Various pre-processing steps for the estimation included static correction for gun delay, geometric correction, data interpolation, and Fourier transform. Based on the constant Q model, quality factor was computed for the uppermost layer within the basement using the spectral-ratio method. The computation gives values between 10.4 and 13.6, which fall under the range for water-saturated clastic sedimentary rocks. Using seismic events refracted from the layer boundaries within the acoustic basement in the study area, sedimentary layers were successfully defined. A short window AGC (automatic gain control) is an effective tool to reveal existence of the refraction boundaries. Based on a model for horizontal layers, refraction velocity and thickness were computed for each layer under a short seismic line of 3.75 km long in the continental shelf. From four distinct linear events, three layers were interpreted under the water body of 150 m deep. The computed thickness is 275 m for the top layer and 200 m for the middle one. The corresponding refraction velocities are approximately 3,900 m/s and 5,100 m/s, respectively. The refraction event from the top of the lowest layer suggests that its phase velocity is greater than 6,400 m/s.

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

    NASA Astrophysics Data System (ADS)

    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

  12. 75 FR 62418 - Notice of Intent To Conduct a Review of Categorical Exclusions for Outer Continental Shelf Decisions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-08

    ...The Department of the Interior (DOI), Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) is announcing its intent to conduct a broad review of its categorical exclusions (CEs) for Outer Continental Shelf (OCS) decisions. This review is being conducted in accordance with section 102 of the National Environmental Policy Act of 1969 (NEPA), as amended, 42 U.S.C. 4332; the......

  13. 77 FR 4360 - Notice of Availability of the Proposed Notice of Sale for Outer Continental Shelf (OCS) Oil and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-27

    ... Continental Shelf (OCS) Oil and Gas Lease Sale 216/222 in the Central Planning Area (CPA) in the Gulf of... 556.29(c) as a matter of information to the public. With regard to oil and gas leasing on the OCS, the... proposed NOS for Sale 216/222 and a ``Proposed Notice of Sale Package'' containing information essential...

  14. 77 FR 43355 - Notice of Availability of the Proposed Notice of Sale for Outer Continental Shelf (OCS) Oil and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-24

    ... Continental Shelf (OCS) Oil and Gas Lease Sale 229 in the Western Planning Area (WPA) in the Gulf of Mexico... Oil and Gas Leasing Program for 2012-2012. With regard to oil and gas leasing on the OCS, the... for Sale 229 and a ``Proposed Notice of Sale Package'' containing essential information for...

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

    SciTech Connect

    Pomeroy, L R

    1981-02-01

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

  16. Sediment and Lower Water Column Oxygen Consumption in the Seasonally-hypoxic Region of the Louisiana Continental Shelf

    EPA Science Inventory

    We report sediment and bottom water respiration rates from 10 cruises from 2003-2007 on the Louisiana Continental Shelf (LSC) where summer hypoxia regularly occurs. Cruises were conducted during spring (5 cruises), summer (3 cruises) and fall (2 cruises). Cruise average sediment ...

  17. 78 FR 59632 - Oil and Gas and Sulphur Operations on the Outer Continental Shelf-Oil and Gas Production Safety...

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  18. 76 FR 19122 - Record of Decision (ROD) for Authorizing the Use of Outer Continental Shelf (OCS) Sand Resources...

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  19. 75 FR 25291 - Outer Continental Shelf (OCS) Mid-Atlantic Proposed Oil and Gas Lease Sale 220

    Federal Register 2010, 2011, 2012, 2013, 2014

    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... May 17, 2010 (see 75 FR 16830). Pursuant to the regulations implementing the procedural provisions...

  20. 75 FR 63504 - Outer Continental Shelf, Alaska OCS Region, Chukchi Sea Planning Area, Oil and Gas Lease Sale 193

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-15

    ... 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, Alaska OCS Region, Chukchi Sea Planning Area, Oil and Gas Lease Sale 193 AGENCY: Bureau of Ocean Energy...

  1. 76 FR 30956 - Outer Continental Shelf, Alaska OCS Region, Chukchi Sea Planning Area, Oil and Gas Lease Sale 193

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  2. 75 FR 63609 - Oil and Gas and Sulphur Operations in the Outer Continental Shelf-Safety and Environmental...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-15

    ... published an Advance Notice of Proposed Rulemaking (71 FR 29277), and then on June 17, 2009, BOEMRE... Environmental Management Systems for Outer Continental Shelf Oil and Gas Operations'' (74 FR 28639). The comment...) in the Federal Register (71 FR 29277) related to requiring a SEMS program. This was followed on...

  3. 78 FR 54417 - Oil and Gas and Sulphur Operations on the Outer Continental Shelf-Oil and Gas Production Safety...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-04

    ... Operations on the Outer Continental Shelf--Oil and Gas Production Safety Systems Correction In proposed rule....802 Design, installation, Sec. 250.819 Specification and operation of surface production- for surface... features. Sec. 250.803 Additional production Sec. 250.850 Production system requirements....

  4. 77 FR 44231 - Delegation of Authority To Implement and Enforce Outer Continental Shelf Air Regulations to the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-27

    ...On February 2, 2012, EPA sent the Virginia Department of Environmental Quality (VADEQ) a letter acknowledging VADEQ will be delegated the authority to implement and enforce sections of the Outer Continental Shelf (OCS) Air Regulations. To inform regulated facilities and the public of VADEQ's delegation of authority to implement and enforce OCS regulations, EPA is making available a copy of......

  5. 77 FR 44232 - Delegation of Authority To Implement and Enforce Outer Continental Shelf Air Regulations to the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-27

    ...On July 21, 2010, EPA sent the Delaware Department of Natural Resources and Environmental Control (DNREC) a letter acknowledging DNREC has been delegated the authority to implement and enforce sections of the Outer Continental Shelf (OCS) Air Regulations. To inform regulated facilities and the public of DNREC's delegation of authority to implement and enforce OCS regulations, EPA is making......

  6. 76 FR 28178 - Renewable Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf-Acquire a...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-16

    ... 9, 2008 (73 FR 39376). The North American Industry Classification System (NAICS) code for the... on February 16, 2011 (76 FR 8962), and received a total of 76 comments. The Offshore Wind Development... Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf--Acquire a...

  7. ON THE WIND-INDUCED EXCHANGE BETWEEN INDIAN RIVER BAY, DELAWARE AND THE ADJACENT CONTINENTAL SHELF. (R826945)

    EPA Science Inventory

    The structure of the wind-induced exchange between Indian River Bay, Delaware and the adjacent continental shelf is examined based on current measurements made at the Indian River Inlet which represents the only conduit of exchange between the bay and the coastal ocean. Local ...

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

    EPA Science Inventory

    We conducted a multi-year study of the Louisiana continental shelf (LCS) to better understand the linkages between water column metabolism and the formation of hypoxia (dissolved oxygen <2 mg L-1) in the region. Water column community respiration rates (WR) were measured on 10 cr...

  9. 77 FR 40380 - Outer Continental Shelf, Gulf of Mexico, Oil and Gas Lease Sales, Western Planning Area Lease...

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  10. 77 FR 51568 - Outer Continental Shelf, Gulf of Mexico, Oil and Gas Lease Sales, Western Planning Area Lease...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-24

    ... and Central Planning Area (CPA) Lease Sale 231 (WPA/CPA Supplemental EIS) (77 FR 40380). Due to a BOEM... 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...

  11. 78 FR 52562 - Outer Continental Shelf (OCS), Gulf of Mexico (GOM), Oil and Gas Lease Sales, Central Planning...

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  12. 78 FR 64242 - Outer Continental Shelf (OCS), Gulf of Mexico (GOM), Oil and Gas Lease Sales, Western Planning...

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  13. 78 FR 8190 - Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore North Carolina...

    Federal Register 2010, 2011, 2012, 2013, 2014

    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 December 13, 2012 (77 FR 7204). DATES: BOEM must receive your nomination describing your interest...

  14. 78 FR 14116 - Gulf of Mexico (GOM), Outer Continental Shelf (OCS), Eastern Planning Area (EPA) Lease Sale 225...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-04

    ... Bureau of Ocean Energy Management Gulf of Mexico (GOM), Outer Continental Shelf (OCS), Eastern Planning Area (EPA) Lease Sale 225 and 226, Oil and Gas Lease Sales AGENCY: Bureau of Ocean Energy Management... Bureau of Ocean Energy Management, Gulf of Mexico OCS Region, Public Information Office (GM 250I),...

  15. 76 FR 82319 - Gulf of Mexico (GOM), Outer Continental Shelf (OCS), Western Planning Area (WPA) and Central...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-30

    ... Bureau of Ocean Energy Management Gulf of Mexico (GOM), Outer Continental Shelf (OCS), Western Planning... Ocean Energy Management (BOEM), Interior. ACTION: Notice of Availability (NOA) of the Draft... draft Multisale EIS, you may contact the Bureau of Ocean Energy Management, Gulf of Mexico OCS...

  16. 78 FR 21969 - Gulf of Mexico (GOM), Outer Continental Shelf (OCS), Western Planning Area (WPA) Lease Sale 233...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-12

    ... Bureau of Ocean Energy Management Gulf of Mexico (GOM), Outer Continental Shelf (OCS), Western Planning... MMAA104000 AGENCY: Bureau of Ocean Energy Management (BOEM), Interior. ACTION: Notice of Availability (NOA... Management, Gulf of Mexico OCS Region, Public Information Office (GM 250G), 1201 Elmwood Park Boulevard,...

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

    EPA Science Inventory

    We conducted a multi-year study of the Louisiana continental shelf (LCS) to better understand the linkages between water column net metabolism and the formation of hypoxia (dissolved oxygen <2 ml O2 L-1) in the region. Rates of water column community respiration (R) and primary p...

  18. 77 FR 5820 - Commercial Leasing for Wind Power on the Outer Continental Shelf Offshore Massachusetts-Call for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-06

    ... Bureau of Ocean Energy Management Commercial Leasing for Wind Power on the Outer Continental Shelf... nominations for commercial leases that would allow a lessee to propose the construction of a wind energy... submission of nominations and other information by February 28, 2011 (75 FR 82055). In response to...

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

    PubMed

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

    2014-12-15

    The Florida Panhandle continental shelf environment was exposed to oil from the BP oil well failure in the Gulf of Mexico during 2010. Floating mats of oil were documented by satellite, but the distribution of dissolved components of the oil in this region was unknown. Shipek® grab samples of sediments were taken during repeated cruises between June 2010 and June 2012 to test for selected polycyclic aromatic hydrocarbons (PAHs) as indicators of this contamination. Sediments were collected as composite samples, extracted using standard techniques, and PAHs were quantified by GC/MS-SIM. PAHs in samples from the continental slope in May 2011 were highest near to the failed well site and were reduced in samples taken one year later. PAHs from continental shelf sediments during the spill (June 2010) ranged from 10 to 165 ng g(-1). Subsequent cruises yielded variable and reduced amounts of PAHs across the shelf. The data suggest that PAHs were distributed widely across the shelf, and their subsequent loss to background levels suggests these compounds were of oil spill origin. PAH half-life estimates by regression were 70-122 days for slope and 201 days for shelf stations. PMID:25444619

  20. A sediment-dispersal model for the South Texas continental shelf, northwest Gulf of Mexico

    USGS Publications Warehouse

    Shideler, G.L.

    1978-01-01

    Textural-distribution patterns of sea-floor sediments on the South Texas continental shelf between Matagorda Bay and the U.S.-Mexico international boundary were evaluated as part of a regional environmental-studies program. Sediment textural gradients support a conceptual model for the regional sediment-dispersal system, which is characterized by both net offshore transport and net south-trending coastwise transport components on a wind-dominated shelf. Coastwise transport results in the net southward migration of both palimpsest sandy mud composing the ancestral Brazos-Colorado delta flank in the northern sector, and modern mud composing the central sector; these migrating sediments are encroaching southward onto immobile relict muddy sands composing the ancestral Rio Grande delta in the southern sector. In the proposed model, the suspension transport of modern silt-enriched mud derived mainly from coastal sources is the dominant dispersal mechanism. Net offshore transport is attributed both to diffusion, and to the advective ebb-tide discharge of turbid lagoonal-estuarine waters from coastal inlets. Net southward transport is attributed mainly to advection by seasonally residual coastwise drift currents reflecting a winter-dominated hydraulic regime. Frequent winter storms characterized by relatively high-speed northerly winds that accompany the passage of cold fronts appear to be dominant regional dispersal agents. ?? 1978.

  1. Seasonal distribution and flux of radium isotopes on the southeastern U.S. continental shelf

    NASA Astrophysics Data System (ADS)

    Moore, Willard S.

    2007-10-01

    Enrichments of radium isotopes in coastal waters have served as indicators of submarine groundwater discharge (SGD). Because coastal waters exchange with the open ocean on a timescale of weeks to months, seasonal patterns of radium isotope distributions may be used to indicate changes in SGD through the year. Here I report the seasonal distributions of four naturally occurring radium isotopes measured throughout the water column of the southeastern U.S. continental shelf, commonly known as the South Atlantic Bight (SAB). The study area extended from Onslow Bay, North Carolina, to Crescent Beach, Florida. Activities of the long-lived isotopes were highest off the coast of Georgia. In the summer, high activities extended throughout the study area, but during spring and winter, they decreased markedly off the coast of SC. The primary source of excess 226Ra and 228Ra (that is activities in excess of open ocean values) is shown to be SGD. Because the activities of these isotopes in SGD differ little with season, the lower excess activities off South Carolina imply lower rates of SGD during the spring and winter. The excess inventories and fluxes of 226Ra and 228Ra provide an estimate of the residence time of water on the shelf. These residence times range from 30 to 60 days with a mean of about 40 days.

  2. Recent benthic foraminifera from the Caribbean continental slope and shelf off west of Colombia

    NASA Astrophysics Data System (ADS)

    Fiorini, Flavia

    2015-07-01

    A quantitative benthic foraminiferal analysis was conducted on 30 sea-floor sediment samples distributed along the continental slope and shelf in Fuerte Area (Colombian Caribbean), between 39 and 2469 m water depth. The aims of the research were to provide data on the distribution of southwestern Caribbean Recent benthic foraminifera, to estimate changes in the foraminiferal distribution related to the bathymetry and the characteristics of the substrate, to define a data-bank on distribution of recent tropical benthic foraminifera from the southwestern Caribbean, to provide reference on foraminiferal distribution that can be used in bathymetric reconstructions of ancient environments. Three different assemblages corresponding to three different environments were identified by cluster analysis. Assemblage A, characterized by variable percentages of porcellaneous, hyaline and agglutinated benthic foraminifera indicative of shelf environments. Assemblage B, dominated by calcareous hyaline foraminifera mainly composed of infaunal foraminifera corresponding to upper bathyal, marine conditions. Assemblage C, composed by agglutinated and calcareous hyaline foraminifera characteristic of normal deep-water marine environments.

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

    USGS Publications Warehouse

    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.

  4. The intensity, duration, and severity of low aragonite saturation state events on the California continental shelf

    NASA Astrophysics Data System (ADS)

    Hauri, C.; Gruber, N.; McDonnell, A. M. P.; Vogt, M.

    2013-07-01

    Ocean acidification will progress in an episodic manner, yet this has rarely been considered. Here, we investigate how the intensity, duration, and severity of episodic low aragonite saturation state events along the California continental shelf have changed since ~1750, and how they might change up to 2050 under the A2 scenario from the Special Report on Emissions Scenarios by the Intergovernmental Panel on Climate Change. Our model-based results suggest that between 1750 and 2010, aragonite undersaturation events along the shelf have quadrupled in their number and lengthened in duration, but that even larger changes are bound to occur within the next 20 to 40 years. Undersaturation will become very likely the norm near the seafloor by 2030, and if atmospheric CO2 increases beyond ~500 ppm, this layer will become permanently undersaturated. Combined with a fourfold increase in intensity, the resulting increase in severity of low aragonite saturation state events will substantially affect the viability of calcifying organisms and will alter ecosystem structure.

  5. The sensitivity of the northwest European continental shelf ecosystem to anthropogenic pressures

    NASA Astrophysics Data System (ADS)

    Wakelin, Sarah; Artioli, Yuri; Holt, Jason; Butenschön, Momme

    2013-04-01

    Anthropogenic pressure is exerted on ecosystems in several ways, through direct drivers such as eutrophication and levels of fishing effort and by changes in the physical environment brought about by climate change. Changes in water temperature, the timing and duration of seasonal stratification, circulation patterns and ocean-shelf exchange all impact on shelf-sea primary production. We use a coupled hydrodynamics-ecosystem model (POLCOMS-ERSEM) to study ecosystem sensitivity to climate change and the anthropogenic drivers of river nutrient loads, impacting on eutrophication, and trawling effort on the northwest European continental shelf, with an emphasis on changes in the North Sea. To force the model we use data from a coupled ocean-atmosphere global model (IPSL-CM4) representative of conditions in the recent past (1983-2000) and possible conditions in the near future (2030-2040) under a business as usual emissions scenario SRES A1B. To study ecosystem sensitivity to direct anthropogenic forcing, we adopt two scenarios impacting on river nutrient loads and trawling effort - one where there is rapid economic growth and limited environmental policies and a second where economic growth is constrained by environmental objectives. The sensitivity of the system to each single driver: climate change, increase in river nutrient loads, decrease in river nutrient loads and reduction in trawling effort is explored. The response of the ecosystem to the combined effects of changes in multiple drivers under the two scenarios of economic growth is also studied. The results are relevant to the Marine Strategy Framework Directive descriptors on marine food webs, eutrophication and biodiversity.

  6. Acoustic and Physical Properties of Mud Deposit in the Southern Continental Shelf of Korea

    NASA Astrophysics Data System (ADS)

    Bae, S.; Kim, D. C.; Lee, G.; Kim, G.; Seo, Y.; Çifci, G.

    2010-12-01

    High-resolution seismic profiles and core sediment sampling have been conducted to investigate the acoustic characteristics and physical properties of shelf mud deposit in the southern continental shelf of Korea. The major sediment source is the Seomjin River. The sediments are transported through the Yeosu Sound. Approximately 1000 line-km data of Chirp subbottom profiling and sparker were used. Along with seismic profiling, 40 piston core samples were collected. High-resolution seismic profiles show the Holocene mud deposits dominated in the study area, ranging from 10 to 40 m in thickness, and gas-related acoustic anomalies were also recorded in the Yeosu Sound and the south of Oenaro Island. The late Quaternary deposits on the study area can be divided into three sequences (Unit Ι, Unit ΙΙ, Unit ΙΙΙ). The seismic units ΙΙ and ΙΙΙ are interpreted as the inner-shelf transgressive sand sheet and the deltaic-estuarine complex, respectively. The highstand systems tract (unit Ι) overlying the maximum flooding surface is recent mud deposits formed during recent highstand of sea level. Core samples were analyzed for sediment texture (grain size, sand, silt and clay contents), physical properties (porosity, water content, bulk density, grain density and shear strength), and acoustic properties (compressional wave velocity and attenuation). Thirty-nine piston core samples were employed for the measurement. The mud sediments in the study area is vertically homogenous in texture. The mean grain size decreases generally from the mouth of Yeosu Sound to seaward. The sound velocity decreases from 1505 to 1485 m/s then increases to 1520 m/s southeastward due to Pleistocene sand ridges. Kim et al. (1992) suggested the grading effect of the Seomjin River discharge transported through the Yeosu Peninsula and Namhae Island results in the physical and acoustic properties.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    USGS Publications Warehouse

    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 <30% of the deposit is Holocene, requires that (1) sediment input is overestimated and/or loss is greatly underestimated, and (2) preservation on the shelf was significant despite deep and active wave scour observed in the form of rapid cliff and bedrock cutting early and late in the transgression. The difference between a basal age of ???14.5 ka and residence time of midshelf sediment (3,273 years), derived from dividing mudbelt volume by modern accumulation rate, implies: (1) significant sediment loss occurred since the mudbelt formed and/or (2) sediment accumulation has varied greatly over time. Although modern sediment budgets are relatively well constrained, it remains uncertain how well we can apply them to the past. An evolving model of sedimentation history explores the likelihood of changes in sediment supply, accumulation patterns, and depositional patterns owing to postglacial sea-level history and human land-use activities while providing important boundary conditions for modeling shoreface evolution.

  9. Measurements of slope currents and internal tides on the Continental Shelf and slope off Newport Beach, California

    USGS Publications Warehouse

    Rosenberger, Kurt J.; Noble, Marlene A.; Norris, Benjamin

    2014-01-01

    An array of seven moorings housing current meters and oceanographic sensors was deployed for 6 months at 5 sites on the Continental Shelf and slope off Newport Beach, California, from July 2011 to January 2012. Full water-column profiles of currents were acquired at all five sites, and a profile of water-column temperature was also acquired at two of the five sites for the duration of the deployment. In conjunction with this deployment, the Orange County Sanitation District deployed four bottom platforms with current meters on the San Pedro Shelf, and these meters provided water-column profiles of currents. The data from this program will provide the basis for an investigation of the interaction between the deep water flow over the slope and the internal tide on the Continental Shelf.

  10. The role of continental shelf width in determining freshwater phylogeographic patterns in south-eastern Australian pygmy perches (Teleostei: Percichthyidae).

    PubMed

    Unmack, Peter J; Hammer, Michael P; Adams, Mark; Johnson, Jerald B; Dowling, Thomas E

    2013-03-01

    Biogeographic patterns displayed by obligate freshwater organisms are intimately related to the nature and extent of connectivity between suitable habitats. Two of the more significant barriers to freshwater connections are seawater and major drainage divides. South-eastern Australia provides a contrast between these barriers as it has discrete areas that are likely influenced to a greater or lesser extent by each barrier type. We use continental shelf width as a proxy for the potential degree of river coalescence during low sea levels. Our specific hypothesis is that the degree of phylogeographic divergence between coastal river basins should correspond to the continental shelf width of each region. This predicts that genetic divergences between river basins should be lowest in regions with a wider continental shelf and that regions with similar continental shelf width should have similar genetic divergences. Pygmy perches (Nannoperca australis and Nannoperca 'flindersi') in south-eastern Australia provide an ideal opportunity to test these biogeographic hypotheses. Phylogeographic patterns were examined based on range-wide sampling of 82 populations for cytochrome b and 23 polymorphic allozyme loci. Our results recovered only limited support for our continental shelf width hypothesis, although patterns within Bass clade were largely congruent with reconstructed low sea-level drainage patterns. In addition, we identified several instances of drainage divide crossings, typically associated with low elevational differences. Our results demonstrate high levels of genetic heterogeneity with important conservation implications, especially for declining populations in the Murray-Darling Basin and a highly restricted disjunct population in Ansons River, Tasmania. PMID:23398527

  11. Stratigraphic framework and heavy minerals of the continental shelf of Onslow and Long Bays, North Carolina

    USGS Publications Warehouse

    Hoffman, Charles W.; Grosz, Andrew E.; Nickerson, John G.

    1999-01-01

    One hundred fourteen vibracores from the Atlantic continental shelf offshore of southeastern North Carolina were opened, described, and processed over several contract years (years 6-9) of the Minerals Management Service-Association of American State Geologists Continental Margins program. Reports for years 9 and 10 of the program compiled the results of the work and assembled the data for release as an interactive CD-ROM report, respectively. The continental shelf of Onslow and Long Bays consists predominantly of outcropping Cretaceous through late Tertiary geologic units. Nearshore these units are covered and incised by late Tertiary and Quaternary units. From oldest to youngest, formally recognized geologic units mapped as part of this study are the Late Cretaceous Peedee Formation-a muddy, fine- to medium-grained quartz sand with trace amounts of glauconite and phosphate; the Paleocene Beaufort Formation-a muddy, fine- to medium-grained glauconitic quartz sand with locally occurring turritelid-mold biosparrudite; the middle Eocene Castle Hayne Formation-a sandy bryozoan biomicrudite and biosparrudite; the Oligocene River Bend Formation-a sandy molluscan-mold biosparrudite; and the Miocene Pungo River Formation-a medium-grained, poorly sorted slightly shelly phosphatic sand. Informal units include a very widespread, unnamed fine- to very fine grained, well-sorted, dolomitic muddy quartz sand that is biostratigraphically equivalent to the Oligocene River Bend Formation; several large valley-fill lithosomes composed of biomicrudite, biomicrite, and biosparrudite of Plio/Pleistocene age; muddy, shelly sands and silty clays of Pliocene, Pleistocene, or mixed Plio/Pleistocene age; and loose, slightly shelly, medium- to coarse-grained sands assigned a Holocene age. Heavy minerals (SG > 2.96) comprise an average of 0.54 wt% (on a bulk-sample basis) of the sediments in 306 samples derived from the 114 vibracores. Heavy-mineral content ranges from 3 in the sediments. The

  12. Observed bottom boundary layer transport and uplift on the continental shelf adjacent to a western boundary current

    NASA Astrophysics Data System (ADS)

    Schaeffer, A.; Roughan, M.; Wood, J. E.

    2014-08-01

    Western boundary currents strongly influence the dynamics on the adjacent continental shelf and in particular the cross-shelf transport and uplift through the bottom boundary layer. Four years of moored in situ observations on the narrow southeastern Australian shelf (in water depths of between 65 and 140 m) were used to investigate bottom cross-shelf transport, both upstream (30°S) and downstream (34°S) of the separation zone of the East Australian Current (EAC). Bottom transport was estimated and assessed against Ekman theory, showing consistent results for a number of different formulations of the boundary layer thickness. Net bottom cross-shelf transport was onshore at all locations. Ekman theory indicates that up to 64% of the transport variability is driven by the along-shelf bottom stress. Onshore transport in the bottom boundary layer was more intense and frequent upstream than downstream, occurring 64% of the time at 30°S. Wind-driven surface Ekman transport estimates did not balance the bottom cross-shelf flow. At both locations, strong variability was found in bottom water transport at periods of approximately 90-100 days. This corresponds with periodicity in EAC fluctuations and eddy shedding as evidenced from altimeter observations, highlighting the EAC as a driver of variability in the continental shelf waters. Ocean glider and HF radar observations were used to identify the bio-physical response to an EAC encroachment event, resulting in a strong onshore bottom flow, the uplift of cold slope water, and elevated coastal chlorophyll concentrations.

  13. A Field Study of The Behaviour of An Anticyclonic Eddy On The Catalan Continental Shelf (nw Mediterranean)

    NASA Astrophysics Data System (ADS)

    Rubio, A.; Espino, M.; Puigdefàbregas, J.; Jordà, G.; Flexas, M.; Arnau, P. A.; Zúñiga, D.; Salat, J.; Arcilla, A. S.

    Local inversions of the general circulation on the Catalan Continental Shelf have been observed. These inversions are produced by anticyclonic structures that recurrently drift along this shelf. A near real-time experiment was planned to study the evolu- tion of these eddies on the Catalan Continental Shelf. The experiment consisted on an oceanographic cruise to monitor one of these structures through CTD casts and repeated fast surveys with a Nu-Shuttle and ADCP measurements, during 5 days in September 2001. The selection of a suitable anticyclonic eddy was carried out, during the days previous to the cruise, through satellite infrared images (AVHRR, AATSR). During the cruise, a real-time image analysis was also carried out and transmitted to the operating ship in order to follow accurately the targeted eddy. This presentation will focus on the preliminary results of the experiment which show the behaviour of a very well developed anticyclonic structure. It was located on the continental shelf, 60 km north of Barcelona. This eddy was 50 m deep, with a diameter of near 50 km and surface velocities of around 50 cm/s it was moving southwestwards at a speed of 5 km/day.

  14. Transport of terrestrially-derived nutrients across the continental shelf of the Western Antarctic Peninsula, Anvers Island

    NASA Astrophysics Data System (ADS)

    Crenshaw, J.; Corbett, D. R.; Walsh, J. P.; Null, K.; Peterson, L.; Hawkins, D.; Peterson, R. N.; Viso, R. F.; Lyons, W. B.; Sybert, D.

    2013-12-01

    Primary productivity in the waters offshore of the Western Antarctic Peninsula (WAP) accounts for a large portion of the global oceans' CO2 drawdown, but is limited by the amount of bio-available iron (Fe) in surface waters and the duration of exposure to sunlight. The mechanisms that supply Fe to surface waters off the coast of the WAP play a key role in the global climate system by fueling primary production in this vast and ecologically important environment. To date, the Antarctic continent remains an important, yet unquantified source of nutrients to the waters offshore of the WAP. During the 2012-2013 austral summer, seawater samples were collected along the WAP offshore of Anvers Island to investigate the source and mixing of water masses across the continental shelf. We evaluated the transport of Fe- and macro-nutrient rich waters derived from the Antarctic continent along and across the continental shelf of the WAP using radon (222Rn) and radium isotopes (223,224Ra). Offshore surface waters were elevated in radon and short-lived radium isotopes relative to shelf waters closer to shore, suggesting longshore rather than shore-normal processes dominate water mass transport on the continental shelf near Anvers Island. These water column features suggest that the Antarctic Peninsula Coastal Current possibly influences circulation patterns offshore of Anvers Island. These findings about water mass characteristics near Anvers Island provide insight to understanding transport of terrestrially-derived nutrients to offshore waters that may stimulate productivity.

  15. Pyruvate Oxidoreductases Involved in Glycolytic Anaerobic Metabolism of Polychaetes from the Continental Shelf off Central-South Chile

    NASA Astrophysics Data System (ADS)

    González, R. R.; Quiñones, R. A.

    2000-10-01

    The presence of low oxygen conditions in extensive areas of the continental shelf off central-south Chile has important effects on the biochemical adaptations of the organisms living in this ecosystem. Polychaetes assemblages cohabit on the shelf with an extensively distributed prokaryotic community made up of giant filamentous sulfur bacteria (mainly Thioploca sp.). The aim of this research was to characterize the pyruvate oxidoreductases enzymes involved in the biochemical adaptation of these benthic polychaetes. Nine polychaete species ( Paraprionospio pinnata, Nephtys ferruginea, Glycera americana, Haploscoloplos sp., Lumbrineris composita, Sigambra bassi, Aricidea pigmentata , Cossura chilensis, and Pectinaria chilensis) were assayed for lactic dehydrogenase (LDH), octopine dehydrogenase (OPDH), strombine dehydrogenase (STRDH) and alanopine dehydrogenase (ALPDH). Each species had a characteristic number of the pyruvate oxidoreductases assayed ranging from 4 in Paraprionospio pinnata to 1 in Pectinaria chilensis . The pyruvate saturation curves obtained for the enzymes from all species analysed, except L. composita, suggest that NADH can be oxidized at different rates depending on the amino acid used in the reaction with pyruvate. Our results indicate that organisms having more that one pyruvate oxidoreductase present a greater metabolic capacity to cope with functional and environmental hypoxia because these enzymes would better regulate the pyruvate consumption rate during the transition period. Thus, the dominance of Paraprionospio pinnata in the study area and its worldwide distribution is consistent with its higher number of pyruvate oxidoreductases with different pyruvate consumption rates involved in anaerobic metabolism. Finally, a positive allometric relationship was found between body size and the specific activity of ALPDH, STRDH, and maximum pyruvate oxidoreductase specific activity. This latter result suggests a positive scaling of the specific

  16. Circulation and exchange processes on the South Atlantic Bight Continental Shelf: Progress report, July 1, 1988 to June 30, 1989

    SciTech Connect

    Lee, T.N.

    1989-03-01

    The work reported here is part of the Department of Energy sponsored Southeast US Continental Shelf Program. The DOE Program is a coordinated, multi-university, interdisciplinary investigation aimed at understanding the physical, chemical and biological processes in the South Atlantic Bight (SAB: east coast continental shelf region from Cape Hatteras to Cape Canaveral). The program is coordinated by Dr. David Menzel of Skidaway Oceanographic Institute. The activities of the other Program Investigators will be discussed briefly under Program Overview. The University of Miami component of the program involves an investigation of the physical processes regulating the transport and exchange of materials in the shelf waters. The guiding scientific objective of this work is to improve the capability for prediction of the physical environment. The principal scientific task is to determine the relative importance of the forces driving shelf circulation and exchange and to measure the shelf waters' response over variable time and space scales. The influence of physical processes on chemical and biological distributions and their interactions is studied through interdisciplinary investigations, joint analysis and interpretation of data and joint publications. 103 refs., 14 figs.

  17. Marine geological and geophysical records of the last British-Irish Ice Sheet on the continental shelf west of Ireland

    NASA Astrophysics Data System (ADS)

    O'Cofaigh, Colm; Callard, S. Louise; Benetti, Sara; Chiverell, Richard C.; Saher, Margot; van Landeghem, Katrien; Livingstone, Stephen J.; Scourse, James; Clark, Chris D.

    2015-04-01

    The record of glaciation on the continental shelf west of Ireland has, until recently, been relatively poorly studied. The UK NERC funded project BRITICE-CHRONO collected marine geophysical data in the form of multibeam swath bathymetry and sub-bottom profiles supplemented by over 50 vibro- and piston cores across the continental shelf west of Ireland during cruise JC106 of the RRS James Cook in 2014. Across the western Irish shelf, offshore of counties Galway and Clare, a series of large arcuate moraines record the former presence of a grounded ice sheet on the shelf. However, geophysical data from further to the west across the Porcupine Bank show a series of ridges and wedge-shaped sedimentary features whose form is consistent with an origin as moraines and/or grounding-zone wedges. Sediment cores from several of these landforms recovered stiff, massive diamictons containing reworked shells that are interpreted as subglacial tills. Cores from the eastern Porcupine Bank recovered laminated muds with cold-water glacimarine foraminifera, in some cases overlying till. Collectively the geophysical and sedimentary data imply the presence of grounded ice across the northern Porcupine Bank and thus much further west on the Irish margin than has previously been considered. This ice underwent retreat in a glacimarine setting. The large 'Olex Moraine' on the western Irish shelf is thus interpreted as recessional feature. Work is currently underway to dates these features and to obtain a retreat chronology for this sector of the last British-Irish Ice Sheet.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Physical associations to spring phytoplankton biomass interannual variability in the U.S. Northeast Continental Shelf

    NASA Astrophysics Data System (ADS)

    Saba, Vincent S.; Hyde, Kimberly J. W.; Rebuck, Nathan D.; Friedland, Kevin D.; Hare, Jonathan A.; Kahru, Mati; Fogarty, Michael J.

    2015-02-01

    The continental shelf of the Northeast United States and Nova Scotia is a productive marine ecosystem that supports a robust biomass of living marine resources. Understanding marine ecosystem sensitivity to changes in the physical environment can start with the first-order response of phytoplankton (i.e., chlorophyll a), the base of the marine food web. However, the primary physical associations to the interannual variability of chlorophyll a in these waters are unclear. Here we used ocean color satellite measurements and identified the local and remote physical associations to interannual variability of spring surface chlorophyll a from 1998 to 2013. The highest interannual variability of chlorophyll a occurred in March and April on the northern flank of Georges Bank, the western Gulf of Maine, and Nantucket Shoals. Complex interactions between winter wind speed over the Shelf, local winter water levels, and the relative proportions of Atlantic versus Labrador Sea source waters entering the Gulf of Maine from the previous summer/fall were associated with the variability of March/April chlorophyll a in Georges Bank and the Gulf of Maine. Sea surface temperature and sea surface salinity were not robust correlates to spring chlorophyll a. Surface nitrate in the winter was not a robust correlate to chlorophyll a or the physical variables in every case suggesting that nitrate limitation may not be the primary constraint on the interannual variability of the spring bloom throughout all regions. Generalized linear models suggest that we can resolve 88% of March chlorophyll a interannual variability in Georges Bank using lagged physical data.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Bottom-boundary-layer measurements on the continental shelf off the Ebro River, Spain

    USGS Publications Warehouse

    Cacchione, D.A.; Drake, D.E.; Losada, M.A.; Medina, R.

    1990-01-01

    Measurements of currents, waves and light transmission obtained with an instrumented bottom tripod (GEOPROBE) were used in conjunction with a theoretical bottom-boundary-layer model for waves and currents to investigate sediment transport on the continental shelf south of the Ebro River Delta, Spain. The current data show that over a 48-day period during the fall of 1984, the average transport at 1 m above the seabed was alongshelf and slightly offshore toward the south-southwest at about 2 cm/s. A weak storm passed through the region during this period and caused elevated wave and current speeds near the bed. The bottom-boundary-layer model predicted correspondingly higher combined wave and current bottom shear velocities at this time, but the GEOPROBE optical data indicate that little to no resuspension occurred. This result suggests that the fine-grained bottom sediment, which has a clay component of 80%, behaves cohesively and is more difficult to resuspend than noncohesive materials of similar size. Model computations also indicate that noncohesive very fine sand in shallow water (20 m deep) was resuspended and transported mainly as bedload during this storm. Fine-grained materials in shallow water that are resuspended and transported as suspended load into deeper water probably account for the slight increase in sediment concentration at the GEOPROBE sensors during the waning stages of the storm. The bottom-boundary-layer data suggest that the belt of fine-grained bottom sediment that extends along the shelf toward the southwest is deposited during prolonged periods of low energy and southwestward bottom flow. This pattern is augmented by enhanced resuspension and transport toward the southwest during storms. ?? 1990.

  2. Oceanographic and atmospheric conditions on the continental shelf north of the Monterey Bay during August 2006

    NASA Astrophysics Data System (ADS)

    Ramp, Steven R.; Lermusiaux, Pierre F. J.; Shulman, Igor; Chao, Yi; Wolf, Rebecca E.; Bahr, Frederick L.

    2011-09-01

    A comprehensive data set from the ocean and atmosphere was obtained just north of the Monterey Bay as part of the Monterey Bay 2006 (MB06) field experiment. The wind stress, heat fluxes, and sea surface temperature were sampled by the Naval Postgraduate School's TWIN OTTER research aircraft. In situ data were collected using ships, moorings, gliders and AUVs. Four data-assimilating numerical models were additionally run, including the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS ®) model for the atmosphere and the Harvard Ocean Prediction System (HOPS), the Regional Ocean Modeling System (ROMS), and the Navy Coastal Ocean Model (NCOM) for the ocean. The scientific focus of the Adaptive Sampling and Prediction Experiment (ASAP) was on the upwelling/relaxation cycle and the resulting three-dimensional coastal circulation near a coastal promontory, in this case Point Año Nuevo, CA. The emphasis of this study is on the circulation over the continental shelf as estimated from the wind forcing, two ADCP moorings, and model outputs. The wind stress during August 2006 consisted of 3-10 day upwelling favorable events separated by brief 1-3 day relaxations. During the first two weeks there was some correlation between local winds and currents and the three models' capability to reproduce the events. During the last two weeks, largely equatorward surface wind stress forced the sea surface and barotropic poleward flow occurred over the shelf, reducing model skill at predicting the circulation. The poleward flow was apparently remotely forced by mesoscale eddies and alongshore pressure gradients, which were not well simulated by the models. The small, high-resolution model domains were highly reliant on correct open boundary conditions to drive these larger-scale poleward flows. Multiply-nested models were no more effective than well-initialized local models in this respect.

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

    PubMed

    Bi, Hongsheng; Ji, Rubao; Liu, Hui; Jo, Young-Heon; Hare, Jonathan A

    2014-01-01

    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. PMID:24498177

  4. Decadal Changes in Zooplankton of the Northeast U.S. Continental Shelf

    PubMed Central

    Bi, Hongsheng; Ji, Rubao; Liu, Hui; Jo, Young-Heon; Hare, Jonathan A.

    2014-01-01

    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. PMID:24498177

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

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

  6. Investigation Into the Origin of Submarine Channelized Deposits Found on the Continental Shelf of Southern Alaska

    NASA Astrophysics Data System (ADS)

    Elmore, R.; Gulick, S. P.; Mohrig, D.; Willems, B. A.; Powell, R. D.; Jaeger, J. M.

    2007-12-01

    The interaction between tectonic exhumation and climatic events along the southern coast of Alaska provides a unique setting in which the interplay of these significant processes can be evaluated. High precipitation rates and topographic relief in conjunction with the cool, temperate nature of the Alaskan coast produce large-scale glaciation across the margin. As such, glacial erosion processes control much of the sediment yield to the continental shelf during advance and retreat stages that have persisted throughout the last ~2.5 myr. Numerous large-scale channel structures preserved within continental shelf sediments may serve as markers of glacial advances or retreats and may illustrate significant glacial-marine processes. We have undertaken an integrated study into the origin of these structures using 1979 industry seismic data provided courtesy of the USGS and NSF-funded, high-resolution seismic data. Channel geometries range in scale from 513 m wide by 60 m deep, up to 4700 m wide and 355 m deep. Differentiation of the channels from the surrounding sediment is possible due to the hummocky, unstratified seismic character of the deposits filling the channels. Bright reflectors in the seismic data, likely representing glacial retreat surfaces, tend to terminate at channel margins. Packages of stacked or overlapping channels are common, suggesting reactivation of the channel surfaces. Although the exact nature of channel formation is still ambiguous, their considerable size and abundance speaks to their potentially significant role in piecing together a geologic history of the margin. Preliminary results suggest that glacially driven physical processes during advance and/or retreat are responsible for their formation. Interpretation of the seismic data will provide a means to determine if the channels are related to sub-ice movement of water or ice proximal erosional processes. Concurrently, with correct interpretation of channels and major erosional horizons

  7. Splay faults and tsunamigenic sources across the continental shelf from 1964 great Alaska earthquake

    NASA Astrophysics Data System (ADS)

    Liberty, L. M.; Haeussler, P. J.; Moeller, M.

    2013-12-01

    Using tsunami run up, seismic reflection and bathymetric data, we identify tsunamigenic sea floor ruptures that resulted from the 1964 Great Alaska earthquake. These sea floor lineaments are rooted in megathrust splay faults that appear across the 500-km wide Gulf of Alaska continental shelf. Based on estimated tsunami travel times, we identify two splay faults that produced 5-10 m wave heights in the coastal town of Seward and remote settlements along the Kenai Peninsula. These faults splay from the megathrust along the trailing edge of the subducted Yakutat terrane that is sandwiched between the Pacific and North American plates. Duplexing along the megathrust likely transferred lateral motion along the decollement to vertical splay fault motion that resulted in multi-meter sea floor uplifts. We identify the Cape Cleare fault as the source of the earliest tsunami arrival for Seward, Puget Bay and Whidbey Bay. Sparker seismic data, pre- and post-earthquake bathymetry and crustal seismic data characterize the along-strike Holocene motion on this 70-km long fault that parallels the Patton Bay fault that ruptured on nearby Montague Island. We define a strand of the Middleton Island fault system as the source of the second arrival in Puget and Whidbey Bays and the earliest tsunami source on Middleton Island and other sites in the eastern Gulf of Alaska. Sea floor displacements of more than 20 m suggest both of these faults have repeatedly ruptured during Holocene earthquakes. Additionally, we identify a series of active thrust faults along the length of the Gulf of Alaska to Kodiak Island that likely initiated tsunami waves from smaller sea floor displacements. Sea floor offsets and splay faults that are mapped along the length of the continental shelf suggest Holocene coseismic rupture patterns are not reflected in interseismic GPS measurements along the Kenai Peninsula, but are consistent with seismic, tsunami, and geodetic measurements from the 1964 earthquake

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

    NASA Astrophysics Data System (ADS)

    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 ( < 500 m) permeable sands and carbonate reservoirs within 80 km of the present-day coastline around the world (Post et al., 2013). Most of the offshore freshwater was emplaced during the Pleistocene during periods of sea level low stands and when ice sheets over ran passive margins at high latitudes. We have analyzed a series of continental shelf cross sections from around the world estimating the average freshwater volume emplaced with distance offshore. We compare the distribution of fresh-brackish water with distance from the coastline to 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

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

    NASA Astrophysics Data System (ADS)

    Shan, Xiujuan; Jin, Xianshi; Zhou, Zhipeng; Dai, Fangqun

    2011-11-01

    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

  10. Geomorphology and sediment processes on the continental shelf and the submarine Akhziv canyon offshore north Galilee, eastern Mediterranean.

    NASA Astrophysics Data System (ADS)

    Ashqar, Lana; Bookman, Revital; Almogi-Labin, Ahuva; Ben-Avraham, Zvi

    2013-04-01

    The northern continental shelf of Israel is relatively steep and incised by submarine canyons. The Akhziv canyon is the largest and most developed and the southernmost in a series of canyons that formed off-shore Lebanon up to Beirut. The canyon is incised into the continental shelf 3 km from the northwestern Galilee coast to a depth of 1200 m. This study aims to understand processes responsible for the canyon morphology and the nature of sediment transport and accumulation mechanisms in the continental shelf and down the canyon to the deep sea. Moreover, the geological section in which the canyon is incised to, and the connection to the western Galilee fault system that transverse the continental shelf is explored for the regional perspective. Akhziv canyon consists of two main channels incised in cross-section V-shape at the upper part of the canyon that connect at 700m depth to produce a U-shaped main channel. The canyon's channels orientation implies a possible connection with the region's fault system. The high-resolution bathymetric map (the National Bathymetry Project) was used for the geomorphologic and morphometric analysis to define the connection between the canyon and the north- western Galilee streams that flow in a main east-west direction, parallel to the terrestrial fault system. Gaps in the submarine aeolian calcarenite ridge on the shallow shelf represent the continuation of terrestrial streams westward during low glacial sea level. Alluvial fans, mapped at 40m water depth, testify for sediment transport from land to the continental shelf toward the canyon head. Shallow high-resolution seismic lines (Sparker) were carried out along the continental shelf and canyon head to reveal the sub-surface structure. The seismic interpretation indicates the presence of channel incisions at depths of 10-15 m under the seafloor, with infill of young sediments which represents phases of deposition and erosion along the continental shelf. In addition, Piston

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

    NASA Astrophysics Data System (ADS)

    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

  12. Plate motions at the transition from the Lomonosov Ridge to Eurasian Continental Shelf

    NASA Astrophysics Data System (ADS)

    Artyushkov, Eugene; Chekhovich, Peter; Petrov, Eugene

    2016-04-01

    Distribution of the Cenozoic plate motions in the Amerasian Basin is a serious problem. Cenozoic opening of the Gakkel Ridge has resulted in the eastward drift of the Lomonosov Ridge and Podvodnikov Basin. According to a popular point of view these two structures are separated from the Eurasian continent by the Khatanga-Lomonosov Transform Fault. It is supposed that this fault with a right-lateral displacement of about 300 km begins at the southern end of the Gakkel Ridge, passes between the southern end of the Lomonosov Ridge and the Asian Shelf probably continuing further to the east into the Podvodnikov Basin. During the last decade the area was covered by a number of seismic profiles. In 2007 reference profile A-7 was shot (Kazanin, Ivanov, UNCLOS Symposium, St.-Petersburg, May 26, 27 2014). This longitudinal profile 832 km long includes both seismic reflection and deep seismic profiling. It follows the eastern slope of the Lomonosov Ridge in the north and crosses the Asian Continental Rise and shelf of the Laptev Sea terminating near the Novosibirsk Islands in the south. The quality of the data is very high because at that time the area was completely free of ice. Transform faults with large strike-slip displacement are crossing many sedimentary basins (Liemiszki, Brown, GSA Bull., 1988, v. 100, p. 665-676 and others). In such basins the structure of the sedimentary cover changes completely across the fault. Not only sedimentary beds become disrupted but the thicknesses of synchronous sedimentary units on the fault walls commonly appear to be quite different. This indicates that during their movement the units were far one from another. The Khatanga-Lomonosov Transform Fault, if it exists, should cross profile A-7 in its middle part. The profile includes some normal faults slightly disrupting the sedimentary sequences. However, on both fault walls the thickness of the main units of the sedimentary cover separated by regional unconformities remains the same

  13. Climatic fluctuations during the Holocene based on eastern Mediterranean continental shelf sediment cores

    NASA Astrophysics Data System (ADS)

    Mor-Federman, Tsofit; Bookman, Revital; Almogi-Labin, Ahuva; Herut, Barak

    2013-04-01

    Sediments deposited on the south eastern Mediterranean continental shelf are sensitive recorders of climatic and oceanographic variability affected by the north Atlantic and indirectly by monsoonal systems. In order to reconstruct the influence of these climatic systems two cores were taken off shore the southern and central Israeli coast at water depths of ~35 m. The sediments were characterized by majors and traces elements, and the sediment provenance was determined using 87Sr/86Sr ratios. Detrital input from the Nile and local environment was studied using grain size distribution and sedimentation rates. Water column productivity was inferred by TOC and δ13Corg. The cores, dated to 7,630 and 8,440 14C years BP, show two distinct sedimentation regimes. The early Holocene is characterized by high sedimentation rates (190-140 cm/ka) that decrease in the last 5,500 years (50-60 cm/ka) in both north and central cores. Coarse grain size is dominant in the early Holocene, with a decreasing trend in the northern core. This distribution is probably connected to eustatic sea level rise and recycling of coarse sediments from the flooded shallow Nile cone. In the late Holocene, as sea level stabilized, grain size is finer in the south; while to the north, cycles of ~1,500 years in coarse grain size characterize the period. Carbonate and organic carbon further present the change along the period. Decrease in carbonate content and increase in δ13Corg during the late Holocene indicate decrease in water column productivity. In contradiction, organic carbon is relatively high in the late Holocene. This is explained by the coarse sediment texture in the early Holocene leading to better oxidation of buried organic matter. Strontium isotopes show changes in sediment provenance. In the early Holocene high 87Sr/86Sr values of ~0.71 reflect a dominant signature of the White Nile and the Yellow Nile and in part the local streams. During the last 5,500 years lower values of ~0

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

    NASA Astrophysics Data System (ADS)

    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

  15. Model for the formation of longshore sand ridges on the continental shelf

    SciTech Connect

    Restrepo, J.M.; Bona, J.L.

    1994-01-05

    A model is proposed for the formation and evolution of three- dimensional sedimentary structures such as longshore sand ridges on the continental shelf in water deeper than that of the shoaling region. Owing to the striking similarity between the bar spacing and the length scales in which interactions among the most energetic modes of shallow water waves take place, we argue that these bars are formed slowly by flows in the turbulent boundary layer generated by weakly nonlinear, dispersive waves. Hence the model is based on the interaction between surficial, weakly nonlinear shallow water waves, having weak spanwise spatial dependence, and the bottom topography. While such underwater structures are not the result of a single formative agent, it is argued that the mechanism proposed in this study does contribute significantly to their generation and evolution. Comparisons of this model with oceanographic data must wait for sufficient data to become available. In conjunction with developing the sand ridge model, this study proposes new mathematical equations of interest in their own right.

  16. Coastal Carbon Synthesis for the Continental Shelf of the North American Pacific Coast (NAPC)

    NASA Astrophysics Data System (ADS)

    Siedlecki, S. A.; Alin, S. R.

    2015-12-01

    The West Coast represents the longest coastline in North America, stretching from Panama all the way northward to the Aleutians. Key advances in the carbon cycling of this margin have been made since the North American Continental Margins report (Hales et al., 2008), notably the convergence of models and observations on air-sea fluxes; more sophisticated coastal carbon cycle models; and increased observational coverage in space and time, allowing for more data synthesis and model-data comparison. The coast was divided up into sub-regions based on differences in oceanographic drivers of coastal carbon cycling. Those sub-regions include the Gulf of Alaska, the Central American Isthmus, and the California Current System (CCS), which is further subdivided into northern, central, and southern sectors. The carbon budget for the Pacific Coast of North America identifies the best-known fluxes as the air-sea exchange of CO2 and terrestrial inputs. The least constrained fluxes include respiration, cross-shelf exchange, and carbon metabolism in estuaries. Spatial trends were typically consistent among models and observations, but the magnitude of the fluxes varied widely. While more modeling and observational studies exist than are presented here, relevant fluxes for the carbon budget were often unreported. In the long-term, investments in research and monitoring will be needed to better constrain the fluxes of many of the highly variable regions described in this study. In addition to the budget, this synthesis identifies gaps and priorities for future research.

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

    PubMed

    Hastings, Philip A; Findley, Lloyd T

    2015-01-01

    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.  PMID:25660803

  18. Influences of salt structures on reservoir rocks in block L-2, Dutch continental shelf

    SciTech Connect

    Dronkert, H. ); Remmelts, G. )

    1993-09-01

    In the subsurface of the Netherlands Continental Shelf, thick layers of Zechstein salt have developed into salt domes and ridges that pierce through the overlying formations. To measure the range of lateral influence of the salt in these structures on the sandstone reservoir rocks of the Mesozoic sequence, a cementation model was developed. The target area, Block L-2, was chosen for the presence of salt domes, wells, and reservoir rocks. The L-2 case study has been performed on two Triassic sandstone intervals. The lower, Volpriehausen, sandstone showed halite cementation in one well, located within several 100 m from a salt dome. Four other wells, located more than 1.5 km from a salt structure, did not show any signs of halite cementation. Therefore, the lateral influence of salt domes on the surrounding reservoir rock is, in this case, limited to less than 1.5 km at 3-4 km depth. A slightly shallower Triassic sandstone (Detfurth) shows more frequent halite cementation. This cementation can be attributed to early seepage from overlying Rot salt brines.Triassic Rot salt is present above depletion areas of the Zechstein salt structures, and in such a way the seepage can be seen as an indirect influence of the salt structures.

  19. The Toms Canyon structure, New Jersey outer continental shelf: A possible late Eocene impact crater

    USGS Publications Warehouse

    Poag, C.W.; Poppe, L.J.

    1998-01-01

    The Toms Canyon structure [~20-22 km wide] is located on the New Jersey outer continental shelf beneath 80-100 m of water, and is buried by ~1 km of upper Eocene to Holocene sedimentary strata. The structure displays several characteristics typical of terrestrial impact craters (flat floor; upraised faulted rim: brecciated sedimentary fill), but several other characteristics are atypical (an unusually thin ejecta blanket; lack of an inner basin, peak ring, or central peak; bearing nearly completely filled with breccia). Seismostratigraphic and biostratigraphic analyses show that the structure formed during planktonic foraminiferal biochron P15 of the early to middle late Eocene. The fill unit is stratigraphically correlating with impact ejecta cored nearby at Deep Sea Drilling Project (DSDP) Site 612 and at Ocean Drilling Program (ODP) Sites 903 and 904 (22-35 km southeast of the Toms Canyon structure). The Toms Canyon fill unit also correlates with the Exmore breccia, which fills the much larger Chesapeake Bay impact crater (90-km diameter; 335 km to the southwest). On the basis of our analyses, we postulate that the Toms Canyon structure is an impact crater, formed when a cluster of relatively small meteorites approached the target site bearing ~N 50 E, and struck the sea floor obliquely.

  20. Sea ice retreat alters the biogeography of the Bering Sea continental shelf.

    PubMed

    Mueter, Franz J; Litzow, Michael A

    2008-03-01

    Seasonal ice cover creates a pool of cold bottom water on the eastern Bering Sea continental shelf each winter. The southern edge of this cold pool, which defines the ecotone between arctic and subarctic communities, has retreated approximately 230 km northward since the early 1980s. Bottom trawl surveys of fish and invertebrates in the southeastern Bering Sea (1982-2006) show a coincident reorganization in community composition by latitude. Survey catches show community-wide northward distribution shifts, and the area formerly covered by the cold pool has seen increases in total biomass, species richness, and average trophic level as subarctic fauna have colonized newly favorable habitats. Warming climate has immediate management implications, as 57% of variability in commercial snow crab (Chionoecetes opilio) catch is explained by winter sea ice extent. Several measures of community distribution and structure show linear relationships with bottom temperature, suggesting warming climate as the primary cause of changing biogeography. However, residual variability in distribution not explained by climate shows a strong temporal trend, suggesting that internal community dynamics also contribute to changing biogeography. Variability among taxa in their response to temperature was not explained by commercial status or life history traits, suggesting that species-specific responses to future warming will be difficult to predict. PMID:18488598

  1. Causes of two slope-failure types in continental-shelf sediment, northeastern Gulf of Alaska

    USGS Publications Warehouse

    Schwab, William C.; Lee, Homa J.

    1988-01-01

    Slumps and sediment-gravity flows have been identified in Holocene glaciomarine sediment on declivities less than 1.3 degrees on the Gulf of Alaska continental shelf. Geologic and geotechnical investigation suggest that the processes responsible for these slope failures are earthquake and storm-wave loading, coupled with cyclic degradation of the sediment-shear strength. We propose that the failure type is related to the nature of the failure load. For example, a slump that occurs approximately 30 km seaward of Icy Bay in water depth of 70 to 150 m was most likely caused by earthquake loading, whereas sediment-gravity flows on the Alsek prodelta, which occur in water depths of 35 to 80 m, probably were caused primarily by storm-wave loading. Sediment remolding and redistribution and incorporation of water, which occurs more readily during wave loading from a long storm than during the limited number of loading cycles generated by an earthquake, reduces the shear strength and increases the fluidity of the failed sediment mass. Wave-induced slope failures thereby tend to transform into sediment-gravity flows.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Maps Showing Distribution of Heavy Minerals on the South Texas Outer Continental Shelf

    USGS Publications Warehouse

    Shideler, Gerald L.; Flores, Romeo M.

    1976-01-01

    Heavy minerals constitute a natural resource which, under proper conditions, could have potential economic significance. The purpose of this report is to describe the heavy-mineral distribution in sea-floor sediments On the South Texas Outer Continental Shelf (OCS) within the northwestern Gulf of Mexico. The South Texas OCS encompasses approximately 24,500 sq km extending southward from Matagorda Bay to the U.S.-Mexico border (fig. 1). In a shoreward direction, the OCS extends from the 180-m isobath to the Federal-State water boundary (16.6 km offshore); however, the mineral distribution patterns presented in these maps have been extrapolated slightly shoreward of the l5-m isobath. This work was part of a regional environmental studies program in the South Texas OCS that was conducted in conjunction with the offshore petroleum-lease sales, under the auspices of the U.S. Bureau of Land Management. Some previous work on heavy minerals within the OCS had been done by van Andel and Poole (1960) and van Andel (1960); the fOrIner work was based on relatively few OCS samples and was part of a broader regional study of the northern Gulf of Mexico.

  5. Petroleum exploration opportunities on the U.S.-Russia Chukchi Sea continental shelf

    SciTech Connect

    Warren, T.; Sherwood, K.W.; Thurston, D.K.; Zerwick, S.A.; Kruglyak, F.F.; Shcherban, O.V.; Grevtsev, A.V.

    1995-12-31

    The Russian Federation and US Minerals Management Service are exchanging information regarding offshore oil and gas exploration and development opportunities on the Chukchi Sea Outer Continental Shelf (OCS) between Wrangel Island and northwestern Alaska north of Bering Strait. Lease terms and mineral extraction laws of the two countries differ. Cooperation creates the opportunity for shared exploration and development infrastructure, possibly enhancing prospects for economic success in both areas. Russian and US agencies will benefit from data sharing and cooperative studies of the biological and sociological environment, resulting in a more comprehensive environmental risk assessment. Russian regulatory agencies will benefit from the historical experience of safe and environmentally sound operations in the Alaska OCS. The Chukchi Sea area includes several geologic basins and structural zones that extend across the US-Russian Provisional Maritime Boundary along 169 {degree} West Longitude. An extensive seismic data network and 5 exploratory wells on the US Chukchi OCS indicate great promise for large, undiscovered oil accumulations in that area. With only sparse seismic data and no test wells, only the broadest geological features of the Russian Chukchi OCS are known at present, but appear to include some of the geological elements recognized as favorable to formation of oil and gas accumulations in the US Chukchi OCS.

  6. Comparison of remotely sensed continental-shelf wave spectra with spectra computed by using a wave refraction computer model

    NASA Technical Reports Server (NTRS)

    Poole, L. R.

    1976-01-01

    An initial attempt was made to verify the Langley Research Center and Virginia Institute of Marine Science mid-Atlantic continental-shelf wave refraction model. The model was used to simulate refraction occurring during a continental-shelf remote sensing experiment conducted on August 17, 1973. Simulated wave spectra compared favorably, in a qualitative sense, with the experimental spectra. However, it was observed that most of the wave energy resided at frequencies higher than those for which refraction and shoaling effects were predicted, In addition, variations among the experimental spectra were so small that they were not considered statistically significant. In order to verify the refraction model, simulation must be performed in conjunction with a set of significantly varying spectra in which a considerable portion of the total energy resides at frequencies for which refraction and shoaling effects are likely.

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

    USGS Publications Warehouse

    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

  8. Influence of the Atchafalaya River on recent evolution of the chenier-plain inner continental shelf, northern Gulf of Mexico

    USGS Publications Warehouse

    Draut, A.E.; Kineke, G.C.; Velasco, D.W.; Allison, M.A.; Prime, R.J.

    2005-01-01

    This study examines the influence of the Atchafalaya River, a major distributary of the Mississippi River, on stratigraphic evolution of the inner continental shelf in the northern Gulf of Mexico. Sedimentary, geochemical, and shallow acoustic data are used to identify the western limit of the distal Atchafalaya subaqueous delta, and to estimate the proportion of the Atchafalaya River's sediment load that accumulates on the inner shelf seaward of Louisiana's chenier-plain coast. The results demonstrate a link between sedimentary facies distribution on the inner shelf and patterns of shoreline accretion and retreat on the chenier plain. Mudflat progradation on the eastern chenier-plain coast corresponds to the location of deltaic mud accumulation on the inner shelf. On the central chenier-plain shelf, west of the subaqueous delta, relict sediment is exposed that was originally deposited between ???1200 and 600 years BP during activity of the Lafourche lobe of the Mississippi Delta complex. Mass-balance calculations indicate that the eastern chenier-plain inner shelf and coastal zone form a sink for 7??2% of the sediment load carried by the Atchafalaya River. ?? 2004 Elsevier Ltd. All rights reserved.

  9. Plutonium, 241Am and 137Cs ratios, inventories and vertical profiles in Washington and Oregon continental shelf sediments

    NASA Astrophysics Data System (ADS)

    Beasley, T. M.; Carpenter, R.; Jennings, C. D.

    1982-10-01

    Continental shelf sediments from nine locations off Washington and Oregon have 239,240Pu inventories which average 8.0 ± 2.6 mCi/km 2. The Columbia River and seawaters advecting over the shelf supply Pu which is removed to underlying sediments, principally through scavenging by inorganic paniculate matter. Mass balance calculations argue that less than 20 percent of the advected Pu need be scavenged from the water column to balance river input and total shelf sediment inventories. The percentage of the Pu removed through scavenging is consistent with observed participate concentrations in shelf waters and published sediment/water distribution coefficients. No marked separation of Pu from 137Cs is observed with depth in Pacific shelf sediments as has been reported in Atlantic coastal sediments. This interocean distinctness can be explained by differences in particle mixing and downward diffusion of Cs in sediments of varying porosities. The transuranic inventories and Pu/Cs ratios in the Pacific sediments do not support the hypothesis of Livingston and Bowen that Pu is remobilized within the sediment column by 'complexone' formation with (principally) organic substances. Excess 210Pb/ 239,240Pu inventory ratios in eight representative cores from the Washington shelf average 100 ± 19, even though absolute values of both inventories vary by much larger factors. This reasonably constant ratio, for a given water depth, permits estimation of total Pu inventories and prediction of sites of unusual Pu accumulation from data on the more easily measured natural radionuclide.

  10. Monitoring estuarine circulation and ocean waste dispersion using an integrated satellite-aircraft-drogue approach. [Continental Shelf and Delaware Bay

    NASA Technical Reports Server (NTRS)

    Klemas, V. (Principal Investigator); Davis, G. R.; Wang, H.

    1975-01-01

    The author has identified the following significant results. An integrated satellite-aircraft-drogue approach was developed which employs remotely tracked expendable drogues together with satellite and aircraft observations of oil slicks, waste plumes, and natural tracers, such as suspended sediment. Tests conducted on the Continental Shelf and in Delaware Bay indicate that the system provides a cost effective means of monitoring current circulation and verifying oil slick and ocean waste dispersion models even under severe environmental conditions.

  11. Arctic summary report: Outer Continental Shelf oil and gas activities in the Arctic and their onshore impacts

    NASA Astrophysics Data System (ADS)

    Lynch, C.; Slitor, D. L.; Rudolph, R. W.

    1985-01-01

    Issues and developments occuring in the Arctic Outer Continental Shelf subregion are discussed. The geology and hydrocarbon potential of the Diapir Field petroleum provinces are detailed. Recent lease sales, exploration activities, and the first development proposals for offshore areas of the North slope are considered. Issues relating to transporting resources from production islands to shore and various proposals for moving Arctic hydrocarbons to market are presented. Production projects onshore and possible support bases for offshore activity are also examined.

  12. Hurricane Andrew's impact on natural gas and oil facilities on the outer continental shelf (interim report as of November 1993)

    SciTech Connect

    Daniels, G.R.

    1994-01-01

    The interim report reviews Hurricane Andrew's impact on Federal Outer Continental Shelf (OCS) natural gas and oil drilling and production facilities. The report provides background on Hurricane Andrew's progression, discusses how OCS operators responded to the storm, summarizes the types of damage to offshore facilies caused by Hurricane Andrew, and discusses Minerals Management Service's continuing damage assessment and repair efforts. The summaries of damage estimates are presented in tables in Appendix 1. A glossary of report terminology is provided in Appendix 2.

  13. 75 FR 51943 - Safety Zone; DEEPWATER HORIZON at Mississippi Canyon 252 Outer Continental Shelf MODU in the Gulf...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-24

    ...The Coast Guard is extending the effective period for the temporary safety zone around the riser for the DEEPWATER HORIZON, a Mobile Offshore Drilling Unit (MODU), at Mississippi Canyon 252, in the Outer Continental Shelf. The safety zone in place at 33 CFR 147.T08-849 terminates on August 26, 2010. Extending the effective period for this safety zone provides continued and uninterrupted......

  14. Surficial bioturbation and rapid benthic remineralization in the Cape Hatteras shelf/slope region. Final report

    SciTech Connect

    Robert C. Aller; Josephine Y. Aller; C. Lee; J. Kirk Cochran

    1999-03-17

    This is a final report for the DOE of grant DE-FG02-92ER61464 ''Surficial bioturbation and rapid benthic remineralization in the Cape Hatteras shelf slope region''. Over the past 6 years we have participated in a multidisciplinary field study called the Ocean margins Program (OMP) to examine the importance of continental margins in the global carbon cycle. Specifically, we have focused on the southern portion of the Mid-Atlantic Bight between Cape Hatteras and Chesapeake Bay where a large flux of freshwater and organic carbon enters the North Atlantic Ocean. Additionally, during the first stage of this project, we developed the use of CM-a distributions in sediments as a quantitative indicator of benthic C flux and remineralization rates. The primary objective of our research group has been to understand mechanisms and quantify biogeochemical processes in the seabed that affect cycling, flux, and storage of carbon on the ocean margin of the Mid-Atlantic Bight.

  15. Macrobenthic assemblages of the Changjiang River estuary (Yangtze River, China) and adjacent continental shelf relative to mild summer hypoxia

    NASA Astrophysics Data System (ADS)

    Liao, Yibo; Shou, Lu; Tang, Yanbin; Zeng, Jiangning; Gao, Aigen; Chen, Quanzhen; Yan, Xiaojun

    2016-06-01

    To assess the effects of hypoxia, macrobenthic communities along an estuarine gradient of the Changjiang estuary and adjacent continental shelf were analyzed. This revealed spatial variations in the communities and relationships with environmental variables during periods of reduced dissolved oxygen (DO) concentration in summer. Statistical analyses revealed significant differences in macrobenthic community composition among the three zones: estuarine zone (EZ), mildly hypoxic zone (MHZ) in the continental shelf, and normoxic zone (NZ) in the continental shelf (Global R =0.206, P =0.002). Pairwise tests showed that the macrobenthic community composition of the EZ was significantly different from the MHZ (pairwise test R =0.305, P =0.001) and the NZ (pairwise test R =0.259, P =0.001). There was no significant difference in macrobenthic communities between the MHZ and the NZ (pairwise test R =0.062, P =0.114). The taxa included small and typically opportunistic polychaetes, which made the greatest contribution to the dissimilarity between the zones. The effects of mild hypoxia on the macrobenthic communities are a result not only of reduced DO concentration but also of differences in environmental variables such as temperature, salinity, and nutrient concentrations caused by stratification.

  16. Lower Cretaceous Fossil Record of The Lavrasian Continental Shelf in Northwestern Turkey and Its Correlation with Surrounding Areas

    NASA Astrophysics Data System (ADS)

    Menteş, Merve; Özkar Öngen, İzver

    2015-04-01

    This study contains Zonguldak, Amasra and Kırkalerli (İğneada) area in the Northwestern Turkey. In this region, The Istanbul-Zonguldak Composite Terrane consists of two Paleozoic terranes and their Mesozoic overstep sequences around Zonguldak and Amasra. However The Istranca Terrane is characterized by a complex nappe-pile that includes metamorphic assemblages unconformably overlain by Tertiary sediments of the Thrace basin around İğneada. The original purpose of this study to analyze fossil records of Kozlu-Zonguldak, Amasra and Kırklareli (İğneada) in which Lower Cretaceous of shallow nautical sedimentary stacking which is regarding to The Lavrasian continental shelf in Northwestern Turkey. After analysing about 90 thin section and 30 samples we followed and associated lito-biostratigraphical similarities and contrasts, horizontal and vertical variation in facies which includes Orbitolina, Neotrocholina, megalospheric Rudists and various benthic foraminifera fossil records. Correlation between sections with detailed paleontological analyse wasn't presented until today, however there are several geological examination in these areas. In accordance with this purpose, this study tries to determine possible paleogeographic borders, which are in Northwestern Anatolian of The Lavrasian continental shelf, with benthic foraminiferal assemblages . In this examination, the other aim is to correlate with researches of Lower Cretaceous continental shelf of Iranian in East, Bulgaria, Romania, Italy and Spain in West, to present comparisons and contrasts in Western Pontids. Keywords: Lower Cretaceous, Benthic Foraminifera, Correlation.

  17. New Regional-Scale Geophysical Observations of the Delmarva Peninsula, U.S.A. Inner Continental Shelf

    NASA Astrophysics Data System (ADS)

    Brothers, L. L.; Thieler, E. R.; Pendleton, E. A.; Foster, D. S.; Danforth, W. W.; Baldwin, W. E.; Ackerman, S. D.

    2014-12-01

    The Delmarva Peninsula is a 220-kilometer-long headland, spit and barrier island complex located in the central Mid-Atlantic Bight. This region's antecedent geology, sediment type and distribution, deposit geometry, and transport pathways are poorly constrained. Here we present preliminary findings from chirp and 16-channel boomer seismic reflection profiles, swath bathymetry, acoustic backscatter data and sediment samples collected in June-July, 2014, over 3220 km2 of the inner continental shelf. These co-located datasets characterize the broad-scale geologic framework of the central offshore Delmarva Peninsula, and also provide the geologic underpinnings to National Ocean Service (NOS) hydrographic bathymetry and previously unpublished acoustic backscatter data collected in the region between 2007 and 2011. The combined datasets extend 100 km along the coast from approximately the 8-m isobath to 30 km offshore in water depths up to ~ 30 m. They provide unprecedented resolution and spatial coverage of an inner continental shelf environment along the U.S. eastern seaboard. Analyses of these high-resolution datasets will improve understanding of inner continental shelf features and processes including: shoal massif origins, sand-ridge development, barrier-island system migration, shallow natural gas occurrence and distribution, paleochannel evolution, regional sea-level history and the role of antecedent geology in the central Delmarva coastal system. In addition to scientific insights, these data provide the foundation for a variety of management applications, such as sand resource, habitat, and coastal vulnerability assessments.

  18. Currents and water characteristics around the West Flower Garden Bank. [West Flower Garden Bank, coral reef, Texas continental shelf

    SciTech Connect

    Horne, D.J.

    1986-01-01

    The West Flower Garden Bank is a coral reef on the Texas Continental shelf. The corals on the bank are vulnerable to sediment contamination and to excess turbidity in the overlying water column. Concern for the environmental impact on this and other banks in the region exposed to nearby hydrocarbon production prompted the Bureau of Land Management to fund a data collection effort on the Texas/Louisiana shelf which provided the data analyzed here. Data analyzed includes profiles of velocity, temperature and salinity taken around the Bank in Oct., 1980 and March, 1981. Fixed current meter moorings and a dye experiment conducted in the bottom boundary layer provided additional input. The data reveals a very complicated flow regime around the bank, with some intensification of flow around and over the bank but no movement of water from the bottom of the surrounding shelf up onto the bank.

  19. Environmental risk assessment of the Moroccan Atlantic continental shelf: the role of the industrial and urban area.

    PubMed

    Maanan, Mohamed; Zourarah, Bendahhou; Sahabi, Mohamed; Maanan, Mehdi; Le Roy, Pascal; Mehdi, Khalid; Salhi, Fouad

    2015-04-01

    The present research presents the first large-scale analysis of heavy metal assessment in the Moroccan Atlantic shelf. This work provides scientific basis for future studies on environmental research and fills the gap in knowledge on the worldwide continental platforms. Metal distributions identified three different zones, mainly influenced by industrial and urban sewer (northern areas), agriculture runoffs (central zone), and estuarine discharges (southern areas), respectively. In the north part of the shelf, metal enrichments are observed near industrial and urban sewer mouths (Casablanca and Mohammedia cities). In the south and central areas, the probable absence of human impact on sediments is attributed to effective trapping in the estuary (Oum Er Rbia) and coastal zones, as well as dilution with less contaminated sediments and shelf sediments and removal with fine fractions due to estuary discharges. PMID:25569576

  20. Flux of energy and essential elements through the Continental Shelf ecosystem. Progress report, June 1, 1983-May 31, 1984

    SciTech Connect

    Pomeroy, L.R.

    1983-12-01

    The summer of 1981 was one of unusually intense intrusion of cold Gulf Stream subsurface water onto the southeastern continental shelf, not only off northern Florida, where summer intrusions are frequent, but off Georgia as well. Numbers of free bacteria were 10/sup 6//ml over most of the continental shelf throughout the period of observation. These high numbers, an order of magnitude above usual numbers for the outer shelf, were associated with both newly arrived intrusions and old, stranded intrusions. Our third study of the coastal water and coastal front (FRNFLX II) in April 1981 showed that microbial numbers and heterotrophic activity are quite uniformly and continuously high in the coastal water and in water on both sides of the coastal front. Heterotrophic uptake of glucose shows that microorganisms are not substrate limited but probably are limited by protozoan grazers. The populations appear to be in steady state at high rates of production. Numbers of bacteria attached to particles are high in the coastal water compared with the water of the outer shelf, even during periods of Gulf Stream intrusion. 21 references, 11 figures, 2 tables.

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

    USGS Publications Warehouse

    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

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

    Angelescu, V.; Sánchez, R. P.

    1995-03-01

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

  4. High-resolution seismic stratigraphy of the late Neogene of the central sector of the Colombian Pacific continental shelf: A seismic expression of an active continental margin

    NASA Astrophysics Data System (ADS)

    Martínez, Jaime Orlando; López Ramos, Eduardo

    2011-02-01

    The sedimentary prism of the central Pacific continental shelf of Colombia was affected by regional folding and faulting, and probably later mud diapirism, from the Late Miocene to the Holocene. Interpretation of high-resolution seismic lines (2 s/dt) revealed that the prism consists of 13 high-resolution seismic units, that can be separated into 5 seismic groups. Deposition of the prism and the associated stacking pattern, are probably the response to variable uplift and subsidence in a fore-arc basin that underwent important tectonic events by the end of the Miocene. Throughout the Pliocene, the continental shelf sedimentation was affected by the growing of a dome structure probable due to mud diapirism. This fact caused peripheral faults both normal and reverse that controlled the distribution of some of the seismic units. During the Late Pleistocene (Wisconsin stage?) a eustatic sea level fall caused the shoreline to advance about 50 km westward of its present position. Because of this eustatic sea level change, a strong fluvial dissection took place and is interpreted as the probable extension of the San Juan River to the south of the present day river mouth. Within this framework it is believed that the Malaga and Buenaventura Bays were the passageways of branches of the old drainage system of the San Juan River. The inner branch circulated through the present Buenaventura Bay and runs southward leaving the mark of an apparent valley identified in the seismic information in the eastern sector of the study area. This old fluvial valley and its filling material located in the present day inner continental shelf front of Buenaventura are postulated as important targets to find placer minerals such as gold and platinum.

  5. Interactions between Freshwater Input, Light, and Phytoplankton Dynamics on the Louisiana Continental Shelf.

    EPA Science Inventory

    Light attenuation (kd), chlorophyll a (chl a), and primary production (PP) were measured across the Louisiana shelf, encompassing the area of the shelf where summer hypoxia forms, on 7 spring/summer cruises from 2005 to 2007. Shelf-wide average kd (1/m) co-varied with Mississipp...

  6. On the distribution of dissolved lead in the Loire estuary and the North Biscay continental shelf, France

    NASA Astrophysics Data System (ADS)

    Waeles, Matthieu; Riso, Ricardo D.; Maguer, Jean-François; Guillaud, Jean-François; Le Corre, Pierre

    2008-07-01

    The dissolved lead was studied in the whole salinity gradient of the system composed of the Loire estuary and the North Biscay continental shelf. About 130 samples were collected in winter 2001 and spring 2002 during Nutrigas and Gasprod campaigns (Programme PNEC-Golfe de Gascogne, RV Thalassa) and metal measurements were conducted on board by Potentiometric Stripping Analysis. In the Loire estuary, levels of dissolved lead ranged from 0.15 to 0.24 nM and from 0.04 to 0.26 nM in winter and spring, respectively. Compared to the concentrations reported in 1987 and 1990 (0.4-1.7 nM; Boutier, B., Chiffoleau, J.F., Auger, D., Truquet, I., 1993. Influence of the Loire river on dissolved lead and cadmium concentrations in coastal waters of Brittany. Estuar. Coast. Shelf S., 36:133-143, Estuarine, Coastal and Shelf Science 36, 133-143) our study indicated much lower values. The fall in concentration in the estuary could be attributed to the stopping of activity of Octel, a big manufacturer of tetra alkyl lead. Discharge in dissolved metal to the continental shelf by the Loire river was assessed as 7.5 and 1.9 kg day - 1 for winter and spring, respectively. On the continental shelf, levels of dissolved lead varied within 0.06 and 0.27 nM in winter (0.15 ± 0.06 nM, sd = 1.96, n = 49), whereas concentrations measured in spring were in the range 0.06-0.17 nM (0.09 ± 0.03 nM, sd = 1.96, n = 60). This difference in metal concentration was related to the amounts of rainfall that have fallen over the continental shelf: estimations of inputs by this way (74 and 32 kg day - 1 in winter and spring, respectively) appeared to be significantly higher than inputs from the Loire river (7.5 and 1.9 kg day - 1 in winter and spring, respectively). The distributions of dissolved metal in the surface waters highlighted the role of suspended particular matter (SPM) for a rapid "trapping" of lead near the mouth of the estuary. The vertical distributions showed, in the stratified area, a

  7. Evolution and extensional history of the Antarctic Peninsula Ice Sheet from the NW Weddell Sea continental shelf, Antarctica

    NASA Astrophysics Data System (ADS)

    Smith, R. T.; Anderson, J. B.

    2006-12-01

    The continental margins around Antarctica show dramatic changes in the style of deposition over the last 30 Ma years. Ice sheets are believed to have dominated shallow marine deposition around Antarctica from the Late Miocene to present. The shift in depositional regime from fluvial/deltaic to glacial is manifested in the stratigraphic architecture and seismic facies of the continental margin. Evidence of these changes has been studied in detail along the Pacific side of the Antarctic Peninsula (Larter and Barker, 1991; Larter and Cunningham, 1993; Bart and Anderson, 1995; Rebesco, 1997, 2006). However, tectonic influences on the Pacific side result in high rates of shelf erosion and large unconformities during critical time periods when ice sheets took hold as the dominant depositional mechanism. The northwestern Weddell Sea is the ideal location to study the transition to an ice dominated margin because it has remained in a passive margin/back arc basin tectonic setting throughout the climate change. Evidence from the Weddell Sea continental shelf shows that the onset of glaciation in the Antarctic Peninsula may have been a more gradual event that post- dated the establishment of the West Antarctic ice sheet. The stratigraphic architecture of the NW Weddell Sea continental shelf shows three major phases of deposition: pre-glacial, transitional, and ice sheet dominated. The pre-glacial phase shows stratigraphic sequences similar to low latitude margins. During the transitional phase there are intermittent large erosion events caused by ice sheets coupled with what appears to be long hiatuses during which fluvial/deltaic systems predominate. The ice sheet-dominated phase exhibits all the classic features indicative of glacial strata; large scoured troughs 100's of meters deep and 10's of kilometers wide, truncation of underlying sequences followed by chaotic seismic facies and topped with coherent laminated reflections, and oversteepening of the continental slope

  8. Consumption by marine mammals on the Northeast U.S. continental shelf.

    PubMed

    Smith, Laurel A; Link, Jason S; Cadrin, Steven X; Palka, Debra L

    2015-03-01

    The economic and ecological impacts of fish consumption by marine mammals, the associated interactions with commercial fish stocks, and the forage demands of these marine mammal populations are largely unknown. Consumption estimates are often either data deficient or not fully evaluated in a rigorous, quantitative manner. Although consumption estimates exist for the Northeast United States (NEUS) Large Marine Ecosystem, there is considerable uncertainty in those estimates. We examined consumption estimates for 12 marine mammal species inhabiting the regional ecosystem. We used sensitivity analyses to examine metabolically driven daily individual consumption rates, resulting in a suite of feasible parameter-pair ranges for each of three taxonomic groups: mysticetes, odontocetes, and pinnipeds. We expanded daily individual consumption to annual consumption based on abundance estimates of marine mammals found on the NEUS continental shelf coupled with estimates of annual residence time for each species. To examine consumptive removals for specific prey, diet compositions were summarized into major prey categories, and predatory removals by marine mammal species as well as for total marine mammal consumption were estimated for each prey taxa. Bounds on consumption estimates for each marine mammal species were determined using Monte Carlo resampling simulations. Our results suggest that consumption for these 12 marine mammal species combined may be similar in magnitude to commercial fishery landings for small pelagic and groundfish prey groups. Consumption by marine mammals warrants consideration both as a source of mortality in assessments of prey-stocks, and to determine marine mammal forage demands in ecosystem assessment models. The approach that we present represents a rigorous, quantitative method to scope the bounds of the biomass that marine mammals are expected to consume, and is appropriate for use in other ecosystems where the interaction between marine

  9. Large and very large subaqueous dunes on the continental shelf off southern Vietnam, South China Sea

    NASA Astrophysics Data System (ADS)

    Kubicki, A.

    2008-08-01

    In the course of two regional side-scan sonar surveys on the continental shelf off southern Vietnam after the winter monsoon seasons of 2003 and 2004, and covering a total distance of over 1,000 km, the widespread occurrence of large and very large subaqueous dunes was discovered. On the basis of their size, shape, depth of occurrence and orientation, the dunes were grouped into five spatially distinct regions. In each case, a different height/wavelength relationship is observed. With the exception of region no. 3 where dune dimensions follow the mean global trend, the dimensions in the other regions lie below the mean global trend. The most plausible explanation for this is sediment starvation and/or insufficient time for the larger dunes to fully adjust to changing flow conditions. A good correlation is observed between average dune height in each region and water depth, although this is not the case for dune length. The orientation of the dunes corresponds to the direction of the current pattern induced by the regional winter monsoon winds (NE to SW and S). The generally well-developed asymmetrical shapes and the large size of the dunes suggest that the wind-induced currents are strong enough to reactivate most of the dunes during the winter monsoon season, a conclusion supported also by theoretical calculations of critical current velocities. The largest dunes, which seem to have reached their maximum sizes for the local water depths, may not be reactivated regularly but rather only by exceptionally strong episodic flows.

  10. Rippled scour depressions on continental shelf bank slopes off Nordland and Troms, Northern Norway

    NASA Astrophysics Data System (ADS)

    Bellec, Valérie K.; Bøe, Reidulv; Rise, Leif; Slagstad, Dag; Longva, Oddvar; Dolan, Margaret F. J.

    2010-05-01

    Multibeam bathymetry acquired under the MAREANO programme from the continental shelf off Nordland and Troms, northern Norway, show bedforms that we have interpreted as rippled scour depressions. They occur in three areas offshore on bank slopes facing southeast, more than 15 km from land. They are generally found where the slope gradient is low, in water depths of 70-160 m. Individual depressions are up to 3 km long, 1 m deep and up to 300 m wide. They occur in areas where sediments evolve quickly from glacial deposits on the banks to post-glacial muddy sediments on the glacial troughs. Multibeam backscatter and underwater video data show that depression floors are covered by rippled, gravelly, shelly sand. Ripple crests are parallel or slightly oblique to the depression axis orientation. Sand without bedforms is observed between the depressions. TOPAS seismic lines show that the uppermost seismic unit consists of the sand between the depressions. The base of this unit may be the last transgressive/tidal/wave ravinement surface. Physical oceanographic modelling indicates that maximum current velocities are up to 0.6 m/s in the rippled scour depression areas. Stronger currents appear to inhibit the building of these features. Tidal currents play an important role as they trend parallel to the southeast banks slopes and are likely responsible of the gravelly ripples formation inside the depressions as well as the persistence of these depressions which are not covered by finer sediments. On Malangsgrunnen bank, some of the rippled scour depressions are in the extension of NW-SE furrows located on the bank. Simulated bottom currents indicate currents mainly perpendicular to these furrows, as for the rippled scour depressions on the bank slopes. Nevertheless, these features could also highlight currents coming from the northwest which reach the bank margin and continue down to the areas of the rippled scour depressions. These currents could be responsible for the

  11. Distribution of the East China Sea continental shelf basins and depths of magnetic sources

    NASA Astrophysics Data System (ADS)

    Lin, J.-Y.; Sibuet, J.-C.; Hsu, S.-K.

    2005-11-01

    The acoustic basement map of the East China Sea, established by the Shanghai Offshore Petroleum Bureau with all available industry seismic data, shows the existence of a 30-km-wide, 10-km-deep basin, that we named the Ho Basin. The Ho Basin belongs to a series of elongated deep basins extending over 600 km east of the Taiwan-Sinzi Ridge and flanked to the East by a ridge named the Longwan Ridge in its northern part. This new system of basin and ridge was probably formed during middle Miocene, sometimes in between rifting episodes occurring in the Taipei Basin and Okinawa Trough. It complements the already defined system of five belts of backarc basins and associated arc volcanic ridges in the East China Sea, which are progressively younger from the Mainland China shoreline (late Cretaceous/early Tertiary) to the Okinawa Trough (Present). In order to determine the crustal thickness beneath the East China Sea continental shelf, we used a power spectrum method to calculate the depth of the top (Zt) and the centroid (Zo) of the magnetic basement by fitting a straight line through the high- and low-wave number portions of the power spectrum, respectively. Then, the depth of the base (Zb)is estimated from Zt and Zo. After optimizing the size of the data squares, we demonstrate that, except for basins more than 10 km deep, Zt corresponds to the basement depths and Zb, the depth of the Curie point, to the Moho depth. As wide-angle reflection and refraction data are scarce in the East China Sea, this method provides a way to characterize the crustal thickness of the East China Sea and to compute the theoretical heat flow values.

  12. Evidence of post-Pleistocene faults on New Jersey Atlantic outer continental shelf

    USGS Publications Warehouse

    Sheridan, R.E.; Knebel, H. J.

    1976-01-01

    Recently obtained high-resolution seismic profiles (400-4,000-Hz band) show evidence of faults in shallow sedimentary strata near the edge of the Atlantic continental shelf off New Jersey. Apparent normal faults having a throw of about 1.5 m displace sediments to within 7 m of the sea floor. The faults appear to be overlain by undeformed horizontal beds of relatively recent age. Several faults 1 to 2 km apart strike approximately N70°E and dip northwest. The data suggest that the faults are upthrown on the southeast. Projection of the faults on the high-resolution profiles to a nearby multichannel seismic-reflection profile indicates that these shallow faults might be the near-surface expression of a more fundamental deep-seated fault. Several prominent reflectors in the multichannel records are offset by a high-angle normal fault reaching depths of 4.0 to 5.0 sec (6.0 to 6.5 km). The deep fault on the multichannel line also is upthrown on the southeast. Throws of as much as 90 m are apparent at depth, but offsets of as much as 10 m could be present in the shallower parts of the section that may not be resolved in the multichannel data. The position and strike of these faults coincide with and parallel the East Coast magnetic anomaly interpreted as the fundamental seaward basement boundary of the Baltimore Canyon trough. Recurring movements along such boundary faults are expected theoretically if the marginal basins are subsiding in response to the plate rotation of North America and seafloor spreading in the Atlantic.

  13. Biodiversity, Community Structural Shifts, and Biogeography of Prokaryotes within Antarctic Continental Shelf Sediment

    PubMed Central

    Bowman, John P.; McCuaig, Robert D.

    2003-01-01

    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. PMID:12732511

  14. Stable isotope variations in benthic filter feeders across a large depth gradient on the continental shelf

    NASA Astrophysics Data System (ADS)

    Nerot, Caroline; Lorrain, Anne; Grall, Jacques; Gillikin, David P.; Munaron, Jean-Marie; Le Bris, Hervé; Paulet, Yves-Marie

    2012-01-01

    Spatial variations in carbon and nitrogen stable isotopes (δ 13C and δ 15N) of benthic filter feeders were investigated on an inshore-offshore gradient (0-250 km) along the continental shelf of the northern Bay of Biscay (NE Atlantic Ocean). δ 13C and δ 15N values were measured in muscle tissues of four filter-feeding mollusc species (epifaunal: Pecten maximus, Aequipecten opercularis; infaunal: Glycymeris glycymeris, Venus casina) and in benthic particulate organic matter along a corresponding water-depth gradient from 6 to 220 m. All four species showed a decreasing pattern of muscle δ 13C and δ 15N values with increasing depth. At the Ushant front (˜130 m water depth), where there is a decrease in both bottom water chlorophyll a and suspended particulate matter, muscle δ 13C and δ 15N values decreased in all species. Although δ 13C values of infaunal clams initially decreased at 30 m depth, δ 13C values of epifaunal scallops decreased around 120 m depth, far below the expected depth reduction in microphytobenthic production suggesting that carbon isotopes might not simply track microphytobenthic utilization. The difference between infaunal and epifaunal bivalve stable isotope values may reflect differences in feeding strategies. Muscle δ 15N values at the deepest stations (˜2‰) were lower than expected considering the typical trophic enrichment value of 3-4‰ between prey and consumers. These low δ 15N values may result from low metabolic rates and suggest the classic trophic enrichment may not hold true in species inhabiting deep waters. Stable isotopes in benthic filter feeders can reveal much information regarding their ecology and environment, but are not straightforward recorders of stable isotope baseline variations as is often assumed.

  15. Geological and technological assessment of artificial reef sites, Louisiana outer continental shelf

    USGS Publications Warehouse

    Pope, D.L.; Moslow, T.F.; Wagner, J.B.

    1993-01-01

    This paper describes the general procedures used to select sites for obsolete oil and gas platforms as artificial reefs on the Louisiana outer continental shelf (OCS). The methods employed incorporate six basic steps designed to resolve multiple-use conflicts that might otherwise arise with daily industry and commercial fishery operations, and to identify and assess both geological and technological constraints that could affect placement of the structures. These steps include: (1) exclusion mapping; (2) establishment of artificial reef planning areas; (3) database compilation; (4) assessment and interpretation of database; (5) mapping of geological and man-made features within each proposed reef site; and (6) site selection. Nautical charts, bathymetric maps, and offshore oil and gas maps were used for exclusion mapping, and to select nine regional planning areas. Pipeline maps were acquired from federal agencies and private industry to determine their general locations within each planning area, and to establish exclusion fairways along each pipeline route. Approximately 1600 line kilometers of high-resolution geophysical data collected by federal agencies and private industry was acquired for the nine planning areas. These data were interpreted to determine the nature and extent of near-surface geologic features that could affect placement of the structures. Seismic reflection patterns were also characterized to evaluate near-bottom sedimentation processes in the vicinity of each reef site. Geotechnical borings were used to determine the lithological and physical properties of the sediment, and for correlation with the geophysical data. Since 1987, five sites containing 10 obsolete production platforms have been selected on the Louisiana OCS using these procedures. Industry participants have realized a total savings of approximately US $1 500 000 in salvaging costs by converting these structures into artificial reefs. ?? 1993.

  16. Oil and gas exploration on mid-Norway Continental Shelf: a brief history

    SciTech Connect

    Nelson, P.H.

    1988-02-01

    For 20 years, oil and gas exploration on the Mid-Norway continental shelf has been a process of evaluation carefully orchestrated by the government, leading to today's proven reserves of 2.3 million bbl of oil and 12.4 tcf of gas. For the first eleven years from 1969, only the Norwegian authorities and Statoil shot seismic surveys in the region. Together they acquired nearly 21,000 km of data from More in the south, through Haltenbanken, to Traenabanken in the north. Oil companies that wished to apply for a license first had to purchase selected, relevant state seismic. These purchases, particularly important in the early concession rounds, have largely financed the government's investment. In the Haltenbanken area, the first license (436 km/sup 2/; 107,750 ac) was issued in 1980; by 1983, after the issue of four more licenses adjacent to the first, two gas/condensate fields had been discovered, Midgard and Tyrihans (total gas reserves = 5 tcf). Despite disappointing results from Traenabanken, further successes came from additional licensing in Haltenbanken with the discovery of oil, gas, and condensate in the Draugen, Smoerbukk, Heidrun, and Njord fields and a handful of single well successes. Though little open acreage remains in the golden diamond of Haltenbanken, the Norwegian government will probably further respond to industry by licensing the remainder of this highly prospective tract, as well as encouraging higher-risk exploration in unproven areas. Today, development plans are far advanced for the Draugen oil field operated by A/S Norske Shell, with first production expected in 1992. To mature development plans for the gas-rich fields requires securing international gas sales contracts, the Norwegian oil industry's current preoccupation.

  17. Assessment of the physical disturbance of the northern European Continental shelf seabed by waves and currents

    NASA Astrophysics Data System (ADS)

    Aldridge, J. N.; Parker, E. R.; Bricheno, L. M.; Green, S. L.; van der Molen, J.

    2015-10-01

    Natural seabed disturbance was quantified by estimating the number of days in a year that movement of the seabed occurred due to waves and currents. Disturbance over gravel substrates was based on the concept of a critical threshold for bed movement. For mud substrates disturbance was assessed on the basis of bed failure under extreme hydrodynamic stress. For sand beds the disturbance frequency was calculated by reference to the predicted occurrence of small scale bedforms using established relationships for estimating ripple and megaripple height. The method was applied to the northern European Continental Shelf (48°N to 58.5°N and 10°W to 10°E) using modelled annual wave and current forcing with a temporal resolution of one hour and spatial resolution of approximately 11 km. Highest levels of disturbance occurred in areas of high tidal stress where dune/megaripple type bedforms were predicted and in shallow regions exposed to waves with large fetch. However, the detailed distribution of disturbance showed a complex relationship between water depth, tidal stress, wave fetch and grain size. An assessment of the uncertainty in the results was made by use of a simple Monte Carlo approach. In most locations this indicated a large uncertainty in disturbance frequency values suggesting that present predictive relationships need improvement if assessments of natural disturbance are to be made with confidence. Nevertheless the results give a broad understanding of the location and intensity of natural physical bed disturbance and the ability to compare the relative intensity between different regions. This has applications to management of the seabed where human impacts have to be assessed in the context of the underlying natural disturbance. Recommendations are given for further research that might help decrease the uncertainty in natural disturbance prediction.

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

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

    USGS Publications Warehouse

    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

  20. Long-term observations of bottom current and bottom sediment movement on the mid-Atlantic continental shelf

    USGS Publications Warehouse

    Butman, Bradford; Noble, Marlene A.; Folger, David W.

    1979-01-01

    Long-term in situ observations made at three locations on the mid-Atlantic continental shelf during 1975–1976 clearly show intermittent movement of bottom sediment caused by currents, waves, and other forcing mechanisms. In winter, storm-associated bottom currents greater than 30 cm s−1 resuspended and transported sediments. Net water particle excursions during storms were about 20–30 km longshelf and 5–10 km cross-shelf. Wave-induced bottom currents also resuspended sediments during periods of low mean flow. Sediment motion was observed in summer, although bottom conditions were generally tranquil. Significant changes in suspended matter concentration were observed that were only partially related to bottom currents. These changes may have been caused by biological activity or advection. Bottom currents on the mid-Atlantic region of the continental shelf were characterized by a coherent, primarily cross-shelf tidal flow of 5–10 cm s−1 and a low-frequency longshelf component of 5–20 cm s−1. The longshelf current was coherent over length scales of 100 km at tidal frequencies and for motions with periods greater than 50 hours. For these longer periods the longshelf flow was coherent with wind stress, which implies that winds were a major driving force of the longshelf current. The cross-shelf current was not coherent at stations separated by 100 km except at tidal frequencies. Packets of high-frequency internal waves were observed during stratified conditions in summer with bottom currents as large as 20 cm s−1.

  1. Lower trophic levels and detrital biomass control the Bay of Biscay continental shelf food web: Implications for ecosystem management

    NASA Astrophysics Data System (ADS)

    Lassalle, G.; Lobry, J.; Le Loc'h, F.; Bustamante, P.; Certain, G.; Delmas, D.; Dupuy, C.; Hily, C.; Labry, C.; Le Pape, O.; Marquis, E.; Petitgas, P.; Pusineri, C.; Ridoux, V.; Spitz, J.; Niquil, N.

    2011-12-01

    The Bay of Biscay (North-East Atlantic) has long been subjected to intense direct and indirect human activities that lead to the excessive degradation and sometimes overexploitation of natural resources. Fisheries management is gradually moving away from single-species assessments to more holistic, multi-species approaches that better respond to the reality of ecosystem processes. Quantitative modelling methods such as Ecopath with Ecosim can be useful tools for planning, implementing and evaluating ecosystem-based fisheries management strategies. The aim of this study was therefore to model the energy fluxes within the food web of this highly pressured ecosystem and to extract practical information required in the diagnosis of ecosystem state/health. A well-described model comprising 30 living and two non-living compartments was successfully constructed with data of local origin, for the Bay of Biscay continental shelf. The same level of aggregation was applied to primary producers, mid-trophic-levels and top-predators boxes. The model was even more general as it encompassed the entire continuum of marine habitats, from benthic to pelagic domains. Output values for most ecosystem attributes indicated a relatively mature and stable ecosystem, with a large proportion of its energy flow originating from detritus. Ecological network analysis also provided evidence that bottom-up processes play a significant role in the population dynamics of upper-trophic-levels and in the global structuring of this marine ecosystem. Finally, a novel metric based on ecosystem production depicted an ecosystem not far from being overexploited. This finding being not entirely consistent over indicators, further analyses based on dynamic simulations are required.

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

    USGS Publications Warehouse

    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.

  3. Surface and bottom temperature and salinity climatology along the continental shelf off the Canadian and U.S. East Coasts

    NASA Astrophysics Data System (ADS)

    Richaud, Benjamin; Kwon, Young-Oh; Joyce, Terrence M.; Fratantoni, Paula S.; Lentz, Steven J.

    2016-08-01

    A new hydrographic climatology has been created for the continental shelf region, extending from the Labrador shelf to the Mid-Atlantic Bight. The 0.2-degree climatology combines all available observations of surface and bottom temperature and salinity collected between 1950 and 2010 along with the location, depth and date of these measurements. While climatological studies of surface and bottom temperature and salinity have been presented previously for various regions along the Canadian and U.S. shelves, studies also suggest that all these regions are part of one coherent system. This study focuses on the coherent structure of the mean seasonal cycle of surface and bottom temperature and salinity and its variation along the shelf and upper slope. The seasonal cycle of surface temperature is mainly driven by the surface heat flux and exhibits strong dependency on latitude (r≈-0.9). The amplitude of the seasonal cycle of bottom temperature is rather dependent on the depth, while the spatial distribution of bottom temperature is correlated with latitude. The seasonal cycle of surface salinity is influenced by several components, such as sea-ice on the northern shelves and river discharge in the Gulf of St. Lawrence. The bottom salinity exhibits no clear seasonal cycle, but its spatial distribution is highly correlated with bathymetry, thus Slope Water and its intrusion on the shelf can be identified by its relatively high salinity compared to shallow, fresher shelf water. Two different regimes can be identified, especially on the shelf, separated by the Laurentian Channel: advection influences the phasing of the seasonal cycle of surface salinity and bottom temperature to the north, while in the southern region, river runoff and air-sea heat flux forcing are dominant, especially over the shallower bathymetry.

  4. Surface and bottom temperature and salinity climatology along the continental shelf off the Canadian and U.S. East Coasts

    NASA Astrophysics Data System (ADS)

    Richaud, Benjamin; Kwon, Young-Oh; Joyce, Terrence M.; Fratantoni, Paula S.; Lentz, Steven J.

    2016-08-01

    A new hydrographic climatology has been created for the continental shelf region, extending from the Labrador shelf to the Mid-Atlantic Bight. The 0.2-degree climatology combines all available observations of surface and bottom temperature and salinity collected between 1950 and 2010 along with the location, depth and date of these measurements. While climatological studies of surface and bottom temperature and salinity have been presented previously for various regions along the Canadian and U.S. shelves, studies also suggest that all these regions are part of one coherent system. This study focuses on the coherent structure of the mean seasonal cycle of surface and bottom temperature and salinity and its variation along the shelf and upper slope. The seasonal cycle of surface temperature is mainly driven by the surface heat flux and exhibits strong dependency on latitude (r≈-0.9). The amplitude of the seasonal cycle of bottom temperature is rather dependent on the depth, while the spatial distribution of bottom temperature is correlated with latitude. The seasonal cycle of surface salinity is influenced by several components, such as sea-ice on the northern shelves and river discharge in the Gulf of St. Lawrence. The bottom salinity exhibits no clear seasonal cycle, but its spatial distribution is highly correlated with bathymetry, thus Slope Water and its intrusion on the shelf can be identified by its relatively high salinity compared to shallow, fresher shelf water. Two different regimes can be identified, especially on the shelf, separated by the Laurentian Channel: advection influences the phasing of the seasonal cycle of surface salinity and bottom temperature to the north, while in the southern region, river runoff and air-sea heat flux forcing are dominant, especially over the shallower bathymetry.

  5. Latest Pleistocene Sediment Wedge on the New Jersey Outer Continental Shelf - Forced Regressive Paleo-Hudson Delta?

    NASA Astrophysics Data System (ADS)

    Santra, M.; Goff, J. A.; Steel, R. J.

    2011-12-01

    The offlapping sediment wedge on the outer shelf off New Jersey that overlies the regional reflector R-horizon shows many of the characteristic features of a progradational succession deposited during falling sea level (forced regression). This interpretation is consistent with the estimated latest Pleistocene age of the wedge - a well-established period of large-scale eustatic sea level fall. The sediment wedge occupies the outer shelf of New Jersey south of the Hudson Shelf Valley, extending down to the shelf edge. The sediment wedge appears to be strongly strike-oriented. The absence of any record of time-equivalent fluvial/distributary channels on the proximal part of the sediment wedge led some previous workers to the interpretation that the wedge was a product of redistribution of sediment on the shelf rather than a deltaic feature supplied by a fluvial source. The absence of fluvial and coastal plain deposits capping the proximal end of the wedge is actually a characteristic feature of forced regressive deposits and does not preclude a fluvial source for the sediments constituting the wedge. Reinterpretation of high-resolution (1-12 kHz), deep-towed and hull-mounted CHIRP seismic data collected on the New Jersey outer shelf in 2001, 2002 and 2006 shows possible terminal distributary channel deposits and mass transport deposits preserved in the distal part of the wedge that have not been described previously. These channel-like features are restricted in their distribution and their preservation in the sedimentary record is possibly due to punctuated sea-level rise within the overall falling trajectory of sea level that preceded the last glacial maximum (LGM). The presence of these channels and the mass transport complexes point to a direct fluvial feeder, which supplied the sediments to build the sediment wedge on New Jersey outer continental shelf. Detailed mapping of the sediment wedge using the CHIRP data shows that the sediment wedge is composed of

  6. Shelf life extension for POL products. Final report

    SciTech Connect

    Rhee, I.S.; Rutkowski

    1995-04-01

    Extending the shelf life cycle of petroleum, oil, and lubricant (POL) products is clearly conservation effective for military petroleum and water handling distribution equipment (PWHE) as well as other vehicles and equipment To review shelf life requirements of POL products, a total twenty-three (23) specification products were evaluated using the Maximum Likelihood (ML) method for the Weibull distribution. Data utilized for this study were the results of routine shelf life testing from Army Petroleum Center (APC) and Air Force San Antonio Air logistics Center (SAALC). The results showed that the ML methodology can he used to predict the minimum/maximum shelf life of POL products, and the shelf life testing frequency of eleven of the twenty-three products evaluated can be extended from two years to three years without reformulation. These shelf life extensions will minimize the current problems related to lubricants used in preservation and refurbishment of PWHE for prepositioning, and logistics and supply burdens of lubricants.

  7. A continental shelf sedimentary record of Little Ice Age to modern glacial dynamics: Bering Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Jaeger, John M.; Kramer, Branden

    2014-09-01

    The Bering Glacier System is the world's largest surging temperate glacier with seven events occurring over the past century under a range of north Pacific climatic conditions. Onshore records reveal changes in glacial termini positions and evidence of late Holocene glacial advances, but the Little Ice Age (LIA) record of potential glacial surging and associated flooding has not been examined. A 13.6 m-long jumbo core collected on the adjacent continental shelf reveals a 600-yr-long record of sedimentation associated with changing glacifluvial discharge. The chronology is based on 210Pb geochronology and five radiocarbon dates, and the core can be separated into three distinct lithologic units based on the examination of X-radiographs and physical properties: (1) an uppermost unit dating from ∼125 cal yr BP to the present characterized by bioturbated mud interbedded with laminated, thick (5-20 cm) low-bulk density clay-rich beds; (2) a middle unit dating from ∼120-400 cal yr BP that includes numerous interlaminated-to-interbedded low- and high-bulk density beds with infrequent evidence of bioturbation; thick laminated clay-rich beds are rare; (3) a lowermost unit that predates ∼400 cal yr BP and is composed of rare laminated beds grading down into mottled to massive mud. In each of these units, the laminated lithofacies from this mid-shelf location indicates both flood deposition and likely sediment transport in the wave-current bottom-boundary layer. The thick low-density, clay-rich beds in the uppermost unit correlate with historic outburst floods associated with known surge events. Based on previous terrestrial studies, the terminus was at its Holocene Neoglacial maximum extent close to the modern coastline at some point in the middle to late stages of the LIA in southern Alaska (100-350 cal yr BP). During the LIA, preservation of bioturbated intervals is rare while laminated intervals are common. This style of interbedding indicates frequent (<10 yr

  8. Sediment-transport events on the northern California continental shelf during the 1990-1991 STRESS experiment

    USGS Publications Warehouse

    Sherwood, C.R.; Butman, B.; Cacchione, D.A.; Drake, D.E.; Gross, T.F.; Sternberg, R.W.; Wiberg, P.L.; Williams, A. J., III

    1994-01-01

    Measurements of currents and light transmission were made at bottom tripods and moorings arrayed across the northern California continental shelf along the Coastal Ocean Dynamics Experiment (CODE) "C" transect as part of the 1990-1991 Sediment Transport Events on Shelves and Slopes (STRESS) experiment. In combination with meteorological and wave data from the National Data Buoy Center Buoy 46013, these measurements provide information about the physical forcing and resultant resuspension and transport of bottom material between 21 November and 8 March. Sixteen events were identified in the wave, wind and current-meter records for this period. Only two were local storms with southerly winds, but they caused about half of the seasonal net transport. Seven were swell events that combined long-period waves generated by distant storms with local currents. At the 90-m site, swells interacted with the mean northward flow to produce northward transport. During six northerly wind events, upwelling-favorable winds often were sufficient to slow or reverse the mean northward flow and thus caused southward transport. A single current event, which produced moderate southward transport, was observed at the 130-m site. Net transport during the winter experiment was offshore at all sites, northward at the inner- and mid-shelf sites, but southward at the outer-shelf site. The results suggest that local storms with southerly winds may dominate seasonal transport, as on the Washington shelf, but significant transport also can occur during fair weather and during periods of northerly winds. ?? 1994.

  9. Data assimilative modeling investigation of Gulf Stream Warm Core Ring interaction with continental shelf and slope circulation

    NASA Astrophysics Data System (ADS)

    Chen, Ke; He, Ruoying; Powell, Brian S.; Gawarkiewicz, Glen G.; Moore, Andrew M.; Arango, Hernan G.

    2014-09-01

    A data assimilative ocean circulation model is used to hindcast the interaction between a large Gulf Stream Warm Core Ring (WCR) with the Mid-Atlantic Bight (MAB) shelf and slope circulation. Using the recently developed Incremental Strong constraint 4D Variational (I4D-Var) data assimilation algorithm, the model assimilates mapped satellite sea surface height (SSH), sea surface temperature (SST), in situ temperature, and salinity profiles measured by expendable bathythermograph, Argo floats, shipboard CTD casts, and glider transects. Model validations against independent hydrographic data show 60% and 57% error reductions in temperature and salinity, respectively. The WCR significantly changed MAB continental slope and shelf circulation. The mean cross-shelf transport induced by the WCR is estimated to be 0.28 Sv offshore, balancing the mean along-shelf transport by the shelfbreak jet. Large heat/salt fluxes with peak values of 8900 W m-2/4 × 10-4 kg m-2 s-1 are found when the WCR was impinging upon the shelfbreak. Vorticity analysis reveals the nonlinear advection term, as well as the residual of joint effect of baroclinicity and bottom relief (JEBAR) and advection of potential vorticity (APV) play important roles in controlling the variability of the eddy vorticity.

  10. Observed sub-inertial current variability and volume transport over the continental shelf in the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Fang, Wendong; Guo, Pu; Liu, Changjian; Fang, Guohong; Li, Shujiang

    2015-05-01

    Sub-inertial currents (SICs) over the continental shelf of the northern South China Sea (NSCS) are investigated using the in-situ current observations of acoustic Doppler current profiler (ADCP) mooring arrays off the Pearl River Estuary in 2006 and 2007. The survey was carried out in four separate time periods: summer, winter, spring (before the onset of the southwesterly monsoon), and fall (after the establishment of the northeasterly monsoon). The observations showed that the current directions were generally along the shelf, consistent with the directions of monsoonal winds. The currents were also affected by a few of mesoscale eddy events. In summer 2006, the volume transport was northeastward with a mean magnitude of 1.4 Sv through a cross-shelf section from the site of the depth of 135 m to the coast; in winter 2006/2007, spring 2007 and fall 2007, the volume transports were all southwestward with magnitudes of 2.0, 2.1, and 0.9 Sv, respectively, through a cross-shelf section from the site of the depth of 290 m to the coast. The standard deviations of the SICs were generally smaller than the velocities of the mean currents, and the variability of SICs showed significant correlation with the local sea surface winds. No persistent counter-wind currents were observed in the study area during the fall and winter observational periods.

  11. Records of sedimentary dynamics in the continental shelf and upper slope between Aveiro-Espinho (N Portugal)

    NASA Astrophysics Data System (ADS)

    Martins, Virgínia; Abrantes, Isabel; Grangeia, Carlos; Martins, Paula; Nagai, Renata; Sousa, Sílvia H. M.; Laut, Lazaro L. M.; Dias, João M. Alveirinho; Dias, João M.; da Silva, Eduardo Ferreira; Rocha, Fernando

    2012-08-01

    The sedimentary unconsolidated cover of the Aveiro-Espinho continental shelf and upper slope (NW Portugal) records a complex interplay of processes including wave energy and currents, fluvial input, sediment transport alongshore and cross-shelf, geological and oceanographic processes and sediment sources and sinks. In order to study this record, a set of surface sediment samples was studied. Sediment grain size and composition, as well as the mineralogical composition (by XRD) of the fine (< 63 μm) and clay (< 2 μm) fractions and benthic microfaunal (foraminifera) data were analysed. Cluster analysis applied to the sedimentological data (grain size, sediment composition and mineralogy) allowed the establishment of three main zones corresponding to the: inner-, mid- and outer-shelf/upper slope. On the inner-shelf, the sedimentary coverture is composed of siliciclastic fine to very fine sand, essentially comprising modern (immature) terrigenous particles. The sediment grain size, as well as mineralogical and microfaunal composition, denote the high energetic conditions of this sector in which the alongshore transport of sand is predominantly southward and occurs mostly during the spring-summer oceanographic regime, when the main river providing sediments to this area, the River Douro, undergoes periods of drought. This effect may emphasize the erosive character of this coastal sector at present, since the Ria de Aveiro provides the shelf with few sediments. On the mid-shelf, an alongshore siliciclastic band of coarse sand and gravel can be found between the 40 m and 60 m isobaths. This gravelly deposit includes relic sediments deposited during lower sea-level stands. This structure stays on the surface due to the high bottom energy, which promotes the remobilization of the fine-grained sediments, and/or events of sediments bypassing. Benthic foraminifera density and "Benthic Foraminifera High Productivity" (BFHP) proxy values are in general low, which is consistent

  12. Shallow geology, seafloor texture, and physiographic zones of the Inner Continental Shelf from Nahant to northern Cape Cod Bay, Massachusetts

    USGS Publications Warehouse

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

    2013-01-01

    The Massachusetts inner continental shelf between Nahant and northern Cape Cod Bay has been profoundly affected by the occupation and retreat of glacial ice sheets and relative sea-level change during the Quaternary. Marine geologic mapping of this area is a component of a statewide cooperative effort involving the U.S. Geological Survey and the Massachusetts Office of Coastal Zone Management. Interpretation of high-resolution geophysical data (interferometric and multibeam swath bathymetry, lidar, backscatter, and seismic reflection), sediment samples, and bottom photographs was used to produce a series of maps that describe the distribution and texture of seafloor sediments, shallow geologic framework, and physiographic zones of this inner-shelf region. These data and interpretations are intended to aid efforts to inventory and manage coastal and marine resources, and provide baseline information for research focused on coastal evolution and environmental change.

  13. An oilspill risk analysis for the South Atlantic (proposed sale 78) outer continental shelf lease area

    USGS Publications Warehouse

    Samuels, W.B.

    1982-01-01

    An oilspill risk analysis was conducted for the South Atlantic (proposed sale 78) Outer Continental Shelf (OCS) lease area. The analysis considered the probability of spill occurrences based on historical trends; likely movement of oil slicks based on a climatological model ; and locations of environmental resources which could be vulnerable to spilled oil. The times between spill occurrence and contact with resources were estimated to aid analysts in estimating slick characteristics. Critical assumptions made for this particular analysis were: (1) that oil exists in the lease area, (2) that either 0.228 billion (mean case) or 1.14 billion (high case) barrels of oil will be found and produced from tracts sold in sale 78, and (3) that all the oil will be found either in the northern or the southern portion of the lease area. On the basis of these resource estimates, it was estimated that 1 to 5 oilspills of 1,000 barrels or greater will occur over the 25 to 30-year production life of the proposed sale 78 tracts. The results also depend upon the routes and methods chosen to transport oil from OCS platforms to shore. Given the above assumptions, the estimated probability that one or more oilspills of 1,000 barrels or larger will occur and contact land after being at sea less than 30 days is less than 15 percent for all cases considered; for spills 10,000 barrels or larger, the probability is less than 10 percent. These probabilities also reflect the following assumptions: oilspills remain intact for up to 30 days, do not weather, and are not cleaned up. It is noteworthy that over 80 percent of the risk of oilspill occurrence from proposed sale 78 is due to transportation rather than production of oil. In addition, the risks of oilspill occurrence from proposed sale 78 (mean resource estimate) are less than one-tenth of the risks of existing tanker transportation of crude oil imports and refined products in the South Atlantic area.

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

    NASA Astrophysics Data System (ADS)

    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

  15. Oxygen, a regulating factor for nitrogen cycling in continental shelf sediments?

    NASA Astrophysics Data System (ADS)

    Neubacher, E.; Parker, R.; Trimmer, M.

    2009-04-01

    Oxygen is a fundamental parameter in regulating the cycling of carbon and nitrogen in continental shelf seas. Recent studies and models have shown that some regions of coastal seas are prone to a lack of oxygen and under such conditions, the dynamics of the nitrogen cycle could be altered. We measured rates of denitrification, anaerobic ammonium oxidation (anammox), oxygen uptake, nutrient exchange and pore water profiles of oxygen in sediments of the southern North Sea experimentally exposed to different oxygen saturations. The incubation of sediment at 33% (of air-saturation) for oxygen reduced the penetration and consumption of oxygen by the sediment by of approximately 50%, with a new steady state being reached after approximately 75 min. The rates of the various processes showed strong seasonality over the survey period (2007-2008), with denitrification ranging from 0.6 to 21.2 mol N m-2 h-1, anammox 0.2 to 4.4 mol N m-2 h-1 and oxygen uptake 46.5 to 631.8 mol O2 m-2 h-1. At the reduced saturation for oxygen (~ 33%), denitrification increased significantly (30%) while anammox remained constant. On average anammox accounted for 14-28% of the total production of di-nitrogen (N2) gas. Under ambient oxygen saturation, the rates of oxygen uptake and total production of N2 were positively correlated with each other (r = 0.73, p = 0.01, n = 230). The increase in denitrification was coupled to a change in NO3- flux. Under ambient oxygen there was a net release of 10.5 mol NO3- m-2 h-1 from the sediment to the water column, whereas under reduced oxygen, the sediments became a sink for NO3- (-1.2 mol NO3- m-2 h-1) from the overlaying water. These results suggest that facultative denitrifying bacteria were able to exploit the newly extended suboxic sediment layer, while the monophyletic group of anammox bacteria were not as flexible.

  16. Oil spills, 1971-75, Gulf of Mexico outer continental shelf

    USGS Publications Warehouse

    Danenberger, Elmer P.

    1976-01-01

    Oil spillage connected with federally supervised drilling and production activities has been a matter of wide public concern. In its supervision of mineral-resource development on the Outer Continental Shelf (OCS), the U.S. Geological Survey is responsible for the day-to-day inspection and monitoring of OCS oil and gas operations. During these activities, the U.S. Geological Survey records and investigates hydrocarbon discharges resulting from such operations. Beginning in 1971, all spills have been recorded, and a computer file has been maintained on all spills of 1 barrel or more. The total Gulf of Mexico OCS oil spillage recorded during January 1, 1971-December 31, 1975, amounted to 51,421 barrels. Production during that period amounted to 35,219 barrels per barrel spilled. In all, 5,857 spills were recorded, but 85.5 percent of the total spill volume was contributed by just 5 incidents. The environmental effect of these incidents apparently was minimal and of short duration. No spills of more than 50 barrels resulted from drilling operations during the period. The only spillage resulting from blowouts was caused by nondrilling incidents, including completion, production, and workover. The amount of oil discharged from spills of less than 50 barrels decreased by more than half between 1971 and 1975. The improvement reflects changes in the operating philosophy of the offshore industry, tightening of U.S. Geological Survey operating orders, and substantial increases in the inspection force. Most production-platform spills involve failures in the sump system, the separator system, or other hydrocarbon-handling equipment; improved sump-system designs and better high-low-level controls have reduced both the number and the volume of spills. Pipeline and pump spills also declined significantly, although the decline appears less attributable to revisions in OCS operating requirements. No operator consistently contributed a disproportionate amount of spillage. Most of

  17. Marine biological valuation mapping of the Basque continental shelf (Bay of Biscay), within the context of marine spatial planning

    NASA Astrophysics Data System (ADS)

    Pascual, Marta; Borja, Angel; Eede, Sarah Vanden; Deneudt, Klaas; Vincx, Magda; Galparsoro, Ibon; Legorburu, Irati

    2011-11-01

    Marine Biological Valuation (BV) has increased in importance in recent years, due to the need to establish accurate maps of biodiversity value. However, there have been few exercises undertaken in Southern Europe, in putting a value on marine biodiversity whilst at the same time looking at several biological components. This paper presents the complete Biological Valuation Map (BVM) of the Basque continental shelf and estuaries, using the methodology developed for the Belgian Continental Shelf. It includes all available biological data (zooplankton, macroalgae, macrobenthos, demersal fish, seabirds and cetaceans), from 2003 to 2010. BVMs aim to compile all available biological and ecological information for a selected study area, allocating an integrated intrinsic biological value to the subzones within the study area. Here, the results highlight specific areas (such as Jaizkibel or Cap Breton Canyon), as having high or very high integrated BV, using all of the components. Furthermore, some biodiversity 'hotspots' have been identified, according to a specific ecosystem component (e.g. mid-parts of the Oka estuary, for macroalgae, and the Cap Breton Canyon, for cetaceans). Comparison with the results obtained from other European countries, and with previously high-importance delimited zones within the study area, showed similar spatial trends and patterns. Therefore, the objectives of this contribution are: (i) to analyse and establish a spatial ecological value map of the continental shelf of the Basque Country (southern Bay of Biscay), using present BV methods; (ii) to compare the results obtained to other European countries, and (iii) to explore the application of these results to the Marine Spatial Planning (MSP) and the European Marine Strategy Framework Directive (MSFD) requirements. This map can serve as a baseline for future MSP and can also be used for the determination of the environmental status, within the MSFD, for the qualitative descriptor 1

  18. Shelf-edge deltas and drowned barrier-island complexes on the northwest Florida outer continental shelf

    USGS Publications Warehouse

    Gardner, J.V.; Dartnell, P.; Mayer, L.A.; Hughes, Clarke J.E.; Calder, B.R.; Duffy, G.

    2005-01-01

    A high-resolution multibeam survey of the northwest Florida shelf mapped six relict shelf-edge deltas, each with a drowned barrier-island system developed on its south and southwestern rims. The deltas appear to have formed during periods of sea-level stasis that occurred between 58,000 and 28,000 years ago. The barrier islands formed on the deltas during periods of slow regression during this same time interval. Large fields of asymmetric dunes are found on the delta surfaces as well as on the south and southwestern flanks of the deltas. The asymmetry and orientation of the dunes suggest that a northward-flowing current was sheared by the presence of the delta topography, and as a result, the upper layer of the flow continued to the north, whereas the lower layer was steered by the topography. The topographic steering accelerated the northward flow around the south and southwestern flanks with speeds adequate to form large dunes. The flow slowed after rounding southwestern flank but accelerated again as it encountered the next delta flank to the north. The age of the dune formation is unknown, and no northward-flowing geostrophic flow has been reported in the literature from this area. ?? 2004 Elsevier B.V. All rights reserved.

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

    USGS Publications Warehouse

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

    2013-01-01

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

  20. Continental shelf processes affecting the oceanography of the South Atlantic Bight. Progress report, June 1, 1979-May 31, 1980

    SciTech Connect

    Atkinson, L P

    1980-02-29

    Progress is reported on research conducted from June, 1979 to May, 1980 on various oceanographic aspects of the South Atlantic Bight. Research topics included: (1) A flashing model of Onslow Bay, North Carolina based on intrusion volumes; (2) A description of a bottom intrusion in Onslow Bay, North Carolina; (3) Detailed observations of a Gulf Stream spin-off eddy on the Georgia continental shelf; (4) Pelagic tar of Georgia and Florida; (5) A surface diaton bloom in response to eddy-forced upwelling; and (6) Hydrographic observations off Savannah and Brunswick, Georgia.