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Sample records for north sea application

  1. North Sea difficult but prime area for applications

    SciTech Connect

    Skattum, K.S. )

    1990-04-02

    The Norwegian North Sea sector has been considered a very expensive area for subsea developments compared to the Gulf of Mexico and Brazil, where, the cost of a completed subsea well is several times less. An analysis of these large differences shows how the costs for North Sea projects can be reduced.

  2. Estimating decadal variability in sea level from tide gauge records: An application to the North Sea

    NASA Astrophysics Data System (ADS)

    Frederikse, Thomas; Riva, Riccardo; Slobbe, Cornelis; Broerse, Taco; Verlaan, Martin

    2016-03-01

    One of the primary observational data sets of sea level is represented by the tide gauge record. We propose a new method to estimate variability on decadal time scales from tide gauge data by using a state space formulation, which couples the direct observations to a predefined state space model by using a Kalman filter. The model consists of a time-varying trend and seasonal cycle, and variability induced by several physical processes, such as wind, atmospheric pressure changes and teleconnection patterns. This model has two advantages over the classical least-squares method that uses regression to explain variations due to known processes: a seasonal cycle with time-varying phase and amplitude can be estimated, and the trend is allowed to vary over time. This time-varying trend consists of a secular trend and low-frequency variability that is not explained by any other term in the model. As a test case, we have used tide gauge data from stations around the North Sea over the period 1980-2013. We compare a model that only estimates a trend with two models that also remove intra-annual variability: one by means of time series of wind stress and sea level pressure, and one by using a two-dimensional hydrodynamic model. The last two models explain a large part of the variability, which significantly improves the accuracy of the estimated time-varying trend. The best results are obtained with the hydrodynamic model. We find a consistent low-frequency sea level signal in the North Sea, which can be linked to a steric signal over the northeastern part of the Atlantic.

  3. Estimating decadal variability in sea level from tide gauge records: an application to the North Sea.

    NASA Astrophysics Data System (ADS)

    Riva, R.; Frederikse, T.; Slobbe, C.; Broerse, T.; Verlaan, M.

    2015-12-01

    One of the primary observational datasets of sea level is represented by the tide gauge record. We propose a new method to estimate trends and variability on decadal time scales from tide gauge data by using a state space formulation, which couples the direct observations to a predefined state space model by using a Kalman filter. The model consists of a time-varying trend and seasonal cycle, and variability induced by several physical processes, such as wind, atmospheric pressure changes and teleconnection patterns. This model has two advantages over the classical least-squares method that uses regression to explain variations due to known processes: a seasonal cycle with time-varying phase and amplitude can be estimated, and the trend is allowed to vary over time. This time-varying trend consists of a secular trend and low-frequency variance that is not explained by any other term in the model. As a test case, we have used tide gauge data from stations around the North Sea over the period 1980-2013. We compare a model that only estimates a trend with two models that also remove intra-annual variability: one by means of time series of wind stress and sea level pressure, and one by using a two-dimensional hydrodynamic model. Explaining variability significantly improves the accuracy of the found decadal variability signal, where the best results are obtained with the hydrodynamic model. We find a consistent decadal sea level signal in the North Sea, which significantly influences estimates of a linear trend over the 34-year period.

  4. The application of DNA sequence data for the identification of benthic nematodes from the North Sea

    NASA Astrophysics Data System (ADS)

    Vogt, Philipp; Miljutina, Maria; Raupach, Michael J.

    2014-12-01

    Nematodes or roundworms represent one of the most diverse and dominant taxon in marine benthic habitats. Whereas a morphological identification of many species is challenging, the application of molecular markers represents a promising approach for species discrimination and identification. In this study, we used an integrative taxonomic approach, combining both molecular and morphological methods, to characterize nematodes of distinct sex and ontogenetic stages from three sampling sites of the North Sea. Morphospecies were discriminated after first visual determination, followed by a molecular analysis of the nuclear 28S rDNA: D2-D3 marker. By linking each sequence to a morphological voucher, discordant morphological identification was subjected to a so-called reverse taxonomic approach. Molecular operational taxonomic units (MOTUs) and morphospecies were compared for all of the three sampling sites to assess concordance of methodology. In total, 32 MOTUs and 26 morphospecies were assigned, of which 12 taxa were identified as described species. Both approaches showed high concordance in taxon assignment (84.4 %) except for a cluster comprising various Sabatieria species. Our study revealed the high potential of the analyzed fragment as a useful molecular marker for the identification of the North Sea nematodes and highlighted the applicability of this combined taxonomic approach in general.

  5. The north Sulu Sea productivity

    NASA Astrophysics Data System (ADS)

    Xiao, Z.

    2009-12-01

    The Sulu Sea is a part of the western North Pacific. It is a closed sea for its deep water and a semi-closed sea for its upper layer. The Sulu Sea exchanges mainly surface waters with the South China Sea and the Celebes Sea. The Sulu Sea is more productive than the adjacent South China Sea (Jones, 2002). On the basis of MERIS satellite observations from 2002 to 2008, we focus on the high-chlorophyll area as an indicator of the abundance of primary productivity in the Sulu Sea. Strong chlorophyll concentration in the north Sulu Sea close to the Mindoro Strait mainly occurs from December to March and low chlorophyll concentration happens in April to November. The adjacent South China Sea on the other side of Mindoro Strait has shown persistent signs of low chlorophyll concentration. Based on 1/8° Global Navy Coastal Ocean Model, the intrusion of the South China Sea waters through the Mindoro Strait to the Sulu Sea from April to November is the main reason for the low chlorophyll concentration observed in the north Sulu Sea. During April to November, the South China Sea waters flow through the Mindoro Strait and stay on the surface of the north Sulu Sea because of their low density. The north Sulu Sea waters mix with fresher waters coming from the South China Sea without new nutrients supply. When the inflow from South China Sea to Sulu Sea ceases in December to March, the upwelling due to the summer monsoon wind becomes an important mechanism supplying deep nutrients to the surface water which lead to high chlorophyll concentration. Jones, I.S.F., 2002. Primary production in the Sulu Sea. Proceedings of the Indian Academy of Sciences-Earth and Planetary Sciences 111, 209-213.

  6. North Sea platforms revamped

    SciTech Connect

    O'Hare, J.

    1999-12-01

    Many of the early North Sea platforms are reaching their end-of-field life. Most are still equipped with their original drilling package. In a few cases the package has either been removed or decommissioned. The early installations were designed for much simpler and less demanding wells than the horizontal, extended-reach or designer wells common today. Extended-reach wells now can be drilled realistically from ageing platforms, without incurring massive capital expenditure. This can be achieved using the existing drilling package to the limit of its capabilities and supplementing where necessary with relatively minor upgrades or the use of temporary equipment. Drilling even a few more wells from existing platforms not only prolongs field life, it enables any surplus processing capacity to be made available to develop near-field potential with extended-reach drilling (ERD) or by tying back subsea satellite wells, or for processing third-party fluids. The paper describes well design, surface equipment, mud pumps, shakers and solids control equipment, drill cuttings disposal systems, derrick and hoisting system, top drive and drillstring, downhole equipment, well planning, casing wear, logistics, rig preparations, and ERD vs. subsea tie-backs.

  7. Applications of high resolution sequence stratigraphy in North Sea syn-rift reservoir correlation and development

    SciTech Connect

    Howell, H.; Flint, S.

    1995-08-01

    Tectonically active basins may host a spectrum of sequence stratigraphic expressions previously considered to be spatially mutually exclusive. In low accommodation areas with high sediment supply, fourth order eustatic cyclicity results in high frequency sequence sets while within rapidly subsiding areas, time-equivalent Type-2 sequences are expressed by highly asymmetrical coarsening upward successions, resembling large parasequences. In the shallow marine Fulmar Formation, of the U.K. North Sea Central Graben a sequence boundary and overlying lowstand deposits, which illustrate the effects of laterally variable subsidence rate and intrabasinal topography on the expression of a eustatic sea-level fall, lie between the Glosense and Serratum (J54a and J54b) maximum flooding surfaces. The syn-rift physiography comprises major tilted fault blocks, with the Central Graben dipping parallel to the major faults, simulating a ramp setting. Where the throw of the faults were greatest (SE), the structure acted as a local shelf-slope break. Adjacent to the basin margin, incised valley were cut at fluvial input points (structural transfer zones) and laterally, interfluvial sequence boundaries developed. During early lowstand, sand bypassed the footwall shelf and was deposited as lowstand fan sediments within the deepest part of the hangingwall, with the fault zone acting as a local shelf slope break. Within the shallower water areas of the hangingwall a localised ramp geometry existed parallel to the fault zone. Forced regression deposits developed here were coeval but not physically related to the deep water lowstand turbidite fan deposits.

  8. The Application of DNA Barcodes for the Identification of Marine Crustaceans from the North Sea and Adjacent Regions

    PubMed Central

    Raupach, Michael J.; Barco, Andrea; Steinke, Dirk; Beermann, Jan; Laakmann, Silke; Mohrbeck, Inga; Neumann, Hermann; Kihara, Terue C.; Pointner, Karin; Radulovici, Adriana; Segelken-Voigt, Alexandra; Wesse, Christina; Knebelsberger, Thomas

    2015-01-01

    During the last years DNA barcoding has become a popular method of choice for molecular specimen identification. Here we present a comprehensive DNA barcode library of various crustacean taxa found in the North Sea, one of the most extensively studied marine regions of the world. Our data set includes 1,332 barcodes covering 205 species, including taxa of the Amphipoda, Copepoda, Decapoda, Isopoda, Thecostraca, and others. This dataset represents the most extensive DNA barcode library of the Crustacea in terms of species number to date. By using the Barcode of Life Data Systems (BOLD), unique BINs were identified for 198 (96.6%) of the analyzed species. Six species were characterized by two BINs (2.9%), and three BINs were found for the amphipod species Gammarus salinus Spooner, 1947 (0.4%). Intraspecific distances with values higher than 2.2% were revealed for 13 species (6.3%). Exceptionally high distances of up to 14.87% between two distinct but monophyletic clusters were found for the parasitic copepod Caligus elongatus Nordmann, 1832, supporting the results of previous studies that indicated the existence of an overlooked sea louse species. In contrast to these high distances, haplotype-sharing was observed for two decapod spider crab species, Macropodia parva Van Noort & Adema, 1985 and Macropodia rostrata (Linnaeus, 1761), underlining the need for a taxonomic revision of both species. Summarizing the results, our study confirms the application of DNA barcodes as highly effective identification system for the analyzed marine crustaceans of the North Sea and represents an important milestone for modern biodiversity assessment studies using barcode sequences. PMID:26417993

  9. Danish North Sea crude assayed

    SciTech Connect

    Rhodes, A.K.

    1994-09-12

    Danish North Sea blend was assayed earlier this year. The light, sweet crude comprises crude oil from 10 fields. The crude is piped from offshore production facilities to the A/S Dansk Shell refinery at Fredericia, Denmark. Fig. 1 shows the boiling point curve for the crude, and Fig. 2 illustrates the metals content (vanadium, nickel, and iron), as a function of distillation temperature. The table lists properties of the crude and its fractions.

  10. North Sea development activity surges

    SciTech Connect

    Not Available

    1992-08-10

    This paper reports that operators in the North Sea have reported a burst of upstream activity. Off the U.K.: Amoco (U.K.) Exploration Co. installed three jackets in its North Everest and Lomond fields. It also completed laying the Central Area Transmission System (CATS) pipeline, which will carry the fields' gas to shore. BP Exploration Operating Co. Ltd. installed the jacket for it Unity riser platform 5 {1/2} km from its Forties Charlie platform. Conoco (U.K.) Ltd. tested a successful appraisal well in Britannia field in Block 15/30, about 130 miles northeast of Aberdeen. In the Norwegian North Sea, Saga Petroleum AS placed Snorre oil and gas field on production 6 weeks ahead of schedule and 1.5 billion kroner under budget at a cost of 16.6 billion kroner; and downstream off the U.K., Phillips Petroleum Co. (U.K.) Ltd. awarded Allseas Marine Contractors SA, Essen, Belgium, a pipelay and trenching contract for its Ann field development project in Block 49/6a.

  11. Underwater manifold marks North Sea first

    SciTech Connect

    Steven, R.R.

    1981-01-01

    In the 12 years since commercial oil was first discovered in the area, the North Sea has been the stimulus for technologic development unrivalled in the history of the petroleum industry. However, technology still has a long way to go before the North Sea can be mastered, insuring that there will be no let-up as long as there is oil to be found. Evidence for this will be provided later this year when Shell UK exploration and production, on behalf of Shell and Esso, installs an Underwater Manifold Center (UMC) in 490 ft of water as part of the $650-million development of the Central Cormorant field, northeast of Shetland. While the East Shetland Basin can no longer be described as frontier territory in terms of environment and water depth, Shell/Esso's UMC is certainly in the frontier class. The manfold center is characterized as a revolution in underwater techniques and an extremely important landmark, not only in North Sea history but in world oil production. The UMC will have future applications in 3 distinct situations. It will be suitable for economically developing satellite fields out of reach of a centrally installed platform. It also will foster exploitation of marginal oil deposits in combination with a floating platform and possible surface storage. However, perhaps the most exciting possibility raised by the UMC is its application in deep-water production.

  12. Diseases in North Sea fishes

    NASA Astrophysics Data System (ADS)

    Dethlefsen, V.

    1984-03-01

    Prior to the studies reviewed here, only lymphocystis and skeletal deformities of a variety of fish species and certain diseases of eel were known to occur in the German Bight (North Sea). From 1977 until now, 9 externally visible lesions on North Sea fishes were observed; in addition to those mentioned before, they comprise: fin rot, ulcerations, epidermal papilloma, hyperplasia, pseudobranchial tumour, eye diseases and gill swellings. With the exception of information on changes in frequencies of vertebral deformities of herring from the 1950's to the 1970's, there are no long-term data characterizing changes in frequencies of the diseases under study. For pseudobranchial tumours of cod and epidermal papilloma of dab, information is provided on occurrence and abundance. The distribution pattern of cod afflicted with pseudobranchial tumours is strongly influenced by the migratory behaviour of the fish. Epidermal papillomas of dab were more frequently found at stations within the inner German Bight than in neighbouring areas. The Bight is used for dumping of wastes from titaniumdioxide production. Further disease hot spots are areas off the Humber estuary and the British coast. Analysis of chromium in dab from the German Bight revealed elevated concentrations in epidermal tissues of specimens from the dumping area compared with that found in dab from neighbouring localities. Particulate iron was demonstrated to occur in mucous cells of dab from the dumping area. From increased levels of heavy metals with cancerogenic potential in sensitive target tissues and from increased prevalences of diseased fish in the dumping area it is concluded that these phenomena are possibly causally linked. In the vicinity of the Humber estuary high disease rates were encountered and areas with high prevalences of dab afflicted with epidermal papilloma extended over regions shown to be transport routes for persistent pollutants such as radioactive materials. It is therefore suggested

  13. A remote-sensing/GIS application for analysis of sea surface temperature off the western coast of North America

    EPA Science Inventory

    Recent work reports a warming trend in Pacific Ocean temperatures over the last 50 years. Coastal regions along western North America are particularly sensitive to climatic change, an important indicator of which is sea surface temperature (SST). In situ SST measurements (typica...

  14. Introduction to the petroleum geology of the North Sea

    SciTech Connect

    Glennie, K.W.

    1984-01-01

    This book presents papers on North Sea oil and gas deposits. Topics considered include North Sea exploration from 1964-1983, the structural framework and the pre-Permian history of the North Sea area, the late Permian period, the Triassic period, the Jurasic period, the Cretaceous period, the Cenozoic era, source rocks of the North Sea, and North Sea hydrocarbon plays.

  15. Development and application of an algorithm for detecting Phaeocystis globosa blooms in the Case 2 Southern North Sea waters

    PubMed Central

    Astoreca, Rosa; Rousseau, Véronique; Ruddick, Kevin; Knechciak, Cécile; Van Mol, Barbara; Parent, Jean-Yves; Lancelot, Christiane

    2009-01-01

    While mapping algal blooms from space is now well-established, mapping undesirable algal blooms in eutrophicated coastal waters raises further challenge in detecting individual phytoplankton species. In this paper, an algorithm is developed and tested for detecting Phaeocystis globosa blooms in the Southern North Sea. For this purpose, we first measured the light absorption properties of two phytoplankton groups, P. globosa and diatoms, in laboratory-controlled experiments. The main spectral difference between both groups was observed at 467 nm due to the absorption of the pigment chlorophyll c3 only present in P. globosa, suggesting that the absorption at 467 nm can be used to detect this alga in the field. A Phaeocystis-detection algorithm is proposed to retrieve chlorophyll c3 using either total absorption or water-leaving reflectance field data. Application of this algorithm to absorption and reflectance data from Phaeocystis-dominated natural communities shows positive results. Comparison with pigment concentrations and cell counts suggests that the algorithm can flag the presence of P. globosa and provide quantitative information above a chlorophyll c3 threshold of 0.3 mg m−3 equivalent to a P. globosa cell density of 3 × 106 cells L−1. Finally, the possibility of extrapolating this information to remote sensing reflectance data in these turbid waters is evaluated. PMID:19461860

  16. The North Sea - A shelf sea in the Anthropocene

    NASA Astrophysics Data System (ADS)

    Emeis, Kay-Christian; van Beusekom, Justus; Callies, Ulrich; Ebinghaus, Ralf; Kannen, Andreas; Kraus, Gerd; Kröncke, Ingrid; Lenhart, Hermann; Lorkowski, Ina; Matthias, Volker; Möllmann, Christian; Pätsch, Johannes; Scharfe, Mirco; Thomas, Helmuth; Weisse, Ralf; Zorita, Eduardo

    2015-01-01

    Global and regional change clearly affects the structure and functioning of ecosystems in shelf seas. However, complex interactions within the shelf seas hinder the identification and unambiguous attribution of observed changes to drivers. These include variability in the climate system, in ocean dynamics, in biogeochemistry, and in shelf sea resource exploitation in the widest sense by societies. Observational time series are commonly too short, and resolution, integration time, and complexity of models are often insufficient to unravel natural variability from anthropogenic perturbation. The North Sea is a shelf sea of the North Atlantic and is impacted by virtually all global and regional developments. Natural variability (from interannual to multidecadal time scales) as response to forcing in the North Atlantic is overlain by global trends (sea level, temperature, acidification) and alternating phases of direct human impacts and attempts to remedy those. Human intervention started some 1000 years ago (diking and associated loss of wetlands), expanded to near-coastal parts in the industrial revolution of the mid-19th century (river management, waste disposal in rivers), and greatly accelerated in the mid-1950s (eutrophication, pollution, fisheries). The North Sea is now a heavily regulated shelf sea, yet societal goals (good environmental status versus increased uses), demands for benefits and policies diverge increasingly. Likely, the southern North Sea will be re-zoned as riparian countries dedicate increasing sea space for offshore wind energy generation - with uncertain consequences for the system's environmental status. We review available observational and model data (predominantly from the southeastern North Sea region) to identify and describe effects of natural variability, of secular changes, and of human impacts on the North Sea ecosystem, and outline developments in the next decades in response to environmental legislation, and in response to

  17. Offshore North Sea pipeline and riser loss of containment study (PARLOC) -- applications and limitations in the assessment of operating risks

    SciTech Connect

    Robertson, J.L.M.; Smart, D.; Al-Hassan, T.

    1996-05-01

    Since the Piper Alpha disaster in 1988, there has been an urgent requirement to prevent such tragedies occurring by the introduction of higher safety standards and by improving the confidence in the statistical information available for the assessment of the risks of loss of containment associated with operation of North Sea pipelines. In order to achieve the latter, two databases have been compiled: (1) a pipeline database containing details of pipelines and risers installed in the North Sea; (2) an incident database containing details of reported occurrences (covering the period from 1975 to end 1993), which directly resulted or threatened to result in loss of containment from a pipeline or riser, The data has been compiled from information obtained from: U.K., Norwegian, Dutch and Danish Regulatory Authorities; Operators in the U.K., Dutch and Danish Sectors; reports from previous studies made available to the study; published sources. The databases have been used to perform assessments of factors affecting the frequency of incidents, such as: incident cause; part of pipeline or riser affected; pipeline or riser diameter, length, contents, age, type; whether the line is trenched or buried, piggy-backed or not; hydrotest pressure; location of pipeline or riser in the North Sea. The PARLOC study identifies potential hazards and provides an indication of likely loss of containment frequency associated with the operation of North Sea pipelines and risers. Furthermore, PARLOC provides a continually updated key reference for comparative risk assessment and ultimately for the implementation of risk control as part of an overall risk management program.

  18. Regime shifts in North Sea and Baltic Sea: A comparison

    NASA Astrophysics Data System (ADS)

    Dippner, Joachim W.; Möller, Caroline; Hänninen, Jari

    2012-12-01

    The ICES subdivisions in the North Sea (SD IIIa, SD IVa, and SD IVb) and the subdivisions in the Baltic Sea (SD 29, SD 27/28-2, and SD 25/26) are selected to compare the response in long term monitoring data (1970-2000) with respect to climate regime shifts. A modified AMOEBA model is applied to the data sets to identify the status and development of the North Sea and Baltic Sea system during two recent regime shifts. Biological regime shifts can be identified 1989/1990 in SD IIIa in the North Sea and in SD 25/26 in the Baltic Sea. A synchronous appearance of regime shifts could only be identified in the central and southern Baltic Sea for both regime shifts 1975/76 and 1989/90 where the AMOEBA model indicated a high similarity in ecosystem response. A clear difference was identified in the response of the North Sea and the Baltic Sea. Inter-annual and inter-decadal variability as well as regime shifts are driven in the Baltic Sea by direct atmospheric forcing only. In contrast, the changes in the North Sea are influenced by both the direct atmospheric forcing and the indirect forcing from the changes in North Atlantic. The fact that regime shifts as well as their synchronous appearance can be identified with the AMOEBA model might be of major interest for the management of sustainable use of ecosystem goods and services, the development of ecosystem approach to management and the implementation of the Marine Strategy Framework Directive (MSFD) of the European Union (EU).

  19. North Sea research: Where might it go?

    NASA Astrophysics Data System (ADS)

    Gerlach, S. A.

    1995-03-01

    Seven research suggestions are discussed: the phenomenon of the rare species, the life conditions of meiofauna in suboxic sediment layers, the part-time dormancy of animals and bacteria in the sediment, the importance of lateral advection for the flux of organic matter to the benthos, the selection of sites representative of larger North Sea regions, the selection of monitoring stations, and the importance of viruses, bacteria and other parasites for the North Sea ecosystem.

  20. Paleomagnetic studies of Carboniferous and Permian in the U. K. Southern North Sea: Core orientation, paleocurrent analysis, and diagenetic application

    SciTech Connect

    Turner, P. ); Hartley, A.J. )

    1991-03-01

    The U.K. southern North Sea is a major gas province with production from Carboniferous and Permian reservoirs. It was a foreland basin in Carboniferous times uplifted to form a Lower Permian desert basin and subsequently deeply buried during the Mesozoic. Paleomagnetic methods have been used for burial analysis, core orientation, and paleocurrent studies. VRM is shown to be of only limited value for core orientation; problems relating to drilling effects and deflection by ChRM will be discussed. Detailed thermal demagnetization studies are most valuable. Blocking temperature spectra can be related to burial history curves, and ChRM directions isolated and compared with Carboniferous and Permian reference directions. ChRM is a valuable parameter for core orientation and thus paleocurrent studies. Examples will be shown from the Carboniferous and Lower Permian.

  1. Conversion of existing tanker to North Sea FPSO use

    SciTech Connect

    Voorst, O. van; Baan, J. de; Loenhout, A. van; Krekel, M.

    1995-12-01

    The use of existing tankers as a permanently moored floating storage off loading (FSO) or floating production storage and off loading (FPSO) has been wide spread in the oil industry ever since tankers were used for storage. However, the application of an existing tanker for North Sea FPSO use meeting the stringent demands of the regulatory bodies and the harsh environment of the North Sea has withheld operators from using existing tankers in the North Sea. The acceptance of FPSO technology in the North Sea and the proven ability to moor a tanker with a passive mooring system in a harsh environment has opened the avenue to use existing tankers for use as an FPSO in the North Sea. This is also driven by the search for cost effective solutions for field development plans in order to make marginal fields economically exploitable. The potential reuse of an FPSO on a different location also makes the depreciation period of the FPSO vessel life related instead of field life related. Many issues related to the use of an FPSO in the North Sea are currently subject of papers at various forums. This paper, however, only addresses three crucial areas: (1) the criteria for selection of an existing tanker; (2) the use of a passive mooring system; (3) the fatigue assessment and required modifications. The paper is based on experiences gained during the engineering, design and construction phase of the UISGE GORM, the FPSO, which Bluewater will initially use for Amerada Hess Limited`s Fife Field on the UK continental shelf and confirms that the conversion of a suitable tanker to North Sea FPSO use is a technically flexible and an economically attractive solution.

  2. Education challenges in the North Sea area.

    PubMed

    Ducrotoy, Jean Paul

    2003-01-01

    This paper introduces the North Sea as a fast evolving coastal ecosystem. The variability of natural conditions relates to the global climatic change and to human disturbances, which originate regionally. Education is an integral part of the strategy to improve environmental awareness. Considering contemporary challenges for educating the wider public about the main issues of environmental concern, attention is paid to various plans, which are being developed in North-Western Europe from primary schools to universities. "Learning for life" relies on an opening of the vocation of traditional universities and on the creation of a European university. Sharing resources in a competitive environment is one response given by British universities in the framework of a Discipline Network in Coastal Sciences and Management in 1996-2000. Networking is truly the key to a fast evolving teaching and learning context, notably in relation to ever developing information and communication technologies. The dissemination of scientific information is primordial in this context; a case study relating to the European project "Marine biodiversity in Europe" (BIOMARE) demonstrates the need for an elaborated strategy leading to socio-economic considerations. Empowering communities and governance are the main possible outcomes of such an enlarged approach to education, involving teachers, students, researchers, professionals, and volunteers. Proposals are made for amplifying the involvement of non-scientists into scientific research and its applications to management. Finally, a case is made for facilitating the mobility of all concerned, with a view to annihilate language and cultural barriers.

  3. Education challenges in the North Sea area.

    PubMed

    Ducrotoy, Jean Paul

    2003-01-01

    This paper introduces the North Sea as a fast evolving coastal ecosystem. The variability of natural conditions relates to the global climatic change and to human disturbances, which originate regionally. Education is an integral part of the strategy to improve environmental awareness. Considering contemporary challenges for educating the wider public about the main issues of environmental concern, attention is paid to various plans, which are being developed in North-Western Europe from primary schools to universities. "Learning for life" relies on an opening of the vocation of traditional universities and on the creation of a European university. Sharing resources in a competitive environment is one response given by British universities in the framework of a Discipline Network in Coastal Sciences and Management in 1996-2000. Networking is truly the key to a fast evolving teaching and learning context, notably in relation to ever developing information and communication technologies. The dissemination of scientific information is primordial in this context; a case study relating to the European project "Marine biodiversity in Europe" (BIOMARE) demonstrates the need for an elaborated strategy leading to socio-economic considerations. Empowering communities and governance are the main possible outcomes of such an enlarged approach to education, involving teachers, students, researchers, professionals, and volunteers. Proposals are made for amplifying the involvement of non-scientists into scientific research and its applications to management. Finally, a case is made for facilitating the mobility of all concerned, with a view to annihilate language and cultural barriers. PMID:12787627

  4. Cenozoic stratigraphic evolution, North Sea and Labrador Sea

    SciTech Connect

    Gradstein, F.M.; Grant, A.C.; Mudford, B.S. ); Berggren, W.A. ); Kaminski, M.A. ); D'Lorio, M.A. ); Cloetingh, S. ); Griffiths, C.M. )

    1990-05-01

    The authors are studying Cenozoic correlation patterns, burial trends, and subsidence history of the Central North Sea, Labrador, and Orphan basins. The authors objectives are (1) to detail intraregional mid-high latitude biozonations using noise filtering and probabilistic zonation techniques; (2) to detail paleobathymetric trends from basin margins to centers; (3) to apply this knowledge to model basin evolution, in the perspective of the evolving North Atlantic Ocean; (4) to evaluate causes for the occurrence of major hiatuses and rapid changes of subsidence; and (5) to relate rapid changes in sedimentation in the last few millions of years to model observed undercompaction trends. Cenozoic microfossil assemblages in these basins are similar, related to similarities in sedimentary and paleoeceanographic conditions. In more basinal wells, flysch-type agglutinated foraminiferal assemblages occur, also known from Carpathians, Trinidad, and Moroccan foredeeps. Over 90% of agglutinated taxa are common between these basins, although local stratigraphic ranges vary sufficiently to rely on the concept of average ranges, rather than total ones for correlations. Cenozoic stratigraphic resolution in the North Sea and Labrador basins generally is in 3-5-Ma units. and paleobathymetric zonations define a minimum of five niches, from inner shelf to middle slope regimes. Significant hiatuses occurred in the late Eocene through the Miocene, particularly in northern Labrador and northern North Sea. Subsidence in the Labrador/Grand Banks passive margin half grabens was strongly influenced by Labrador Sea opening between anomalies 34 (Campanian) and 13 (early Oligocene), when subsidence exceeded sedimentation and bathyal conditions prevailed along the margin. Thermally induced subsidence in the central North Sea grabens was considerable in the late Paleocene, when the Norwegian Sea started to open.

  5. No slowdown yet for busy North Sea

    SciTech Connect

    McNally, R

    1989-08-01

    This article reports on oil and gas operations in the North Sea. Current offshore licensing rounds for both the United Kingdom and Norwegian sides are described. Developmental projects are detailed, including the installation of a tank barrier to protect a Norwegian drilling complex from seafloor subsidence. Dutch and Danish exploration is also discussed.

  6. Habitats of North American sea ducks.

    USGS Publications Warehouse

    Derksen, Dirk V.; Petersen, Margaret R.; Savard, Jean-Pierre L.

    2015-01-01

    Breeding, molting, fall and spring staging, and wintering habitats of the sea duck tribe Mergini are described based on geographic locations and distribution in North America, geomorphology, vegetation and soil types, and fresh water and marine characteristics. The dynamics of habitats are discussed in light of natural and anthropogenic events that shape areas important to sea ducks. Strategies for sea duck habitat management are outlined and recommendations for international collaboration to preserve key terrestrial and aquatic habitats are advanced. We follow the definition of habitat advanced by Odum (1971), which is the place or space where an organism lives. Weller (1999) emphasized that habitats for waterbirds required presence of sufficient resources (i.e., food, water, cover, space) for maintenance during a portion of their annual cycle. Habitats exploited by North American sea ducks are diverse, widespread across the continent and adjacent marine waters and until recently, most were only superficially known. Even following a 15-year-long effort through the Sea Duck Joint Venture and U.S. and Canadian Endangered/Threatened Species programs to fund research focused on sea duck habitats there are still important gaps in our understanding of key elements required by some species during various life stages. Importantly, many significant habitats, especially staging and wintering sites, have been and continue to be destroyed or altered, largely as a result of anthropogenic effects. Our goal here is to develop a comprehensive summary of marine, freshwater, and terrestrial habitats and their characteristics by considering sea duck species with similar needs as groups (e.g., eiders) within the tribe Mergini. Additionally, this chapter will examine threats and changes to sea duck habitats from human-caused and natural events. Finally, we will evaluate conservation and management programs underway or available for maintenance and enhancement of habitats critical for

  7. Applicability of the Decision Matrix of North Eastern Atlantic, Mediterranean and connected seas Tsunami Warning System to the Italian tsunamis

    NASA Astrophysics Data System (ADS)

    Tinti, S.; Graziani, L.; Brizuela, B.; Maramai, A.; Gallazzi, S.

    2012-03-01

    After the 2004 Indian Ocean tsunami catastrophe, UNESCO through the IOC (Intergovernmental Oceanographic Commission) sponsored the establishment of Intergovernmental Coordination Groups (ICG) with the aim to devise and implement Tsunami Warning Systems (TWSs) in all the oceans exposed to tsunamis, in addition to the one already in operation in the Pacific (PTWS). In this context, since 2005, efforts have begun for the establishment of TWSs in the Indian Ocean (IOTWS), in the Caribbean area (CARIBE EWS) and in the North Eastern Atlantic, the Mediterranean and Connected Seas (NEAMTWS). In this paper, we focus on a specific tool that was first introduced in the PTWS routine operations, i.e., the Decision Matrix (DM). This is an easy-to-use table establishing a link between the main parameters of an earthquake and the possible ensuing tsunami in order to make quick decision on the type of alert bulletins that a Tsunami Warning Center launches to its recipients. In the process of implementation of a regional TWS for the NEAM area, two distinct DMs were recently proposed by the ICG/NEAMTWS, one for the Atlantic and the other for the entire Mediterranean area. This work applies the Mediterranean NEAMTWS DM to the earthquakes recorded in Italy and compares the action predicted by the DM vs. the action that should be appropriate in view of the observed tsunami characteristics with the aim to establish how good the performance of the Italian TWS will be when it uses the DM for future events. To this purpose, we make use of the parametric catalogue of the Italian earthquakes (CPTI04) compiled in 2004 and the most recent compilation of the Italian tsunami, based on the Italian Tsunami Catalogue of 2004 and the subsequent revisions. In order to better compare the TWS actions, we have identified four different kinds of action coding them from 0 to 3 according to the tsunami severity and have further considered three different distance ranges where these actions apply, that is

  8. Variability of slope current positioning from space: Application to the Northern Current in the North Western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Bouffard, Jerome; Marmain, Julien; Bosse, Anthony; Petrenko, Anne; Forget, Philippe; Doglioli, Andrea; Testor, Pierre; Mortier, Laurent

    The space-time variability of slope currents plays a key role on the across-shore transport of natural and anthropogenic elements. It is therefore of critical importance to monitor the front positioning associated with these hydrodynamical features in a synoptic way, in particular along densely populated coasts such as the littoral zone of the Mediterranean Sea. Our paper proposes to address this issue by developing a new multi-satellite altimetric-based approach aiming at monitoring the long-term behaviour of the Northern Current, from 2002 to 2012. Our method is assessed by direct comparisons with observations from glider transects of the current, coastal HF radar and a moored current-meter. Despite important limitations due to the current altimetric sampling and a lower accuracy in the 50 km coastal band, we demonstrate the ability of our new method to characterize the variability of the front positioning from intra-seasonal to annual scales. We particularly focus the analysis on the Gulf of Lion, where the distance between the mean geostrophic flow and the coast allows a good detection of high frequency signals associated with slope current intrusions over the continental shelf. We show that such abrupt events generally occur in autumn and are forced by heterogeneous, strong and rapidly evolving south-easterly wind events. This work is based on an original exploitation of the existing along-track altimetry data and paves the way for new applications within the prospect of the next satellite generation whose technology is more suitable for coastal studies.

  9. Methodology for filling gaps and forecast in sea level: Applications to the eastern English Channel and the North Atlantic Sea (western France)

    NASA Astrophysics Data System (ADS)

    Turki, Imen; Laignel, Benoit; Kakeh, Nabil; Chevalier, Laetitia; Costa, Stephane

    2014-05-01

    This research was carried out in the framework of the program Surface Water and Ocean Topography (SWOT) which is a partnership between NASA and CNES. Sea level is a key variable in marine, climate, and coastal process studies. In this research, a new methodology was implemented for filling gaps and forecasting the sea level by combining classical harmonic models to high statistical methods. In agreement with previous studies, this work indicates that sea level heights are correlated to climate conditions of sea level pressures (SLP). After averaging out surface waves from the mean sea level, the deterministic tides and the stochastic processes of residual surges were investigated using classical harmonic analyses and a statistical model of autoregressive moving average (ARMA), respectively. The estimation of the residual surges was also investigated together with the SLP. This new methodology was applied to the Atlantic sea and the eastern English Channel (western France). Results have shown that the developed model reproduces the observations with RMSE of 4.5 cm and 7 cm for 12 days and 30 days of gaps, respectively. For medium scales of 6 months, the RMSE reaches 9,2 cm. Larger scales more than 10 months were also statistically reproduced. Accordingly, the proposed model seems to be more promising for filling gaps and estimating the sea level at short- to large- time scales. This new methodology presents a coherent, simple, and easy tool to estimate the deterministic nature of tidal processes and the stochastic framework of residual surges. Key words: sea level forecast, astronomical tides, residual surges, ARMA, sea level pressure.

  10. A compaction front in North Sea chalk

    NASA Astrophysics Data System (ADS)

    Japsen, P.; Dysthe, D. K.; Hartz, E. H.; Jamtveit, B.

    2012-04-01

    North Sea chalk from 18 wells shows a pronounced porosity drop, from ˜20% to less than 10% over a compaction front of less than 300 m. The position of the compaction frontis independent of stratigraphic position, temperature, and actual depth, but closely tied to an effective stress of ˜17 MPa. These observations require a strongly nonlinear rheology with a marked increase in compaction rate at a specific effective stress. Grain-scale observations demonstrate that the compaction front coincides with marked grain coarsening and recrystallization of fossils and fossil fragments. We propose that this nonlinear rheology is caused by stress-driven failure of the larger pores and the associated generation of reactive surface area by subcritical crack propagation away from these pores. Before the onset of this instability, compaction by pressure solution is slowed down by the inhibitory effect of organic compounds associated with the fossils. Although the compaction mechanism is mainly by pressure solution, the rheological response to burial may still be dominantly plastic and controlled by the (fracturing controlled) rate of exposure of reactive surface area. The nonlinear compaction of chalk has significant implications for the evolution of petroleum systems in the central North Sea, both with respect to sea-floor subsidence above hydrocarbon-producing chalk reservoirs and for the formation of low-porosity pressure seals within the chalk.

  11. A compaction front in North Sea chalk

    NASA Astrophysics Data System (ADS)

    Japsen, P.; Dysthe, D. K.; Hartz, E. H.; Stipp, S. L. S.; Yarushina, V. M.; Jamtveit, B.

    2011-11-01

    North Sea chalk from 18 wells shows a pronounced porosity drop, from ˜20% to less than 10% over a compaction front of less than 300 m. The position of the compaction front is independent of stratigraphic position, temperature, and actual depth, but closely tied to an effective stress (load stress minus fluid pressure) of ˜17 MPa. These observations require a strongly nonlinear rheology with a marked increase in compaction rate at a specific effective stress. Grain-scale observations demonstrate that the compaction front coincides with marked grain coarsening and recrystallization of fossils and fossil fragments. We propose that this nonlinear rheology is caused by stress-driven failure of the larger pores and the associated generation of reactive surface area by subcritical crack propagation away from these pores. Before the onset of this instability, compaction by pressure solution is slowed down by the inhibitory effect of organic compounds associated with the fossils. Although the compaction mechanism is mainly by pressure solution, the rheological response to burial may still be dominantly plastic and controlled by the (fracturing controlled) rate of exposure of reactive surface area. The nonlinear compaction of chalk has significant implications for the evolution of petroleum systems in the central North Sea, both with respect to sea-floor subsidence above hydrocarbon-producing chalk reservoirs and for the formation of low-porosity pressure seals within the chalk.

  12. The North Sea: Satellite colour atlas

    NASA Astrophysics Data System (ADS)

    Holligan, P. M.; Aarup, T.; Groom, S. B.

    Satellite imagery of the North Sea from the Coastal Zone Color Scanner (CZCS) shows complex seasonal changes in the optical and biological properties of surface waters, features which have not been resolved, hitherto, through direct observations from ships. Selected scenes for the period 1979-1986, presented as single band (channel 3), colour composite (channels 1 + 2 + 3) and chlorophyll (channels 1/3 or 2/3) images, are used to demonstrate the relative surface distributions between February and October of suspended sediments, coccolithophores and plant pigments. Comparison are made also with sea surface temperature images from the Advanced Very High Resolution Radiometer (AVHRR). Quantitative evaluation of the CZCS data is restricted by a lack of contemporary in situ optical and biological measurements. However, chlorophyll and Secchi disc distributions, determined by measurements from research ships have been compared qualitatively with images from the Southern Bight (13 May 1986) and for the east central North Sea (24 August 1984 and 24 October 1985). Mini series of CZCS images are presented to show the annual coccolithophore blooms, the development of the spring bloom in the Skagerrak, June 1983 and summer chlorophyl distributions in the German Bight.

  13. Phytoplankton Bloom in North Sea off Scotland

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The northern and western highlands of Scotland were still winter-brown and even dusted with snow in places, but the waters of the North Sea were blooming with phytoplankton on May 8, 2008, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite passed over the region and captured this image. The tiny, plant-like organisms swirled in the waters off the country's east coast, coloring the shallow coastal waters shades of bright blue and green. Phytoplankton are tiny organisms--many are just a single cell--that use chlorophyll and other pigments to capture light for photosynthesis. Because these pigments absorb sunlight, they change the color of the light reflected from the sea surface back to the satellite. Scientists have used observations of 'ocean color' from satellites for more than 20 years to track worldwide patterns in phytoplankton blooms. Phytoplankton are important to the Earth system for a host of reasons, including their status as the base of the ocean food web. In the North Sea, they are the base of the food web that supports Scotland's commercial fisheries, including monkfish and herring. As photosynthesizers, they also play a crucial role in the carbon cycle, removing carbon dioxide from the atmosphere. Some oceanographers are concerned that rising ocean temperatures will slow phytoplankton growth rates, harming marine ecosystems and causing carbon dioxide to accumulate more rapidly in the atmosphere.

  14. A new hybrid model for filling gaps and forecast in sea level: application to the eastern English Channel and the North Atlantic Sea (western France)

    NASA Astrophysics Data System (ADS)

    Turki, Imen; Laignel, Benoit; Kakeh, Nabil; Chevalier, Laetitia; Costa, Stephane

    2015-04-01

    This research is carried out in the framework of the program Surface Water and Ocean Topography (SWOT) which is a partnership between NASA and CNES. Here, a new hybrid model is implemented for filling gaps and forecasting the hourly sea level variability by combining classical harmonic analyses to high statistical methods to reproduce the deterministic and stochastic processes, respectively. After simulating the mean trend sea level and astronomical tides, the nontidal residual surges are investigated using an autoregressive moving average (ARMA) methods by two ways: (1) applying a purely statistical approach and (2) introducing the SLP in ARMA as a main physical process driving the residual sea level. The new hybrid model is applied to the western Atlantic sea and the eastern English Channel. Using ARMA model and considering the SLP, results show that the hourly sea level observations of gauges with are well reproduced with a root mean square error (RMSE) ranging between 4.5 and 7 cm for 1 to 30 days of gaps and an explained variance more than 80 %. For larger gaps of months, the RMSE reaches 9 cm. The negative and the positive extreme values of sea levels are also well reproduced with a mean explained variance between 70 and 85 %. The statistical behavior of 1-year modeled residual components shows good agreements with observations. The frequency analysis using the discrete wavelet transform illustrate strong correlations between observed and modeled energy spectrum and the bands of variability. Accordingly, the proposed model presents a coherent, simple, and easy tool to estimate the total sea level at timescales from days to months. The ARMA model seems to be more promising for filling gaps and estimating the sea level at larger scales of years by introducing more physical processes driving its stochastic variability.

  15. Mesozoic Rifting in the German North Sea

    NASA Astrophysics Data System (ADS)

    Lutz, R.; Jähne, F.; Arfai, J.

    2013-12-01

    The Central Graben is the southernmost expressions of the Mesozoic North Sea rift system that includes the Viking Graben, Moray Firth-Witch Ground grabens and the Horda-Egersund half graben. In the southern North Sea the Central Graben extends across the Dutch and the German exclusive economic zones. The structure of the Central Graben in German territorial waters was mapped in great detail in 2D and 3D seismic data and the stratigraphy has been constraint by borehole data. We provide a detailed review of the rifting activity in the German North Sea sector both in time and space and the link between rifting and salt movement. Major rifting activity started in the Central Graben during the Late Triassic and peaked during the Late Jurassic when extensive rift grabens formed, further influenced by halokinetic movements. First subsidence in the Central Graben area appears in the Early Triassic. This is documented by thickness variations in the sedimentary strata from the Triassic to the Jurassic. Remarkably thick sediments were deposited during the Late Triassic along the eastern border fault of the Central Graben and in the Late Jurassic sediments accumulated along graben-wide extensional faults and in rim-synclines of salt-structures. A basin inversion commenced in the Late Cretaceous resulting in an erosion of wide portions of Lower Cretaceous rocks or even complete removal in some parts. The area to the east of the Central Graben faced a completely different evolution. In this area major rifting activity initiated already in the Early to Middle Triassic. This is evident from huge packages of Middle Buntsandstein to Muschelkalk (Middle Triassic) sediments in the Horn Graben. Jurassic doming, forming the Mid-North Sea High, resulted in almost complete erosion of Lower and Middle Jurassic sediments in the central German North Sea. Sedimentation continued during the Early and Late Cretaceous. The Glückstadt Graben, which is a structure located farther east has a

  16. West Germany's first North Sea production due

    SciTech Connect

    Bleakley, W.B.

    1986-05-01

    Deutsche Texaco A.G. will be the first operator on behalf of itself and Wintershall A.G. to produce oil from the German sector of the North Sea, with its first oil due end of 1986 from the Mittelplate pilot project. Texaco also was the first to produce oil from the Baltic Sea when Schwedeneck-See field, near Kiel Bay, went on production last year. The pilot project at Mittelplate will yield more data on the reservoirs confirmed by four wells drilled in 1980-1981, and will be carried out in spite of adverse operating conditions. Problems facing Texaco engineers in their project design include: A mud-flat location dry at low tide but submerged at high tide. Efforts to convince environmental groups that no permanent harm would result from company activities. Shipment of low-gravity crude containing asphaltenes. Logistics of transporting equipment and supplies on a schedule dictated by tides.

  17. Another look at North Sea pole tide dynamics

    NASA Technical Reports Server (NTRS)

    Dickman, S. R.; Preisig, J. R.

    1986-01-01

    The mechanism proposed by Wunsch (1974) to explain pole tide observations in the North Sea is evaluated. Wunsch's equations governing pole tide in the North Sea are presented, and solutions for correcting the depth, stream function, and deviation of the tidal height from the equilibrium values are described. The similarity between the Stokes paradox and the tidal equations of the North Sea, and the need for inclusion of inertial terms in the tidal equations are discussed.

  18. North Sea HPHT wells require changes in drilling procedures

    SciTech Connect

    Baller, H.

    1991-03-11

    Such equipment as casing, drillstrings, mud, logging, and rigs that were adequate to drill most of the North Sea wells to date will require modifications to drill the high-pressure, high-temperature (HPHT) formations in the Central Graben of the North Sea. HPHT exploration wells are slowly becoming part of the drilling scenario in the North Sea Central Graben. Predominantly drilled in the U.K., an increasing number are now planned for the Norwegian sector during 1991.

  19. Compaction of North-sea chalk

    NASA Astrophysics Data System (ADS)

    Keszthelyi, Dániel; Dysthe, Dag Kristian; Jamtveit, Bjørn

    2014-05-01

    The Ekofisk field is the largest petroleum field in the Norwegian North Sea territory where oil is produced from chalk formations. Early stage of oil production caused considerable changes in pore fluid pressure which led to a reservoir compaction. Pore collapse mechanism caused by the dramatic increase of effective stress, which in turn was caused by the pressure reduction by hydrocarbon depletion, was early identified as a principal reason for the reservoir compaction (Sulak et al. 1991). There have been several attempts to model this compaction. They performed with variable success on predicting the Ekofisk subsidence. However, the most of these models are based on empirical relations and do not investigate in detail the phenomena involved in the compaction. In sake of predicting the Ekofisk subsidence while using only independently measurable variables we used a chalk compaction model valid on geological time-scales (Japsen et al. 2011) assuming plastic pore-collapse mechanism at a threshold effective stress level. We identified the phenomena involved in the pore collapse. By putting them in a sequential order we created a simple statistical analytical model. We also investigated the time-dependence of the phenomena involved and by assuming that one of the phenomena is rate-limiting we could make estimations of the compaction rate at smaller length-scales. By carefully investigating the nature of pressure propagation we could upscale our model to reservoir scale. We found that the predicted compaction rates are close enough to the measured rates. We believe that we could further increase accuracy by refining our model. Sulak, R. M., Thomas, L. K., Boade R. R. (1991) 3D reservoir simulation of Ekofisk compaction drive. Journal of Petroleum Technology, 43(10):1272-1278, 1991. Japsen, P., Dysthe, D. K., Hartz, E. H., Stipp, S. L. S., Yarushina, V. M., Jamtveit. (2011) A compaction front in North Sea chalk. Journal of Geophysical Research: Solid Earth (1978

  20. Black Sea and Mediterranean Sea interaction: influence of the North Aegean dynamics

    NASA Astrophysics Data System (ADS)

    Androulidakis, Yannis; Krestenitis, Yannis; Kourafalou, Vassiliki

    2013-04-01

    The brackish Black Sea Waters outflow to the Aegean Sea, through the Dardanelles Straits, affects and determines significantly the hydrodynamic and physical characteristics of the Aegean Sea. At the same time, it affects several biological parameters, like chl-a concentrations, and, therefore, the general quality of the marine environment. The investigation and mathematical simulation of the North Aegean's physical oceanography contributes to the knowledge and understanding of the buoyant waters' circulation initial conditions in the wider East Mediterranean region. The implementation and adaptation of the 3-d hydrodynamic mathematical model HYCOM (Hybrid Coordinate Ocean Model) in the North Aegean Sea (1/50οx1/50o), significantly contributes to the investigation of the area's hydrodynamic circulation. HYCOM, due to its hybrid coordinate operation, can describe at a satisfactory level, all the different topography and mixing cases of the complicated N. Aegean region. In addition, the high resolution atmospheric forcing and the nesting with a data assimilated broader Mediterranean HYCOM model along the southern open boundary of the North Aegean model, benefit the quality of the results and constitutes an important tool on the description and understanding of the Black Sea influence to the region's dynamics. A fundamental objective is the application and comparison of different Dardanelles outflow parameterizations based a) on the Black Sea water budget, b) on current measurements from a telemetric station in Limnos Island, and c) on historical time series. The Black Sea Waters plume evolution and the circulation patterns are dependant on the outflow rate magnitude, the flow distribution inside the straits and the prevailing winds. The long-term simulation covers the period of the last 20 years (1990-2010), investigating several physical characteristics of the North Aegean Sea, such as the deep water masses evolution, the major Black Sea waters circulation patterns

  1. Projected climate change impacts to the North Sea marine system

    NASA Astrophysics Data System (ADS)

    Schrum, Corinna

    2015-04-01

    Future climate change impacts to the North Sea marine system are driven by a combination of changes induced by the globally forced oceanic boundary conditions and the regional atmospheric and terrestrial changes. We reviewed the recent progress and the projected future change of the North Sea marine system as part of the North Sea Climate Change Assessment (NOSCCA) and focussed on three major aspects, namely the change of (i) sea level, the (ii) hydrographic and circulation changes of the North Sea and the (iii) changes in lower trophic level dynamics, biogeochemistry and ocean acidification. In recent years more and more regional climate change assessments became available for the North Sea and new developments contributed important understanding on regional processes mediating climate change impacts in the North Sea. Important new knowledge on regional future sea level change was gained by improved understanding of processes contributing to global sea level rise during the last decade. Assessment of climate change impacts to hydrography, circulation and biogeochemistry has benefited from new and advanced downscaling methods. The large number of regional studies enables now a critical review of the current knowledge on climate change impacts on the North Sea and allows the identification of challenges, robust changes, uncertainties and specific recommendations for future research. The long term trends in the climate conditions are superposed on the natural modes of variability and separating these to give a clear anthropogenic climate change signal is one of the 'grand challenges' of climate change impact studies in marine regions and of particular relevance for North Sea. The impact of natural variability on future annual average steric sea level, sea surface temperature and ocean acidification is less dominant compared to the climate change signal and their projected changes for the North Sea, namely rising future sea level, increasing surface temperature and

  2. Not normally manned compression platforms for the North Sea

    SciTech Connect

    Kumaran, K.S.

    1994-12-31

    Gas turbine driven gas compressors have been widely used on manned offshore facilities. Similarly unmanned gas turbine driven compressor stations have been in operation onshore with major gas transmission companies in Europe, North America and elsewhere. This paper summarizes a recent joint industry study to investigate the technical and economic feasibility of Not Normally Manned (NNM) Offshore Compression Facilities in terms of reliability, availability and maintainability. Classification of not normally manned (or unmanned) offshore facilities in the UK North Sea is in accordance with HSE Operations Notice 8. ON8 specifies criteria for offshore visits, visit hours and number of personnel on board for the operation of NNM platforms. This paper describes a typical Southern North Sea gas platform being considered for NNM compressor application. The conclusions from the study was that NNM compression is technically feasible with the facilities being able to provide an availability in excess of 98%. Life cycle costs were of the order of 70% of manned facilities thus significantly improving field development economics.

  3. Space Radar Image of North Sea, Germany

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This is an X-band image of an oil slick experiment conducted in the North Sea, Germany. The image is centered at 54.58 degrees north latitude and 7.48 degrees east longitude. This image was acquired by the Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the space shuttle Endeavour on October 6, 1994, during the second flight of the spaceborne radar. The experiment was designed to differentiate between petroleum oil spills and natural slicks floating on the sea surface. Two types of petroleum oil and six types of oils resembling natural sea surface slicks were poured on the sea surface from ships and a helicopter just before the space shuttle flew over the region. At the bottom of the image is the Sylt peninsula, a famous holiday resort. Twenty-six gallons (100 liters) of diesel oil was dissipated due to wave action before the shuttle reached the site. The oil spill seen at the uppermost part of the image is about 105 gallons (400 liters) of heavy heating oil and the largest spill is about 58 gallons (220 liters) of oleyl alcohol, resembling a 'natural oil' like the remaining five spills used to imitate natural slicks that have occurred offshore from various states. The volume of these other oils spilled on the ocean surface during the five experimental spills varied from 16 gallons to 21 gallons (60 liters to 80 liters). The distance between neighboring spills was about half a mile (800 meters) at the most. The largest slick later thinned out to monomolecular sheets of about 10 microns, which is the dimension of a molecule. Oceanographers found that SIR-C/X-SAR was able to clearly distinguish the oil slicks from algae products dumped nearby. Preliminary indications are that various types of slicks may be distinguished, especially when other radar wavelengths are included in the analysis. Radar imaging of the world's oceans on a continuing basis may allow oceanographers in the future to detect and clean up oil spills much more

  4. The zooplankton of the north sea

    NASA Astrophysics Data System (ADS)

    Fransz, H. G.; Colebrook, J. M.; Gamble, J. C.; Krause, M.

    This review summarizes available knowledge on herbivorous and omnivorous zooplankton of the North Sea. After an introductory chapter on history and general approach of zooplankton studies, the four main contributions review distribution patterns, cycles and trends in temporal variation, trophic interactions and population dyamics and production. The distribution of zooplankton species in relation to hydrography and origin of watermasses is described for copepods. It highlights the influence of Atlantic Ocean influx from the northwest, which to a large extent dominates the species composition and its seasonal variation in the summer-stratified waters. In contrast, the more neritic communities in the southeast region mainly depend on the local populations of the species abundant in coastal mixed waters. The chapter on cycles and trends in temporal variation discusses the differences in seasonal variation with respect to species, area, and community structure in terms of herbivores, omnivores and carnivores. The year-to-year changes are considered as dependent on the overwintering stocks and strategies. Patterns in long-term variation appearing from long-term data series are related to climatic changes, leading to two hypotheses with respect to the effects of changes in wind regime. The chapter on trophic interactions deals with the utilization of primary particulate production by planktonic herbivores and its variation in time and space. Emphasis is put on differences between north and south, which are partly due to differences in species composition, community structure and seasonal variation already discussed in foregoing chapters. The various aspects of copepod grazing are reviewed, but also the role of microzooplankton as both grazers and food organisms is brought to attention. The last chapter deals with population dynamics and production of key species. Seasonal fluctuations in abundance and biomass are discussed and related to underlying population processes

  5. Fishing effects on energy use by North Sea fishes

    NASA Astrophysics Data System (ADS)

    Jennings, Simon; van Hal, Ralf; Hiddink, Jan G.; Maxwell, Tracy A. D.

    Fishing affects patterns of energy use in fish populations, as demonstrated by changes in population energy consumption and the size and age when energy demands are greatest. We compare theoretical predictions and observed patterns of energy use (expressed as the primary production required to support fish production) by North Sea fish, based on simple and widely applicable theory that links life history parameters, fishing mortality ( F), trophic transfer efficiency and relationships between size and trophic level (as determined using nitrogen stable isotope analysis). For the demersal species that dominate total biomass, relationships between size and trophic level were quite consistent among years. There were large decreases in relative energy requirements of all exploited demersal populations except plaice Pleuronectes platessa during the last 3 to 4 decades. Relative energy requirements of plaice were more stable because smaller plaice, which now dominate the exploited population, feed at higher trophic levels than larger plaice. The sizes and ages when population energy demands were greatest fell with increasing fishing mortality and differences between the predicted ( F = 0) and observed ages at maximum energy demand were greater in larger species. Currently, the energy demands of most species peak early in life (1-3 years) and largely reflect patterns of recruitment, leading to a homogenisation of the trophodynamics of the fish community. The fate of energy that is no longer used by commercially exploited species is not clear, partly because of the infrequent and untargeted monitoring of species that are more resilient to fishing. However, we conducted a preliminary assessment of the energy demands of solenette Buglossidium luteum, a very abundant small flatfish in the central North Sea that has increased in abundance in recent years. The solenette's high abundance and resilience to fishing, suggests that it now requires 35% of primary production in part of

  6. May organic pollutants affect fish populations in the North Sea?

    PubMed

    Hylland, Ketil; Beyer, Jonny; Berntssen, Marc; Klungsøyr, Jarle; Lang, Thomas; Balk, Lennart

    2006-01-01

    The North Sea is a highly productive area with large fish populations that have been extensively harvested over the past century. North Sea fisheries remain important to the surrounding countries despite declining fish stocks over the past decades. The main reason for declining fish stocks is nearly certainly overfishing, but other environmental pressures also affect fish populations, such as eutrophication, climate change, and exposure to metals and organic pollutants, including polyaromatic hydrocarbons (PAHs), alkylphenols, and organochlorine compounds. There are three main sources of organic pollutants in the North Sea: atmospheric, land-based sources, and inputs from offshore gas and oil installations. All three sources contribute to elevated concentrations of organic pollutants in the North Sea compared to the Norwegian Sea. There is evidence that chlorinated organic contaminants were present in sufficiently high concentrations in the southern North Sea two decades ago, to alter embryonal development in fish. The results from extensive, long-term monitoring programs show that some diseases decreased whereas other increased in the southern North Sea and that, among other factors, contaminants may play a role in the temporal changes recorded in disease prevalence. Recent studies demonstrated that components in offshore effluents may affect fish reproduction and that tissues of fish near oil rigs are structurally different to tissues of fish from reference areas. Data on effluents from offshore activities have recently become available through an international workshop (BECPELAG) and follow-up studies.

  7. The microbiome of North Sea copepods

    NASA Astrophysics Data System (ADS)

    Gerdts, G.; Brandt, P.; Kreisel, K.; Boersma, M.; Schoo, K. L.; Wichels, A.

    2013-12-01

    Copepods can be associated with different kinds and different numbers of bacteria. This was already shown in the past with culture-dependent microbial methods or microscopy and more recently by using molecular tools. In our present study, we investigated the bacterial community of four frequently occurring copepod species, Acartia sp., Temora longicornis, Centropages sp. and Calanus helgolandicus from Helgoland Roads (North Sea) over a period of 2 years using DGGE (denaturing gradient gel electrophoresis) and subsequent sequencing of 16S-rDNA fragments. To complement the PCR-DGGE analyses, clone libraries of copepod samples from June 2007 to 208 were generated. Based on the DGGE banding patterns of the two years survey, we found no significant differences between the communities of distinct copepod species, nor did we find any seasonality. Overall, we identified 67 phylotypes (>97 % similarity) falling into the bacterial phyla of Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria. The most abundant phylotypes were affiliated to the Alphaproteobacteria. In comparison with PCR-DGGE and clone libraries, phylotypes of the Gammaproteobacteria dominated the clone libraries, whereas Alphaproteobacteria were most abundant in the PCR-DGGE analyses.

  8. The internal consistency of the North Sea carbonate system

    NASA Astrophysics Data System (ADS)

    Salt, Lesley A.; Thomas, Helmuth; Bozec, Yann; Borges, Alberto V.; de Baar, Hein J. W.

    2016-05-01

    In 2002 (February) and 2005 (August), the full suite of carbonate system parameters (total alkalinity (AT), dissolved inorganic carbon (DIC), pH, and partial pressure of CO2 (pCO2) were measured on two re-occupations of the entire North Sea basin, with three parameters (AT, DIC, pCO2) measured on four additional re-occupations, covering all four seasons, allowing an assessment of the internal consistency of the carbonate system. For most of the year, there is a similar level of internal consistency, with AT being calculated to within ± 6 μmol kg- 1 using DIC and pH, DIC to ± 6 μmol kg- 1 using AT and pH, pH to ± 0.008 using AT and pCO2, and pCO2 to ± 8 μatm using DIC and pH, with the dissociation constants of Millero et al. (2006). In spring, however, we observe a significant decline in the ability to accurately calculate the carbonate system. Lower consistency is observed with an increasing fraction of Baltic Sea water, caused by the high contribution of organic alkalinity in this water mass, not accounted for in the carbonate system calculations. Attempts to improve the internal consistency by accounting for the unconventional salinity-borate relationships in freshwater and the Baltic Sea, and through application of the new North Atlantic salinity-boron relationship (Lee et al., 2010), resulted in no significant difference in the internal consistency.

  9. First oilfields of the Central and Northern North Sea

    SciTech Connect

    Swarbrick, R.E. ); Martin, J.A. )

    1991-03-01

    Only 25 years ago the areas now termed the Central and Northern North Sea were the true frontier exploration basins. Stratigraphy and structure were essentially unknown, except inferences drawn from the Mesozoic outcrops of Britain and Denmark. At that time the majority of small British onshore oil fields were reservoired in Paleozoic strata. In the Central North Sea, oil was first discovered in Paleocene deep-water sandstone and Upper Cretaceous chalk reservoirs. The first commercial reserves were proven with the discovery of the Ekofisk field (Upper Cretaceous) in 1969 and Forties field (Paleocene) in 1970, both now classed as giants. Subsequently stratigraphically deeper reservoirs were established, including Jurassic sandstones (Piper field) and Permian carbonates and sandstones (Auk and Argyll fields). Diversity of trap type and reservoir age is now a hallmark of the Central North Sea basin. In the Northern North Sea, the first exploration well in 1971 on the Brent field structure, a true wildcat whose nearest UK well control was 320 mi to the south, found oil in Middle Jurassic deltaic sandstones. A spate of discoveries on similar tilted fault blocks with Middle Jurassic and underlying Triassic alluvial-fluvial sandstone targets followed. Later, Upper Jurassic deep-water sandstones became established as a further significant reservoir with the Brae field and Magnus field discoveries. Original seismic data, well prognoses, and structure maps tell the story of these early discoveries. Public response in Norway and the UK to the emergence of the North Sea oil province on their doorstep will be reviewed.

  10. North-Australian tropical seas circulation study

    NASA Technical Reports Server (NTRS)

    Burrage, Derek; Coleman, R.; Bode, L.; Inoue, M.

    1991-01-01

    This investigation is intended to fully address the stated objective of the TOPEX/POSEIDON mission (National Aeronautics and Space Administration, 1986). Hence, we intend to use TOPEX/POSEIDON altimetry data to study the large-scale circulation of the Coral Sea Basin and the Arafura Sea and the mass exchange between these and adjoining basins. We will obtain data from two such cruises in 1993 and 1994 and combine them with TOPEX/POSEIDON radar altimetry data to identify interannual and seasonal changes in: (1) the location of the major ocean currents and the South Equatorial Current bifurcation in the Coral Sea; (2) the source region of the South Tropical Counter Current (STCC); and (3) the water exchange between the Coral Sea and the adjoining seas. We will also estimate seasonal and interannual variations in the horizontal transport of mass and heat associated with near-surface geostrophic and wind-driven currents. In addition, the tidal components of the Coral Sea will be studied to provide a correction for altimetry subtidal sea level changes and to develop a regional numerical model for tidal forcing in the Great Barrier Reef (GBR) and Papua New Guinea Reef regions.

  11. Floating production systems hit stride in North Sea fields

    SciTech Connect

    Knott, D.

    1994-05-23

    Floating production system (FPS) technology has come of age in the North Sea. That's apparent in plans to use FPSs to tap two of Northwest Europe's largest offshore oil discoveries in the last 10 years. First North Sea oil production with a floater involved a converted semisubmersible drilling rig. Floaters have been in use for small field development projects ever since. Now, industry's rising interest in FPSs reflects two trends: As the North Sea matures, discoveries are likely to be in deeper, more remote locations; and Operators increasingly are under pressure to slash costs. The paper discusses UK trends, Norway's needs, the Norne field, Norne contract, discovery of oil west of the Shetland Islands, Shell-Esso plans, the UK Machar field test, the UK Fife field, and prospects for other potential floater developments.

  12. Ecology and conservation of North American sea ducks

    USGS Publications Warehouse

    Savard, Jean-Pierre L.; Derksen, Dirk V.; Esler, Daniel N.; Eadie, John M.

    2015-01-01

    Harvest history The book presents a comprehensive synthesis of sea duck ecology, documents factors that have caused population declines of some species, and provides managers with measures to enhance recovery of depressed populations of sea ducks in North America. Capturing the current state of knowledge of this unique tribe, it provides a benchmark for where we are in conservation efforts and suggests future directions for researchers, managers, students, conservationists, and avian enthusiasts.

  13. Wind stress forcing of the North Sea `pole tide'

    NASA Astrophysics Data System (ADS)

    O'Connor, William P.; Chao, Benjamin Fong; Zheng, Dawei; Au, Andrew Y.

    2000-08-01

    We conduct numerical simulations of the wind forcing of sea level variations in the North Sea using a barotropic ocean model with realistic geography and bathymetry to examine the forcing of the 14 month `pole tide', which is known to be anomalously large along the Denmark-Netherlands coast. The simulation input is the monthly mean surface wind stress field from the National Centers for Environmental Prediction (NCEP) reanalysis for the 40 year period 1958-1997. The ocean model output sea level response is then compared with 10 coastal tide gauge records from the Permanent Service for Mean Sea Level (PSMSL) over the same period of time. Besides the strong seasonal variations, several prominent quasi-periodicities exist near 7 years, 3 years, 14 months, 9 months and 6.5 months. Correlations and spectral analyses show remarkable agreement between the model output and the observations, particularly in the 14 month, or Chandler, period band. The latter indicates that the enhanced pole tide found in the North Sea along the Denmark-Netherlands coast is actually the coastal set-up response to wind stress forcing with a periodicity of around 14 months. We find no need to invoke a geophysical explanation involving resonance enhancement of the pole tide in the North Sea to explain the observations.

  14. Wind Stress Forcing of the North Sea "Pole Tide"

    NASA Technical Reports Server (NTRS)

    OConnor, William P.; Chao, Benjamin Fong; Zheng, Dawei; Au, Andrew Y.

    1998-01-01

    We conducted numerical simulations of the wind-forcing of the sea level variations in the North Sea using a barotropic ocean model with realistic geography, bathymetry, and boundary conditions, to examine the forcing of the 14-month "pole tide" which is known to be strong along the Denmark- Netherlands coast. The simulation input is the monthly-mean surface wind stress field from the National Centers for Environmental Prediction (NCEP) reanalysis for the 40-year period 1958-1997. The output sea level response was then compared with 10 coastal tide gauge records from the Permanent Service for Mean Sea Level (PSMSL). Besides the strong seasonal variations, several prominent quasi-periodicities exist at around 7 years, 3 years, 14 months, 9 months, and 6.5 months. Correlation and spectral analyses show remarkable agreement between the model output and the observations, particularly in the 14-month, or Chandler period band. The latter indicates that the enhanced pole tide found in the North Sea along the Denmark-Netherlands coast is actually the coastal setup response to wind stress forcing with a periodicity of 14 months. We find no need to invoke a geophysical explanation involving resonance-enhancement of pole tide in the North Sea to explain the observations.

  15. Unstructured-grid model for the North Sea and Baltic Sea: Validation against observations

    NASA Astrophysics Data System (ADS)

    Zhang, Yinglong J.; Stanev, E. V.; Grashorn, S.

    2016-01-01

    A new unstructured-grid model and its application to the North Sea and Baltic Sea are described. The research focus is on the dynamics in the two basins and in the multiple straits connecting them and more specifically on how the model replicates the temporal and spatial variability of physical processes. The comparison against observed data indicates the realism in the simulations of the exchange flows. The simulations demonstrated that in contrast to the tidal variability which decreases in the strait, the role of the barotropic forcing due to weather systems increases. In this zone reversal of transport is well manifested by the increased difference between the surface and bottom salinity values. Small sub-basins like Arkona and Bornholm play the role of reservoirs for denser water which under specific conditions cascades on its way to the Gotland Deep. Unlike the intermediate and deep water salinity in the Baltic Sea, which is strongly affected by fluxes in the straits, the simulated winter-refill and evolution of cold intermediate water are rather driven by surface cooling and processes in the upper mixed layer.

  16. Phylogenetics, phylogeography and population genetics of North American sea ducks (tribe: Mergini)

    USGS Publications Warehouse

    Talbot, Sandra; Sonsthagen, Sarah A.; Pearce, John M.; Scribner, Kim T.

    2015-01-01

    Many environments occupied by North American sea ducks are remote and difficult to access, and as a result, detailed information about life history characteristics that drive population dynamics within and across species is limited. Nevertheless, progress on this front during the past several decades has benefited by the application of genetic technologies, and for several species, these technologies have allowed for concomitant tracking of population trends and genetic diversity, delineation of populations, assessment of gene flow among metapopulations, and understanding of migratory connectivity between breeding and wintering grounds. This chapter provides an overview of phylogenetic, phylogeographic, and population genetics studies of North American sea duck species, many of which have sought to understand the major and minor genetic divisions within and among sea duck species, and most of which have been conducted with the understanding that the maintenance of genetic variation in wild sea duck populations is fundamental to the group’s long-term persistence.

  17. Estimation of successive coseismic vertical offsets using coeval sedimentary events - application to the southwestern limit of the Sea of Marmara's Central Basin (North Anatolian Fault)

    NASA Astrophysics Data System (ADS)

    Beck, C.; Campos, C.; Eriş, K. K.; Çağatay, N.; Mercier de Lepinay, B.; Jouanne, F.

    2015-02-01

    In the deep part of the Sea of Marmara (Turkey), the sedimentation developing upon the North Anatolian Fault is strongly influenced by the associated seismic activity, through gravity reworking (fluidized landslides) and tsunamis. Specific layers (homogenites + turbidites, HmTu), representing individual sedimentary events, have been characterized along three giant piston cores retrieved from the Çinarcik and Central (or Orta) basins. Pre-Holocene, nonmarine sediments, were analyzed, representing the last 12-17 kyr BP (before present). For a 2 kyr long interval, 11 events could be precisely correlated on both sides of the Central Basin's southwestern scarp. For each of them, based on the specific depositional process, the thickness difference between the two sites was considered as a direct estimation of the vertical component of a coeval coseismic offset. The homogenite (upper) component accounts for the major part of the thickness difference (ranging from 36 to 144 cm). These offsets were considered as likely representing dominantly vertical throws, along the transtensional southwestern boundary of the inner, pull-apart Central Basin. In terms of natural hazards, further investigations on this local behavior should rather be directed to tsunami genesis.

  18. Estimation of successive co-seismic vertical offsets using coeval sedimentary events - application to the Sea of Marmara's Central Basin (North Anatolian Fault)

    NASA Astrophysics Data System (ADS)

    Beck, C.; Campos, C.; Eriş, K.; Çağatay, N.; Mercier de Lepinay, B.; Jouanne, F.

    2014-06-01

    In the deep part of the Sea of Marmara (Turkey), the sedimentation developing upon the North Anatolian Fault is strongly influenced by the associated seismic activity. Specific layers (homogenites-turbidites), representing individual sedimentary events, have been characterized along three giant piston cores retrieved from Çinarcik and Central (or Orta) basins. Analyzed sediments represent the last 12 to 17 kyr BP. For a 2 kyr-lasting interval, 11 events could be precisely correlated on both sides of the Central Basin's southern scarp. For each of them, based on the specific depositional process, the thickness difference between the two sites was considered as a direct estimation of the vertical component of a coeval co-seismic offset. The homogenite (upper) term accounts for the major part of the thickness difference. The 6 most significant values range from 36 cm to 144 cm and are likely representing dominantly normal throws, with estimated paleomagnitudes (Mw) ranging from 5.9 to 6.6.

  19. A novel adaptive biogeochemical model, and its 3-D application for a decadal hindcast simulation of the biogeochemistry of the southern North Sea

    NASA Astrophysics Data System (ADS)

    Kerimoglu, Onur; Hofmeister, Richard; Wirtz, Kai

    2016-04-01

    Adaptation and acclimation processes are often ignored in ecosystem-scale model implementations, despite the long-standing recognition of their importance. Here we present a novel adaptive phytoplankton growth model where acclimation of the community to the changes in external resource ratios is accounted for, using optimality principles and dynamic physiological traits. We show that the model can reproduce the internal stoichiometries obtained at marginal supply ratios in chemostat experiments. The model is applied in a decadal hindcast simulation of the southern North Sea, where it is coupled to a 2-D benthic model and a 3-D hydrodynamic model in an approximately 1.5km horizontal resolution at the German Bight coast. The model is shown to have good skill in capturing the steep, coastal gradients in the German Bight, suggested by the match between the estimated and observed dissolved nutrient and chlorophyll concentrations. We then analyze the differential sensitivity of the coastal and off-shore zones to major drivers of the system, such as riverine nutrient loads. We demonstrate that the relevance of phytoplankton acclimation varies across coastal gradients and can become particularly significant in terms of summer nutrient depletion.

  20. Introduced marine species of the North Sea coasts

    NASA Astrophysics Data System (ADS)

    Reise, K.; Gollasch, S.; Wolff, W. J.

    1998-09-01

    About 80 non-indigenous species are assumed to have been introduced into the North Sea by transoceanic shipping and aquaculture. The number is certainly underestimated as most small organisms received insufficient attention at the species level. Also, the seafaring tradition of the North Sea countries is much longer than our biological surveys are. Most exotic invertebrates originate from the western Atlantic and were introduced by shipping, while most algae stem from the Pacific and came with the introduced oysters. A peak of newcomers was observed in the 1970s. Most of the arrivals became established in brackish environments, at harbor sites and in the vicinity of oyster farms, fouling on hard substrates or living as epibionts. A few live in sediments, are holoplanktonic or are parasites. At the open coast, approximately 6% of the macrobenthic species are exotics, while in estuaries their share is up to 20%. Most exotics have been encountered in the southern North Sea first, and many did not spread further north. About 25% of the established non-natives are widespread and attain locally high abundances. As a consequence, some inshore habitats are entirely dominated by exotics. The overall effect on the ecosystem seems to be more additive than one of displacement. This suggests that the coastal biota of the North Sea are quite capable of accommodating newcomers. However, this is no guarantee that the next introduced species may not cause severe ecological change or economic harm. There is a need to minimize the risk of unintentional introductions by ballast water treatment and by adhering to quarantine procedures in aquaculture. Current research on exotics in the North Sea is regarded as inadequate for proper evaluation and management requirements.

  1. Regulation of CO2 Air Sea Fluxes by Sediments in the North Sea

    NASA Astrophysics Data System (ADS)

    Burt, William; Thomas, Helmuth; Hagens, Mathilde; Brenner, Heiko; Pätsch, Johannes; Clargo, Nicola; Salt, Lesley

    2016-04-01

    A multi-tracer approach is applied to assess the impact of boundary fluxes (e.g. benthic input from sediments or lateral inputs from the coastline) on the acid-base buffering capacity, and overall biogeochemistry, of the North Sea. Analyses of both basin-wide observations in the North Sea and transects through tidal basins at the North-Frisian coastline, reveal that surface distributions of the δ13C signature of dissolved inorganic carbon (DIC) are predominantly controlled by a balance between biological production and respiration. In particular, variability in metabolic DIC throughout stations in the well-mixed southern North Sea indicates the presence of an external carbon source, which is traced to the European continental coastline using naturally-occurring radium isotopes (224Ra and 228Ra). 228Ra is also shown to be a highly effective tracer of North Sea total alkalinity (AT) compared to the more conventional use of salinity. Coastal inputs of metabolic DIC and AT are calculated on a basin-wide scale, and ratios of these inputs suggest denitrification as a primary metabolic pathway for their formation. The AT input paralleling the metabolic DIC release prevents a significant decline in pH as compared to aerobic (i.e. unbuffered) release of metabolic DIC. Finally, long-term pH trends mimic those of riverine nitrate loading, highlighting the importance of coastal AT production via denitrification in regulating pH in the southern North Sea.

  2. Pipeline incidents and emergency repair in the North Sea

    SciTech Connect

    Wood, G.D.

    1988-12-01

    The failures of submarine pipelines in the North Sea, and the response of pipeline operators are first discussed. Against this background, the methods currently available for submarine pipeline repairs are reviewed. The Emergency Pipeline Repair Services available are described, and some future developments in the field of submarine pipeline repair are briefly outlined.

  3. Another platform for the North Sea grows in Norway

    SciTech Connect

    Not Available

    1983-09-01

    The Stratfjord D, a combined drilling, production, and living quarters platfrom has been under construction since 1981 in the North Sea. It remains ahead of schedule, with the engineering nearing completion. When completed, the C will look like the twin of the Stratfjord B; the principal difference will be its increased production capacity.

  4. Regional patterns of sea level change in the German North Sea in a worldwide context

    NASA Astrophysics Data System (ADS)

    Wahl, Thomas; Frank, Torsten; Jensen, Jürgen

    2010-05-01

    Sea Level Rise (SLR) is one of the major consequences we are facing in times of a warming climate and it is obvious that a higher sea level influences the heights of occurring storm surges and thus results in a higher risk of inundation for the affected coastal areas. Therefore, regional and global sea level rise are subjects to many recent scientific publications. In contrast, the mean sea level (MSL) and its variability over the last centuries in the German North Sea area have not been analysed in detail up to now. A methodology to analyse observed sea level rise (SLR) in the German Bight, the shallow south-eastern part of the North Sea, is presented. The contribution focuses on the description of the methods used to generate and analyse high quality mean sea level (MSL) time series. Parametric fitting approaches as well as non-parametric data adaptive filters, such as Singular System Analysis (SSA) are applied. For padding non-stationary sea level time series, an advanced approach named Monte-Carlo autoregressive padding (MCAP) is introduced. This approach allows the specification of uncertainties of the behaviour of smoothed time series near the boundaries. The results for the North Sea point to a weak negative acceleration of SLR since 1844 with a strong positive acceleration at the end of the 19th century, to a period of almost no SLR around the 1970s with subsequent positive acceleration and to high recent rates. The comparison between the German North Sea and a global sea level reconstruction clearly reveals the existence of different patterns of SLR. A stronger SLR in the German North Sea area is detected for a period covering some decades starting at the end of the 19th century and for another period covering the last ten to fifteen years. These findings and the indications for the natural variability of this complex system and further research topics will be discussed. This is a German Coastal Engineering Research Council (KFKI) project, funded by the

  5. Review of the physical oceanography of the North Sea

    NASA Astrophysics Data System (ADS)

    Otto, L.; Zimmerman, J. T. F.; Furnes, G. K.; Mork, M.; Saetre, R.; Becker, G.

    After a general consideration of the physical factors that are of special interest to ecology, the typical character of the North Sea is discussed. The emphasis is on the processes that are responsible for the physical environment. The dominant feature is the tidal motion. This is not only a mechanism for vertical and horizontal mixing. The tidal residuals also contribute to a basic circulation pattern that together with the long-term net effects of the wind-driven circulation and the baroclinic effects results in an overall transport that determines the major features of the distribution of the water properties. Superimposed on this there are variations (mainly wind-induced) and regional differences in a wide range of time- and length-scales. Some typical features of both the southern and northern part of the North Sea are discussed. The review is concluded with a discussion on the long-term variations in the physical conditions of the North Sea. These are mainly to changes in temperature, salinity and sea-level.

  6. Revisiting sea level changes in the North Sea during the Anthropocene

    NASA Astrophysics Data System (ADS)

    Jensen, Jürgen; Dangendorf, Sönke; Wahl, Thomas; Niehüser, Sebastian

    2016-04-01

    The North Sea is one of the best instrumented ocean basins in the world. Here we revisit sea level changes in the North Sea region from tide gauges, satellite altimetry, hydrographic profiles and ocean reanalysis data from the beginning of the 19th century to present. This includes an overview of the sea level chapter of the North Sea Climate Change Assessment (NOSCCA) complemented by results from more recent investigations. The estimates of long-term changes from tide gauge records are significantly affected by vertical land motion (VLM), which is related to both the large-scale viscoelastic response of the solid earth to ice melting since the last deglaciation and local effects. Removing VLM (estimated from various data sources such as GPS, tide gauge minus altimetry and GIA) significantly reduces the spatial variability of long-term trends in the basin. VLM corrected tide gauge records suggest a transition from relatively moderate changes in the 19th century towards modern trends of roughly 1.5 mm/yr during the 20th century. Superimposed on the long-term changes there is a considerable inter-annual to multi-decadal variability. On inter-annual timescales this variability mainly reflects the barotropic response of the ocean to atmospheric forcing with the inverted barometer effect dominating along the UK and Norwegian coastlines and wind forcing controlling the southeastern part of the basin. The decadal variability is mostly remotely forced and dynamically linked to the North Atlantic via boundary waves in response to long-shore winds along the continental slope. These findings give valuable information about the required horizontal resolution of ocean models and the necessary boundary conditions and are therefore important for the dynamical downscaling of sea level projections for the North Sea coastlines.

  7. North Sea wind climate in changing weather regimes

    NASA Astrophysics Data System (ADS)

    Anders, Ivonne; Rockel, Burkhardt

    2015-04-01

    Results from regional climate models (RCMs) are getting more and more important in future wind climate assessment. From RCMs often only the daily wind speed is available, but no information on prevailing wind direction of each day. Weather regime classification can close this gap and models ability of simulating surface wind speed can be analysed in detail. Several objective regime classifications have been investigated to be a sufficient diagnostic tool to evaluate the present wind climate at the German and Dutch coastal area of the North Sea. The classification by Jenkinson and Collison (1977) uses values for mean sea level pressure at 16 locations centered over the North Sea. Beside the predefined 8 prevailed wind directions and the two possibilities on cyclonic or anticyclonic turbulence, 2x8 hybrid weather types can be defined. In this way 27 different regimes can be distinguished including a class of non-classifiable cases. The 27 regimes could be reduced to a number of 11 by allotting the hybrid types to the directional or the centered types. As the classification is carried out for the North Sea based on ERA40 mean sea level pressure the different regimes clearly reflect the mean wind characteristics at the stations. Comparing the wind roses for the individual observations leads to the assumption that the regime classification described before fits the requirements to carry out the regime dependent evaluation of the RCMs with a focus on the German and Dutch coast. Trends in the occurrence of the regimes in the winter period of 1961 to 2000 show an increase of the regimes with Western and Southwestern wind directions and a decrease of wind events from Eastern directions in the North Sea. The trend is dominated by the strong positive phase of the NAO especially in the months January to March starting in the beginning of the 1980s. Due to the applied method ERA40 and the RCMs do not necessarily show the same regime at each day. The agreement among the RCM

  8. The Netherlands' environmental policy for the North Sea and Wadden Sea.

    PubMed

    Beukema, A A; Hekstra, G P; Venema, C

    1986-09-01

    The water quality management of The Netherlands' part of the North Sea (57 000 km(2) continental shelf of which 7600 km(2) is territorial sea to 12 miles) and the Wadden Sea (a wetland area behind the northern coastal islands), is described on the basis of recent scientific studies and governmental policy documents. The links with international conventions and treaties are mentioned. The overall water quality in these areas has significantly deteriorated over the last century, notably since the post-war industrial revival, due to a great number of emissions of heavy metals and organochlorine substances. A dramatic decline of seals and porpoises has occurred. However, over the last few years some emissions have been reduced. A national ecological research programme for the North Sea is developing. Monitoring is concentrated on levels of pollutants as well as on effects upon biota. Baseline standards are now being developed as references for further action against pollution. If the recent trend towards improvement is to continue, it requires that the increased economic activities (notably the mining of oil and gas, petrochemical production, and incineration and dumping of chemical wastes) be kept sufficiently under control. A need is felt for a continued rational harmonization and planning of all activities on the North Sea. An even more stringent planning is required for the Wadden Sea which is now an international nature reserve under the Wetland Convention and is eligible for designation as a Biosphere Reserve under the UNESCO-MAB-programme. The river Rhine as greatest polluter of the North Sea and Wadden Sea urgently needs a clean-up.

  9. Phytoplankton of the North Sea and its dynamics: A review

    NASA Astrophysics Data System (ADS)

    Reid, P. C.; Lancelot, C.; Gieskes, W. W. C.; Hagmeier, E.; Weichart, G.

    Phytoplankton is the major contributor to algal biomass and primary production of the North Sea, although crops of macroalgae can locally be up to 2000 g C.m -2 along the coast of the U.K. and Norway, and microphytobenthos dominates production in the shallow tidal flat areas bordering the coasts of England, the Netherlands, Germany and Denmark. Data collected since 1932 during the Continuous Plankton Recorder Survey show consistent patterns of geographical, seasonal and annual variation in the distribution of phytoplankton and its major taxonomic components. There is a trend of increased colouration in Recorder silks in the southern North Sea until approximately 1975 since when Colour levels (assumed to be indicative of algal biomass) have declined. In the eutrophic Dutch Wadden Sea the algal crop continued to increase; in Dutch coastal North Sea waters a trend of biomass increase reversed since 1984, apparently due to a reduction in Rhine river outflow. Long-term observations made at Helgoland since the 60's also show trends of increasing nutrients and phytoplankton biomass only to 1984. Adverse effects such as deoxygenation, foam formation and toxin production have been linked to mass concentrations of algae known as blooms. There is no evidence from existing reports for an increase in their frequency, although some years stand out with larger numbers. Occurrence of blooms can partly be explained by hydrographic conditions. More than 30 taxa are recognised as occurring in bloom proportions in the North Sea, approximately one third of which can be toxic. The crop of Bacillariophyceae (diatoms) is not likely to increase with eutrophication due to silicate limitation. An extensive subsurface maximum of armoured dinoflagellates, its abundance gouverned by hydrographic conditions, is the most characteristic feature of the central and northern North Sea in the summer months. Abundance, sometimes dominance, of picoplankton and of species that are not readily detected by

  10. Wind Forcing of the North Sea Pole Tide

    NASA Technical Reports Server (NTRS)

    OConnor, W.; Chao, B. F.; Zheng, D. W.; Au, Z. Y.

    1998-01-01

    The Chandler wobble of the earth's rotation has a period near 14 months and sets up the 0.5 cm amplitude pole tide in the deep oceans, However, the pole tide is anomalously large in the North Sea, where the amplitude increases sharply up to 3 cm along the continental coast. It is shown here that the sea levels are well correlated with winds at the pole tide frequency. The Princeton Ocean Model is used to investigate the response of the North Sea to wind forcing. The barotropic numerical ocean model depicts realistic coastlines and bathymetry at 5 ft x 5 ft resolution, with 97 x 73 grid points. The monthly mean wind fields for the 40-year period (1958-1997) from the National Centers for Atmospheric Prediction (NCEP) reanalysis were used to force the model. The winds were converted to stress with a neutral drag coefficient that varied linearly with windspeed (instead of using the NCEP windstress). A 5-day simulation was made for each month until the resulting flow regime came into equilibrium, and model water levels at various station locations were saved for comparison with tidal-gauge observed sea levels from the Permanent Service for Mean Sea Level (PSMSL). The comparison is made for 10 North Sea stations with high quality tide gauge data. We find: (1) good agreement in annual and semi-annual phases and in the trend of amplitude w.r.t. latitude; (2) more importantly for this study, the model-predicted and observed non-seasonal sea level variations show a very significant temporal correlation as well as spectral coherence. However, a large amplitude difference exists between the two sets -- the overall amplitude variability of the observed is generally a factor of 2-3 larger than the model prediction (this same phenomenon has been reported in ocean circulation studies, although the cause is not yet clear.) Our results indicate that the wind forcing is the main cause of the observed large pole tide in the North Sea.

  11. Spatial sensitivity of inorganic carbon to model setup: North Sea and Baltic Sea with ECOSMO

    NASA Astrophysics Data System (ADS)

    Castano Primo, Rocio; Schrum, Corinna; Daewel, Ute

    2015-04-01

    In ocean biogeochemical models it is critical to capture the key processes adequately so they do not only reproduce the observations but that those processes are reproduced correctly. One key issue is the choice of parameters, which in most cases are estimates with large uncertainties. This can be the product of actual lack of detailed knowledge of the process, or the manner the processes are implemented, more or less complex. In addition, the model sensitivity is not necessarily homogenous across the spatial domain modelled, which adds another layer of complexity to biogeochemical modelling. In the particular case of the inorganic carbon cycle, there are several sets of carbonate constants that can be chosen. The calculated air-sea CO2 flux is largely dependent on the parametrization chosen. In addition, the different parametrizations all the underlying processes that in some way impact the carbon cycle beyond the carbonate dissociation and fluxes give results that can be significantly different. Examples of these processes are phytoplankton growth rates or remineralization rates. Despite their geographical proximity, the North and Baltic Seas exhibit very different dynamics. The North Sea receives important inflows of Atlantic waters, while the Baltic Sea is an almost enclosed system, with very little exchange from the North Sea. Wind, tides, and freshwater supply act very differently, but dominantly structure the ecosystem dynamics on spatial and temporal scales. The biological community is also different. Cyanobacteria, which are important due to their ability to fix atmospheric nitrogen, and they are only present in the Baltic Sea. These differentiating features have a strong impact in the biogeochemical cycles and ultimately shape the variations in the carbonate chemistry. Here the ECOSMO model was employed on the North Sea and Baltic Sea. The model is set so both are modelled at the same time, instead of having them run separately. ECOSMO is a 3-D coupled

  12. North Sea platform cathodic protection -- A performance vs design review

    SciTech Connect

    Ridd, B.R.; Queen, D.M.E.; Osvoll, H.; Bjornaas, F.

    1999-07-01

    Modern day cathodic protection (CP) design codes are typically highly conservative when compared with early CP system designs. Review of historical survey data from platforms in service for approximately 25 to 30 years illustrates the conservatism now employed when constructing new structures for installation in the North Sea. This paper illustrates this level of conservatism by reviewing the CP system performance of a gas gathering platform complex in the Southern North Sea and comparing the results of that review with present day design codes. The paper details the findings of a CP design review and ROV validation inspection to determine the present system status. The effect of combined impressed current and sacrificial anode systems is also illustrated. Finally a discussion on the definition and optimization of additional CP system requirements and future survey strategy to ensure protection is maintained to the anticipated end of field life is provided highlighting the cost benefits of basing retrofit designs on system performance rather than design theory.

  13. Norway eclipses U. K. in North Sea oil flow

    SciTech Connect

    Not Available

    1991-09-02

    This paper reports that despite new internal rankings, the North Sea has maintained its position as the world's fourth largest oil producing province behind the Middle East, the Soviet Union, and the U.S. Average production remains 3.7-4 million b/d. During 1991, however, sources of production within the total have shifted significantly. Britain no longer tops the North Sea production table. Early this year, major offshore shutdowns required for installation of mandatory safety equipment slashed production. At the same time, Norwegian output remained just below 1.95 million b/d, exceeding flow from neighboring U.K. waters for the first time since the mid- 1970s.

  14. Plankton effect on cod recruitment in the North Sea.

    PubMed

    Beaugrand, Grégory; Brander, Keith M; Alistair Lindley, J; Souissi, Sami; Reid, Philip C

    2003-12-11

    The Atlantic cod (Gadus morhua L.) has been overexploited in the North Sea since the late 1960s and great concern has been expressed about the decline in cod biomass and recruitment. Here we show that, in addition to the effects of overfishing, fluctuations in plankton have resulted in long-term changes in cod recruitment in the North Sea (bottom-up control). Survival of larval cod is shown to depend on three key biological parameters of their prey: the mean size of prey, seasonal timing and abundance. We suggest a mechanism, involving the match/mismatch hypothesis, by which variability in temperature affects larval cod survival and conclude that rising temperature since the mid-1980s has modified the plankton ecosystem in a way that reduces the survival of young cod.

  15. Ecology of the North Sea: Problems, successes, failures, future needs

    NASA Astrophysics Data System (ADS)

    Kinne, O.

    1995-03-01

    After defining ‘ecology’, outlining the basic categories of ecological research and listing examples of modern ecological investigations, this introductory paper focusses on basic considerations; it is, in essence, a programmatic contribution. Research details on the ecology of the North Sea are the subject of the following papers. The problems of ecological North Sea research are formidable. Hydrological and biological fluctuations and variabilities are pronounced. Exchange patterns with the Atlantic are complex, and the inputs of rivers and rain defy exact measurement and prediction. Season, weather, climate—and as yet insufficiently known and controlled human-caused impacts—further complicate the situation. All this results in an unusually high degree of uncertainty. New questions and problems arise before the old ones can be answered or solved. Nevertheless, ecological North Sea research has achieved many successes. The North Sea is the most intensively investigated sea area on our planet. Generations of zoologists, botanists and hydrographers — and more recently microbiologists, meteorologists, climatologists, chemists, pathologists and toxicologists — have produced an impressive body of knowledge. Slowly we are beginning to understand the forces that govern energy budgets and balances, material fluxes, and the factors that control and direct ecosystem dynamics. Essential driving forces of ecosystem dynamics result from microbial, especially bacterial, activities. Ecological modelling has paved the way for new theories and insights, and holds promise for progress towards a predictive ecology. Failures and shortcomings include insufficient long-term research, inadequately designed experiments, and misconceptions in environmental protection. Net changes in ecological processes of an heterogeneous and intensely varying environment such as the North Sea can only be comprehended adequately against the background of sustained measurements over decades

  16. Shallow gas in Cenozoic sediments of the Southern North Sea

    NASA Astrophysics Data System (ADS)

    Trampe, Anna F.; Lutz, Rüdiger; Franke, Dieter; Thöle, Hauke; Arfai, Jashar

    2013-04-01

    Shallow petroleum systems in the southern North Sea are known for several decades but they were not actively explored for a long time. In recent years these unconventional shallow petroleum systems are studied in greater detail and one shallow gas field (A-12) is in production in the Netherlands. Additionally, oil was encountered in Miocene sandstones in the southern Danish North Sea (Lille John well) just north of the Danish-German border. Seismic amplitude anomalies are an indication for hydrocarbons in sediments. Therefore we have mapped the occurrence of seismic amplitude anomalies in the German North Sea based on more than 25.000 km of 2D seismic data and around 4.000 km2 of 3D seismic data. Amplitude anomalies are ubiquitous phenomena in the study area. These anomalies are not only caused by hydrocarbons but also by changing lithologies e.g. peat or fluid migration. Therefore several classes of seismic anomalies, e.g. bright spots, chimneys, blanking areas and velocity pull-down were mapped. Examples for these classes were studied with AVO (amplitude variation with offset) analyses to verify the existence or non-existence of gas in the sediments. Shallow gas can be produced and transported through the dense pipeline grid of the southern and central North Sea or it could be burned offshore close to wind parks in small power plants and the electric energy then transported through the existing power connections of the wind parks. Thus enabling a continuous energy supply during calm wind periods. This study is carried out within the framework of the project "Geoscientific Potential of the German North Sea (GPDN)" in which the Cenozoic sedimentary system was mapped in great detail. A detailed model of delta evolution (Baltic river system) was developed which serves as a structural framework. The studied interval is time equivalent to the Utsira formation which is used offshore Norway for sequestration of CO2. These different possibilities of using or exploiting

  17. Report on ICDP workshop CONOSC (COring the NOrth Sea Cenozoic)

    NASA Astrophysics Data System (ADS)

    Westerhoff, Wim; Donders, Timme; Luthi, Stefan

    2016-08-01

    ICDP workshop COring the NOrth Sea Cenozoic focused on the scientific objectives and the technical aspects of drilling and sampling. Some 55 participants attended the meeting, ranging from climate scientists, drilling engineers, and geophysicists to stratigraphers and public outreach experts. Discussion on the proposed research sharpened the main research lines and led to working groups and the necessary technical details to compile a full proposal that was submitted in January 2016.

  18. Offshore safety management - in the North Sea and worldwide

    SciTech Connect

    Krahn, D.R. )

    1993-11-01

    The development of hydrocarbon resources in the North Sea began in the mid-1960s. Our world was a very different place then. In the early 1970s, security of oil supply was a national priority of the North Sea coastal states, as with most other Western nations with hydrocarbon potential. A high priority was assigned to realizing rapid results from exploitable reserves to insulate these countries from the economic shock that a disruption in supply would cause. The world is much less politically adversarial now than during the 1970s. In the North Sea coastal states, there is no longer a headlong rush to develop secure supplies, partly because the threat of disruption has lessened, but also because there exist large proven reserves in the area. Movements highlighting human rights and the environment have heightened the concern for occupational safety and health of people at work. This paper will examine and contrast two of the primary agents of this change--the Norwegian Petroleum Directorate (NPD) and the Health and Safety Executive (HSE) of the United Kingdom. Some aspects of their development will be examined for insight to the present state of regulatory affairs. Also they will look into the future to see what choices exist for regulators in other countries, keeping in mind developments form bodies like the International Maritime Organization (IMO) and the International Labor Organization (ILO).

  19. Temporal variation of iodine isotopes in the North Sea.

    PubMed

    He, Peng; Aldahan, Ala; Possnert, Göran; Hou, Xiaolin

    2014-01-01

    Monitoring temporal variability of (129)I in the North Sea, a relatively large reservoir of radioactive discharges from the nuclear fuel reprocessing facilities, is vital for the environmental situation in the region. New information on concentration levels and distribution of (129)I and (127)I and their species forms (iodide and iodate) are gained here through sampling of surface water in 2010. The results show generally large spatial and temporal (compared to data from 2005) fluctuations of total (129)I and (127)I, and iodide and iodate. In samples south of 53°N, the level of (127)I(-) in 2010 was generally comparable or higher than in 2005. The results also show total (129)I concentrations comparable in the south, but 2-8 times lower in the north, to the analyses made in 2005. Different from total (129)I, the (129)I(-)/(129)IO3(-) values in the northern part were 2 times higher in 2010 than values observed in 2005. These variations in total (129)I and (127)I and their species are related to coastal water offshore propagation and surface currents that are linked to long-term and seasonal climatic changes over the North Atlantic and North Sea. Inventory estimation shows that >90% of (129)I resides in the Southern and German Bights, which also suggests negligible contribution from the Sellafield facility discharges when compared with that from the La Hague. Variability in discharge rate from La Hague may also affect the distribution patterns of (129)I in the North Sea on the monthly scale.

  20. Local and remote response of the North Sea dynamics to morphodynamic changes in the Wadden Sea

    NASA Astrophysics Data System (ADS)

    Jacob, Benjamin; Stanev, Emil Vassilev; Zhang, Yinglong Joseph

    2016-05-01

    The response of the tidal system in the southern North Sea to morphodynamic changes was investigated in a modelling study using fine resolution bathymetric observations available for 1982-2011. The Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM) was set up for the different sets of bathymetries. One set of bathymetry was compiled from a large number of bathymetric measurements over many years, while the other two reflected bathymetry state in the area of Wadden Sea during 2000 and 2011, respectively. The temporal and spatial evolution of bathymetry was dominated by migration of tidal channels. The M4 tide showed larger sensitivity to bathymetric change in the Wadden Sea than the M2 tide, whereas the structure of the latter remained rather robust. The largest change of the tidal wave due to the differences in bathymetries was located off the North Frisian Wadden Sea. Traces of changes were also found far away from the regions of their origin because the tidal waves in the North Sea propagate the local disturbances basin-wide. This illustrated an efficient physical mechanism of teleconnectivity, i.e. effecting the local responses to the larger-scale or remote change of ocean bottom caused by erosion and deposition. The tidal distortion resulting from the relatively small bathymetric changes was substantial, particularly in the coastal zone. This is a manifestation of the nonlinear tidal transformation in shallow oceans and is crucial for the sediment transport and the morphodynamic feedback, because of the altered tidal asymmetry.

  1. Intrusion of radioactive industrially polluted water from North Sea into central Baltic Sea

    SciTech Connect

    Vakulovskiy, S.M.; Nikitin, A.I.

    1985-02-01

    The problem of penetration of radioactive industrially polluted water into the central Baltic Sea was studied. The content of Cs-134 as determined in water near the bottom of deep water trenches along the path traveled by North Sea water entering the Baltic. Samples were taken at 5 locations, with Cs-134 concentrated from samples of several thousands of liters. It was found that radioactive pollution caused by the entry of water from the North Sea extends through the system of deep water depressions into the Baltic as far as the Gotland trench. The greatest degree of contamination is found in the Arkona depression adjacent to the straits. The concentration of Cs-134 in the Gdansk trench is one-half as great and in the Gotland trench one-third as great as in the Arkona depression. Radioactive contamination in the Baltic is attributed to discharge of radioactive wastes by plants at Windscale.

  2. Reserve growth in oil fields of the North Sea

    USGS Publications Warehouse

    Klett, T.R.; Gautier, D.L.

    2005-01-01

    The assessment of petroleum resources of the North Sea, as well as other areas of the world, requires a viable means to forecast the amount of growth of reserve estimates (reserve growth) for discovered fields and to predict the potential fully developed sizes of undiscovered fields. This study investigates the utility of North Sea oil field data to construct reserve-growth models. Oil fields of the North Sea provide an excellent dataset in which to examine the mechanisms, characteristics, rates and quantities of reserve growth because of the high level of capital investments, implementation of sophisticated technologies and careful data collection. Additionally, these field data are well reported and available publicly. Increases in successive annual estimat es of recoverable crude oil volumes indicate that oil fields in the North Sea, collectively and in each country, experience reserve growth. Specific patterns of reserve growth are observed among countries and primary producing reservoir-rock types. Since 1985, Norwegian oil fields had the greatest volume increase; Danish oil fields increased by the greatest percentage relative to 1985 estimates; and British oil fields experienced an increase in recoverable oil estimates for the first ten years since 1985, followed by a slight reduction. Fields producing primarily from clastic reservoirs account for the majority of the estimated recoverable oil and, therefore, these fields had the largest volumetric increase. Fields producing primarily from chalk (limestone) reservoirs increased by a greater percentage relative to 1985 estimates than did fields producing primarily from clastic reservoirs. Additionally, the largest oil fields had the greatest volumetric increases. Although different reserve-growth patterns are observed among oil fields located in different countries, the small number of fields in Denmark precludes construction of reserve-growth models for that country. However, differences in reserve

  3. Variability patterns of the general circulation and sea water temperature in the North Sea

    NASA Astrophysics Data System (ADS)

    Mathis, M.; Elizalde, A.; Mikolajewicz, U.; Pohlmann, T.

    2015-06-01

    This study investigates patterns of spatio-temporal variability in the North Sea and their major driving mechanisms. Leading variability modes of the general circulation and sea water temperature are extracted from model results by means of Empirical Orthogonal Functions (EOF) analysis. The model results originate from an uncoupled simulation with the global ocean model MPIOM, forced with ERA40 reanalysis data at the air-sea interface. For this regional model study, MPIOM has been run with a stretched grid configuration enabling higher horizontal resolution in the Northwest European Shelf and North Atlantic ocean. The analysis is applied to interannual variabilities of winter and summer separately. The results indicate that on seasonal scales the leading variability mode of the general circulation affects the entire North Sea, accompanied by significant inflow anomalies through the Fair-Isle Passage. Correlations of the corresponding Principal Component (PC) with wind density functions reveal the circulation anomalies to coincide with westerly and south-westerly wind anomalies. The second mode describes circulation anomalies along the Norwegian Trench and English Channel, which correlate with north-westerly wind anomalies caused by variations in large-scale atmospheric pressure areas centered over the British Isles. For sea water temperature, distinct variability patterns are induced by variable surface heat fluxes, vertical mixing, and variable advective heat fluxes. The first mode of both the general circulation and water temperature in winter mainly represents the response to atmospheric variations in the North Atlantic Oscillation (NAO). However, the higher modes account for such variabilities that cannot be explained by the NAO. As a consequence of the integrated effects of the different variability modes on the circulation system and heat content, local correlations of the NAO with volume transports and water temperature are weakened in the regions of

  4. Vertical material flux under seasonal sea ice in the Okhotsk Sea north of Hokkaido, Japan

    NASA Astrophysics Data System (ADS)

    Hiwatari, Takehiko; Shirasawa, Kunio; Fukamachi, Yasushi; Nagata, Ryuichi; Koizumi, Tomoyoshi; Koshikawa, Hiroshi; Kohata, Kunio

    Downward material fluxes under seasonal sea ice were measured using a time-series sediment trap installed at an offshore site in the Okhotsk Sea north of Hokkaido, Japan, from 13 January to 23 March 2005. The maximum fluxes of lithogenic material (753 mg m -2 day -1) and organic matter (mainly detritus; 333 mg m -2 day -1) were recorded during the period in which sea ice drifted ashore and increased in extent, from 13 January to 9 February. Organic matter as fecal pellets (81-93 mg m -2 day -1) and opal as biosilica (51-67 mg m -2 day -1), representing diatom fluxes, were abundant in sediment trap samples obtained during the period of full sea ice coverage from 10 February to 9 March. Microscopic observations revealed that fecal pellets were largely diatom frustules, suggesting that zooplankton actively grazed on ice algae during the period of full sea ice coverage. During the period of retreating sea ice, from 10 to 23 March, the phytoplankton flux showed a rapid increase (from 9.5 to 22.5 × 10 6 cells m -2 day -1), reflecting their release into the water column as the sea ice melted. Our results demonstrate that the quantity and quality of sinking biogenic and lithogenic materials vary with the seasonal extent of sea ice in mid-winter.

  5. Air-sea exchange fluxes of synthetic polycyclic musks in the North Sea and the Arctic.

    PubMed

    Xie, Zhiyong; Ebinghaus, Ralf; Temme, Christian; Heemken, Olaf; Ruck, Wolfgang

    2007-08-15

    Synthetic polycyclic musk fragrances Galaxolide (HHCB) and Tonalide (AHTN) were measured simultaneously in air and seawater in the Arctic and the North Sea and in the rural air of northern Germany. Median concentrations of gas-phase HHCB and AHTN were 4 and 18 pg m(-3) in the Arctic, 28 and 18 pg m(-3) in the North Sea, and 71 and 21 pg m(-3) in northern Germany, respectively. Various ratios of HHCB/AHTN implied that HHCB is quickly removed by atmospheric degradation, while AHTN is relatively persistent in the atmosphere. Dissolved concentrations ranged from 12 to 2030 pg L(-1) for HHCB and from below the method detection limit (3 pg L(-1)) to 965 pg L(-1) for AHTN with median values of 59 and 23 pg L(-1), respectively. The medians of volatilization fluxes for HHCB and AHTN were 27.2 and 14.2 ng m(-2) day(-1) and the depositional fluxes were 5.9 and 3.3 ng m(-2) day(-1), respectively, indicating water-to-air volatilization is a significant process to eliminate HHCB and AHTN from the North Sea. In the Arctic, deposition fluxes dominated the air-sea gas exchange of HHCB and AHTN, suggesting atmospheric input controls the levels of HHCB and AHTN in the polar region.

  6. North Sea report. Economics crucial in UK projects

    SciTech Connect

    Not Available

    1983-09-01

    In developing the large discoveries that turned the North Sea into an oil province, it was enough of a problem to find technical solutions to the problems posed by the environment without worrying whether they might be the most inexpensive. Now that fields are smaller, and proportionally up to 10 times more expensive to develop, the pressure is to find technical solutions which can be applied economically. With an oil price that seems likely to remain no more than static in real terms, the oil industry can no longer rely on a rising price for its product to convert marginal prospects into viable development projects. The recent UK government tax measures to encourage new development have resulted in the reassessment of numerous projects. However, it is clear that before many of these become economic, significant savings must be made in development costs. This need is highlighted in a discussion of the potential Shell/Esso development of a cluster of small fields in the central North Sea. With the help of the new package and improved technology, such a project could be possible now, but it requires improvements in costs over even second generation developments such as North Cormorant and Fulmar. Further cost reductions of 15% are considered realistic and achievable.

  7. Illicit drugs and their metabolites in 36 rivers that drain into the Bohai Sea and north Yellow Sea, north China.

    PubMed

    Wang, De-Gao; Zheng, Qiu-Da; Wang, Xiao-Ping; Du, Juan; Tian, Chong-Guo; Wang, Zhuang; Ge, Lin-Ke

    2016-08-01

    Illicit drugs and their metabolites have recently been recognized as an emerging group of contaminants due to their potential ecotoxicological impact in aquatic ecosystems. To date, information on the occurrence of these compounds in the aquatic environment of China remains limited. In this study, we collected surface water samples from 36 rivers in north China that discharge into the Bohai Sea and north Yellow Sea and measured the concentrations of amphetamine-like compounds, ketamines, cocainics, and opioids. The occurrence and spatial patterns of these substances show significant differences between the rivers and regions. Two designer drugs, methamphetamine (METH) and ketamine (KET), were the most abundant compounds detected in the entire set of samples (detection frequency of 92 and 69 %). The concentrations of METH and KET ranged from <0.1 to 42.0 ng L(-1) (mean = 4.53 ng L(-1)) and <0.05 to 4.50 ng L(-1) (mean = 0.49 ng L(-1)), respectively. The high detection frequencies of METH and KET are consistent with the fact that they are the main illicit drugs consumed in China. The high concentrations of these illicit drugs and their metabolites were found in areas that have a high population density. The riverine input of total illicit drugs into the Bohai Sea and north Yellow Sea was estimated to be in the range of 684 to 1160 kg per year. PMID:27167374

  8. Bioaccumulation and biomarkers in the sea star Asterias rubens (Echinodermata: Asteroidea): a North Sea field study.

    PubMed

    den Besten, P J; Valk, S; van Weerlee, E; Nolting, R F; Postma, J F; Everaarts, J M

    2001-05-01

    During two North Sea field trips in March 1995 and September 1996 sea stars, Asterias rubens, were collected at various stations along pollution gradients in order to study the relation between biochemical markers and levels of accumulated contaminants. Biomarkers measured were: cytochrome P450 level, benzo[a]pyrene hydroxylase (BPH) activity, acetylcholinesterase (AChE) activity and DNA integrity. Accumulation levels of heavy metals, polychlorinated biphenyls, organochlorine pesticides and polycyclic aromatic hydrocarbons (PAHs) in the pyloric caeca of sea stars indicate different pollution gradients, influenced by rivers in The Netherlands, UK and Germany. For some contaminants, especially PAHs, relatively high levels were found in the central part of the North Sea (Dogger Bank). On the basis of multivariate statistics, stations near the mouth of the Elbe and the Rhine/Meuse were shown to have different patterns of biomarker responses. Sea stars from stations in coastal zones showed relatively high levels of cytochrome P450 and 'P418', another haemoprotein that is present in most marine invertebrates. The station nearest to the Elbe Estuary showed the lowest BPH and AChE activity. DNA integrity was lower especially in stations near the Dutch coast and in a station near the Tees/Tyne estuaries. Using these biomarkers as early warning signals of exposure and/or adverse effects, this type of monitoring can be used also in the future to study the spatial and temporal trends in the quality of coastal waters.

  9. Phytoplankton of the North Sea and its dynamics: A review

    NASA Astrophysics Data System (ADS)

    Reid, P. C.; Lancelot, C.; Gieskes, W. W. C.; Hagmeier, E.; Weichart, G.

    Phytoplankton is the major contributor to algal biomass and primary production of the North Sea, although crops of macroalgae can locally be up to 2000 g C.m -2 along the coast of the U.K. and Norway, and microphytobenthos dominates production in the shallow tidal flat areas bordering the coasts of England, the Netherlands, Germany and Denmark. Data collected since 1932 during the Continuous Plankton Recorder Survey show consistent patterns of geographical, seasonal and annual variation in the distribution of phytoplankton and its major taxonomic components. There is a trend of increased colouration in Recorder silks in the southern North Sea until approximately 1975 since when Colour levels (assumed to be indicative of algal biomass) have declined. In the eutrophic Dutch Wadden Sea the algal crop continued to increase; in Dutch coastal North Sea waters a trend of biomass increase reversed since 1984, apparently due to a reduction in Rhine river outflow. Long-term observations made at Helgoland since the 60's also show trends of increasing nutrients and phytoplankton biomass only to 1984. Adverse effects such as deoxygenation, foam formation and toxin production have been linked to mass concentrations of algae known as blooms. There is no evidence from existing reports for an increase in their frequency, although some years stand out with larger numbers. Occurrence of blooms can partly be explained by hydrographic conditions. More than 30 taxa are recognised as occurring in bloom proportions in the North Sea, approximately one third of which can be toxic. The crop of Bacillariophyceae (diatoms) is not likely to increase with eutrophication due to silicate limitation. An extensive subsurface maximum of armoured dinoflagellates, its abundance gouverned by hydrographic conditions, is the most characteristic feature of the central and northern North Sea in the summer months. Abundance, sometimes dominance, of picoplankton and of species that are not readily detected by

  10. Physical processes in the transition zone between North Sea and Baltic Sea. Numerical simulations and observations

    NASA Astrophysics Data System (ADS)

    Stanev, Emil V.; Lu, Xi; Grashorn, Sebastian

    2015-09-01

    The dynamics in the transition zone between the North Sea and Baltic Sea are analyzed here using data from a 22-year-long climatic simulation with a focus on the periods 1992-1994 and 2001-2003 when two recent major inflow events occurred. Observations from gauges and in situ measurements are used to validate the model. Parameters, which cannot be easily measured, such as water and salt transports through straits, have been compared against similar previous estimates. The good performance of simulations is attributed to the finer resolution of the model compared to earlier set ups. The outflow in the Kattegat, which is an analogue of the tidal outflows, tends to propagate to the North over the shallows without showing a substantial deflection to the right due to the Earth's rotation. The inflow follows the topography. The different inflow and outflow pathways are explained as a consequence of the specific combination of bathymetry, axial and lateral processes. The circulation in Kattegat is persistently clockwise with an eastern intensification during inflow and a western one during outflow regimes. The tidal wave there propagates as Kelvin wave, keeping the coast on its right. The flows in the two main straits reveal very different responses to tides, which are also highly asymmetric during inflow and outflow conditions. The circulation has a typical two-layer structure, the correlation between salinity and velocity tends to increase the salt transport in the salinity conveyor belt. The transversal circulation in the entrance of the Sound enhances the vertical mixing of the saltier North Sea water. The long-term averaged ratio of the water transports through the Great Belt and the Sound is ∼2.6-2.7 but this number changes reaching lower values during the major inflow in 1993. The transports in the straits are asymmetric. During inflow events the repartition of water penetrating the Baltic Sea is strongly in favor of the pathway through the Sound, which provides

  11. The North Sea Andrea storm and numerical simulations

    NASA Astrophysics Data System (ADS)

    Bitner-Gregersen, E. M.; Fernandez, L.; Lefèvre, J. M.; Monbaliu, J.; Toffoli, A.

    2014-06-01

    A coupling of a spectral wave model with a nonlinear phase-resolving model is used to reconstruct the evolution of wave statistics during a storm crossing the North Sea on 8-9 November 2007. During this storm a rogue wave (named the Andrea wave) was recorded at the Ekofisk field. The wave has characteristics comparable to the well-known New Year wave measured by Statoil at the Draupner platform 1 January 1995. Hindcast data of the storm at the nearest grid point to the Ekofisk field are here applied as input to calculate the evolution of random realizations of the sea surface and its statistical properties. Numerical simulations are carried out using the Euler equations with a higher-order spectral method (HOSM). Results are compared with some characteristics of the Andrea wave record measured by the down-looking lasers at Ekofisk.

  12. Floating debris in the Ligurian Sea, north-western Mediterranean.

    PubMed

    Aliani, Stefano; Griffa, Annalisa; Molcard, Anne

    2003-09-01

    Results from visual sightings of large floating debris are presented, taken in the Ligurian Sea, a sub-basin of the north-western Mediterranean Sea which belongs to the recently stated "Cetacean Sanctuary". Data have been collected during three oceanographic cruises, during the summer of 1997 and 2000. Results for the 1997 data suggest a debris density of the order of 15-25 objects km(-2), while for the 2000 data, a lower density of the order of 3-1.5 objects km(-2) is found. The difference between the two results appears statistically significant using simple tests. Possible reasons for the observed variability are discussed, including meteorological forcing, marine currents and debris input variability.

  13. Marine litter ensemble transport simulations in the southern North Sea.

    PubMed

    Neumann, Daniel; Callies, Ulrich; Matthies, Michael

    2014-09-15

    The drift of marine litter in the southern North Sea was simulated with the offline Lagrangian transport model PELETS-2D. Assuming different source regions, passive tracer particles were released every 28 h within a nine-year period. Based on pre-calculated hourly wind and ocean current data, drift simulations were carried out forward and backward in time with and without the assumption of extra wind forces influencing particle movement. Due to strong variability of currents, backward simulations did not allow for the identification of particular source regions influencing given monitoring sites. Neither accumulation regions at open sea could be identified by forward simulations. A seasonal signal, however, could be identified in the number of tracer particles that reached the coastal areas. Both particle drift velocity and variability of drift paths further increased when an extra wind drift was assumed. PMID:25125287

  14. Wasp-Waist Interactions in the North Sea Ecosystem

    PubMed Central

    Fauchald, Per; Skov, Henrik; Skern-Mauritzen, Mette; Johns, David; Tveraa, Torkild

    2011-01-01

    Background In a “wasp-waist” ecosystem, an intermediate trophic level is expected to control the abundance of predators through a bottom-up interaction and the abundance of prey through a top-down interaction. Previous studies suggest that the North Sea is mainly governed by bottom-up interactions driven by climate perturbations. However, few studies have investigated the importance of the intermediate trophic level occupied by small pelagic fishes. Methodology/Principal Findings We investigated the numeric interactions among 10 species of seabirds, two species of pelagic fish and four groups of zooplankton in the North Sea using decadal-scale databases. Linear models were used to relate the time series of zooplankton and seabirds to the time series of pelagic fish. Seabirds were positively related to herring (Clupea harengus), suggesting a bottom-up interaction. Two groups of zooplankton; Calanus helgolandicus and krill were negatively related to sprat (Sprattus sprattus) and herring respectively, suggesting top-down interactions. In addition, we found positive relationships among the zooplankton groups. Para/pseudocalanus was positively related to C. helgolandicus and C. finmarchicus was positively related to krill. Conclusion/Significance Our results indicate that herring was important in regulating the abundance of seabirds through a bottom-up interaction and that herring and sprat were important in regulating zooplankton through top-down interactions. We suggest that the positive relationships among zooplankton groups were due to selective foraging and switching in the two clupeid fishes. Our results suggest that “wasp-waist” interactions might be more important in the North Sea than previously anticipated. Fluctuations in the populations of pelagic fish due to harvesting and depletion of their predators might accordingly have profound consequences for ecosystem dynamics through trophic cascades. PMID:21829494

  15. Radioactive Contamination of the North-western Black Sea Sediments

    NASA Astrophysics Data System (ADS)

    Gulin, S. B.; Polikarpov, G. G.; Egorov, V. N.; Martin, J. M.; Korotkov, A. A.; Stokozov, N. A.

    2002-03-01

    The paper deals with the input and deposition of the man-made radionuclides 137Cs, 238 Pu, 239+240Pu and 241Am introduced to the north-western Black Sea, over the last few decades, as the result of atmospheric nuclear weapons testing and the Chernobyl nuclear accident. One approach taken was to retrieve the deposition records of these radionuclides in the sediments. The deposition chronology was compared with monitoring data of the post-Chernobyl input of 137Cs to the NW Black Sea sediments from the Danube River. The partitioning of 137 Cs between suspended matter and water was traced along the salinity gradient in the Danube mixing zone. In sediments deposited in the vicinity of the Danube delta and the Dniepr estuary, the activity of Chernobyl 137Cs had reached its maximum 5 and 10 years after the accident, respectively. The activity ratio of 137Cs to 239+240Pu and 241 Am revealed a higher mobility of 137Cs in the Danube River basin compared to plutonium and americium. The percentage of particulate 137Cs and its distribution coefficient vs salinity have allowed the estimation of sedimentary scavenging and desorption of caesium in the Danube mixing zone. Comparison of the post-Chernobyl 137Cs input from the Danube to the 137Cs inventory in the adjacent Black Sea sediments showed that more than 70% of this radionuclide was deposited in the Danube-Black Sea mixing zone.

  16. Sea Ice and Hydrographic Variability in the Northwest North Atlantic

    NASA Astrophysics Data System (ADS)

    Fenty, I. G.; Heimbach, P.; Wunsch, C. I.

    2010-12-01

    Sea ice anomalies in the Northwest North Atlantic's Labrador Sea are of climatic interest because of known and hypothesized feedbacks with hydrographic anomalies, deep convection/mode water formation, and Northern Hemisphere atmospheric patterns. As greenhouse gas concentrations increase, hydrographic anomalies formed in the Arctic Ocean associated with warming will propagate into the Labrador Sea via the Fram Strait/West Greenland Current and the Canadian Archipelago/Baffin Island Current. Therefore, understanding the dynamical response of sea ice in the basin to hydrographic anomalies is essential for the prediction and interpretation of future high-latitude climate change. Historically, efforts to quantify the link between the observed sea ice and hydrographic variability in the region has been limited due to in situ observation paucity and technical challenges associated with synthesizing ocean and sea ice observations with numerical models. To elaborate the relationship between sea ice and ocean variability, we create three one-year (1992-1993, 1996-1997, 2003-2004) three-dimensional time-varying reconstructions of the ocean and sea ice state in Labrador Sea and Baffin Bay. The reconstructions are syntheses of a regional coupled 32 km ocean-sea ice model with a suite of contemporary in situ and satellite hydrographic and ice data using the adjoint method. The model and data are made consistent, in a least-squares sense, by iteratively adjusting several model control variables (e.g., ocean initial and lateral boundary conditions and the atmospheric state) to minimize an uncertainty-weighted model-data misfit cost function. The reconstructions reveal that the ice pack attains a state of quasi-equilibrium in mid-March (the annual sea ice maximum) in which the total ice-covered area reaches a steady state -ice production and dynamical divergence along the coasts balances dynamical convergence and melt along the pack’s seaward edge. Sea ice advected to the

  17. Drivers of summer oxygen depletion in the central North Sea

    NASA Astrophysics Data System (ADS)

    Queste, B. Y.; Fernand, L.; Jickells, T. D.; Heywood, K. J.; Hind, A. J.

    2015-06-01

    In stratified shelf seas, oxygen depletion beneath the thermocline is a result of a greater rate of biological oxygen demand than the rate of supply of oxygenated water. Suitably equipped gliders are uniquely placed to observe both the supply through the thermocline and the consumption of oxygen in the bottom layers. A Seaglider was deployed in the shallow (≈ 100 m) stratified North Sea in a region of known low oxygen during August 2011 to investigate the processes regulating supply and consumption of dissolved oxygen below the pycnocline. The first deployment of such a device in this area, it provided extremely high resolution observations, 316 profiles (every 16 min, vertical resolution of 1 m) of CTD, dissolved oxygen concentrations, backscatter and fluorescence during a three day deployment. The high temporal resolution observations revealed occasional small scale events that supply oxygenated water into the bottom layer at a rate of 2±1 μmol dm-3 day-1. Benthic and pelagic oxygen sinks, quantified through glider observations and past studies, indicate more gradual background consumption rates of 2.5±1 μmol dm-3 day-1. This budget revealed that the balance of oxygen supply and demand is in agreement with previous studies of the North Sea. However, the glider data show a net oxygen consumption rate of 2.8±0.3 μmol dm-3 day-1 indicating a localised or short-lived increase in oxygen consumption rates. This high rate of oxygen consumption is indicative of an unidentified oxygen sink. We propose that this elevated oxygen consumption is linked to localised depocentres and rapid remineralisation of resuspensded organic matter. The glider proved to be an excellent tool for monitoring shelf sea processes despite challenges to glider flight posed by high tidal velocities, shallow bathymetry, and very strong density gradients. The direct observation of these processes allows more up to date rates to be used in the development of ecosystem models.

  18. Skeleton of Extinct North American Sea Mink ( Mustela macrodon)

    NASA Astrophysics Data System (ADS)

    Mead, Jim I.; Spiess, Arthur E.; Sobolik, Kristin D.

    2000-03-01

    Mustela macrodon (extinct sea mink) is known only from prehistoric and historic Native American shell middens dating less than 5100 years old along coastal islands of the Gulf of Maine, northeastern North America. The species is distinct from all known extant subspecies of M. vison (American mink) but still belongs to the North American subgenus Vison. Metric comparisons between M. macrodon and five subspecies of M. vison, using skull, mandible, humerus, radius, femur, and tibia skeletal elements, show that M. macrodon is larger in overall size and robustness and is proportionately larger in the dental region. Many habitat-related parallels exist between coastal island mink of the Gulf of Maine and those of the Alexander Archipelago, southeastern Alaska, where the overall largest living subspecies of mink is found (M. v. nesolestes).

  19. Chemostratigraphy of Upper Cretaceous chalk sequences in Norwegian-Danish basin and North Sea Central Trough

    SciTech Connect

    Joergensen, N.O.

    1987-05-01

    Geochemical studies of subsurface sections and outcrops in the Upper Cretaceous chalk sequences from the Norwegian-Danish basin and the North Sea Central Trough have resulted in a detailed chemostratigraphy for these strata. The most applicable chemostratigraphic markers are based on the distribution of strontium, magnesium, manganese, the /sup 13/C//sup 12/C ratio, and the variations in the carbonate contents. It is demonstrated that the chemostratigraphic approach is valid at two levels: (1) a superior chemostratigraphy in which deep-sea cores from the Atlantic Ocean and sections from western Europe are correlated on the basis of significant geochemical anomalies and long-term variations most likely induced by oceanic geochemical cycles and sea level fluctuations; (2) a subordinate but detailed intrabasinal chemostratigraphic correlation which primarily reflects the physicochemical conditions in the depositional environment. The Upper Cretaceous chemostratigraphy established in the Danish area allows a detailed correlation between relatively continuous chalk sequences in the Norwegian-Danish basin and the rather condensed and hiati-influenced sections in the oil fields of the North Sea. The results emphasize the applicability of chemostratigraphy in the subsurface exploration for hydrocarbon reservoirs in chalk.

  20. Recent trends in Sea ice in the southern and western Baltic and the North Sea

    NASA Astrophysics Data System (ADS)

    Holfort, Jürgen; Schmelzer, Natalija; Schwegmann, Sandra

    2016-04-01

    We analyzed sea ice charts and observations of a 50 year long period starting in 1961 to produce two climatological ice atlases, one for the western and southern Baltic and one for the German Bight and Limfjord. As the year to year variability is large we subdivided the 50 year into three overlapping 30 year periods (1961-1990, 1971-2000 and 1981-2010) to look for trends in the sea ice. In the southern and western Baltic as well as in the North Sea there was a clear decrease in the total frequency of ice occurrence. Other parameters like begin and end of the ice season, ice thickness, etc. did not show such clear signal and also showed larger regional differences. The ice conditions mainly changed in accordance with the changes in air temperature in the same period, although some more regional changes in some parameters were most probably also influenced by other factors like the deepening of fairways.

  1. The influence of Black Sea Water inflow and its synoptic time-scale variability in the North Aegean Sea hydrodynamics

    NASA Astrophysics Data System (ADS)

    Mavropoulou, Apostolia-Maria; Mantziafou, Anneta; Jarosz, Ewa; Sofianos, Sarantis

    2016-02-01

    The exchange water fluxes between the Black Sea and the North Aegean Sea through the Dardanelles Strait constitute an essential factor for the general circulation of the region. The Black Sea Water (BSW) inflow to the Aegean plays an important role in the hydrography and circulation of the basin and can affect the North Aegean deep water formation processes. Numerical experiments evaluating the influence of the time-scale variability (synoptic and seasonal) and the seasonality (period of maximum/minimum) of the Black Sea Water inflow on the dynamics of the North Aegean basin were performed. The experiments were carried out for the period from August 2008 to October 2009, using observed upper and lower-layer fluxes from the Dardanelles Strait, high-resolution atmospheric forcing, and boundary conditions derived from an operational system (ALERMO). The large-scale spatial patterns of the circulation and the seasonal variability of the North Aegean circulation show that dynamics of the basin can effectively absorb most of the Black Sea Water inflow variability. The overall cyclonic circulation of the North Aegean Sea and the predominant cyclonic and anti-cyclonic features are robust and are little affected by the different lateral fluxes. However, differences in the seasonality of the BSW inflow have an important impact in the North Aegean water column structure, while the synoptic variability observed in the Black Sea Water inflow affects the kinetic energy of the basin and the pathway of the Black Sea Water plume.

  2. Reevaluation of mid-Pliocene North Atlantic sea surface temperatures

    USGS Publications Warehouse

    Robinson, Marci M.; Dowsett, Harry J.; Dwyer, Gary S.; Lawrence, Kira T.

    2008-01-01

    Multiproxy temperature estimation requires careful attention to biological, chemical, physical, temporal, and calibration differences of each proxy and paleothermometry method. We evaluated mid-Pliocene sea surface temperature (SST) estimates from multiple proxies at Deep Sea Drilling Project Holes 552A, 609B, 607, and 606, transecting the North Atlantic Drift. SST estimates derived from faunal assemblages, foraminifer Mg/Ca, and alkenone unsaturation indices showed strong agreement at Holes 552A, 607, and 606 once differences in calibration, depth, and seasonality were addressed. Abundant extinct species and/or an unrecognized productivity signal in the faunal assemblage at Hole 609B resulted in exaggerated faunal-based SST estimates but did not affect alkenone-derived or Mg/Ca–derived estimates. Multiproxy mid-Pliocene North Atlantic SST estimates corroborate previous studies documenting high-latitude mid-Pliocene warmth and refine previous faunal-based estimates affected by environmental factors other than temperature. Multiproxy investigations will aid SST estimation in high-latitude areas sensitive to climate change and currently underrepresented in SST reconstructions.

  3. Freespan analysis, correction method saves time on North Sea project

    SciTech Connect

    Kaye, D.; Ingram, J. ); Galbraith, D.N.; Davies, R. )

    1994-02-21

    A new procedure for assessing and rectifying subsea pipeline free-spans was successfully used in 1992 in Mobil North Sea Ltd.'s Beryl field and the Scottish Areas Gas Evacuation (SAGE) pipeline. The span-assessment methods is in two parts, each part having two stages, and consists of preliminary stress and vibration-frequency checks followed by detailed strain and fatigue-life checks where appropriate. Comprehensive software, automatically linked to an inspection data base, has been written to allow efficient use of the methodology. Results from the freespan assessment indicate that the assessment procedure, and in particular the strain-based and fatigue analyses, gave significant savings in terms of reduced number of free-spans for rectification. Critical freespans were stabilized by grout bags positioned by an ROV. The ROV-based system enabled both risks and costs to be reduced in a normally hazardous and costly environment, and utilized technology already on board a pipeline-inspection vessel. The overall freespan assessment and rectification program represents a significant step forward for Mobil North Sea in terms of reducing costs, while simultaneously improving the speed and simplicity of free-span assessment.

  4. Seasonality of floc strength in the southern North Sea

    NASA Astrophysics Data System (ADS)

    Fettweis, Michael; Baeye, Matthias; Zande, Dimitry; Eynde, Dries; Joon Lee, Byung

    2014-03-01

    The suspended particulate matter (SPM) concentration in the high turbidity zones of the southern North Sea is inversely correlated with chlorophyll (Chl) concentration. During winter, SPM concentration is high and Chl concentration is low and vice versa during summer. This seasonality has often been associated with the seasonal pattern in wind forcing. However, the decrease in SPM concentration corresponds well with the spring algal bloom. Does the decrease of SPM concentration caused by changing wind conditions cause the start of algae bloom, or does the algae bloom decrease SPM concentrations through enhanced flocculation and deposition? To answer the question, measurements from 2011 of particle size distribution (PSD), SPM, and Chl concentrations from the southern North Sea have been analyzed. The results indicate that the frequency of occurrence of macroflocs has a seasonal signal, while seasonality has little impact upon floc size. The data from a highly turbid coastal zone suggest that the maximum size of the macroflocs is controlled by turbulence and the available flocculation time during a tidal cycle, but the strength of the macroflocs is controlled by the availability of sticky organic substances associated with enhanced primary production during spring and summer. The results highlight the shift from mainly microflocs and flocculi in winter toward more muddy marine snow with larger amounts of macroflocs in spring and summer. The macroflocs will reduce the SPM concentrations in the turbidity maximum area as they settle faster. Consequently, the SPM concentration decreases and the light condition increases in the surface layer enhancing algae growth further.

  5. Seasonal oxygen depletion in the North Sea, a review.

    PubMed

    Topcu, H D; Brockmann, U H

    2015-10-15

    Seasonal mean oxygen depletion in offshore and coastal North Sea bottom waters was shown to range between 0.9 and 1.8 mg/L, corresponding to 95-83% saturation, between July and October over a 30-year assessment period (1980-2010). The magnitude of oxygen depletion was controlled by thermal stratification, modulated by water depth and nitrogen availability. Analyses were based on about 19,000 combined data sets. Eutrophication problem areas were identified mainly in coastal waters by oxygen minima, the lower 10th percentile of oxygen concentrations, and deviations of oxygen depletion from correlated stratification values. Connections between oxygen consumption and nitrogen sources and conversion, including denitrification, were indicated by correlations. Mean oxygen consumption reflected a minimum seasonal turnover of 3.1 g N/m(2) in the south-eastern North Sea, including denitrification of 1 g N/m(2). Oxygen depletion was underestimated in shallow coastal waters due to repeated erosion of stratification as indicated by local high variability.

  6. Modelling the impact of Black Sea water inflow on the North Aegean Sea hydrodynamics

    NASA Astrophysics Data System (ADS)

    Tzali, Margarita; Sofianos, Sarantis; Mantziafou, Anneta; Skliris, Nikolaos

    2010-06-01

    The impact of the Black Sea Water (BSW) inflow on the circulation and the water mass characteristics of the North Aegean Sea is investigated using a high-resolution 3D numerical model. Four climatological numerical experiments are performed exploring the effects of the exchange amplitude at the Dardanelles Straits in terms of the mean annual volume exchanged and the amplitude of its seasonal cycle. Larger inflow of low salinity BSW influences the water characteristics of the whole basin. The largest salinity reduction is encountered in the upper layers of the water column, and the most affected region is the northeastern part of the basin. The winter insulation character of the BSW layer (low-salinity layer) is reduced by the seasonal cycle of the inflow (minimum during winter). The maximum atmospheric cooling coincides with the minimum BSW inflow rate, weakening the vertical density gradients close to the surface and thus facilitating the vertical mixing. The inflow rate of BSW into the North Aegean Sea constitutes an essential factor for the circulation in the basin. Increased inflow rate results into considerably higher kinetic energy, stronger circulation and reinforcement of the mesoscale circulation features. Although the position of the front between BSW and waters of Levantine origin does not vary significantly with the intensity of the BSW inflow rate, the flow along the front becomes stronger and more unstable as the inflow rate increases, forming meanders and rings. The changes in the intensity of BSW inflow rate overpower the wind and thermohaline forcing and largely determine the general circulation of the North Aegean Sea.

  7. Early Permian (Rotliegendes) palaeowinds of the north sea

    NASA Astrophysics Data System (ADS)

    Glennie, K. W.

    1983-03-01

    The classical desert sediments of the Early Permian Upper Rotliegendes were deposited in a post-Variscan basin that extends from eastern England to the Russo-Polish border, which has been referred to as the Southern Permian Basin. These sediments comprise four main depositional facies: fluvial (wadi), aeolian, sabkha and lacustrine. The lacustrine facies includes important bedded halites. The Southern Permian Basin is separated from the smaller Northern Permian Basin by the fragmented Mid North Sea-Ringkøbing-Fyn system of highs: and beyond the Grampian Spur lies the even smaller Moray Firth Basin. These latter basins contain rock sequences similar to those of the southern basin, with the exception that bedded halite has not been recognised in the lacustrine facies. The Rotliegendes of the southern basin apparently conforms to deposition in a Northern Hemisphere tradewind desert similar to the modern southern Sahara. Apart from regional palaeomagnetic considerations and the occurrence of sediments of a non-arid nature south of the Variscan Highlands, the strongest evidence supporting this interpretation is the pattern of palaeowind directions deduced from the orientations of dune bedding. This is seen in both outcrop and core and derived from the continuous dip-meter logs of many North Sea wells by plotting the poles to the bedding attitudes on polar nets. Palaeowind directions have also been deduced from the dip-meter logs of wells drilled in the Northern and Moray Firth Basins. In general, they indicate winds that blew in a direction opposed to those of the Southern Basin. Thus an area of high barometric pressure seems to have been located over the Mid North Sea High. When the bedding attitudes in a well are roughly unidirectional, an origin on a transverse dune is normally indicated. With some wells, the indicated palaeowind direction is regionally anomalous. In many cases this can be rectified if the well is presumed to have drilled down through one flank of a

  8. Drivers of summer oxygen depletion in the central North Sea

    NASA Astrophysics Data System (ADS)

    Queste, Bastien Y.; Fernand, Liam; Jickells, Timothy D.; Heywood, Karen J.; Hind, Andrew J.

    2016-02-01

    In stratified shelf seas, oxygen depletion beneath the thermocline is a result of a greater rate of biological oxygen demand than the rate of supply of oxygenated water. Suitably equipped gliders are uniquely placed to observe both the supply through the thermocline and the consumption of oxygen in the bottom layers. A Seaglider was deployed in the shallow (≍ 100 m) stratified North Sea in a region of known low oxygen during August 2011 to investigate the processes regulating supply and consumption of dissolved oxygen below the pycnocline. The first deployment of such a device in this area, it provided extremely high-resolution observations, 316 profiles (every 16 min, vertical resolution of 1 m) of conductivity, temperature, and depth (CTD), dissolved oxygen concentrations, backscatter, and fluorescence during a 3-day deployment.The high temporal resolution observations revealed occasional small-scale events (< 200 m or 6 h) that supply oxygenated water to the bottom layer at a rate of 2 ± 1 µmol dm-3 day-1. Benthic and pelagic oxygen sinks, quantified through glider observations and past studies, indicate more gradual background consumption rates of 2.5 ± 1 µmol dm-3 day-1. This budget revealed that the balance of oxygen supply and demand is in agreement with previous studies of the North Sea. However, the glider data show a net oxygen consumption rate of 2.8 ± 0.3 µmol dm-3 day-1, indicating a localized or short-lived (< 200 m or 6 h) increase in oxygen consumption rates. This high rate of oxygen consumption is indicative of an unidentified oxygen sink. We propose that this elevated oxygen consumption is linked to localized depocentres and rapid remineralization of resuspended organic matter.The glider proved to be an excellent tool for monitoring shelf sea processes despite challenges to glider flight posed by high tidal velocities, shallow bathymetry, and very strong density gradients. The direct observation of these processes allows more up to date

  9. Impact of spatial resolution of ocean models in depicting climate change patterns of the North Sea.

    NASA Astrophysics Data System (ADS)

    Narayan, Nikesh; Klein, Birgit; Mathis, Moritz; Klein, Holger; Mikolajewicz, Uwe

    2016-04-01

    The impact of enhanced spatial resolution of models in simulating large scale climate change has been of interest for the modeling community for quite some time. It has been noticed in previous studies that the pattern of Sea Surface Temperature anomalies are better captured by higher resolution models. Significant changes in simulating sea-ice loss associated with global warming was also noticed when the spatial resolution of climate models were enhanced. Spatial resolution is a particular important issue in climate change scenarios of shelf seas such as the North Sea. The North Sea is strongly influenced by its water mass exchanges with North Atlantic to the west and north and Baltic Sea to east. Furthermore, local forcing and changes in advected water masses significantly affect the thermodynamics and stratification patterns in the North Sea, making it a challenging area to study. Under the newly started RACE2 project we are looking at global simulations of Representative Concentration Pathway (RCP) scenarios 4.5 and 8.5 at lower and higher resolutions, performed using the Max Planck Institute Earth System Model (MPIESM). The model resolution is non uniform and achieves the highest resolution over the European Seas by shifting the model poles over Chicago and Central Europe. In the high resolution run, the grid reaches up to a spatial resolution of up to 4 km in part of the German Bight and close to 20 km in the Northern part of North Sea. The placement of model poles at specific locations enables the global model to obtain higher resolution at regional scales (North Sea), without the inherent complications of open boundary conditions. High and low resolution simulations will be compared to determine differences in spatial and temporal pattern of temperature anomalies, fresh water intrusion from the Baltic Sea to North Sea etc. Also taken into consideration will be the changes in simulating local sea level change and response to basin scale oscillations like NAO.

  10. Brief: Offshore North Sea case histories of the environmentally friendly testing vessel, the Crystal Sea

    SciTech Connect

    Tjelta, O.; Ashwell, C.; Hilmarsen, G.; Taylor, R.W.

    1996-04-01

    One problem during offshore well-test operations, stimulations, and routine workovers are discharges into the air and sea while flaring. These procedures are usually performed by mobile drilling rigs with no storage capacity, and thus, hydrocarbons sequestered must be burned off from the rig flare booms. Another major problem has been the inability of the flare to operate at high flow rates. Because the burning process slows the pace of a test, restricting full flow testing, valuable well information is lost. Flaring of hydrocarbons also represents an economic loss. In the case of oil rigs, for example, flaring not only emits CO{sub 2} into the atmosphere but also burns off usable oil. The Crystal Sea well-test vessel was designed to address the problems inherent to flaring and, at the same time, provide cost efficiency by salvaging usable oil during well testing. The success of her initial two jobs on the Statfjord North satellite field in the Norwegian sector of the North Sea confirms that sale of the salvaged oil normally lost during the flaring process could generate sufficient economic return to pay for the vessel. In addition, with its capability to receive products at twice the flow rate of conventional methods, the increased accuracy of the technical information obtained from the well test further enhances its value for improved reservoir management.

  11. Shoreline responses to storm impacts: North Norfolk coast, southern North Sea

    NASA Astrophysics Data System (ADS)

    Brooks, Sue; Spencer, Thomas

    2016-04-01

    Recent phases of enhanced mid-latitude storminess (e.g. NW European winter of 2013 - 14) have led to a growing awareness of the considerable impacts of storms on coastal landscapes and their communities. Using aerial photography, bi-annual cross-shore profiles, detailed alongshore ground survey, and offshore/inshore wave buoy and regional tide gauge datasets, this paper considers storm impacts on the barrier coastline of North Norfolk, UK. Firstly, at Scolt Head Island, we show that the barrier dune crest has been progressively set back landwards since 2006 in three storm-related phases, with each shoreline translation being of the order of 5-8 m. However, a fourth storm produced no significant shoreline change, demonstrating that the threshold for morphological change is a function of the combined effects of still water level and wave height at the shore, the magnitude and duration of these components, and the timing of their interaction. Secondly, we consider recovery times in the system against periods of quiescence and heightened storm activity on this coast. Thirdly, it has been argued that future changes in extreme water level will be governed by mean sea level rise. Long-term rates of North Norfolk barrier retreat (1.15 m a-1, 1891-2013) have occurred under a regional rate of relative sea level rise over the 20th century of 2.7 ± 0.4 mm a-1 (Lowestoft tide gauge, 1900-2014). If there is a broad correlation between rates of barrier retreat and sea level rise, then recent increases in the rate of regional sea level rise (4.4 ± 1.1 mm a-1, 1993-2011) imply a considerable acceleration in the rate of barrier migration over the remainder of the 21st century.

  12. End of field life economics in the North Sea

    SciTech Connect

    Kellas, G.K.; Kemp, A.G.; Rose, D.

    1987-01-01

    With many North Sea oil fields now well into the decline phase of their production profiles, interest is now being shown in the management of a field in its latter years of production. The realization that reservoirs have a finite limit and that this limit is approaching prompts two questions: What determines how much of the remaining oil reserves can be produced and how can this be maximized while retaining economic efficiency. What determines when a field should be abandoned and what constraints are there on the decision to abandon. This paper attempts, firstly, to identify those variables that will determine the extent to which production should combine, and the effects of shifts in these variables on the remaining productive life of the field. Secondly, the manner in which the abandonment decision might be approached is discussed. The implications of changes in the variables described earlier for both the abandonment date, and any corresponding fiscal relief for abandonment costs, are highlighted.

  13. Investigating completion strategies; Cormorant Field, U. K. North Sea

    SciTech Connect

    Stiles, J.H. Jr. ); Valenti, N.P. )

    1990-03-01

    This paper describes studies that evaluate various completion strategies for new subsea wells in the Cormorant field, U.K. North Sea. These studies, which complement work done by the field operator, include detailed reservoir description work to define oil-in-place (OIP) and permeability distribution and a waterflood simulation for a representative reservoir cross section. Wellbore, flowline, and pipeline hydraulics for the complex production/injection system are included to model well rates more accurately. The results provide general insight into the nature of displacement during waterflooding of a stratified section with a limited number of wells. They also provide specific guidance on dual vs. single completions; perforating, testing, and stimulation sequence; and the benefits of partially perforating high-permeability sands.

  14. The 14 month wind stressed residual circulation (pole tide) in the North Sea

    NASA Technical Reports Server (NTRS)

    Oconnor, W. P.

    1986-01-01

    From published research it is known that a quasi-periodic 14 month atmospheric pressure oscillation of a few tenths of a millibar exists in the region of the North and Baltic Seas. At some time in the cycle the associated wind stress has a westerly component that drives a circulation in the North Sea. The results of a dynamical model and comparisons with several North Sea residual circulation studies show that a large sea level gradient results along the Dutch coast. It is this feature that has been referred to as the enhanced pole tide. The dynamical similarity of this pole tide in the North and Baltic Seas to the annual and seasonal wind forced circulations is considered. It is inferred that the large deviations of the pole tide from equilibrium at coastal stations are the result of this sea level set up forces by the 14 month wind stress cycle.

  15. Potential Impacts of Offshore Wind Farms on North Sea Stratification.

    PubMed

    Carpenter, Jeffrey R; Merckelbach, Lucas; Callies, Ulrich; Clark, Suzanna; Gaslikova, Lidia; Baschek, Burkard

    2016-01-01

    Advances in offshore wind farm (OWF) technology have recently led to their construction in coastal waters that are deep enough to be seasonally stratified. As tidal currents move past the OWF foundation structures they generate a turbulent wake that will contribute to a mixing of the stratified water column. In this study we show that the mixing generated in this way may have a significant impact on the large-scale stratification of the German Bight region of the North Sea. This region is chosen as the focus of this study since the planning of OWFs is particularly widespread. Using a combination of idealised modelling and in situ measurements, we provide order-of-magnitude estimates of two important time scales that are key to understanding the impacts of OWFs: (i) a mixing time scale, describing how long a complete mixing of the stratification takes, and (ii) an advective time scale, quantifying for how long a water parcel is expected to undergo enhanced wind farm mixing. The results are especially sensitive to both the drag coefficient and type of foundation structure, as well as the evolution of the pycnocline under enhanced mixing conditions-both of which are not well known. With these limitations in mind, the results show that OWFs could impact the large-scale stratification, but only when they occupy extensive shelf regions. They are expected to have very little impact on large-scale stratification at the current capacity in the North Sea, but the impact could be significant in future large-scale development scenarios.

  16. Hydroacoustic seafloor classification in the SE North Sea

    NASA Astrophysics Data System (ADS)

    Hass, H. C.; Bartholomä, A.; Bürk, D.; Holler, P.; Mielck, F.; Reimers, H.-C.

    2012-04-01

    Over the last years hydoacoustic investigations of the seafloor became a strong tool for habitat mapping. Directives of the European Union emphasize the need for reliable, high resolution and at the same time cost-effective methods to map the ecologic status of coastal marine areas which are highly dynamic and vulnerable to disturbances. Aside from the difficulties that arise from monitoring extended areas, standardized methods are still not existing. This results in habitat maps that cannot easily be brought together over larger areas. We present here initial results of the project WIMO ("Scientific concepts for monitoring the German Bight, SE North Sea") that aims at testing different hydroacoustic mapping tools in order to work out a standard routine for habitat mapping purposes. We studied five areas using an IMAGENEX YellowFin sidescan sonar, a BENTHOS 1624 sidescan sonar, a SONAVISION RoxAnn seafloor classification system among other seafloor classification systems, and a Kongsberg EM710 multibeam system. Sediment samples for groundtruthing were taken with a HELCOM grab sampler. The working areas are all in the coastal zone of the SE North Sea with water depth between 10 and 40 m. The parameters measured include depth and backscatter (multibeam), hardness and roughness (RoxAnn), seafloor sonographic imagery, and granulometry (grab samples). We present classification methods that implement selected parameters and all of the parameters, partly based on self-programmed routines. The results reveal that all methods are capable to gather information important for habitat assessment. However, the information provided by the different systems is not always the same and simply merging the data is no solution. We show different approaches to take advantage of the data and suggest combinations of instruments and parameters for efficient mapping standards.

  17. Potential Impacts of Offshore Wind Farms on North Sea Stratification.

    PubMed

    Carpenter, Jeffrey R; Merckelbach, Lucas; Callies, Ulrich; Clark, Suzanna; Gaslikova, Lidia; Baschek, Burkard

    2016-01-01

    Advances in offshore wind farm (OWF) technology have recently led to their construction in coastal waters that are deep enough to be seasonally stratified. As tidal currents move past the OWF foundation structures they generate a turbulent wake that will contribute to a mixing of the stratified water column. In this study we show that the mixing generated in this way may have a significant impact on the large-scale stratification of the German Bight region of the North Sea. This region is chosen as the focus of this study since the planning of OWFs is particularly widespread. Using a combination of idealised modelling and in situ measurements, we provide order-of-magnitude estimates of two important time scales that are key to understanding the impacts of OWFs: (i) a mixing time scale, describing how long a complete mixing of the stratification takes, and (ii) an advective time scale, quantifying for how long a water parcel is expected to undergo enhanced wind farm mixing. The results are especially sensitive to both the drag coefficient and type of foundation structure, as well as the evolution of the pycnocline under enhanced mixing conditions-both of which are not well known. With these limitations in mind, the results show that OWFs could impact the large-scale stratification, but only when they occupy extensive shelf regions. They are expected to have very little impact on large-scale stratification at the current capacity in the North Sea, but the impact could be significant in future large-scale development scenarios. PMID:27513754

  18. Holocene deposits in the Mangyshlak Peninsula, North Caspian Sea region

    NASA Astrophysics Data System (ADS)

    Bezrodnykh, Yu. P.; Deliya, S. V.; Romanyuk, B. F.; Fedorov, V. I.; Sorokin, V. M.; Luksha, V. L.

    2014-07-01

    Comprehensive analysis of the data of high-precision seismoacoustic profiling, drilling and sampling of deposits using seabed corers, biostratigraphic studies, and radiocarbon age data was performed for the first time for Mangyshlak sediments in several bottom sites of the North Caspian. It was found that the Mangyshlak sediments comprise numerous linearly stretched depressions of 5-10 m in depth (morphologically similar to modern substeppe ilmen areas in the Volga River delta), which are covered by the Novocaspian sedimentary cover, and river incisions (among them the largest Volga River valley). In addition, the Mangyshlak sediments comprise the deltaic alluvial fans of different sizes along the shelf zone of the North Caspian. Analysis of mollusks and biogenic remains indicates that accumulation of the Mangyshlak sediments occurred in freshwater and slightly salty water environments under various hydrodynamic and hydrochemical conditions. According to radiocarbon dating of organic matter, the Mangyshlak sediments formed during sea regression in the range of 10-8 ka (isotopic age) or 11.5-8.5 ka (calendar age). Several types of sediments are distinguished: clayey-carbonate sediments, enriched with organic matter up to the formation of sapropel and peat, accumulated at the lowest sea level; weakly calcareous silty-clayey silts, formed during the subsequent intense filling of paleodepressions with terrigenous material. The features of the mineral composition of sediments are as follows: polymineral composition of clayey material with a high proportion of hydromica and disordered mixed-layered formations, a high content of minerals of the epidote group, amphiboles, and other accessory minerals. All of this indicates a genetic relationship between the Mangyshlak sediments and the Volga terrigenous material.

  19. Diet overlap among flatfish species in the southern North Sea.

    PubMed

    Schückel, S; Sell, A F; Kröncke, I; Reiss, H

    2012-06-01

    The diets of two non-commercial flatfish species (solenette Buglossidium luteum and scaldfish Arnoglossus laterna) and two commercial flatfish species (dab Limanda limanda and plaice Pleuronectes platessa) were compared in a study area in the German Bight (southern North Sea) to investigate prey-resource partitioning between these species. The diets of A. laterna and B. luteum mainly comprised crustaceans (harpacticoids, amphipods, cumaceans and decapods), whereas the diet of L. limanda and P. platessa consisted mainly of polychaetes. The Schoener index, calculated for different fish size classes between these flatfish species, showed a biologically significant diet overlap between small-sized L. limanda and P. platessa and B. luteum and A. laterna, using similar prey resources of smaller prey (e.g. amphipods, harpacticoids and juvenile bivalves). In contrast, with increasing body size, a change in the diet of L. limanda and P. platessa towards larger prey occurred (e.g. polychaetes and decapods), resulting in low diet overlap values with B. luteum and A. laterna. Due to these size-related differences in resource use, it is assumed that there is reduced interspecific competition for prey between larger L. limanda and P. platessa and both non-commercial flatfishes, probably facilitating resource partitioning within the same area. In contrast, smaller L. limanda and P. platessa may compete directly for the same prey resources with B. luteum and A. laterna. Furthermore, prey availability of most important prey items of the studied flatfishes was relatively low in the study area. Therefore, increasing abundances of B. luteum and A. laterna in the southern North Sea since the late 1980s, owing to fishing effects and climate change, might affect the population dynamics of L. limanda and P. platessa.

  20. Potential Impacts of Offshore Wind Farms on North Sea Stratification

    PubMed Central

    Carpenter, Jeffrey R.; Merckelbach, Lucas; Callies, Ulrich; Clark, Suzanna; Gaslikova, Lidia; Baschek, Burkard

    2016-01-01

    Advances in offshore wind farm (OWF) technology have recently led to their construction in coastal waters that are deep enough to be seasonally stratified. As tidal currents move past the OWF foundation structures they generate a turbulent wake that will contribute to a mixing of the stratified water column. In this study we show that the mixing generated in this way may have a significant impact on the large-scale stratification of the German Bight region of the North Sea. This region is chosen as the focus of this study since the planning of OWFs is particularly widespread. Using a combination of idealised modelling and in situ measurements, we provide order-of-magnitude estimates of two important time scales that are key to understanding the impacts of OWFs: (i) a mixing time scale, describing how long a complete mixing of the stratification takes, and (ii) an advective time scale, quantifying for how long a water parcel is expected to undergo enhanced wind farm mixing. The results are especially sensitive to both the drag coefficient and type of foundation structure, as well as the evolution of the pycnocline under enhanced mixing conditions—both of which are not well known. With these limitations in mind, the results show that OWFs could impact the large-scale stratification, but only when they occupy extensive shelf regions. They are expected to have very little impact on large-scale stratification at the current capacity in the North Sea, but the impact could be significant in future large-scale development scenarios. PMID:27513754

  1. A North Sea template well tieback system: design and operational experience

    SciTech Connect

    Ingram, G.W.; Humphrey, B.

    1983-09-01

    The North West Hutton field is located in Block 211/27 of the UK sector of the North Sea. It is 80 miles north east of the Shetland Islands, in 473' of water. The field was discovered in 1974. Amoco (U.K.) Exploration Company is operator on behalf of British Gas North Sea Oil Holdings Limited, Amerada Petroleum Corporation of the United Kingdom Limited, Texas Eastern North Sea Inc. and Mobil North Sea Oil Limited. Attention to accuracy and alignment in drilling the wells and in fabricating and installing the template and jacket can ensure that the tieback operation is relatively straightforward. Wellhead survey tools extending from the platform through the wave zone are adversely affected by wave action. Wellhead surveys would be more conveniently and accurately performed using tools carried to the wellhead and manipulated by diver or RCV.

  2. General circulation model simulations of winter and summer sea-level pressures over North America

    USGS Publications Warehouse

    McCabe, G.J.; Legates, D.R.

    1992-01-01

    In this paper, observed sea-level pressures were used to evaluate winter and summer sea-level pressures over North America simulated by the Goddard Institute for Space Studies (GISS) and the Geophysical Fluid Dynamics Laboratory (GFDL) general circulation models. The objective of the study is to determine how similar the spatial and temporal distributions of GCM-simulated daily sea-level pressures over North America are to observed distributions. Overall, both models are better at reproducing observed within-season variance of winter and summer sea-level pressures than they are at simulating the magnitude of mean winter and summer sea-level pressures. -from Authors

  3. Delineating recurrent fish spawning habitats in the North Sea

    NASA Astrophysics Data System (ADS)

    Lelièvre, S.; Vaz, S.; Martin, C. S.; Loots, C.

    2014-08-01

    The functional value of spawning habitats makes them critically important for the completion of fish life cycles and spawning grounds are now considered to be “essential habitats”. Inter-annual fluctuations in spawning ground distributions of dab (Limanda Limanda), plaice (Pleuronectes platessa), cod (Gadus morhua) and whiting (Merlangius merlangus) were investigated in the southern North Sea and eastern English Channel, from 2006 to 2009. The preferential spawning habitats of these species were modelled using generalised linear models, with egg distribution being used as proxy of spawners' location. Egg spatial and temporal distributions were explored based on six environmental variables: sea surface temperature and salinity, chlorophyll a concentration, depth, bedstress and seabed sediment types. In most cases, egg density was found to be strongly related to these environmental variables. Egg densities were positively correlated with shallow to intermediate depths having low temperature and relatively high salinity. Habitat models were used to map annual, i.e. 2006 to 2009, winter spatial distributions of eggs, for each species separately. Then, annual maps were combined to explore the spatial variability of each species' spawning grounds, and define recurrent, occasional, rare and unfavourable spawning areas. The recurrent spawning grounds of all four species were located in the south-eastern part of the study area, mainly along the Dutch and German coasts. This study contributes knowledge necessary to the spatial management of fishery resources in the area, and may also be used to identify marine areas with particular habitat features that need to be preserved.

  4. Influence of the arrival of radioactive industrially contaminated North Sea water upon the radiation conditions in the Baltic Sea

    SciTech Connect

    Vakulovskii, S.M.; Nikitin, A.I.; Chumichev, V.B.

    1987-08-01

    The authors present and evaluate data from a four-year period of monitoring the movement of radioactive effluents from the radiochemical plants of Western Europe from the North Sea to the Baltic Sea and determine the concentrations at various regions along this pathway for cesium 134 and 137 and strontium 90 isotopes.

  5. Neustonic microplastic and zooplankton in the North Western Mediterranean Sea.

    PubMed

    Collignon, Amandine; Hecq, Jean-Henri; Glagani, François; Voisin, Pierre; Collard, France; Goffart, Anne

    2012-04-01

    Neustonic microplastic and zooplankton abundance was determined in the North Western Mediterranean Sea during a summer cruise between July 9th and August 6th 2010, with a break between July 22 th and 25th due to a strong wind event. Ninety percent of the 40 stations contained microplastic particles (size 0.3-5mm) of various compositions: e.g., filaments, polystyrene, thin plastic films. An average concentration of 0.116 particles/m(2) was observed. The highest abundances (>0.36 particles/m(2)) were observed in shelf stations. The neustonic plastic particles concentrations were 5 times higher before than after the strong wind event which increased the mixing and the vertical repartition of plastic particles in the upper layers of the water column. The values rise in the same order of magnitude than in the North Pacific Gyre. The average ratio between microplastics and mesozooplankton weights was 0.5 for the whole survey and might induce a potential confusion for zooplankton feeders.

  6. CO2 miscible displacement enhanced oil recovery in Dutch North Sea

    SciTech Connect

    Alkemade, P.J.C.

    1995-12-31

    In the Dutch sector of the North Sea several relatively small oil deposits are present. Their locations are spread and only few oil fields are being produced. An attempt is made to investigate the feasibility of EOR application i.e. CO2 miscible displacement by a commonly available pressurized CO2 supply system. This feasibility study is based on an utilizes as much as possible past and present data bout existing oil fields, CO2 availability, compression and distribution pipelines to be installed and injection methods at existing production facilities.

  7. Changes in size and trends of North American sea duck populations associated with North Pacific oceanic regime shifts

    USGS Publications Warehouse

    Flint, Paul L.

    2013-01-01

    Broad-scale multi-species declines in populations of North American sea ducks for unknown reasons is cause for management concern. Oceanic regime shifts have been associated with rapid changes in ecosystem structure of the North Pacific and Bering Sea. However, relatively little is known about potential effects of these changes in oceanic conditions on marine bird populations at broad scales. I examined changes in North American breeding populations of sea ducks from 1957 to 2011 in relation to potential oceanic regime shifts in the North Pacific in 1977, 1989, and 1998. There was strong support for population-level effects of regime shifts in 1977 and 1989, but little support for an effect of the 1998 shift. The continental-level effects of these regime shifts differed across species groups and time. Based on patterns of sea duck population dynamics associated with regime shifts, it is unclear if the mechanism of change relates to survival or reproduction. Results of this analysis support the hypothesis that population size and trends of North American sea ducks are strongly influenced by oceanic conditions. The perceived population declines appear to have halted >20 years ago, and populations have been relatively stable or increasing since that time. Given these results, we should reasonably expect dramatic changes in sea duck population status and trends with future oceanic regime shifts.

  8. From the European slope to the North Sea

    NASA Astrophysics Data System (ADS)

    Dale, Andy; Porter, Marie

    2015-04-01

    The European slope current is a density driven poleward current tracing the shelf edge from the Bay of Biscay into the Nordic Seas. This current is not entirely coherent along its length and is known to be disrupted by the wind, bathymetric irregularities and local circulation, potentially providing a source of relatively warm and nutrient rich water to the local shelf. On the Malin Shelf, to the north of Ireland and the west of Scotland, persistent intrusions of oceanic water occur onto the shelf near a bend in the slope. Additional pathways onto the shelf result from strong wind events, which cause ingress of slope water at multiple locations, while eddies in the Rockall Trough are known to pull water off the slope into deeper, abyssal regions. In July 2013, 30 surface drifters, 15 drogued at 15 m and 15 at 70 m, were deployed on the Malin Shelf slope. Of these drifters, all of those drogued at 15 m and 10 of those drogued at 70 m moved north-eastward from their release onto the shelf. The majority crossed onto the shelf within a relatively small area, within a 30km radius of 55.5°N, 10°W, and continued as a coherent group along the edge of the Irish coastal front for approximately 38 days. This current, estimated to transport approximately 0.5 Sv of water towards the Scottish coast, follows the Irish Coastal front and then the Islay front until it bifurcates around the Outer Hebrides, with half of the drifters passing inside, to the east through the Minch, and half passing outside, to the west. The control over the path taken is likely to have been the position and strength of the Islay Front. The tendency for the shallow drifters to cross onto the shelf more readily than the deeper ones suggests that the ingress onto the shelf varies with depth and is strongest at the surface. The deeper drifters generally spent longer in the slope region and were frequently pulled into the Rockall Trough. The drifter trajectories highlight a pathway for surface water (15 m

  9. What Causes the North Sea Level to Rise Faster over the Last Decade ?

    NASA Astrophysics Data System (ADS)

    Karpytchev, Mikhail; Letetrel, Camille

    2013-04-01

    We combined tide gauge records (PSMSL) and satellite altimetry data (TOPEX/POSEIDON-JASON 1-2) to reconstruct the mean level of the North Sea and the Norwegian Sea Shelf (NS-NSS) over 1950-2012. The reconstructed NS-NSS mean sea level fluctuations reveal a pronounced interannual variability and a strong sea level acceleration since the mid-1990's. In order to understand the causes of this acceleration, the NS-NSS mean sea level was cross-correlated with the North Atlantic Oscillation and Arctic Oscillation indices. While the interannual variability of the mean sea level correlates well with the NAO/AO indices, the observed acceleration in the NS-NSS mean level is not linked linearly to the NAO/AO fluctuations. On the other hand, the Empirical Orthogonal Functions (EOF) analysis of steric sea level variations in the eastern North Atlantic gives a dominant EOF pattern (55% of variance explained) that varies on a decadal scale very closely to the NS-NSS mean level flcutuations. Also, the amplification in the temporal amplitude of the dominant steric sea level EOF corresponds to the acceleration observed in the NS-NSS mean sea level signal. This suggests that decadal variations in the mean level of the North Sea - the Norwegian Sea Shelf reflect changes in the Subpolar Front currents (Rossby, 1996).

  10. NOx Emissions from Oil and Gas Production in the North Sea

    NASA Astrophysics Data System (ADS)

    Lee, J. D.; Foulds, A.; Purvis, R.; Vaughan, A. R.; Carslaw, D.; Lewis, A. C.

    2015-12-01

    North Sea oil is a mixture of hydrocarbons, comprising liquid petroleum and natural gas, produced from petroleum reservoirs beneath the North Sea. As of January 2015, the North Sea is the world's most active offshore drilling region with 173 rigs drilling. During the summer of 2015, a series of survey flights took place on the UKs FAAM BAe 146 research aircraft with the primary aim to assess background methane (and other hydrocarbons) levels in the drilling areas of the North Sea. Also measured were Nitrogen Oxides (NO and NO2), which are emitted from almost all combustion processes and are a key air pollutant, both directly and as a precursor to ozone (O3). The oil and gas platforms in the North Sea are often manned and require significant power generation and support vessels for their continued operation, processes that potentially emit significant amounts of NOx into an otherwise relative clean environment. During these flights we were able to measure the NO­­­x (and any subsequently produced O3) emitted from specific rigs, as well as the NOx levels in the wider North Sea oil and gas production region (see figure for example). NOx mixing ratios of <10 ppbv were frequently observed in plumes, with significant perturbation to the wider North Sea background levels. NOx emissions from the rigs are point sources within the UKs National Atmospheric Emission Inventory (NAEI) and the measurements taken in plumes from individual rigs are used to assess the accuracy of these estimates.

  11. A probabilistic storm surge risk model for the German North Sea and Baltic Sea coast

    NASA Astrophysics Data System (ADS)

    Grabbert, Jan-Henrik; Reiner, Andreas; Deepen, Jan; Rodda, Harvey; Mai, Stephan; Pfeifer, Dietmar

    2010-05-01

    The German North Sea coast is highly exposed to storm surges. Due to its concave bay-like shape mainly orientated to the North-West, cyclones from Western, North-Western and Northern directions together with astronomical tide cause storm surges accumulating the water in the German bight. Due to the existence of widespread low-lying areas (below 5m above mean sea level) behind the defenses, large areas including large economic values are exposed to coastal flooding including cities like Hamburg or Bremen. The occurrence of extreme storm surges in the past like e.g. in 1962 taking about 300 lives and causing widespread flooding and 1976 raised the awareness and led to a redesign of the coastal defenses which provide a good level of protection for today's conditions. Never the less the risk of flooding exists. Moreover an amplification of storm surge risk can be expected under the influence of climate change. The Baltic Sea coast is also exposed to storm surges, which are caused by other meteorological patterns. The influence of the astronomical tide is quite low instead high water levels are induced by strong winds only. Since the exceptional extreme event in 1872 storm surge hazard has been more or less forgotten. Although such an event is very unlikely to happen, it is not impossible. Storm surge risk is currently (almost) non-insurable in Germany. The potential risk is difficult to quantify as there are almost no historical losses available. Also premiums are difficult to assess. Therefore a new storm surge risk model is being developed to provide a basis for a probabilistic quantification of potential losses from coastal inundation. The model is funded by the GDV (German Insurance Association) and is planned to be used within the German insurance sector. Results might be used for a discussion of insurance cover for storm surge. The model consists of a probabilistic event driven hazard and a vulnerability module, furthermore an exposure interface and a financial

  12. Dynamical downscaling of warming scenarios with NEMO-Nordic setup for the North Sea and Baltic Sea

    NASA Astrophysics Data System (ADS)

    Gröger, Matthias; Almroth Rosell, Elin; Anderson, Helén; Axell, Lars; Dieterich, Christain; Edman, Moa; Eilola, Kari; Höglund, Anders; Hordoir, Robinson; Hieronymus, Jenny; Karlsson, Bengt; Liu, Ye; Meier, Markus; Pemberton, Per; Saraiva, Sofia

    2016-04-01

    The North Sea and Baltic Sea constitute one of the most complex and challenging areas in the world. The oceanographic setting ranges from quasi open ocean conditions in the northern North Sea to more brackish conditions in the Baltic Sea which is also affected by sea ice in winter. The two seas are connected by narrow straits which sporadically allow the important inflow of salt and oxygen rich bottom waters into the Baltic Sea. For this, the high resolution regional model NEMO-Nordic has recently been developed. Here, the model is applied on hindcast simulations and used to downscale several climate warming scenarios. The model can be interactively coupled to the regional atmosphere model RCA4 by exchanging air sea fluxes of mass and energy (Wang et al., 2015). Comparison with well established models and newly compiled observational data sets (Bersch et al., 2013) indicates NEMO-Nordic performs well on climate relevant time scales. Emphasis is laid on thermal dynamics. Hindcast simulations demonstrate that simulated winter temperatures in the Baltic Sea can benefit from interactive air sea coupling by allowing interactive feedback loops to take place between the ocean and the atmosphere (Gröger et al. 2015). Likewise, a more realistic dynamical behaviour makes the interactive coupled model suitable for dynamic downscaling of climate warming scenarios. Depending on the driving global climate model and IPCC representative concentration pathway scenario NEMO-Nordic shows an average warming of the North Sea between 2 and 4 K at the end of the 21st century. However the warming pattern is spatially inhomogeneous showing strong east west gradients. Involved processes such as circulation changes and changes in radiative forcing will be discussed. Bersch, M., Gouretski, V., Sadikni, R., Hinrichs, I., 2013. Hydrographic climatology of the North Sea and surrounding regions. Centre for Earth System Research and Sustainability, University of Hamburg, www

  13. Modelling transport and reproduction of the invasive comb jelly Mnemiopsis leidyi in the North Sea

    NASA Astrophysics Data System (ADS)

    van der Molen, Johan

    2014-05-01

    Mnemiopsis leidyi is an invasive comb jelly fish species that originates from the Gulf of Mexico and the US east coast. It has high bloom potential, and can survive in a wide variety of environmental conditions. It was first introduced in Europe through ballast water discharges in the Black Sea, where it was associated with the anchovis stock collapse in the 1990's. From there, it has spread through the Mediterranean Sea. Since the mid 2000's it has been observed in ports and estuaries along the English Channel, the North Sea and the Baltic Sea. In the North Sea, M. leidyi blooms occur in the Scheldt estuaries, the Wadden Sea, and in ports and canals. In winter, M. Leidyi has been observed at sea in the German Bight. A particle tracking model was modified to include a simple reproduction mechanism, using food fields from the coupled hydrodynamics-ecosystem model GETM-ERSEM. The model was used to study the potential spreading and bloom potential of M. Leidyi in the southern North Sea under present and increased temperature conditions. Under present conditions, the model suggested that M. Leidyi can survive in the North Sea, and can be transported over distances of several hundreds of km, enabling connectivity between estuarine populations. It could not, however, bloom at open sea because of temperature constraints. These constraints were lifted for increased temperature scenarios, suggesting increased bloom potential under climate change conditions.

  14. Regional carbon and CO2 budgets of North Sea tidal estuaries

    NASA Astrophysics Data System (ADS)

    Volta, C.; Laruelle, G. G.; Regnier, P.

    2016-07-01

    This study presents the first regional application of the generic estuarine reactive-transport model C-GEM (Carbon-Generic Estuary Model) that is here combined with high-resolution databases to produce a carbon and CO2 budget for all tidal estuaries discharging into the North Sea. Steady-state simulations are performed for yearly-averaged conditions to quantify the carbon processing in the six main tidal estuaries Elbe, Ems, Humber, Scheldt, Thames, and Weser, which show contrasted physical and biogeochemical dynamics and contribute the most to the regional filter. The processing rates derived from these simulations are then extrapolated to the riverine carbon loads of all the other North Sea catchments intercepted by smaller tidal estuarine systems. The Rhine-Meuse estuarine system is also included in the carbon budget and overall, we calculate that the export of organic and inorganic carbon from tidal estuaries to the North sea amounts to 44 and 409 Gmol C yr-1, respectively, while 41 Gmol C are lost annually through CO2 outgassing. The carbon is mostly exported from the estuaries in its inorganic form (>90%), a result that reflects the low organic/inorganic carbon ratio of the riverine waters, as well as the very intense decomposition of organic carbon within the estuarine systems. Our calculations also reveal that with a filtering capacity of 15% for total carbon, the contribution of estuaries to the CO2 outgassing is relatively small. Organic carbon dynamics is dominated by heterotrophic degradation, which also represents the most important contribution to the estuarine CO2 evasion. Nitrification only plays a marginal role in the CO2 dynamics, while the contribution of riverine oversaturated waters to the CO2 outgassing is generally significant and strongly varies across systems.

  15. North Sea gas plants get process, scheduling tools

    SciTech Connect

    Mortimer, A.

    1998-11-16

    Mobil North Sea Ltd. has installed an operator guidance tool at its SAGE gas-processing plant at St. Fergus, Scotland (SAGE: Scottish Area Gas Evacuation). The system, supplied by MDC Technology, Teesside, U.K., will aid process decision making at the plant under MDC Technology`s RTO+ software. In addition, Shell U.K. Exploration and Production (Shell Expro) has installed a pipeline-scheduling system, also supplied by MDC Technology, at its Aberdeen control center. The system aids gas-movement scheduling through Shell Expro`s St. Fergus gas plant. The Northern Systems and Plant Scheduling (NSPS) system integrates MDC Technology`s RTO+ package with Microsoft Visual Basic and Excel. Mobil`s SAGE gas terminal at St. Fergus has two identical process trains (NGL recovery and acid-gas treatment), each with a capacity of 16.25 million std. cu m/day. The paper describes the guidance tool, the scheduling aid, and the installation of the NSPS.

  16. Thermocline bulk shear analysis in the northern North Sea

    NASA Astrophysics Data System (ADS)

    Chen, Shengli; Polton, Jeff A.; Hu, Jianyu; Xing, Jiuxing

    2016-04-01

    Thermocline bulk shear is investigated in the northern North Sea using historical observations. The conventional bulk shear is modified to define a thermocline bulk shear (TBS), in order to better represent the shear across the thermocline. The TBS computed by observed currents is decomposed into components at different frequency bands. The near-inertial TBS is the largest component. Its dominance is significant during the period of high wind. It is formed by the wind-driven near-inertial current which has a distinct phase shift (˜180°) across the thermocline. A linear model is presented, which well simulates the observed near-inertial TBS, especially during the period of relatively strong wind. The semidiurnal TBS makes a secondary contribution to the total TBS. It is only slightly smaller than the near-inertial TBS when the wind is relatively weak. The large values of semidiurnal TBS are associated with semidiurnal currents which have a phase shift (˜30-40°) or a magnitude difference (˜5 cm/s) across the thermocline. The low-frequency (<0.7 cpd) TBS also makes an episodic contribution to the total. Its variation coincides with the Ekman transport during the period of relatively strong wind. The low-frequency TBS is mainly formed by an Ekman-like clockwise spiraling of velocity with depth or a distinct magnitude difference in velocities between upper and lower layers.

  17. Cationic polymer mud solves gumbo problems in North Sea

    SciTech Connect

    Welch, O.; Lee, L.J. )

    1992-07-13

    This paper reports on a recently developed cationic polymer mud, compatible with conventional polymer additives and designed to meet environmental regulations, which significantly minimized the gumbo problems common to the water-sensitive shales in the North Sea. The cationic polymer mud was used to drill highly reactive Tertiary shale formations which have caused severe gumbo problems on nearby wells drilled with other inhibitive water-based muds. Although many citonic polymers are toxic, aquatic toxicity tests performed by the Norwegian Statens Forurensningstilsyn (SFT) at the end of the test wells showed results far exceeding the SFT limits on the three species tested. The mud system on these wells was a seawater-based 15.0-ppg mud enhanced with 3% NaCl. A low molecular weight quaternary polyamine and a high molecular weight cationic polyacrylamide were used to suppress the swelling and dispersion of shales, respectively. Starch and polyanionic cellulose (PAC) polymers maintained fluid-loss control, and a lubricant reduced the torque and drag.

  18. Target-oriented Marchenko imaging of a North Sea field

    NASA Astrophysics Data System (ADS)

    Ravasi, Matteo; Vasconcelos, Ivan; Kritski, Alexander; Curtis, Andrew; Filho, Carlos Alberto da Costa; Meles, Giovanni Angelo

    2016-04-01

    Seismic imaging provides much of our information about the Earth's crustal structure. The principal source of imaging errors derives from simplicistically modeled predictions of the complex, scattered wavefields that interact with each subsurface point to be imaged. A new method of wavefield extrapolation based on inverse scattering theory produces accurate estimates of these subsurface scattered wavefields, while still using relatively little information about the Earth's properties. We use it for the first time to create real target-oriented seismic images of a North Sea field. We synthesize underside illumination from surface reflection data, and use it to reveal subsurface features that are not present in an image from conventional migration of surface data. To reconstruct underside reflections, we rely on the so-called downgoing focusing function, whose coda consists entirely of transmission-born multiple scattering. As such, we provide the first field data example of reconstructing underside reflections with contributions from transmitted multiples, without the need to first locate or image any reflectors in order to reconstruct multiple scattering effects.

  19. [Vegetation landscape health assessment in Changshan Archipelago, North Yellow Sea].

    PubMed

    Suo, An-ning; Sun, Yong-guang; Li, Bin-yong; Lin, Yong; Zhang, Yong-hua

    2015-04-01

    Island vegetation is an important component of island ecosystem. Multi-targets of island ecosystem health integrated with landscape ecology theory were employed to construct the index system for island vegetation health assessment in terms of landscape vigor, landscape stressing intensity and landscape stability. The Changshan Archipelago in the North Yellow Sea was chosen as a case to apply the island vegetation health assessment index system. The results showed that the overall vegetation health status in Changshan Archipelago was good and had a big island variation. The vegetation health index for Haiyang Island and Zhangzi Island was above 0.80, belonging to first eco-health level area, whereas that for Dachangshan Island, Xiaochangshan Island and Dawangjia Island ranged from 0.70 to 0.80, which could be categorized as the second eco-health level area. Guanglu Island and Shichen Island could be termed as the third eco-health level area with the vegetation health index below 0.70. The distance of island to mainland, area of island together with industrial structure were the main driving forces for the variation of vegetation landscape heath between different islands.

  20. Visions for the North Sea: the societal dilemma behind specifying good environmental status.

    PubMed

    Gilbert, Alison J; McQuatters-Gollop, Abigail; Langmead, Olivia; Mee, Laurence; Vermaat, Jan

    2015-03-01

    We augment discussions about the Good Environmental Status of the North Sea by developing two extreme visions and assessing their societal benefits. One vision ('Then') assumes restoration of benthic functioning; we contend that trawling had already degraded the southern North Sea a century ago. Available information is used to speculate about benthic functioning in a relatively undisturbed southern North Sea. The second vision ('Now') draws on recent benthic functioning. The supply of five ecosystem services, supported by benthic functioning, is discussed. 'Then' offers confidence in the sustainable supply of diverse services but restoration of past function is uncertain and likely to be paired with costs, notably trawling restraints. 'Now' delivers known and valued services but sustained delivery is threatened by, for example, climate change. We do not advocate either vision. Our purpose is to stimulate debate about what society wants, and might receive, from the future southern North Sea. PMID:24859919

  1. Field verification of Wave Equation tidal dynamics in the English Channel and southern North Sea

    NASA Astrophysics Data System (ADS)

    Werner, Francisco E.; Lynch, Daniel R.

    Finite element results obtained with the implicit Wave Equation algorithm are compared with field data in a blind (uncalibrated) verification exercise. The study area comprises the English Channel and the southern North Sea.

  2. The influence of riverine nitrogen on the dynamics of the North Sea oxygen minimum zone

    NASA Astrophysics Data System (ADS)

    Große, Fabian; Kreus, Markus; Lenhart, Hermann; Pätsch, Johannes

    2016-04-01

    The mitigation of eutrophication and its concomitants, like oxygen deficiency in bottom waters, is one of the major aspects of the ecological management of coastal marine ecosystems. In the past, biogeochemical models helped to significantly improve the understanding of the interaction of the physical and biological processes driving eutrophication. Anthropogenic river input of nitrogen (N) and phosphorus (P) is the main driver for eutrophication. Nevertheless, the quantification of their influence in a specific region remains an important issue, since it is as crucial for an efficient management as it is difficult to obtain. During the past decade, a quantitative method applicable to biogeochemical models - often referred to as `trans-boundary nutrient transports' (TBNT) - became more and more popular in the context of marine ecosystem management. This method allows for the tracing of elements from various sources, e.g., nitrogen (N) from different rivers, throughout the whole process chain of the applied model. By this, it provides valuable information about the contributions from different sources to the overall amount and turnover of an element in different areas of the model domain. This information constitutes the basis for the quantification, evaluation and optimisation of river input reduction targets for the tributaries, which are defined in relation to their ecological consequences in the marine environment. In existing studies, the TBNT method has been applied to a variety of biogeochemical models, e.g. to quantify the atmospheric contribution to total N in the North Sea (Troost et al., 2013). This study presents a novel approach to link the TBNT method applied to N to the biological processes driving the oxygen dynamics in the bottom layer of the North Sea. For this purpose, simulations from the biogeochemical model ECOHAM (ECOlogical model HAMburg) are analysed for the years 2002 and 2010, with the focus on the southern central North Sea, the region of

  3. The Norwegian Danish Basin: A key to understanding the Cenozoic in the eastern North Sea

    NASA Astrophysics Data System (ADS)

    Rasmussen, Thomas L.; Clausen, Ole R.; Andresen, Katrine J.; Goledowski, Bartosz

    2015-04-01

    -level changes and sourced from the Scandinavian hinterland. 3D-Wheeler diagrams have been used for recognizing spatial elements with periods of deposition and non-deposition. Overall, this study thus contributes significantly to a better understanding of the Cenozoic evolution, the position of potential reservoirs and the debate of climate versus tectonics. References: Michelsen, O., M. Danielsen, C. Heilmann-Clausen, H. Jordt, G. V. Laursen and E. Thomsen, Eds. (1995). Occurrence of major sequence stratigraphic boundaries in relation to basin development in Cenozoic deposits of the southeastern North Sea. Sequence Stratigraphy: Advances and Applications for Exploration and Producing in North West Europe vol 5. Amsterdam, Elsevier. Michelsen, O., E. Thomsen, M. Danielsen, C. Heilmann-Clausen, H. Jordt and G. V. Laursen (1998). Cenozoic sequence stratigraphy in the eastern North Sea. Mesozoic-Cenozoic Sequence Stratigraphy of Western European Basins. P. C. de Graciansky, T. Jacquin and P. R. Vail, Society of Economic Palaeontolgists and Mineralogists Special Publication 60. 60: 91-118.

  4. Plastic ingestion by pelagic and demersal fish from the North Sea and Baltic Sea.

    PubMed

    Rummel, Christoph D; Löder, Martin G J; Fricke, Nicolai F; Lang, Thomas; Griebeler, Eva-Maria; Janke, Michael; Gerdts, Gunnar

    2016-01-15

    Plastic ingestion by marine biota has been reported for a variety of different taxa. In this study, we investigated 290 gastrointestinal tracts of demersal (cod, dab and flounder) and pelagic fish species (herring and mackerel) from the North and Baltic Sea for the occurrence of plastic ingestion. In 5.5% of all investigated fishes, plastic particles were detected, with 74% of all particles being in the microplastic (<5mm) size range. The polymer types of all found particles were analysed by means of Fourier transform infrared (FT-IR) spectroscopy. Almost 40% of the particles consisted of polyethylene (PE). In 3.4% of the demersal and 10.7% of the pelagic individuals, plastic ingestion was recorded, showing a significantly higher ingestion frequency in the pelagic feeders. The condition factor K was calculated to test differences in the fitness status between individuals with and without ingested plastic, but no direct effect was detected.

  5. The role of open ocean boundary forcing on potential warming in the North and Baltic Seas

    NASA Astrophysics Data System (ADS)

    Tian, Tian; Su, Jian; Boberg, Fredrik; Yang, Shuting

    2013-04-01

    To study uncertainty in the regional model of using temperature boundary conditions from the ocean models covering larger areas at reduced resolution, like GCMs, the EC-Earth CMIP5 Experiments are used to provide lateral boundary forcing for the regional atmospheric model (HIRHAM) and the regional ocean model (HBM) in the North and Baltic Seas. HIRHAM has been extensively used over the European region to downscale variability and climate change signals from the global model, for instance during the PRUDENCE project. The downscaling simulation started from January 1, 1960 and was implemented for the historical period of 1960 to 2009 and for the continuing future period of 2010 to 2100 for the two scenarios RCP8.5 and RCP4.5. The effects of using different prescribed temperature boundary conditions in the northern North Sea and the English Channel borders on potential warming in the North and Baltic Seas are investigated. The lateral transport of heat and the details of density structure of the boundary conditions have relatively large impact in the deeper oceanic regions in the northern North Sea, but little in the southern North Sea. The effect in the Baltic Sea and the transition area between the two regional seas is negligible.

  6. Artificial radionuclides in the surface waters of the Baltic Sea and the North Sea in the fall of 1984

    SciTech Connect

    Kadzhene, G.I.; Kleiza, I.V.; Korotkov, V.P.; Lukinskene, M.V.; Mironov, V.K.; Styro, D.B.

    1987-10-01

    The authors compare data from the literature with data taken in the fall of 1984 on the concentrations of cesium 137, strontium 90, cesium 144, and tritium in the waters of the Baltic and North seas. Sampling was conducted along the coastal regions as well as offshore and the consequent concentration and distribution profiles are mapped. They attempt to assess the weight of meteorological and water current as well as seasonal factors on the determined levels and also point to possible sources of the isotopes, including nuclear power plants situated along Baltic and North Sea shorelines and an atmospheric test of a thermonuclear bomb carried out by China.

  7. North Atlantic teleconnection patterns signature on sea level from satellite altimetry

    NASA Astrophysics Data System (ADS)

    Iglesias, Isabel; Lázaro, Clara; Joana Fernandes, M.; Bastos, Luísa

    2015-04-01

    Porto (Fernandes et al., 2010; Fernandes et al., 2013). Regular 0.25°x0.25° latitude-longitude grids were generated at a 10-day interval for the NA Ocean (60°W-5°W, 5°N-60°N) using optimal interpolation with a realistic space-time correlation function (Lázaro et al., 2013). These grids are used to inspect the response of sea level anomalies to several teleconnection patterns as well as the NA variability on annual and longer timescales. The teleconnection patterns selected are the ones that have influence on the NA basin: North Atlantic Oscillation, East Atlantic pattern, East Atlantic/Western Russia pattern, Scandinavia pattern, Western Mediterranean Oscillation index, El Niño Southern Oscillation, Tropical North Atlantic Index, and Atlantic Multidecadal Oscillation. Acknowledgments: RAIA tec (0688-RAIATEC-1-P) project. The RAIA Coastal Observatory has been funded by the Programa Operativo de Cooperación Transfronteriza España-Portugal (POCTEP 2007-2013). References: Fernandes M.J., C. Lázaro, A.L. Nunes, N. Pires, L. Bastos, V.B. Mendes (2010). GNSS-derived Path Delay: an approach to compute the wet tropospheric correction for coastal altimetry. IEEE Geosci. Rem. Sens Lett., Vol. 7, NO. 3, 596 - 600, doi: 10.1109/LGRS.2010.2042425. Lázaro, C., M. J. Juliano, M. J. Fernandes (2013): Semi-automatic determination of the Azores Current axis using satellite altimetry: application to the study of the current variability during 1995-2006. Advances in Space Research, Vol. 51(11), pp. 2155-2170, doi:10.1016/j.asr.2012.12.021. Fernandes, M. J., A.L. Nunes, C. Lázaro (2013). Analysis and Inter-Calibration of Wet Path Delay Datasets to Compute the Wet Tropospheric Correction for CryoSat-2 over Ocean. Remote Sensing, 5, 4977-5005.

  8. Processes relevant for decadal changes in primary production of the North Sea and Baltic Sea: hindcast and scenario modelling

    NASA Astrophysics Data System (ADS)

    Daewel, Ute; Schrum, Corinna; Pushpadas, Dhanya

    2016-04-01

    Despite their geographical vicinity, the North Sea and the Baltic Sea ecosystems exhibit very different characteristics in both physical and biological parameters. Nonetheless, since both ecosystems are characterized by the same general functional groups in phytoplankton and zooplankton and, their geographical distribution indicates comparable thermal adaptation of the plankton groups, we propose that the same ecosystem parameterization can be utilized to simulate the dynamics in both ecosystems simultaneously. Here we present results from an updated version of the 3d coupled ecosystem model ECOSMO valid for both areas. The model allows both multi-decadal hind cast simulation of primary production and specific process studies under controlled environmental conditions. Our results from a long-term hind-cast (1948-2008) indicate incoherent "regime shifts" in the primary productivity (PP) between the North Sea and Baltic Sea. Correlation analysis between atmospheric forcing and PP indicates significant correlations for both solar radiation and wind but cannot serve to identify causal relationship. Therefore additional scenario tests with perturbations in individual atmospheric condition where accomplished emphasizing specifically the role of solar radiation, wind and eutrophication. The results revealed that, although all parameters are relevant for the PP in North Sea and Baltic Sea, the dominant impact on long term variability was introduced by modulations of the wind fields.

  9. The Baltic Klint beneath the central Baltic Sea and its comparison with the North Estonian Klint

    NASA Astrophysics Data System (ADS)

    Tuuling, Igor; Flodén, Tom

    2016-06-01

    Along its contact with the Baltic Shield, the margin of the East European Platform reveals a well-developed, flooded terraced relief. The most striking and consistent set of escarpments at the contact of the Lower Palaeozoic calcareous and terrigenous rocks, known as the Baltic Klint (BK), extends from northwest of Russia to the Swedish island of Öland. Marine seismic reflection profiling in 1990-2004 revealed the central Baltic Sea Klint (BSK) section in detail and enabled comparison of its geology/geomorphology with a classical klint-section onshore, namely the North Estonian Klint (NEK). The conception of the BK onshore, which is based on the land-sea separating terraced relief in northern Estonia, is not fully applicable beneath the sea. Therefore, we consider that the BSK includes the entire terraced Cambrian outcrop. We suggest the term "Baltic Klint Complex" to include the well-terraced margin of the Ordovician limestone outcrop, which is weakly developed in Estonia. Because of a steady lithological framework of the bedrock layers across the southern slope of the Fennoscandian Shield, the central BSK in the western and the NEK in the eastern part of the Baltic Homocline have largely identical morphologies. The North Estonian Ordovician limestone plateau with the calcareous crest of the BK extends across the central Baltic Sea, whereas morphological changes/variations along the Klint base occur due to the east-westerly lithostratigraphic/thickness changes in the siliciclastic Cambrian sequence. The verge of the NEK, located some 30-50 m above sea level, starts to drop in altitude as its east-westerly course turns to northeast-southwest in western Estonia. Further westwards, the BK shifts gradually into southerly deepening (0.1-0.2°) layers as its crest drops to c. 150 m below sea level (b.s.l.) near Gotska Sandön. This course change is accompanied by a considerable decrease in thickness of the platform sedimentary cover, as below the central Baltic Sea the

  10. Local adaptation and oceanographic connectivity patterns explain genetic differentiation of a marine diatom across the North Sea-Baltic Sea salinity gradient.

    PubMed

    Sjöqvist, C; Godhe, A; Jonsson, P R; Sundqvist, L; Kremp, A

    2015-06-01

    Drivers of population genetic structure are still poorly understood in marine micro-organisms. We exploited the North Sea-Baltic Sea transition for investigating the seascape genetics of a marine diatom, Skeletonema marinoi. Eight polymorphic microsatellite loci were analysed in 354 individuals from ten locations to analyse population structure of the species along a 1500-km-long salinity gradient ranging from 3 to 30 psu. To test for salinity adaptation, salinity reaction norms were determined for sets of strains originating from three different salinity regimes of the gradient. Modelled oceanographic connectivity was compared to directional relative migration by correlation analyses to examine oceanographic drivers. Population genetic analyses showed distinct genetic divergence of a low-salinity Baltic Sea population and a high-salinity North Sea population, coinciding with the most evident physical dispersal barrier in the area, the Danish Straits. Baltic Sea populations displayed reduced genetic diversity compared to North Sea populations. Growth optima of low salinity isolates were significantly lower than those of strains from higher native salinities, indicating local salinity adaptation. Although the North Sea-Baltic Sea transition was identified as a barrier to gene flow, migration between Baltic Sea and North Sea populations occurred. However, the presence of differentiated neutral markers on each side of the transition zone suggests that migrants are maladapted. It is concluded that local salinity adaptation, supported by oceanographic connectivity patterns creating an asymmetric migration pattern between the Baltic Sea and the North Sea, determines genetic differentiation patterns in the transition zone.

  11. Tidal exchange between the North Sea and Dutch Wadden Sea and mixing time scales of the tidal basins

    NASA Astrophysics Data System (ADS)

    Ridderinkhof, H.; Zimmerman, J. T. F.; Philippart, M. E.

    Particle trajectories in a numerical model of the western Dutch Wadden Sea and the adjacent North Sea are used to study the tidal exchange between the North Sea and the tidal basins. Tidal exchange of water masses appears to depend strongly on the tidal phase at which the computation is started. In general the volume displaced by the large-scale through-flow between connected tidal basins is much smaller than the exchanged volume. For all inlets North Sea water mainly enters the Wadden Sea from the southern side of the inlet whereas basin water leaves the Wadden Sea mainly along the northern coast. Differences in exchanged volume between the inlets are caused by differences in bathymetry at the seaward side of the different inlets. Schematizing each tidal basin as a single well-mixed box, in which an exchange coefficient parameterizes the exchange with the North Sea, allows a rough estimate of the turnover time of a tidal basin. A salt balance for a simple two-box schematization of the Marsdiep and Vlie basins gives an independent estimate of the exchange coefficient between the Marsdiep basin and the North Sea. Its value appears to be larger than the tidally exchanged volume. The revised salt balance, in which the effect of the through-flow between the Marsdiep and Vlie basins is incorporated, is used to calculate the flushing time of fresh water in the western Dutch Wadden Sea which appears to be larger than previous estimates. The tidally exchanged volume through the inlets, as calculated with the numerical model combined with the relation between the exchange coefficient and the tidally exchanged volume for the Marsdiep basin, is used to give a rough estimate of the turnover time of all Dutch Wadden Sea basins. For the Eierlandse Gat and the Borndiep the exchanged volume is calculated by means of our hydrodynamical model. For the other basins it is assumed that its value is a fixed percentage of the tidal prism entering a basin.

  12. Estrogenic Evaluation and Organochlorine Identification in Blubber of North Sea Harbour Porpoise (Phocoena phocoena) Stranded on the North Sea Coast

    PubMed Central

    Brose, François; Jauniaux, Thierry; Das, Krishna; Muller, Marc; Scippo, Marie-Louise

    2015-01-01

    Thirteen individual organochlorine compounds at 3 concentrations (80, 400, and 2000 ng/mL culture medium), as well as mixtures, were assayed for the estrogen receptor (ER) activation or inhibition, using a luciferase reporter gene assay (RGA). None of the PCB 138, 153, or 180 or their mixture induced a response in the RGA. o,p′-DDT was the most potent xenoestrogen from the DDT group, inducing a response already at 80 ng/mL. From the HCH and HCB group, only β-HCH (at 400 and 2000 ng/mL) and δ-HCH (at 2000 ng/mL) displayed estrogenic activities. These 13 organochlorines were determined by GC-MS in 12 samples of North Sea harbor porpoise blubber. The PCBs were the main contaminants. Within each group, PCB 153 (6.0 × 102~4.2 × 104 μg/kg), p,p′-DDE (5.1 × 102~8.6 × 103 μg/kg), and HCB (7.6 × 101~1.5 × 103 μg/kg) were the compounds found in highest concentrations. The hormonal activity of the porpoise blubber samples was also assayed in RGA, where two samples showed estrogenic activity, seven samples showed antiestrogenic activity, and one sample showed both estrogenic and antiestrogenic activity. Our results suggest that the 13 POPs measured by GC-MS in the samples cannot explain alone the estrogenicity of the extracts. PMID:26075240

  13. Estrogenic evaluation and organochlorine identification in blubber of North Sea harbour porpoise (Phocoena phocoena) stranded on the North Sea coast.

    PubMed

    Imazaki, Pedro Henrique; Brose, François; Jauniaux, Thierry; Das, Krishna; Muller, Marc; Scippo, Marie-Louise

    2015-01-01

    Thirteen individual organochlorine compounds at 3 concentrations (80, 400, and 2000 ng/mL culture medium), as well as mixtures, were assayed for the estrogen receptor (ER) activation or inhibition, using a luciferase reporter gene assay (RGA). None of the PCB 138, 153, or 180 or their mixture induced a response in the RGA. o,p'-DDT was the most potent xenoestrogen from the DDT group, inducing a response already at 80 ng/mL. From the HCH and HCB group, only β-HCH (at 400 and 2000 ng/mL) and δ-HCH (at 2000 ng/mL) displayed estrogenic activities. These 13 organochlorines were determined by GC-MS in 12 samples of North Sea harbor porpoise blubber. The PCBs were the main contaminants. Within each group, PCB 153 (6.0 × 10(2)~4.2 × 10(4) μg/kg), p,p'-DDE (5.1 × 10(2)~8.6 × 10(3) μg/kg), and HCB (7.6 × 10(1)~1.5 × 10(3) μg/kg) were the compounds found in highest concentrations. The hormonal activity of the porpoise blubber samples was also assayed in RGA, where two samples showed estrogenic activity, seven samples showed antiestrogenic activity, and one sample showed both estrogenic and antiestrogenic activity. Our results suggest that the 13 POPs measured by GC-MS in the samples cannot explain alone the estrogenicity of the extracts.

  14. Spatial and temporal variability of late Holocene sea-level changes in the North Atlantic (Invited)

    NASA Astrophysics Data System (ADS)

    Kemp, A.; Kopp, R. E.; Horton, B.; Cahill, N.

    2013-12-01

    Proxy sea-level reconstructions spanning the last ~2000 years capture multiple phases of climate and sea level behavior for model calibration, provide a pre-anthropogenic background against which to compare recent trends, and characterize patterns of natural spatial and temporal variability. In the western North Atlantic basin, salt-marsh sediment is an archive for reconstructing sea level with the decimeter and multi-decadal resolution necessary to characterize subtle changes. New and existing salt-marsh reconstructions from northern Florida, North Carolina, New Jersey, Connecticut, and Massachusetts provide a dataset for investigating spatial and temporal sea-level variability during the late Holocene. The reconstructions were developed using foraminifera, plants, and bulk sediment δ13C values as sea-level proxies. The age of sediment deposition was estimated from composite chronologies of radiocarbon and chronohorizons of regional pollution and land-use change that were combined in age depth models. We used a spatio-temporal Gaussian process model to identify and characterize persistent phases of sea level behavior during the late Holocene in the western North Atlantic Ocean. The results indicate an acceleration in global mean sea level from the early 19th century through the early 20th century. The rate of sea-level rise increased significantly in the late 19th century. The timing and magnitude of this rise varied among sites even after accounting for differences in glacio-isostatic adjustment. Sea level in North Carolina rose faster than in New Jersey sea-level during the Medieval Climate Optimum, while sea level in New Jersey rose faster during the Little Ice Age. Spatially variable sea-level rise on the Atlantic coast of North America can be caused by dynamic oceanographic processes and/or melting of the Greenland Ice Sheet. Our analysis suggests that plausible levels of meltwater input from Greenland would be inadequate to explain the reconstructed pattern

  15. Sea surface height variability in the North East Atlantic from satellite altimetry

    NASA Astrophysics Data System (ADS)

    Sterlini, Paul; de Vries, Hylke; Katsman, Caroline

    2016-08-01

    Data from 21 years of satellite altimeter measurements are used to identify and understand the major contributing components of sea surface height variability (SSV) on monthly time-scales in the North East Atlantic. A number of SSV drivers is considered, which are categorised into two groups; local (wind and sea surface temperature) and remote (sea level pressure and the North Atlantic oscillation index). A multiple linear regression model is constructed to model the SSV for a specific target area in the North Sea basin. Cross-correlations between candidate regressors potentially lead to ambiguity in the interpretation of the results. We therefore use an objective hierarchical selection method based on variance inflation factors to select the optimal number of regressors for the target area and accept these into the regression model if they can be associated to SSV through a direct underlying physical forcing mechanism. Results show that a region of high SSV exists off the west coast of Denmark and that it can be represented well with a regression model that uses local wind, sea surface temperature and sea level pressure as primary regressors. The regression model developed here helps to understand sea level change in the North East Atlantic. The methodology is generalised and easily applied to other regions.

  16. Hydrography and biogeochemistry of the north western Bay of Bengal and the north eastern Arabian Sea during winter monsoon

    NASA Astrophysics Data System (ADS)

    Balachandran, K. K.; Laluraj, C. M.; Jyothibabu, R.; Madhu, N. V.; Muraleedharan, K. R.; Vijay, J. G.; Maheswaran, P. A.; Ashraff, T. T. M.; Nair, K. K. C.; Achuthankutty, C. T.

    2008-09-01

    The north eastern Arabian Sea and the north western Bay of Bengal within the Indian exclusive economic zone were explored for their environmental characteristics during the winter monsoons of 2000 and 2001 respectively. The two regions were found to respond paradoxically to comparable intensities of the atmospheric forcing. There is an asymmetry in the net heat exchange of these two basins with atmosphere because of the varying thickness of barrier layer. During winter, the convective mixing in the Arabian Sea is driven by net heat loss from the ocean, whereas the Bay of Bengal does not contribute to such large heat loss to the atmosphere. It appears that the subduction of high saline Arabian Sea water mass is the mechanism behind the formation of a barrier layer in the northeast Arabian Sea; whereas that in the Bay of Bengal and the southeast Arabian Sea are already established as due to low saline water mass. The weak barrier layer in the Arabian Sea yields to the predominance of convective mixing to bring in nitrate-rich waters from the deeper layers to the surface, thereby supporting enhanced biological production. On the other hand, the river discharge into the Bay of Bengal during this period results in the formation of a thick and stable barrier layer, which insulates vertical mixing and provide oligotrophic condition in the Bay.

  17. Virulence Profiles of Vibrio vulnificus in German Coastal Waters, a Comparison of North Sea and Baltic Sea Isolates.

    PubMed

    Bier, Nadja; Jäckel, Claudia; Dieckmann, Ralf; Brennholt, Nicole; Böer, Simone I; Strauch, Eckhard

    2015-12-01

    Vibrio vulnificus is a halophilic bacterium of coastal environments known for sporadically causing severe foodborne or wound infections. Global warming is expected to lead to a rising occurrence of V. vulnificus and an increasing incidence of human infections in Northern Europe. So far, infections in Germany were exclusively documented for the Baltic Sea coast, while no cases from the North Sea region have been reported. Regional variations in the prevalence of infections may be influenced by differences in the pathogenicity of V. vulnificus populations in both areas. This study aimed to compare the distribution of virulence-associated traits and genotypes among 101 V. vulnificus isolates from the Baltic Sea and North Sea in order to assess their pathogenicity potential. Furthermore, genetic relationships were examined by multilocus sequence typing (MLST). A high diversity of MLST sequences (74 sequence types) and differences regarding the presence of six potential pathogenicity markers were observed in the V. vulnificus populations of both areas. Strains with genotypes and markers associated with pathogenicity are not restricted to a particular geographic region. This indicates that lack of reported cases in the North Sea region is not caused by the absence of potentially pathogenic strains.

  18. Virulence Profiles of Vibrio vulnificus in German Coastal Waters, a Comparison of North Sea and Baltic Sea Isolates.

    PubMed

    Bier, Nadja; Jäckel, Claudia; Dieckmann, Ralf; Brennholt, Nicole; Böer, Simone I; Strauch, Eckhard

    2015-12-01

    Vibrio vulnificus is a halophilic bacterium of coastal environments known for sporadically causing severe foodborne or wound infections. Global warming is expected to lead to a rising occurrence of V. vulnificus and an increasing incidence of human infections in Northern Europe. So far, infections in Germany were exclusively documented for the Baltic Sea coast, while no cases from the North Sea region have been reported. Regional variations in the prevalence of infections may be influenced by differences in the pathogenicity of V. vulnificus populations in both areas. This study aimed to compare the distribution of virulence-associated traits and genotypes among 101 V. vulnificus isolates from the Baltic Sea and North Sea in order to assess their pathogenicity potential. Furthermore, genetic relationships were examined by multilocus sequence typing (MLST). A high diversity of MLST sequences (74 sequence types) and differences regarding the presence of six potential pathogenicity markers were observed in the V. vulnificus populations of both areas. Strains with genotypes and markers associated with pathogenicity are not restricted to a particular geographic region. This indicates that lack of reported cases in the North Sea region is not caused by the absence of potentially pathogenic strains. PMID:26694432

  19. Virulence Profiles of Vibrio vulnificus in German Coastal Waters, a Comparison of North Sea and Baltic Sea Isolates

    PubMed Central

    Bier, Nadja; Jäckel, Claudia; Dieckmann, Ralf; Brennholt, Nicole; Böer, Simone I.; Strauch, Eckhard

    2015-01-01

    Vibrio vulnificus is a halophilic bacterium of coastal environments known for sporadically causing severe foodborne or wound infections. Global warming is expected to lead to a rising occurrence of V. vulnificus and an increasing incidence of human infections in Northern Europe. So far, infections in Germany were exclusively documented for the Baltic Sea coast, while no cases from the North Sea region have been reported. Regional variations in the prevalence of infections may be influenced by differences in the pathogenicity of V. vulnificus populations in both areas. This study aimed to compare the distribution of virulence-associated traits and genotypes among 101 V. vulnificus isolates from the Baltic Sea and North Sea in order to assess their pathogenicity potential. Furthermore, genetic relationships were examined by multilocus sequence typing (MLST). A high diversity of MLST sequences (74 sequence types) and differences regarding the presence of six potential pathogenicity markers were observed in the V. vulnificus populations of both areas. Strains with genotypes and markers associated with pathogenicity are not restricted to a particular geographic region. This indicates that lack of reported cases in the North Sea region is not caused by the absence of potentially pathogenic strains. PMID:26694432

  20. Sensitivity of modeled atmospheric nitrogen species and nitrogen deposition to variations in sea salt emissions in the North Sea and Baltic Sea regions

    NASA Astrophysics Data System (ADS)

    Neumann, Daniel; Matthias, Volker; Bieser, Johannes; Aulinger, Armin; Quante, Markus

    2016-03-01

    Coarse sea salt particles are emitted ubiquitously from the ocean surface by wave-breaking and bubble-bursting processes. These particles impact the atmospheric chemistry by affecting the condensation of gas-phase species and, thus, indirectly the nucleation of new fine particles, particularly in regions with significant air pollution. In this study, atmospheric particle concentrations are modeled for the North Sea and Baltic Sea regions in northwestern Europe using the Community Multiscale Air Quality (CMAQ) modeling system and are compared to European Monitoring and Evaluation Programme (EMEP) measurement data. The sea salt emission module is extended by a salinity-dependent scaling of the sea salt emissions because the salinity in large parts of the Baltic Sea is very low, which leads to considerably lower sea salt mass emissions compared to other oceanic regions. The resulting improvement in predicted sea salt concentrations is assessed. The contribution of surf zone emissions is considered separately. Additionally, the impacts of sea salt particles on atmospheric nitrate and ammonium concentrations and on nitrogen deposition are evaluated. The comparisons with observational data show that sea salt concentrations are commonly overestimated at coastal stations and partly underestimated farther inland. The introduced salinity scaling improves the predicted Baltic Sea sea salt concentrations considerably. The dates of measured peak concentrations are appropriately reproduced by the model. The impact of surf zone emissions is negligible in both seas. Nevertheless, they might be relevant because surf zone emissions were cut at an upper threshold in this study. Deactivating sea salt leads to minor increases in NH3 + NH4+ and HNO3 + NO3- and a decrease in NO3- concentrations. However, the overall effect on NH3 + NH4+ and HNO3 + NO3- concentrations is smaller than the deviation from the measurements. Nitrogen wet deposition is underestimated by the model at most

  1. Sensitivity of modeled atmospheric nitrogen species to variations in sea salt emissions in the North and Baltic Sea regions

    NASA Astrophysics Data System (ADS)

    Neumann, D.; Matthias, V.; Bieser, J.; Aulinger, A.; Quante, M.

    2015-10-01

    Coarse sea salt particles are emitted ubiquitously from the oceans' surfaces by wave breaking and bubble bursting processes. These particles impact atmospheric chemistry by affecting condensation of gas-phase species and nucleation of new fine particles, particularly in regions with high air pollution. In this study, atmospheric particle concentrations are modeled for the North and Baltic Sea regions, Northwestern Europe, using the Community Multiscale Air Quality (CMAQ) modeling system and evaluated against European Monitoring and Evaluation Programme (EMEP) measurement data. As model extension, sea salt emissions are scaled by water salinity because of low salinity in large parts of the Baltic Sea and in certain river estuaries. The resulting improvement in predicted sea salt concentrations is assessed. The contribution of surf zone emissions is separately considered. Additionally, the impact of sea salt particles on atmospheric nitrate, ammonium and sulfate concentrations is evaluated. The comparisons show that sea salt concentrations are commonly overestimated at coastal stations and partly underestimated when going inland. The introduced salinity scaling improves predicted Baltic Sea sea salt concentrations considerably. Dates of measured peak concentrations are appropriately reproduced by the model. The impact of surf zone emissions is negligible in both seas. Nevertheless, they might be relevant because surf zone emissions were cut at an upper threshold in this study. Deactivating sea salt leads to a minor increase of NH4+ and NO3- and a minor decrease of SO42- concentrations. However, the overall effect is very low and lower than the deviation from measurements. Size resolved measurements of Na+, NH4+, NO3-, and SO42- are needed for a more detailed analysis on the impact of sea salt particles.

  2. Avian influenza ecology in North Atlantic sea ducks: Not all ducks are created equal

    USGS Publications Warehouse

    Hall, Jeffrey S.; Russell, Robin E.; Franson, J. Christian; Soos, Catherine; Dusek, Robert J.; Allen, R. Bradford; Nashold, Sean W.; Teslaa, Joshua L.; Jónsson, Jón Einar; Ballard, Jennifer R.; Harms, Naomi Jnae; Brown, Justin D.

    2015-01-01

    Wild waterfowl are primary reservoirs of avian influenza viruses (AIV). However the role of sea ducks in the ecology of avian influenza, and how that role differs from freshwater ducks, has not been examined. We obtained and analyzed sera from North Atlantic sea ducks and determined the seroprevalence in those populations. We also tested swab samples from North Atlantic sea ducks for the presence of AIV. We found relatively high serological prevalence (61%) in these sea duck populations but low virus prevalence (0.3%). Using these data we estimated that an antibody half-life of 141 weeks (3.2 years) would be required to attain these prevalences. These findings are much different than what is known in freshwater waterfowl and have implications for surveillance efforts, AIV in marine environments, and the roles of sea ducks and other long-lived waterfowl in avian influenza ecology.

  3. Avian Influenza Ecology in North Atlantic Sea Ducks: Not All Ducks Are Created Equal

    PubMed Central

    Hall, Jeffrey S.; Russell, Robin E.; Franson, J. Christian; Soos, Catherine; Dusek, Robert J.; Allen, R. Bradford; Nashold, Sean W.; TeSlaa, Joshua L.; Jónsson, Jón Eínar; Ballard, Jennifer R.; Harms, Naomi Jane; Brown, Justin D.

    2015-01-01

    Wild waterfowl are primary reservoirs of avian influenza viruses (AIV). However the role of sea ducks in the ecology of avian influenza, and how that role differs from freshwater ducks, has not been examined. We obtained and analyzed sera from North Atlantic sea ducks and determined the seroprevalence in those populations. We also tested swab samples from North Atlantic sea ducks for the presence of AIV. We found relatively high serological prevalence (61%) in these sea duck populations but low virus prevalence (0.3%). Using these data we estimated that an antibody half-life of 141 weeks (3.2 years) would be required to attain these prevalences. These findings are much different than what is known in freshwater waterfowl and have implications for surveillance efforts, AIV in marine environments, and the roles of sea ducks and other long-lived waterfowl in avian influenza ecology. PMID:26677841

  4. Avian Influenza Ecology in North Atlantic Sea Ducks: Not All Ducks Are Created Equal.

    PubMed

    Hall, Jeffrey S; Russell, Robin E; Franson, J Christian; Soos, Catherine; Dusek, Robert J; Allen, R Bradford; Nashold, Sean W; TeSlaa, Joshua L; Jónsson, Jón Eínar; Ballard, Jennifer R; Harms, Naomi Jane; Brown, Justin D

    2015-01-01

    Wild waterfowl are primary reservoirs of avian influenza viruses (AIV). However the role of sea ducks in the ecology of avian influenza, and how that role differs from freshwater ducks, has not been examined. We obtained and analyzed sera from North Atlantic sea ducks and determined the seroprevalence in those populations. We also tested swab samples from North Atlantic sea ducks for the presence of AIV. We found relatively high serological prevalence (61%) in these sea duck populations but low virus prevalence (0.3%). Using these data we estimated that an antibody half-life of 141 weeks (3.2 years) would be required to attain these prevalences. These findings are much different than what is known in freshwater waterfowl and have implications for surveillance efforts, AIV in marine environments, and the roles of sea ducks and other long-lived waterfowl in avian influenza ecology.

  5. Seismic geomorphology of the Danish Chalks, offshore, North Sea

    NASA Astrophysics Data System (ADS)

    Smit, Florian; van Buchem, Frans; Schmidt, Ingelise

    2014-05-01

    The Upper Cretaceous and Lowermost Paleocene chalk deposits of the North Sea Basin constitute a unique phase in the evolution of carbonate facies, through the rock-forming dominance of fine grained calcareous plankton, particularly coccolithophorids. These planktonic organisms were deposited over extensive areas and very often laid down as laterally extensive, regular dm-scale bedded packages, that locally may reach a thickness of up to 1250 m. In the Danish Graben, the depositional conditions for the chalk sedimentation changed dramatically during the middle of the Upper Cretaceous. At this time the basin topography was inverted, radically changing the position of the depocenters and the ocean floor morphology. In uplifted areas local erosion and long phases of non-deposition occurred, whereas in areas of subsidence thick packages of chalk accumulated. Along the newly created highs, mass waste deposition took place at the deca-kilometre scale. In this presentation we will document evidence for the tectonic inversion, and pay particular attention to the rich pallet of geomorphological features that characterise this tectonically active period. This study benefitted from a recently re-processed 3D seismic dataset (6000 km²), and a regional well-log and biostratigraphic dataset. In addition, the seismic interpretation applied advanced seismic interpretation software (PaleoScan™), which uses a patented model grid that links up seismic points and honours interpreted horizon constraints resulting in a seismic Relative Geological Time model. Standard seismic attributes, displayed upon horizons from a 3D RGT model of the chalk package, have shown to be very effective in the illustration and interpretation of complex chalk depositional features. Special attention has been focussed on mass waste deposits around inverted structures and salt diapirs. Several different mass waste complexes have been documented in 3D, illustrating a number of typical features such as

  6. Chemical use in North Sea oil and gas E and P

    SciTech Connect

    Hudgins, C.M. Jr.

    1994-01-01

    In May 1990, the Norwegian Oil Industry Assn., Oljeindustriens Landsforening (OLF), commissioned a survey of chemical use in E and P activities in the North Sea. Ten operating companies and six chemical suppliers provided data on the specific types and quantities of chemicals used in their operations and the properties of those chemicals. These companies operated or supplied chemicals in the Norwegian, British, and Netherlands sectors. Technical discussions on the reasons for using chemicals and their application also were held. The comprehensive results of this survey are available from OLF as a report, with all chemical data on disk. This paper summarizes the primary observations from the OLF report. The quantitative uses are compared with previous summaries of quantities of chemicals used. Probable discharge quantities and concentrations are discussed. Acute aquatic toxicity data submitted by participants are presented and practical aspects discussed.

  7. Influence of the North Atlantic on climate change in the Barents Sea

    NASA Astrophysics Data System (ADS)

    Glok, Natalia; Alekseev, Genrikh; Smirnov, Aleksander; Vyasilova, Anastasia

    2015-04-01

    This study is based on the observations taken from the meteorological archives, satellite and historic visual observations of sea ice, global SST, data of water temperature in the upper layer on the section in the Barents Sea. For processing data was used factor analysis, calculation of correlation matrices with different delay between the Barents Sea and selected areas in North Atlantic. It is shown that the inflow of Atlantic water into the Barents Sea has a major influence on the climate of the region and its changes affect the variations of all climate characteristics. Decadal and interannual changes of air temperature in the Barents Sea are closely related (correlation over 0.8) with temperature of water, coming from the Norwegian Sea. The effect of these changes is seen in the air temperature in the Kara Sea. Atlantic water inflow especially impact on winter sea ice in the Barents Sea. The correlation between the average water temperature at section along the Kola meridian and sea ice extent in the Barents Sea in May reaches values of -0.86. To enhance the predictive capability established dependence, the study was extended to the area of the North Atlantic, where temperature anomalies are formed. In the North Atlantic from the equator to 80 ° N were identified 6 areas where the average annual SST anomalies are associated with SST anomalies and sea ice extent (SIE) in the Barents Sea. Detailed analysis with monthly SST from HadISST for 1951 - 2013 identified two areas with the greatest influence on the Barents Sea. One area is the northern region of the Gulf Stream and other is the equatorial region. The corresponding delays amounted to 26 months and 4-5 years. The relationship between changes AMO index, averaged over August-October, and SIE in the Barents Sea in January is evaluated. Correlation coefficient between them with 3 year delay is -0.54. Implemented study revealed the importance of teleconnection between SST anomalies in the North Atlantic and SST

  8. Late Quaternary Sea-Ice Variability at the North Icelandic Shelf (Sub-Arctic): Reconstruction from Biomarkers

    NASA Astrophysics Data System (ADS)

    Xiao, X.; Zhao, M.; Jiang, H.; Eiriksson, J.; Guo, Z.

    2015-12-01

    Sea ice, prevailing in the polar region and characterized by distinct seasonal and interannual variability, plays a pivotal role in Earth's climate system (Thomas and Dieckmann, 2010). In order to understand processes controlling the recent dramatic reduction in Arctic sea-ice cover, it is essential to determine temporal changes in sea-ice occurrence and its natural variability in the past. The North Icelandic shelf, bordering a marginal area of the Arctic Ocean, is located at the present-day boundary between the cold polar currents and warm Atlantic water masses, very sensitive to the changes in sea-ice cover, ice sheet and oceanic circulation patterns (Knudsen and Eiriksson, 2002). All these processes have been recorded in the marine shelf-sediment cores. We determined the concentrations of sea-ice diatom-derived biomarker "IP25" (monoene highly-branched isoprenoid with 25 carbon atom; Belt et al., 2007), phytoplankton-derived biomarkers (brassicasterol and dinosterol) and terrigenous biomarkers (campesterol and ß-sitosterol) in a sediment core from the North Icelandic shelf to reconstruct the Late Quaternary sea-ice conditions and related surface-water processes. The sea-ice cover reached its maximum during the cold period (i.e., Last Glacial Maximum and Younger dryas), while an open ocean environment existed during less severe periods (e.g. Bølling-Allerød and 8.2 ka event) in the study area. The biomarker records from this sediment core give insights into the variability in sea ice and circulation patterns as well as primary productivity in the Arctic marginal area during the Late Quaternary. References Belt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea ice: IP25. Org. Geochem. 38, 16-27. Knudsen, K.L. and Eiriksson, J., 2002. Application of tephrochronology to the timing and correlation of palaeoceanographic events recorded in Holocene and Late Glacial shelf sediments off North Iceland

  9. Review Article: Storm Britta in 2006: offshore damage and large waves in the North Sea

    NASA Astrophysics Data System (ADS)

    Kettle, A. J.

    2015-09-01

    The Britta storm of 31 October-1 November 2006 was a severe autumn storm that was particularly damaging for shipping and coastal flooding from storm surge effects along the southern North Sea. The main low pressure of the storm propagated from Scotland to southern Norway on 31 October, leading to a system of strong north winds that moved southward across North Sea over an 18 h period. A progression of ship and offshore platform difficulties were registered from the northern part of the North Sea from late on 31 October and culminated near the coasts of Germany and the Netherlands early on 1 November with a series of ship emergencies linked with large waves. In two separate incidents, unusually high waves broke the bridge windows of ships and necessitated emergency rescues, and a Dutch motor lifeboat experienced a triple capsize. In the southern North Sea, several gas production and research platforms experienced wave impact damage. The FINO1 offshore research platform, near the Dutch-German border, experienced some of the worst storm conditions with some structural damage. Its meteorological and oceanographic instrumentation give a unique profile of the severe met-ocean conditions during the storm. Two Waverider buoys at FINO1 and the nearby Dutch coastal site of Schiermonnikoog recorded groups of large waves at different times during the storm. These reports give insight into a little-reported rogue wave phenomenon that sometimes accompanies the "ground sea" conditions of the worst storms of the area.

  10. Radium isotopes as a tracer of sediment-water column exchange in the North Sea

    NASA Astrophysics Data System (ADS)

    Burt, W. J.; Thomas, H.; Pätsch, J.; Omar, A. M.; Schrum, C.; Daewel, U.; Brenner, H.; Baar, H. J. W.

    2014-08-01

    Sediment-water column exchange plays an important role in coastal biogeochemistry. We utilize short-lived radium isotopes (224Ra and 223Ra) to understand and quantify the dominant processes governing sediment-water column exchange throughout the North Sea. Our comprehensive survey, conducted in September 2011, represents the first of its kind conducted in the North Sea. We find that two main sources regulate surface Ra distributions: minor coastal input from rivers and shallow mudflats and North Sea sediments as the dominant source. Pore waters show 100-fold larger activities than the water column. North Sea sediment characteristics such as porosity and mean grain size, as well as turbulence at the sediment-water interface, are the dominant factors contributing to variability of Ra efflux. Ra inventory and mass balance approaches consistently yield high benthic Ra effluxes in the southern North Sea, driven by strong tidal and wind mixing, which in turn cause high sediment irrigation rates. These results exceed incubation-based Ra flux estimates and the majority of previously reported Ra flux estimates for other regions. Ra-based estimates of benthic alkalinity fluxes compare well to observed values, and the high rates of Ra efflux imply a potentially significant exchange of other products of sedimentary reactions, including carbon and nutrient species. Passive tracer simulations lend strong support to the Ra source attribution and imply seasonal variation in the surface water Ra distribution depending on stratification conditions.

  11. Comparison of nematode communities in Baltic and North Sea sublittoral, permeable sands Diversity and environmental control

    NASA Astrophysics Data System (ADS)

    Urban-Malinga, Barbara; Hedtkamp, Stefanie I. C.; van Beusekom, Justus E. E.; Wiktor, Józef; Węsławski, Jan Marcin

    2006-10-01

    The structure of free-living nematode communities was investigated seasonally at two sandy locations representing typical shallow sublittoral, permeable environments of the North Sea and the Baltic Sea. At the Baltic study site the chlorophyll and organic carbon concentrations in the sediment were, on average, four times lower than at the North Sea. Highest nematode densities (1674-4100 ind. 10 cm -2) and a higher number of free-living nematode genera (66) were recorded in the North Sea (Baltic: 206-1227 ind. 10 cm -2, 30 genera). Despite lower salinity and lower food availability the less dense and less diverse Baltic nematode community was similar in generic composition to the North Sea community. At the North Sea site, all trophic groups according to Wieser's classification were present with omnivores/predators, dominated by Viscosia, prevailing and followed by epistrate-feeders. In the food-limited Baltic community, non-selective deposit feeders (mainly Ascolaimus, Axonolaimus and Daptonema) and omnivores/predators dominated by Enoplolaimus were the most abundant trophic groups while selective deposit feeders were absent or their contribution was negligible. An analysis of the vertical generic distribution revealed highest diversity of the Baltic community in deeper sediment layers, below the sediment surface affected by ripple migration and near the interface of oxic and anoxic conditions. The diversity pattern in the North Sea sediment was more variable but generally showed high diversity in the upper centimetre of the sediment. These observations suggest that food supply and sediment oxygenation are the most important factors influencing the vertical pattern of nematode generic diversity in sublittoral, permeable sands.

  12. Impacts of the north and tropical Atlantic Ocean on the Antarctic Peninsula and sea ice.

    PubMed

    Li, Xichen; Holland, David M; Gerber, Edwin P; Yoo, Changhyun

    2014-01-23

    In recent decades, Antarctica has experienced pronounced climate changes. The Antarctic Peninsula exhibited the strongest warming of any region on the planet, causing rapid changes in land ice. Additionally, in contrast to the sea-ice decline over the Arctic, Antarctic sea ice has not declined, but has instead undergone a perplexing redistribution. Antarctic climate is influenced by, among other factors, changes in radiative forcing and remote Pacific climate variability, but none explains the observed Antarctic Peninsula warming or the sea-ice redistribution in austral winter. However, in the north and tropical Atlantic Ocean, the Atlantic Multidecadal Oscillation (a leading mode of sea surface temperature variability) has been overlooked in this context. Here we show that sea surface warming related to the Atlantic Multidecadal Oscillation reduces the surface pressure in the Amundsen Sea and contributes to the observed dipole-like sea-ice redistribution between the Ross and Amundsen-Bellingshausen-Weddell seas and to the Antarctic Peninsula warming. Support for these findings comes from analysis of observational and reanalysis data, and independently from both comprehensive and idealized atmospheric model simulations. We suggest that the north and tropical Atlantic is important for projections of future climate change in Antarctica, and has the potential to affect the global thermohaline circulation and sea-level change.

  13. Impacts of the north and tropical Atlantic Ocean on the Antarctic Peninsula and sea ice.

    PubMed

    Li, Xichen; Holland, David M; Gerber, Edwin P; Yoo, Changhyun

    2014-01-23

    In recent decades, Antarctica has experienced pronounced climate changes. The Antarctic Peninsula exhibited the strongest warming of any region on the planet, causing rapid changes in land ice. Additionally, in contrast to the sea-ice decline over the Arctic, Antarctic sea ice has not declined, but has instead undergone a perplexing redistribution. Antarctic climate is influenced by, among other factors, changes in radiative forcing and remote Pacific climate variability, but none explains the observed Antarctic Peninsula warming or the sea-ice redistribution in austral winter. However, in the north and tropical Atlantic Ocean, the Atlantic Multidecadal Oscillation (a leading mode of sea surface temperature variability) has been overlooked in this context. Here we show that sea surface warming related to the Atlantic Multidecadal Oscillation reduces the surface pressure in the Amundsen Sea and contributes to the observed dipole-like sea-ice redistribution between the Ross and Amundsen-Bellingshausen-Weddell seas and to the Antarctic Peninsula warming. Support for these findings comes from analysis of observational and reanalysis data, and independently from both comprehensive and idealized atmospheric model simulations. We suggest that the north and tropical Atlantic is important for projections of future climate change in Antarctica, and has the potential to affect the global thermohaline circulation and sea-level change. PMID:24451542

  14. Late Tectonic history of Beaufort Sea - North Pacific area

    SciTech Connect

    McWhae, J.R.H.

    1985-02-01

    The Kaltag fault (and its northern associated splay, the Rapid fault array) is the sheared suture between the Eurasian-Alaskan plate and the North American plate in the area between the Mackenzie Delta and the Alaskan Border. This condition has been maintained throughout considerable additional phases of faulting and folding from mid-Cretaceous to the present. Previously, the Alaskan plate had been the northwestern nose of the North America plate. The interplate suture was deflected to the north as the Canadian Shield was approached. The Kaltag fault continued northeastward 2000 km seaward of the Sverdrup rim, northwest of the Canadian Arctic Island, and north of Greenland. The driving force was directed from the southwest by the Eurasian plate after its collision in Early Cretaceous (Hauterivian) with the North American plate and the docking of north-moving exotic terranes from the Pacific. During the early Tertiary, perhaps in concert with the accretion of the Okhotsk block to the Asian plate north of Japan, the northern Pacific subduction zone jumped southward to the Aleutian Arc where it has persisted until today. A distance of 800 km separates the stable shelf of the Canadian craton, at the Alberta Foothills thrust belt, from the subduction zone off Vancouver Island. The foreland thrust belt and the accretion of exotic terranes in Mesozoic and Tertiary times extended the continental crust of the North American plate westward to the present active transform margin with the Pacific plate along the Queen Charlotte fault zone.

  15. Effect of a Pacific sea surface temperature anomaly on the circulation over North America

    NASA Technical Reports Server (NTRS)

    Shukla, J.; Bangaru, B.

    1979-01-01

    During the fall and winter of 1976-1977, sea surface temperature (SST) in the north Pacific was characterized by abnormally cold temperatures in the central and western portions of the north Pacific with a warm pool located off the west coast of the U.S. It was suggested that the north Pacific SST anomalies were one of the multiple causes of the abnormally cold temperatures in eastern North America during the 1976-1977 winter. An attempt was made to test this hypothesis by conducting a numerical experiment with the GLAS general circulation model.

  16. The Holocene palaeogeography and relative sea level for two tidal basins of the German North Sea coast

    NASA Astrophysics Data System (ADS)

    Bungenstock, Friederike; Wartenberg, Wolfram; Mauz, Barbara; Freund, Holger; Frechen, Manfred; Weerts, Henk J. T.; Berner, Heinrich

    2014-05-01

    The response of coasts to global sea-level rise is highly variable. Knowledge of driving coastal parameters alongside the regional sea-level history is therefore indispensable when the response to global sea-level rise is to be assessed. Here, we study the Holocene relative sea-level of the south coast of the North Sea which is controlled by a number of very local parameters, as well as by regional glacio-isostatic adjustments. It is therefore crucial to restrict the data acquisition and evaluation to small coastal sections, ideally to single tidal basins, to minimize the sources of uncertainties (Bungenstock & Weerts 2010, 2012). We present data from two tidal basins, Langeoog and Jade Bay. For Langeoog a database derived from 600 cores, 68 km of Boomer seismic data, 33 radiocarbon ages and 8 OSL dates is available. (Bungenstock & Schäfer 2009, Mauz & Bungenstock 2007). For the Jade bay, the database comprises sedimentary markers, pollen and macro remains derived from 68 cores. The sedentary chronology is based on 54 radiocarbon ages and pollen constraints (Wartenberg & Freund 2011, Wartenberg et al. 2013). For both tidal basins the sedimentological record was interpreted in terms of the local paleogeographical development since about 7000 cal BP and its influence on the local relative sea-level curve. While the trend of the relative sea level is similar for both tidal basins, it shows a different altitude. The timing of the main marine transgression within the Langeoog area takes place ~3000 cal. BP whereas the sedimentological record of the Jade Bay shows two prominent transgressions, one for ~5000 cal. BP and one for ~3000 cal. BP. The Langeoog palaeo-environment is continuously characterised by marine influence. Within the Jade Bay two different palaeo-environments could be identified, documenting that from the West to the centre the landscape development in the Jade Bay was drainage driven feeding the associated fen peat with minerogenic water but being

  17. 78 FR 62610 - North Baja Pipeline, LLC; Notice of Application

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-22

    ... Energy Regulatory Commission North Baja Pipeline, LLC; Notice of Application Take notice that on October 3, 2013, North Baja Pipeline, LLC (North Baja), 717 Texas Street, Suite 2400, Houston, Texas 77002... directed to Richard Parke, Manager, Certificates, North Baja Pipeline, LLC, 717 Texas Street, Suite...

  18. Eutrophication status of the North Sea, Skagerrak, Kattegat and the Baltic Sea in present and future climates: A model study

    NASA Astrophysics Data System (ADS)

    Skogen, Morten D.; Eilola, Kari; Hansen, Jørgen L. S.; Meier, H. E. Markus; Molchanov, Mikhail S.; Ryabchenko, Vladimir A.

    2014-04-01

    A method to combine observations and an ensemble of ecological models has been used to assess eutrophication. Using downscaled forcing from two GCMs under the A1B emission scenario, an assessment of the eutrophication status was made for a control (1970-2000) and a future climate (2070-2100) period. By using validation results from a hindcast to compute individual weights between the models, an assessment of eutrophication is done using a set of threshold values. The final classification distinguishes between three categories: problem area, potential problem area, and non-problem area, in accordance with current management practice as suggested by the Oslo and Paris Commissions (OSPAR) and the Helsinki Commission (HELCOM). For the control run the assessment indicates that the Kattegat, the Danish Straits, the Gulf of Finland, the Gotland Basin as well as main parts of the Arkona Basin, the Bornholm Basin, and the Baltic proper may be classified as problem areas. The main part of the North Sea and also the Skagerrak are non-problem areas while the main parts of the Gulf of Bothnia, Gulf of Riga and the entire southeastern continental coast of the North Sea may be classified as potential problem areas. In the future climate scenarios most of the previous potential problem areas in the Baltic Sea have become problem areas, except for the Bothnian Bay where the situation remain fairly unchanged. In the North Sea there seems to be no obvious changes in eutrophication status in the projected future climate.

  19. Effects of North Sea oil and alkylphenols on biomarker responses in juvenile Atlantic cod (Gadus morhua).

    PubMed

    Sturve, Joachim; Hasselberg, Linda; Fälth, Herman; Celander, Malin; Förlin, Lars

    2006-06-01

    A consequence of oil drilling at sea is the release of produced water contaminated with e.g. polycyclic aromatic hydrocarbons (PAH) and alkylphenols. In the present study, juvenile Atlantic cod were exposed to North Sea oil, nonylphenol and a combination of the North Sea oil and an alkylphenol mixture in a flow-through system. A suite of hepatic biomarkers were analysed. Exposure to North Sea oil resulted in strong induction of CYP1A protein levels and EROD activities. Exposure to nonylphenol, on the other hand, resulted in decreased CYP1A levels and EROD activities. Thus, nonylphenol appears to down-regulate CYP1A expression in Atlantic cod. Combined exposure to North Sea oil with an alkylphenol mixture resulted in lower EROD induction, compared to that in fish exposed to North Sea oil alone. This difference was not statistically significant, but still we believe that the alkylphenols have inhibited CYP1A activities in the fish which may have compromised CYP1A mediated metabolism of other xenobiotics, including PAH. CYP3A protein levels were lower, compared to controls, in fish exposed to nonylphenol and the combination of North Sea oil and alkylphenol mixture. In contrast, the oil alone had no effect on CYP3A protein content. North Sea oil exposure, alone or in combination with alkylphenols, caused oxidative stress observed as elevated levels of GSSG content and GR and CAT activities. Interestingly, exposure to nonylphenol resulted in a marked depletion of total glutathione levels. This apparent depletion may be a consequence of increased conjugation of glutathione to nonylphenol followed by excretion. An increase in conjugation enzyme GST activity was observed in the nonylphenol exposed group, although the difference was not significant. No sign of oxidative damage, measured as lipid peroxidation, was observed in any of the exposures experiments. This study suggests that North Sea oil may lead to oxidative stress and altered CYP1A and CYP3A expression

  20. Interannual variability of monthly sea-ice distributions in the north polar region

    SciTech Connect

    Parkinson, C.L.

    1992-03-01

    Passive-microwave data from the Nimbus 5 and Nimbus 7 satellites have been used to determine and map, by month, the interannual variability of the spatial distribution of north polar sea ice over the period 1973-1987. Results are illustrated for the months of January and July, during the winter ice growth and summer ice decay seasons, respectively. In January, the greatest interannual variability in the distribution of the ice occurs in the Sea of Okhotsk, whereas the portions of the ice edge exhibiting the least interannual variability lie in the southern Greenland Sea and immediately to the southwest of Svalbard. In July, spatial variability is high in Hudson Bay, Baffin Bay, the southern Kara Sea, and the northern Barents Sea. The monthly maps are meant to allow ready comparison with past and future sea ice distributions and aid in the assessment of whether specific changes are climatically important.

  1. Influence of Sea Ice on the Thermohaline Circulation in the Arctic-North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Mauritzen, Cecilie; Haekkinen, Sirpa

    1997-01-01

    A fully prognostic coupled ocean-ice model is used to study the sensitivity of the overturning cell of the Arctic-North-Atlantic system to sea ice forcing. The strength of the thermohaline cell will be shown to depend on the amount of sea ice transported from the Arctic to the Greenland Sea and further to the subpolar gyre. The model produces a 2-3 Sv increase of the meridional circulation cell at 25N (at the simulation year 15) corresponding to a decrease of 800 cu km in the sea ice export from the Arctic. Previous modeling studies suggest that interannual and decadal variability in sea ice export of this magnitude is realistic, implying that sea ice induced variability in the overturning cell can reach 5-6 Sv from peak to peak.

  2. North Sea operators look at every way possible to cut costs

    SciTech Connect

    Not Available

    1987-06-29

    Offshore operators have embarked on a second revolution in North Sea technology. In the 1970s, concepts established in the Gulf of Mexico were adapted using massive injections of manpower and money to produce platforms and pipelines that could survive in the deeper water and harsher environment of the North Sea. Target for the late 1980s is a complete reappraisal of harsh environment technology so that small reservoirs can be exploited at a profit with crude prices at $15-18bbl. Even before the collapse in oil prices, companies were hoping to cut development costs by 15-20%. But goals are more ambitious now. Esso U.K. plc chairman Archie Forster said the Shell/Esso group was close to achieving a 50% reduction in costs and getting front end investment costs for North Sea projects down to $10/bbl.

  3. Development and application of a simultaneous SPE-method for polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs, heterocyclic PAHs (NSO-HET) and phenols in aqueous samples from German Rivers and the North Sea.

    PubMed

    Siemers, Anne-Kathrin; Mänz, Jan Sebastian; Palm, Wolf-Ulrich; Ruck, Wolfgang K L

    2015-03-01

    Polycyclic aromatic hydrocarbons (PAHs), heterocyclic PAHs (NSO-HETs), alkylated PAHs and phenols are known as the prevailing contaminants in groundwater at tar contaminated sites. Besides these local sources, the concentrations and the distribution in particular of NSO-HETs in environmental samples, such as rivers, have received notably less attention. To investigate their occurrence in river basins two sensitive analytical methods for the simultaneous extraction of 86 substances including NSO-HETs, classical EPA-PAHs, alkylated PAHs and phenols were developed: liquid-liquid extraction for the whole water phase and solid phase extraction for the dissolved water phase only. Solely GC-MS or additionally LC-MSMS for fractionated basic nitrogen heterocycles (N-HETs) were used for quantification. Limits of quantification were in the low ngL(-1) range. Concentrations were determined in 29 aqueous samples from 8 relatively large rivers located in Lower Saxony (Germany) and the North Sea. NSO-HETs had comparable or even higher sum concentrations than EPA-PAHs. N-HETs, especially acridine and quinolines with concentrations of up to 20ngL(-1) per substance, were predominant.

  4. Data assimilation with the ensemble Kalman filter in a numerical model of the North Sea

    NASA Astrophysics Data System (ADS)

    Ponsar, Stéphanie; Luyten, Patrick; Dulière, Valérie

    2016-08-01

    Coastal management and maritime safety strongly rely on accurate representations of the sea state. Both dynamical models and observations provide abundant pieces of information. However, none of them provides the complete picture. The assimilation of observations into models is one way to improve our knowledge of the ocean state. Its application in coastal models remains challenging because of the wide range of temporal and spatial variabilities of the processes involved. This study investigates the assimilation of temperature profiles with the ensemble Kalman filter in 3-D North Sea simulations. The model error is represented by the standard deviation of an ensemble of model states. Parameters' values for the ensemble generation are first computed from the misfit between the data and the model results without assimilation. Then, two square root algorithms are applied to assimilate the data. The impact of data assimilation on the simulated temperature is assessed. Results show that the ensemble Kalman filter is adequate for improving temperature forecasts in coastal areas, under adequate model error specification.

  5. Estimating uncertainty caused by ocean heat transport to the North Sea: experiments downscaling EC-Earth

    NASA Astrophysics Data System (ADS)

    Tian, T.; Su, J.; Boberg, F.; Yang, S.; Schmith, T.

    2016-01-01

    The heat content of the North Sea is determined by the surface heat flux and the ocean heat transport into the region. The uncertainty in the projected warming in the North Sea caused by ocean heat transport has rarely been quantified. The difference in the estimates using regional ocean models is known to arise from the poorly prescribed temperature boundary forcing, either provided by global models at coarse grid resolutions, or from anomaly correction (using difference of the simulation from observed climatology) without interannual variation. In this study, two marine downscaling experiments were performed using boundary temperature forcings prepared with the two above mentioned strategies: one interpolated from a global model simulation (MI: model incl. interannual variation), and the other from observed climatology with warming trends in the future ocean derived from the global model simulation (OT: observed climatol. plus trend). The comparative experiments allowed us to estimate the uncertainty caused by ocean heat transport to the North Sea. The global climate model EC-Earth CMIP5 simulations of historical and future scenarios were used to provide lateral boundary forcing for regional models. The OT boundary was found to affect deep water temperatures (below 50 m) in the North Sea because of reduced interannual variability. The difference of mean temperature changes by 2100 (MI - OT) was up to 0.5 °C near the bottom across 58°N. While the deep water temperature in the North Sea did not directly link to the large-scale atmospheric circulation, the Norwegian outflow was highly correlated with the NAO index and heat transport of the Atlantic inflow provided by EC-Earth. It was found that model uncertainty due to the choice of lateral boundary forcing could be significant in the interannual variation of thermal stratification in the northern North Sea in a long-term simulation.

  6. Monthly maps of optimally interpolated in situ hydrography in the North Sea from 1948 to 2013

    NASA Astrophysics Data System (ADS)

    Núñez-Riboni, Ismael; Akimova, Anna

    2015-11-01

    We used a statistical model mainly based on optimal or Gauss-Markov interpolation (OI) to produce monthly maps of in situ hydrography in the North Sea through 66 years (from 1948 to 2013) with a resolution of 0.2° × 0.2°. The in situ hydrography data are approximately 430,000 hydrographic profiles and aggregated thermosalinograph data from various international databases. Duplicates, outliers and vertical density instabilities were removed. Regions with poor OI estimates were replaced with a harmonic reconstruction arising from the most reliable OI estimates. Adjustments for vertical density stability were based on the standards of the World Ocean Atlas. We mapped at 54 depth levels through the water column, focusing on surface and bottom hydrography because this type of map is of particular interest for ecosystem and fisheries research. Average OI temperature and salinity expected errors at the surface are 0.3 °C and 0.1, respectively. OI errors decrease with depth following decrement of signal and noise variances and apparently independent of the data amount (indicating a good data coverage). Alternative error estimates were obtained with the Median Absolute Deviation between our hydrography estimates and time series excluded from the analysis and are on average 0.3 °C and 0.1 salinity units. While our product seems limited for analysis of variability on monthly and seasonal time scales, particularly in the regions of large variability, it is suitable for studies of inter-annual and decadal variability. A comparison with two alternative analyses (KLIWAS and SODA) is discussed. As direct application of our results, we present a new hydrographic climatology of the North Sea at various depths with an improved effective resolution.

  7. Improved oil recovery using bacteria isolated from North Sea petroleum reservoirs

    SciTech Connect

    Davey, R.A.; Lappin-Scott, H.

    1995-12-31

    During secondary oil recovery, water is injected into the formation to sweep out the residual oil. The injected water, however, follows the path of least resistance through the high-permeability zones, leaving oil in the low-permeability zones. Selective plugging of these their zones would divert the waterflood to the residual oil and thus increase the life of the well. Bacteria have been suggested as an alternative plugging agent to the current method of polymer injection. Starved bacteria can penetrate deeply into rock formations where they attach to the rock surfaces, and given the right nutrients can grow and produce exo-polymer, reducing the permeability of these zones. The application of microbial enhanced oil recovery has only been applied to shallow, cool, onshore fields to date. This study has focused on the ability of bacteria to enhance oil recovery offshore in the North Sea, where the environment can be considered extreme. A screen of produced water from oil reservoirs (and other extreme subterranean environments) was undertaken, and two bacteria were chosen for further work. These two isolates were able to grow and survive in the presence of saline formation waters at a range of temperatures above 50{degrees}C as facultative anaerobes. When a solution of isolates was passed through sandpacks and nutrients were added, significant reductions in permeabilities were achieved. This was confirmed in Clashach sandstone at 255 bar, when a reduction of 88% in permeability was obtained. Both isolates can survive nutrient starvation, which may improve penetration through the reservoir. Thus, the isolates show potential for field trials in the North Sea as plugging agents.

  8. Metals in molluscs and algae: a north-south Tyrrhenian Sea baseline.

    PubMed

    Conti, Marcelo Enrique; Finoia, Maria Grazia

    2010-09-15

    We develop a 800 km long relative baseline of metal pollution for the Tyrrhenian Sea, from the north of Naples to south of Sicily (Italy), based on spatio-temporal (1997-2004) concentrations of trace metals in marine organisms and on the bioaccumulative properties of those organisms. The study concerns sites in the gulf of Gaeta-Formia, near Naples, and three islands north, west, and south of Sicily: Ustica, Favignana and Linosa. The five metals are: cadmium, chromium, copper, lead, and zinc; the species include: Monodonta turbinata (n=161), Patella caerulea (n=244) and the algae Padina pavonica (n=84). We use Johnson's (1949) [15] probabilistic method to determine the type of distribution that accounts for our data. It is a system of frequency curves that represents the transformation of the standard normal curves. We find an N-S pollution gradient in molluscs considered: the lowest metal pollution occurs around the Sicilian islands. Our method can accurately characterize marine pollution by contributing to: policy-making, coastal resources management, the assessments of environmental damages from marine accidents and other events. The method here presented is a useful tool for pollution comparisons purposes among ecosystems (i.e., risk monitoring) and it is an ideal starting point for its application on a global scale.

  9. Taxonomy of quaternary deep-sea ostracods from the Western North Atlantic ocean

    USGS Publications Warehouse

    Yasuhara, Moriaki; Okahashi, H.; Cronin, T. M.

    2009-01-01

    Late Quaternary sediments from Ocean Drilling Program (ODP) Hole 1055B, Carolina Slope, western North Atlantic (32??47.041??? N, 76??17.179??? W; 1798m water depth) were examined for deep-sea ostracod taxonomy. A total of 13933 specimens were picked from 207 samples and c. 120 species were identified. Among them, 87 species were included and illustrated in this paper. Twenty-eight new species are described. The new species are: Ambocythere sturgio, Argilloecia abba, Argilloecia caju, Argilloecia keigwini, Argilloecia robinwhatleyi, Aversovalva carolinensis, Bythoceratina willemvandenboldi, Bythocythere eugeneschornikovi, Chejudocythere tenuis, Cytheropteron aielloi, Cytheropteron demenocali, Cytheropteron didieae, Cytheropteron richarddinglei, Cytheropteron fugu, Cytheropteron guerneti, Cytheropteron richardbensoni, Eucytherura hazeli, Eucytherura mayressi, Eucytherura namericana, Eucytherura spinicorona, Posacythere hunti, Paracytherois bondi, Pedicythere atroposopetasi, Pedicythere kennettopetasi, Pedicythere klothopetasi, Pedicythere lachesisopetasi, Ruggieriella mcmanusi and Xestoleberis oppoae. Taxonomic revisions of several common species were made to reduce taxonomic uncertainty in the literature. This study provides a robust taxonomic baseline for application to palaeoceanographical reconstruction and biodiversity analyses in the deep and intermediate-depth environments of the North Atlantic Ocean. ?? The Palaeontological Association, 2009.

  10. Metals in molluscs and algae: a north-south Tyrrhenian Sea baseline.

    PubMed

    Conti, Marcelo Enrique; Finoia, Maria Grazia

    2010-09-15

    We develop a 800 km long relative baseline of metal pollution for the Tyrrhenian Sea, from the north of Naples to south of Sicily (Italy), based on spatio-temporal (1997-2004) concentrations of trace metals in marine organisms and on the bioaccumulative properties of those organisms. The study concerns sites in the gulf of Gaeta-Formia, near Naples, and three islands north, west, and south of Sicily: Ustica, Favignana and Linosa. The five metals are: cadmium, chromium, copper, lead, and zinc; the species include: Monodonta turbinata (n=161), Patella caerulea (n=244) and the algae Padina pavonica (n=84). We use Johnson's (1949) [15] probabilistic method to determine the type of distribution that accounts for our data. It is a system of frequency curves that represents the transformation of the standard normal curves. We find an N-S pollution gradient in molluscs considered: the lowest metal pollution occurs around the Sicilian islands. Our method can accurately characterize marine pollution by contributing to: policy-making, coastal resources management, the assessments of environmental damages from marine accidents and other events. The method here presented is a useful tool for pollution comparisons purposes among ecosystems (i.e., risk monitoring) and it is an ideal starting point for its application on a global scale. PMID:20605327

  11. Bacterial and archaeal communities in sediments of the north Chinese marginal seas.

    PubMed

    Liu, Jiwen; Liu, Xiaoshou; Wang, Min; Qiao, Yanlu; Zheng, Yanfen; Zhang, Xiao-Hua

    2015-07-01

    Microbial communities of the Chinese marginal seas have rarely been reported. Here, bacterial and archaeal community structures and abundance in the surface sediment of four sea areas including the Bohai Sea (BS), North Yellow Sea (NYS), South Yellow Sea (SYS), and the north East China Sea (NECS) were surveyed by 16S ribosomal RNA (rRNA) gene pyrosequencing and quantitative PCR. The results showed that microbial communities of the four geographic areas were distinct from each other at the operational taxonomic unit (OTU) level, whereas the microbial communities of the BS, NYS, and SYS were more similar to each other than to the NECS at higher taxonomic levels. Across all samples, Bacteria were numerically dominant relative to Archaea, and among them, Gammaproteobacteria and Euryarchaeota were predominant in the BS, NYS, and SYS, while Deltaproteobacteria and Thaumarchaeota were prevalent in the NECS. The most abundant bacterial genera were putative sulfur oxidizer and sulfate reducer, suggesting that sulfur cycle processes might prevail in these areas, and the high abundance of dsrB (10(7)-10(8) copies g(-1)) in all sites verified the dominance of sulfate reducer in the north Chinese marginal seas. The differences in sediment sources among the sampling areas were potential explanations for the observed microbial community variations. Furthermore, temperature and dissolved oxygen of bottom water were significant environmental factors in determining both bacterial and archaeal communities, whereas chlorophyll a in sediment was significant only in structuring archaeal community. This study presented an outline of benthic microbial communities and provided insights into understanding the biogeochemical cycles in sediments of the north Chinese marginal seas. PMID:25501892

  12. Bacterial and archaeal communities in sediments of the north Chinese marginal seas.

    PubMed

    Liu, Jiwen; Liu, Xiaoshou; Wang, Min; Qiao, Yanlu; Zheng, Yanfen; Zhang, Xiao-Hua

    2015-07-01

    Microbial communities of the Chinese marginal seas have rarely been reported. Here, bacterial and archaeal community structures and abundance in the surface sediment of four sea areas including the Bohai Sea (BS), North Yellow Sea (NYS), South Yellow Sea (SYS), and the north East China Sea (NECS) were surveyed by 16S ribosomal RNA (rRNA) gene pyrosequencing and quantitative PCR. The results showed that microbial communities of the four geographic areas were distinct from each other at the operational taxonomic unit (OTU) level, whereas the microbial communities of the BS, NYS, and SYS were more similar to each other than to the NECS at higher taxonomic levels. Across all samples, Bacteria were numerically dominant relative to Archaea, and among them, Gammaproteobacteria and Euryarchaeota were predominant in the BS, NYS, and SYS, while Deltaproteobacteria and Thaumarchaeota were prevalent in the NECS. The most abundant bacterial genera were putative sulfur oxidizer and sulfate reducer, suggesting that sulfur cycle processes might prevail in these areas, and the high abundance of dsrB (10(7)-10(8) copies g(-1)) in all sites verified the dominance of sulfate reducer in the north Chinese marginal seas. The differences in sediment sources among the sampling areas were potential explanations for the observed microbial community variations. Furthermore, temperature and dissolved oxygen of bottom water were significant environmental factors in determining both bacterial and archaeal communities, whereas chlorophyll a in sediment was significant only in structuring archaeal community. This study presented an outline of benthic microbial communities and provided insights into understanding the biogeochemical cycles in sediments of the north Chinese marginal seas.

  13. Comparison of Late Ordovician epicontinental seas and their relative bathymetry in North American and China

    SciTech Connect

    Johnson, M.E.; Fox, W.T. ); Jia-Yu, Rong )

    1989-02-01

    Six widely separated areas with Upper Ordovician strata in Canada and the United States are compared with six localities in southern China. Cyclic sedimentation, including evaporites, carbonates, and phosphatic black shales, occurred in relatively shallow epicontinental seas of North America. As many as three Ashgill cycles of regionally different styles may have been coeval throughout North America in response to modest changes in sea level. Environments in South China primarily included carbonates and black shales with a far more uniform distribution. Absence of comparable sedimentary cycles confirms that the platform bathymetry of South China was consistently deeper than in North America. The almost complete exposure of North China (Sino-Korean Plate) by Late Ordovician time underscores the fact that independent cratons have different bathymetric histories. By mid-Silurian time, South China also was fully exposed. Such hypsographic variation is critical to the intercontinental correlation of features related to eustasy, water chemistry, and even the patterns of extinctions.

  14. Temperature affects the timing of spawning and migration of North Sea mackerel

    NASA Astrophysics Data System (ADS)

    Jansen, Teunis; Gislason, Henrik

    2011-01-01

    Climate change accentuates the need for knowing how temperature impacts the life history and productivity of economically and ecologically important species of fish. We examine the influence of temperature on the timing of the spawning and migrations of North Sea Mackerel using data from larvae CPR surveys, egg surveys and commercial landings from Danish coastal fisheries in the North Sea, Skagerrak, Kattegat and inner Danish waters. The three independent sources of data all show that there is a significant relationship between the timing of spawning and sea surface temperature. Large mackerel are shown to arrive at the feeding areas before and leave later than small mackerel and the sequential appearance of mackerel in each of the feeding areas studied supports the anecdotal evidence for an eastward post-spawning migration. Occasional commercial catches taken in winter in the Sound N, Kattegat and Skagerrak together with catches in the first quarter IBTS survey furthermore indicate some overwintering here. Significant relationships between temperature and North Sea mackerel spawning and migration have not been documented before. The results have implications for mackerel resource management and monitoring. An increase in temperature is likely to affect the timing and magnitude of the growth, recruitment and migration of North Sea mackerel with subsequent impacts on its sustainable exploitation.

  15. The influence of the NAO on oxygen dynamics in the North Sea: (EGU2015)

    NASA Astrophysics Data System (ADS)

    Paetsch, Johannes; Thomas, Helmuth; Grosse, Fabian; Kreus, Markus

    2015-04-01

    The North Sea is a semi-enclosed shelf sea attached to the North-east Atlantic. While the strong Atlantic influence in the north and the anthropogenic effects in the southern coastal zone prevail, hydrodynamic and biogeochemical dynamics in the central North Sea are mainly affected by the meteorology and its local variations. Summer observations of bottom layer oxygen concentrations in the central North Sea exhibit similar values in 2001, 2005 and 2008 even though the NAO indices of the corresponding preceding winters were different with lowest index in 2001 and highest index in 2008. Model simulations with ECOHAM show that two effects determining the bottom oxygen concentrations are compensating each other in these years: In the months February to September in 2008 bottom temperature was higher than in the other two years with lower NAO indices. On the other hand stronger winds in winter 2007/2008 induced a well-mixed water column which inhibits the late winter / early spring bloom. Due to the reduced primary production, the amount of vertically exported organic matter in the sediment in 2008 was less compared to the other years. Consequently, the oxygen demand for benthic remineralisation was lowest in 2008. In contrast to the observed bottom oxygen concentrations, the Apparent Oxygen Utilisation (AOU) in summer differs in between the different years. Lowest values were found in 2008 with values being about 2 times less than in 2001 and 2005.

  16. Two centuries of observed atmospheric variability and change over the North Sea region

    NASA Astrophysics Data System (ADS)

    Stendel, Martin; van den Besselaar, Else; Hannachi, Abdel; Kent, Elizabeth; Lefebvre, Christiana; Rosenhagen, Gudrun; Schenk, Frederik; van der Schrier, Gerard; Woollings, Tim

    2016-04-01

    In the upcoming North Sea Region Climate Change Assessment (NOSCCA), we present a synthesis of current knowledge about past, present and possible future climate change in the North Sea region. A climate change assessment from published scientific work has been conducted as a kind of regional IPCC report, and a book has been produced that will be published by Springer in 2016. In the framework of the NOSCCA project, we examine past and present studies of variability and changes in atmospheric variables within the North Sea region over the instrumental period, roughly the past 200 years, based on observations and reanalyses. The variables addressed in this presentation are large-scale circulation, pressure and wind, surface air temperature, precipitation and radiative properties (clouds, solar radiation, and sunshine duration). While air temperature over land, not unexpectedly, has increased everywhere in the North Sea region, with strongest trends in spring and in the north of the region, a precipitation increase has been observed in the north and a decrease in the south of the region. This pattern goes along with a north-eastward shift of storm tracks and is in agreement with climate model projections under enhanced greenhouse gas concentrations. For other variables, it is not obvious which part of the observed changes may be due to anthropogenic activities and which is internally forced. It remains also unclear to what extent atmospheric circulation over the North Sea region is influenced by distant factors, in particular Arctic sea-ice decline in recent decades. There are indications of an increase in the number of deep cyclones (but not in the total number of cyclones), while storminess since the late 19th century shows no robust trends. The persistence of circulation types appears to have increased over the last century, and consequently, there is an indication for 'more extreme' extreme events. However, changes in extreme weather events are difficult to assess

  17. North Sea Scyphomedusae; summer distribution, estimated biomass and significance particularly for 0-group Gadoid fish

    NASA Astrophysics Data System (ADS)

    Hay, S. J.; Hislop, J. R. G.; Shanks, A. M.

    Data on the by-catch of Scyphomedusae from pelagic trawls was collected during the routine ICES International 0-group Gadoid Surveys of the North Sea, in June and July of the years 1971-1986 (except 1984). These data are used to describe the distributions, abundances and biomasses of three common North Sea Scyphomedusae: Aurelia aurita (L.), Cyanea capillata (L.) and C. lamarckii (Péron & Lesuer). Information is also presented on inter-annual variability, size (umbrella diameter) frequencies and, for the Cyanea species, umbrella diameter: wet weight relationships. The general role and ecological significance of Scyphomedusae is discussed and, given the well known 'shelter' relationships between Scyphomedusae and certain 0-group fish, whiting ( Merlangius merlangus) and haddock ( Melanogrammus aeglefinus), in particular. The data were examined for evidence of such relationships. Aurelia aurita, although fairly widespread in the northern North Sea was virtually absent from the central North Sea but very abundant in coastal waters. This species was particularly abundant off the Scottish east coast and especially in the Moray Firth. Cyanea lamerckii was most abundant in the southern and eastern North Sea. More widespread than Aurelia, this species was also most abundant in coastal regions, particularly off the Danish west coast. Cyanea capillata, with a more northern distribution was also more widely distributed and abundant offshore. This species was most abundant in the area between the Orkney/Shetland Isles and the Norwegian Deep and in shelf waters of the north west approaches to the North Sea. As with C. lamarckii it was also, in some years, abundant off the Scottish east coast and west of Denmark. The abundance and the size frequency of the jellyfish show considerable inter-annual variability, and variability between regions of the North Sea. It is considered that hydrographic variability and differences in food supply to both medusae and to their sessile

  18. Sea-ice and North Atlantic climate response to CO2-induced warming and cooling conditions

    NASA Astrophysics Data System (ADS)

    Nazarenko, Larissa; Tausnev, Nickolai; Hansen, James

    Using a global climate model coupled with an ocean and a sea-ice model, we compare the effects of doubling CO2 and halving CO2 on sea-ice cover and connections with the atmosphere and ocean. An overall warming in the 2 × CO2 experiment causes reduction of sea-ice extent by 15%, with maximum decrease in summer and autumn, consistent with observed seasonal sea-ice changes. The intensification of the Northern Hemisphere circulation is reflected in the positive phase of the Arctic Oscillation (AO), associated with higher-than-normal surface pressure south of about 50° N and lower-than-normal surface pressure over the high northern latitudes. Strengthening the polar cell causes enhancement of westerlies around the Arctic perimeter during winter. Cooling, in the 0.5 × CO2 experiment, leads to thicker and more extensive sea ice. In the Southern Hemisphere, the increase in ice-covered area (28%) dominates the ice-thickness increase (5%) due to open ocean to the north. In the Northern Hemisphere, sea-ice cover increases by only 8% due to the enclosed land/sea configuration, but sea ice becomes much thicker (108%). Substantial weakening of the polar cell due to increase in sea-level pressure over polar latitudes leads to a negative trend of the winter AO index. The model reproduces large year-to-year variability under both cooling and warming conditions.

  19. Predicting the consequences of nutrient reduction on the eutrophication status of the North Sea

    NASA Astrophysics Data System (ADS)

    Lenhart, Hermann-J.; Mills, David K.; Baretta-Bekker, Hanneke; van Leeuwen, Sonja M.; van der Molen, Johan; Baretta, Job W.; Blaas, Meinte; Desmit, Xavier; Kühn, Wilfried; Lacroix, Geneviève; Los, Hans J.; Ménesguen, Alain; Neves, Ramiro; Proctor, Roger; Ruardij, Piet; Skogen, Morten D.; Vanhoutte-Brunier, Alice; Villars, Monique T.; Wakelin, Sarah L.

    2010-04-01

    In this paper the results from a workshop of the OSPAR Intersessional Correspondence Group on Eutrophication Modelling (ICG-EMO) held in Lowestoft in 2007 are presented. The aim of the workshop was to compare the results of a number of North Sea ecosystem models under different reduction scenarios. In order to achieve comparability of model results the participants were requested to use a minimum spin-up time, common boundary conditions which were derived from a wider-domain model, and a set of common forcing data, with special emphasis on a complete coverage of river nutrient loads. Based on the OSPAR requirements river loads were derived, taking into account the reductions already achieved between 1985 and 2002 for each country. First, for the year 2002, for which the Comprehensive Procedure was applied, the different horizontal distributions of net primary production are compared. Furthermore, the differences in the net primary production between the hindcast run and the 50% nutrient reduction runs are displayed. In order to compare local results, the hindcast and reduction runs are presented for selected target areas and scored against the Comprehensive Procedure assessment levels for the parameters DIN, DIP and chlorophyll. Finally, the temporal development of the assessment parameter bottom oxygen concentration from several models is compared with data from the Dutch monitoring station Terschelling 135. The conclusion from the workshop was that models are useful to support the application of the OSPAR Comprehensive Procedure. The comparative exercise formulated specifically for the workshop required models to be evaluated for pre-defined target areas previously classified as problem areas according to the first application of the Comprehensive Procedure. The responsiveness of the modelled assessment parameters varied between different models but in general the parameter showed a larger response in coastal rather than in offshore waters, which in some cases

  20. Role of the North Pacific sea surface temperature in the East Asian winter monsoon decadal variability

    NASA Astrophysics Data System (ADS)

    Sun, Jianqi; Wu, Sha; Ao, Juan

    2016-06-01

    In this study, a possible mechanism for the decadal variability in the East Asian winter monsoon (EAWM) is proposed. Specifically, the North Pacific sea surface temperature (SST) may play an important role. An analysis of the observations shows that the North Pacific SST has a remarkable decadal pattern whose phase shifted around the mid-1980s. This North Pacific SST decadal pattern can weaken the East Asian trough and enhance the North Pacific Oscillation through changing air-sea interactions over the North Pacific. The weak East Asian trough enhances the zonal circulation and weakens the meridional circulation over East Asia, consequently leading to a weaker southward cold surge and East Asia warming around the mid-1980s. The numerical experiment further confirms the pronounced physical processes. In addition, over the longer period of 1871-2012, the indices of the EAWM and North Pacific SST decadal pattern are also highly consistent on the decadal timescale, which further confirms the impact of the North Pacific SST decadal pattern on the EAWM decadal variability.

  1. Scenarios of temporal and spatial evolution of hexabromocyclododecane in the North Sea.

    PubMed

    Ilyina, Tatiana; Hunziker, René W

    2010-06-15

    Spatial and temporal distribution of the flame retardant hexabromocyclododecane (HBCD) in the North Sea was examined for the period from 1995 to 2005 using a pollutant transport model FANTOM. Model calculations allow conclusions on relevant sinks and fluxes in and out of the North Sea and on the time needed to establish a steady state. Calculations were performed for two additional scenarios with different rates of primary degradation ranging from fast degrading to absolute persistency. Concentrations calculated in the scenarios with degradation are in line with the monitoring data available for HBCD. Concentrations calculated in the "persistent" scenario disagree with measured data. According to our model calculations, steady state is established within months for the water and the top layer sediment with no evidence for a temporal trend, except for the "persistent" scenario, in which concentrations increase continuously in the southeastern part of the North Sea, where hydrographic and circulation characteristics produce areas of converging currents. Our model study enables a better understanding of the fate of HBCD in the North Sea, its potential for transport and overall elimination. We discuss these findings in the light of different concerns for PBT substances.

  2. Six Pseudoalteromonas Strains Isolated from Surface Waters of Kabeltonne, Offshore Helgoland, North Sea

    PubMed Central

    Wichels, Antje; Sullivan, Matthew B.

    2016-01-01

    Draft genomes are presented for 6 Pseudoalteromonas sp. strains isolated from surface waters at Kabeltonne, Helgoland, a long-term ecological research station in the North Sea. These strains contribute knowledge of the genomic underpinnings of a developing model system to study phage-host dynamics of a particle-associated ocean copiotroph. PMID:26868390

  3. Subsea template, pipeline anchor Troll-Oseberg gas-injection scheme in Norwegian North Sea

    SciTech Connect

    Weibye, B.S.

    1988-01-18

    The author discusses the subsea, gas production template and the 30-mile pipeline that are key elements in supplying as from the Troll field for injection into Oseberg field in the Norwegian North Sea by 1991. The author discusses the design basis and philosophies as well as the production system, template installation and control pods.

  4. Relation between liquid hydrocarbon reserves and geothermal gradients - Norwegian North Sea

    SciTech Connect

    Baird, R.A. )

    1991-03-01

    Comparison of average geothermal gradients and initial liquid hydrocarbon reserves for 28 Norwegian North Sea fields indicates that gradients in the largest North Sea oil fields cluster around 2.1F/100 feet. No reserves are found where gradients are lower than 1.8F/100 feet or higher than 2.3F/100 feet. At 6.89 billion barrels, reserves for 14 fields falling between 2.05 and 2.15/100 feet total over four times the reserves for all other fields put together. Reserves for seven fields at gradients lower than 2.05F/100 feet and for seven higher than 2.15F/100 feet total 594 and 991 million barrels, respectively. The conclusion is that 2.1F/100 feet is the optimum gradient for generation of liquid hydrocarbons in the Norwegian North Sea, given the depth, kerogen type, and source rock potential of the Kimmeridge Clay, the primary source rock there. Gradients lower than this have not stimulated maximum generation from the source rock. At higher gradients, increasing gas production from source rocks and thermal cracking of previously generated liquid hydrocarbons to gas are effective in limiting liquid hydrocarbon reserves. The 2.1F/100 feet gradient should be a useful pathfinder in the search for new oil reserves in the Norwegian North Sea. Determination of the optimum gradient should be a useful pathfinder in other regions as well.

  5. Amphiura filiformis (Ophiuroidea: Echinodermata) in the North Sea. Distribution, present and former abundance and size composition

    NASA Astrophysics Data System (ADS)

    Duineveld, G. C. A.; Künitzer, A.; Heyman, R. P.

    During the North Sea Benthos Survey undertaken by the ICES Benthos Ecology Working Group in spring 1986, a synoptic inventory was made of the benthos in the southern, central and part of the northern North Sea. The present paper deals with the status of the population of the infaunal ophiuroid Amphiura filiformis on the basis of measurements from 150 stations. A. filiformis was found at all the offshore muddy stations, but densities were generally highest in the shallow area south of the Dogger Bank. Stations with more than 1000 ind·m -2 were mainly situated near the frontiers between turbid and summer-stratified water masses, viz. along the southern border of the Oyster Ground, the southern slope of the Dogger Bank and in the northern part of the Pleistocene Elbe river valley. The size-distributions of A. filiformis show that juveniles were generally scarce at stations with high numbers of adults, whereas highest numbers of juveniles occur at stations with few adults. An unequivocal relation between adults and juveniles was, however, absent. This stresses the importance of other factors involved in recruitment. Comparison between the present and former (1938 and 1950) density of A. filiformis suggests that density has increased in the shallower parts but has remained stable in the deeper northern North Sea. An increase of A. filiformis shallow part of the North Sea could point to an enhanced food supply for the benthos, which may have some relation to the eutrophication in nearshore areas.

  6. Vortices generation mechanisms in North western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Fraunie, P.; Redondo, J. M.; Schaeffer, A.; Molcard, A.; Forget, P.; Garreau, P.

    2012-04-01

    Mesoscale eddies have been observed in Northwestern Mediterranean Sea from satellites, RV cruises and more recently using HF radars. Different non linear mechanisms have been identified and investigated using process oriented high resolution numerical modelling. In particular, wind induced inertial motion and baroclinic instability cases have been illustrated and documented. Statistics of vortices occurence allow a better accounting for coherent structures for pollutants and nutriments dispersion and retention. Acknowledgements : GIRAC project (FUI - CG83 -TPM), ESA, HYMEX programme

  7. Oil contamination of fish in the North Sea. Determination of levels and identification of sources

    SciTech Connect

    Johnsen, S.; Restucci, R.; Klungsoyr, J.

    1996-12-31

    Two fish species, cod and haddock have been sampled from five different regions in the Norwegian sector of the North Sea, the Haltenbanken and the Barents Sea, Three of the five sampling areas were located in regions with no local oil or gas production, while the remaining two areas represented regions with high density of oil and gas production fields. A total of 25 specimen of each of the two fish species were collected, and liver (all samples) and muscle (10 samples from each group) were analyzed for the content of total hydrocarbons (THC), selected aromatic compounds (NPD and PAH) and bicyclic aliphatic decalines. The present paper outlines the results of liver samples analyses from four of the sampled regions, & northern North Sea region and the three reference regions Egersundbanken, Haltenbanken and the Barents Sea. In general, no significant difference was observed between the hydrocarbon levels within the sampled regions. The only observed exception was a moderate, but significant increase in decaline levels in haddock liver from the Northern North Sea region. The qualitative interpretation of the results showed that the sources of hydrocarbon contamination varied within the total sampling area. This observation indicates that the local discharge sources in areas with high petroleum production activity are the sources of hydrocarbons in fish from such areas. However, it was not possible to identify single discharges as a contamination source from the present results.

  8. Deriving long-term sea level variations at tide gauge stations in Atlantic North America

    NASA Astrophysics Data System (ADS)

    Ince, E. S.; Sideris, M. G.; Rangelova, E.

    2009-05-01

    Tide gauge recording is an indispensable geodetic tool to study local sea level variations in coastal areas and mean sea level trends on a global scale. Combined with satellite altimetry sea surface heights or GNSS- derived ellipsoidal heights, tide gauge records have been used for deriving estimates of vertical crustal motion elsewhere. The objective of our paper is to study the capabilities of the method of singular spectrum analysis, which is generically related to empirical orthogonal functions/principal component analysis technique, to derive local long-term and secular sea level trends. This method allows one to extract any anomalous sea level signals, which is difficult to achieve by the conventional harmonic analysis. We use a set of tide gauge stations in Atlantic Canada and the USA extracted from the monthly PSMSL data base. To create continuous time series, we fill all time gaps by interpolating the main periodic and trend components of the sea level signal using the least squares harmonic analysis. We analyze all tide gauge time series simultaneously through singular value decomposition of the time-lagged series combined in a data trajectory matrix. This enables us to extract and separate the main modes of variability of the local sea level and to study only the long-term spatio-temporal patterns in the sea level variations. Our preliminary results show that the length of the tide gauge time series and the relative contribution of the signals to the total sea level variance are the two crucial factors that may preclude the separation of the local secular sea level fall or rise from any decadal sea level variability. The outcome of our study will be useful for combined satellite altimetry/TG/GRACE studies of sea level changes in the coastal areas, studies of vertical crustal motion due to postglacial rebound in the region, as well as the definition and realization of a dynamic reference surface for orthometric heights in North America.

  9. Occurrence of Ergasilus megaceros Wilson, 1916, in the sea lamprey and other fishes from North America

    USGS Publications Warehouse

    Muzzall, Patrick M.; Hudson, Patrick L.

    2004-01-01

    Ergasilus megaceros (Copepoda: Ergasilidae) was recovered from the nasal fossae (lamellae) of the olfactory sac in 1 (1.8%) of 56 sea lampreys, Petromyzon marinus Linne, 1758, collected in May 2002 from the Cheboygan River, Michigan. Although the sea lamprey is a new host record for E. megaceros, this fish species may not be a preferred host because of its low prevalence. Ergasilus megaceros is the second ergasilid species reported from the sea lamprey in North America. This is the third report of an ergasilid species infecting the nasal fossae of fishes in North America, with E. rhinos being the only other species reported from this site.

  10. High-resolution area-wide sea-floor mapping: The paleo Elbe valley (S North Sea) revisited

    NASA Astrophysics Data System (ADS)

    Papenmeier, Svenja; Hass, H. Christian

    2014-05-01

    The North Sea Basin is shaped by multiple glacial advances and retreats that left complex sequences of glacio-fluvial and sub-glacial deposits, cut by sub-glacial tunnel valleys. Today, the submerged valley of the Elbe forms one of the most prominent structures of the southern North Sea. Flanked by huge moraine deposits of older glacials, the valley developed to its present form during the Weichselian sea-level lowstand (-130 m below present). Melt waters that discharged in north-westerly directions along the Scandinavian Ice Sheet fed the paleo Elbe at that time. During the Holocene the valley drowned in the rising sea. Here we present an area-wide high-resolution map of the seafloor and high-resolution shallow seismic data covering 1,600 km2 of the paleo Elbe valley (PEV) including its eastern levee. The data allow to shed new light on the PEV development including the historical process of sedimentary infill with the successive Holocene sea level rise in detail. Shallow seismic data with transect distances of 400 m and several cross sections allow 3-D visualization. The eastern flank of the valley is characterized by a relatively steep slope with one or more terraces. At its levee a significant sediment change is present on the modern sea floor, representing moraine and marine deposits. High resolution sidescan sonar data of this area show a much higher heterogeneity and complexity in sediment and habitat distribution as assumed before. Holocene marine sediments form a patchy and thin drape east of the valley floor. The western slip-off slope of the valley slope is much smoother than the eastern undercut slope. As yet, significant sedimentological changes at the present seafloor are not known for the western side of the PEV. Shallow seismic data show the base of the PEV. There are conspicuous internal seismic reflectors above the base, inclined in northeastern direction. They indicate a sedimentary infill of the valley from the southwest when the southern part

  11. Segregation of herring larvae from inshore and offshore spawning grounds in the north-western North Sea — Implications for stock structure

    NASA Astrophysics Data System (ADS)

    Heath, M.

    Herring larvae hatching from spawning sites around the Scottish coast are dispersed by water currents during the weeks following hatching. Hydrographic data, observations on the distribution of caesium-137 and measurements of current velocities by moored meters and drifting buoys, suggest that larvae from offshore spawning sites around the north of Scotland should be more rapidly dispersed than those hatching in inshore areas. This has been confirmed by direct observations on the advection of herring larvae in different regions of the north western North Sea. The conclusion is that larvae hatching in inshore areas, especially in the Moray Firth, are most likely to contribute to nearby juvenile populations, whereas larvae from offshore spawning sites should be widely dispersed over the North Sea. Tagging and parasitology investigations have shown that adult herring spawning in the north-western North Sea have been widely dispersed in the North Sea and adjacent waters as juveniles (six months — one and a half years old). However, a high proportion of adult fish caught at inshore spawning sites and in the Moray Firth were found to have been recruited from more local areas. Taken together with the observations on larval drift, these observations suggest that the stock structure of herring in the northern North Sea may in part be a consequence of the physical oceanography of the area.

  12. Focal mechanism determinations of earthquakes along the North Anatolian fault, beneath the Sea of Marmara and the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Nakano, Masaru; Citak, Seckin; Kalafat, Doğan

    2015-09-01

    We determined the centroid moment tensor (CMT) solutions of earthquakes that occurred along the North Anatolian fault (NAF) beneath the Sea of Marmara and the Aegean Sea, using data obtained from Turkey's broad-band seismograph network. The CMT solution of the 2014 Aegean Sea earthquake ( Mw 6.9) represents a strike-slip fault, consistent with the geometry of the NAF, and the source-time function indicates that this event comprised several distinct subevents. Each subevent is considered to have ruptured a different fault segment. This observation indicates the existence of a mechanical barrier, namely a NAF segment boundary, at the hypocenter. CMT solutions of background seismicity beneath the Aegean Sea represent strike-slip or normal faulting along the NAF or its branch faults. The tensional axes of these events are oriented northeast-southwest, indicating a transtensional tectonic regime. Beneath the Sea of Marmara, the CMT solutions represent mostly strike-slip faulting, consistent with the motion of the NAF, but we identified a normal fault event with a tensional axis parallel to the strike of the NAF. This mechanism indicates that a pull-apart basin, marking a segment boundary of the NAF, is developing there. Because ruptures of a fault system and large earthquake magnitudes are strongly controlled by the fault system geometry and fault length, mapping fault segments along NAF can help to improve the accuracy of scenarios developed for future disastrous earthquakes in the Marmara region.

  13. Use of the Beaufort Sea by king eiders breeding on the North Slope of Alaska

    USGS Publications Warehouse

    Phillips, Laura M.; Powell, A.N.; Taylor, E.J.; Rexstad, E.A.

    2007-01-01

    We estimated areas used by king eiders (Somateria spectabilis) in the Alaskan Beaufort Sea, how distributions of used areas varied, and characteristics that explained variation in the number of days spent at sea, to provide regulatory agencies with baseline data needed to minimize impacts of potential offshore oil development. We implanted sixty king eiders with satellite transmitters at nesting areas on the North Slope of Alaska, USA, in 2002-2004. More than 80% of marked eiders spent >2 weeks staging offshore prior to beginning a postbreeding molt migration. During postbreeding staging and migration, male king eiders had much broader distributions in the Alaskan Beaufort Sea than female eiders, which were concentrated in Harrison and Smith Bays. Distribution did not vary by sex during spring migration in the year after marking. Shorter residence times of eiders and deeper water at locations used during spring migration suggest the Alaskan Beaufort Sea might not be as critical a staging area for king eiders during prebreeding as it is postbreeding. Residence time in the Beaufort Sea varied by sex, with female king eiders spending more days at sea than males in spring and during postbreeding. We conclude the Alaskan Beaufort Sea is an important staging area for king eiders during postbreeding, and eider distribution should be considered by managers when mitigating for future offshore development. We recommend future studies examine the importance of spring staging areas outside the Alaskan Beaufort Sea.

  14. Acceleration of sea-ice Melt Addition Into the Northern North Atlantic

    NASA Astrophysics Data System (ADS)

    Cox, K. A.; Stanford, J. D.; McVicar, A. J.; Rohling, E. J.; Bacon, S.; Bolshaw, M.; de La Rosa, S.; Wilkinson, D.

    2008-12-01

    Observations over the last decade suggest both a thinning of the Arctic sea-ice cover (Rothrock et al., 1999; Laxon et al., 2003) and a dramatic reduction in its spatial extent (Comiso, 2002; Stroeve et al., 2005). We detect a positive change of ~10 ‰ between 1998 and 2005 in the stable oxygen isotope composition of the net freshwater component in the East Greenland Current (EGC) and East Greenland Coastal Current (EGCC), key carriers of freshened surface waters out of the Arctic. This isotopic signal is unique in the context of oxygen isotope measurements in the northern North Atlantic region dating back to the early 1960s. We show that this signal reflects a remarkable increase in the sea-ice melt water transport within these currents, to the equivalent of a net minimum volumetric loss of multi-year ('permanent') Arctic sea-ice of 10 ± 3% per decade. This independent measurement therefore complements and corroborates the sea-ice reduction inferred from satellite data, and places it in a longer-term multi-decadal context. Our findings suggest that a large proportion of the sea-ice meltwater resulting from the rapid reduction of Arctic sea-ice between 1998 and 2005 is exported from the Arctic via the EGC/EGCC into the northern North Atlantic. Additionally it appears that this sea-ice meltwater export is not in phase with atmospheric circulation regimes such as the North Atlantic Oscillation and the Arctic Oscillation. These findings could have important ramifications for the global thermohaline circulation (e.g. Rahmstorf, 2005).

  15. Spatial, seasonal and vertical distributions of currently-used pesticides in the marine boundary layer of the North Sea

    NASA Astrophysics Data System (ADS)

    Mai, Carolin; Theobald, Norbert; Lammel, Gerhard; Hühnerfuss, Heinrich

    2013-08-01

    Pesticides are transported beyond source regions and reach coastal waters and shelf seas. 23 representatives of six chemical classes of currently-used pesticides (CUPs) were simultaneously quantified in the marine boundary layer and the surface seawater of the German Bight and the central North Sea in 2009 and 2010.Terbuthylazine, metolachlor, metazachlor, pendimethalin and trifluralin exhibited the highest concentrations, seasonally highly variable. Advection of contaminated air from land and subsequent atmospheric deposition was shown to contribute to surface seawater contamination significantly, in particular in regions beyond riverine input and during the main seasons of application in agriculture. Deposition was most significant for the seasonal and spatial distributions of pendimethalin and trifluralin. Atrazine and simazine levels in the air are lower than 1-2 decades ago.

  16. Strain migration during multiphase extension: observations from the northern North Sea

    NASA Astrophysics Data System (ADS)

    Bell, Rebecca; Jackson, Christopher; Duffy, Oliver; Whipp, Paul; Clements, Benjamin

    2015-04-01

    Many rifts develop through multiphase extension; it can be difficult, however, to determine how strain is distributed during reactivation because structural and stratigraphic evidence associated with earlier rifting is often deeply buried. Using 2D and 3D seismic reflection and borehole data from the northern North Sea, we examine the style, magnitude and timing of reactivation of a pre-existing, Permian-Triassic (Rift Phase 1) fault array during a subsequent period of Middle Jurassic-to-Early Cretaceous (Rift Phase 2) extension. We show that Rift Phase 2 led to the formation of new N-S-striking faults close to the North Viking Graben, but did not initially reactivate pre-existing, seemingly optimally aligned Rift Phase 1 structures on the Horda Platform. We suggest that, at the beginning of Rift Phase 2, strain was focused in a zone of thermally weakened lithosphere associated with the Middle Jurassic North Sea thermal dome, rather than reactivating extant faults. Diachronous reactivation of the Permian-Triassic fault network did eventually occur, with those faults located closer to the Middle Jurassic-to-Early Cretaceous rift-axis reactivating earlier than those toward the eastern margin. In addition, faults on the southern Horda Platform reactive before those in the north, leading to both an eastward and northward migration in fault reactivation in this area through time. This diachroneity in the timing of fault reactivation may have been related to flexural down-bending as strain became focused within the North Viking Graben and/or the shifting of the locus of rifting from the North Sea to the proto-North Atlantic in the Early Cretaceous. Our study shows that the geometry and evolution of multiphase rifts is not only controlled by the orientation of the underlying fault network, but also by the thermal and rheological evolution of the lithosphere and variations in the regional stress field.

  17. Assimilating NOAA SST data into BSH operational circulation model for North and Baltic Seas

    NASA Astrophysics Data System (ADS)

    Losa, Svetlana; Schroeter, Jens; Nerger, Lars; Janjic, Tijana; Danilov, Sergey; Janssen, Frank

    A data assimilation (DA) system is developed for BSH operational circulation model in order to improve forecast of current velocities, sea surface height, temperature and salinity in the North and Baltic Seas. Assimilated data are NOAA sea surface temperature (SST) data for the following period: 01.10.07 -30.09.08. All data assimilation experiments are based on im-plementation of one of the so-called statistical DA methods -Singular Evolutive Interpolated Kalman (SEIK) filter, -with different ways of prescribing assumed model and data errors statis-tics. Results of the experiments will be shown and compared against each other. Hydrographic data from MARNET stations and sea level at series of tide gauges are used as independent information to validate the data assimilation system. Keywords: Operational Oceanography and forecasting

  18. A new atmospheric proxy for sea level variability in the southeastern North Sea: observations and future ensemble projections

    NASA Astrophysics Data System (ADS)

    Dangendorf, Sönke; Wahl, Thomas; Nilson, Enno; Klein, Birgit; Jensen, Jürgen

    2014-05-01

    Atmosphere-ocean interactions are known to dominate seasonal to decadal sea level variability in the southeastern North Sea. In this study an atmospheric proxy for the observed sea level variability in the German Bight is introduced. Monthly mean sea level (MSL) time series from 13 tide gauges located in the German Bight and one virtual station record are evaluated in comparison to sea level pressure fields over the North Atlantic and Europe. A quasi-linear relationship between MSL in the German Bight and sea level pressure over Scandinavia and the Iberian Peninsula is found. This relationship is used (i) to evaluate the atmospheric contribution to MSL variability in hindcast experiments over the period from 1871-2008 with data from the 20th century reanalysis v2 (20CRv2), (ii) to isolate the high frequency meteorological variability of MSL from longer-term changes, (iii) to derive ensemble projections of the atmospheric contribution to MSL until 2100 with eight different coupled global atmosphere-ocean models (AOGCM's) under the A1B emission scenario and (iv) two additional projections for one AOGCM (ECHAM5/MPI-OM) under the B1 and A2 emission scenarios. The hindcast produces a reasonable good reconstruction explaining approximately 80 % of the observed MSL variability over the period from 1871 to 2008. Observational features such as the divergent seasonal trend development in the second half of the twentieth century, i.e. larger trends from January to March compared to the rest of the year, and regional variations along the German North Sea coastline in trends and variability are well described. For the period from 1961 to 1990 the Kolmogorov-Smirnow test is used to evaluate the ability of the eight AOGCMs to reproduce the observed statistical properties of MSL variations. All models are able to reproduce the statistical distribution of atmospheric MSL. For the target year 2100 the models point to a slight increase in the atmospheric component of MSL with

  19. Heavy metals in sea cucumber juveniles from coastal areas of Bohai and Yellow seas, north China.

    PubMed

    Jiang, Haifeng; Tang, Shizhan; Qin, Dongli; Chen, Zhongxiang; Wang, Jinlong; Bai, Shuyan; Mou, Zhenbo

    2015-05-01

    The study was undertaken to assess the contents of heavy metals (Cu, Zn, Cr, Pb, Cd, As and Hg) in sea cucumber (Apostichopus japonicus) juveniles from coastal areas of Bohai and Yellow seas in northern China. Sea cucumber juveniles were collected from twenty commercial hatcheries distributed in five coastal cities. The mean concentrations obtained for heavy metals in mg/kg were as follows: Cu (0.179), Zn (2.634), Cr (0.108), Pb (0.065), Cd (0.161), As (0.372), Hg (0.034). All the mean concentrations were below the maximum residual limits set by Chinese legislation, but As in 10 % samples exceeded the safety threshold. Significant differences in contents of Cr, Pb and Hg were found among the five investigated areas. Overall, the heavy metal levels in sea cucumber juveniles were relatively low and more attention should be paid to toxic metals Pb, Cd, As and Hg in future routine monitoring program.

  20. The recent arrival of the oceanic isopod Idotea metallica Bosc off Helgoland (German Bight, North Sea): an indication of a warming trend in the North Sea?

    NASA Astrophysics Data System (ADS)

    Franke, H.-D.; Gutow, L.; Janke, M.

    1998-09-01

    In 1988 a long-term study was started of the isopod fauna associated with surface drift material off Helgoland (German Bight, North Sea). In the summer of 1994 specimens of Idotea metallica Bosc were recorded for the first time. There is no evidence that this species has ever been present in the German Bight before. The samples contained males, both gravid and non-gravid females, and juveniles, indicating that the species reproduced successfully in the Helgoland region. Interbreeding of specimens from Helgoland and the western Mediterranean produced fertile off-spring. As a neustonic species, I. metallica shows a high natural capacity for dispersal. It thus seems unlikely that the arrival of the species in the North Sea resulted from an accidental introduction by man. We are probably witnessing an extension of the species’ geographical range by natural means of dispersal, as a response to recent changes in the ecological conditions of the German Bight. Temperature data measured by the Biologische Anstalt Helgoland since 1962 show that the last decade (except 1996) was characterized by unusually mild winters. Following the severe winter of 1996, I. metallica was again absent from the Helgoland region. After the subsequent mild winters (1997 and 1998), however, the species reappeared in the summer of 1998 with higher numbers than ever before. This suggests that the observed phenomena are closely connected with the recent temperature anomalies. I. metallica can be regarded as a potential immigrant to a warmer North Sea, and may be useful as a sensitive indicator of the predicted long-term warming trend.

  1. Modes of sedimentary basin formation in the north-eastern Black Sea

    NASA Astrophysics Data System (ADS)

    Stephenson, Randell; Starostenko, Vitaly; Sydorenko, Grygoriy; Yegorova, Tamara

    2016-04-01

    The Greater Caucasus and Black Sea sedimentary basins developed in a Mesozoic back-arc setting, the former older than the latter (Jurassic v. Cretaceous). Compressional shortening of the former and accompanying ongoing development of marginal basin depocentres in the north-eastern Black Sea - which is closely tied to the formation of the Crimea-Greater Caucasus orogen - is a Cenozoic phenomenon, starting in the Eocene and proceeding until the present day. Recently, the sedimentary basin/crust/lithosphere geometry of the study area has been characterised across a range of scales using regional seismic reflection profiling, long-offset refraction/wide-angle reflection profiling and local earthquake tomography. These provide a new integrated image of the present-day crustal structure and sedimentary basin architecture of the northern margin of the eastern Black Sea, north across the Azov Sea and provide evidence of the deeper expression of sedimentary basins and the processes controlling the geometry of their inversion during the Cenozoic. It is inferred that the Greater Caucasus paleo-Basin, lying stratigraphically below the Black Sea and younger sedimentary successions, extends further to the west than previously known. This basin has significant thickness in the area between the Azov and Black seas and probably forms the deeper core of the Crimea-Caucasus inversion zone. The Crimea-Greater Caucasus orogenic belt is the expression of "basin inversion" of the Jurassic Greater Caucasus paleo-Basin, the degree of inversion of which varies along strike. The Greater Caucasus foredeep basins - Indolo-Kuban and Sorokin-Tuapse troughs -represent syn-inversional marginal troughs to the main inversion zone. The Shatsky Ridge - the northern flank of the main East Black Sea Basin - may also be mainly a syn-inversional structure, underlain by a blind thrust zone expressed as a northward dipping zone of seismicity on the northern margin of the eastern Black Sea.

  2. Tracing back nutrients from Southern North Sea eutrophicated areas up to the watersheds

    NASA Astrophysics Data System (ADS)

    Dulière, Valérie; Gypens, Nathalie; Lancelot, Christiane; Thieu, Vincent; Luyten, Patrick; Lacroix, Geneviève

    2015-04-01

    The Southern North Sea faces eutrophication problems. They result from growing anthropogenic pressure in the river watersheds, and subsequent increase in nutrients (nitrogen and phosphorus) loading to the sea. Establishing the link between human activities and eutrophication problems requires the identification of the major nutrient sources and the ecological response of the coastal ecosystem to these nutrient alterations. This information is crucial to mitigate eutrophication in coastal zones by applying appropriate dual-nutrient reduction strategies, therefore achieving the Good Environmental Status of EU marine waters by 2020. The marine biogeochemical model (MIRO&CO) has been coupled to a newly developed generic watershed model (PyNuts) based on Riverstrahler model. A nutrient tracking approach has been adapted and implemented in MIRO&CO. The transboundary nutrient transport method has been used to track the nutrients in the sea, and trace back their sources (river, ocean, and atmosphere). Here, the relative contributions of the different nutrient sources will be presented. Results show that the nitrogen contribution from atmospheric deposition is not negligible and that the nutrients released by French rivers reach the Southern North Sea in significant proportions. This work has done in the framework of the EMoSEM EU project (http://www.odnature.be/emosem/) that aims at providing support to eutrophication management in the North Atlantic Ocean, using state-of-the-art modelling tools.

  3. The dangers of ignoring stock complexity in fishery management: the case of the North Sea cod.

    PubMed

    Hutchinson, William F

    2008-12-23

    The plight of the marine fisheries is attracting increasing attention as unsustainably high exploitation levels, exacerbated by more extreme climatic conditions, are driving stocks to the point of collapse. The North Atlantic cod (Gadus morhua), a species which until recently formed a major component of the demersal fisheries, has undergone significant declines across its range. The North Sea stock is typical of many, with a spawning stock biomass that has remained below the safe biological limit since 2000 and recruitment levels near the lowest on record. Cod within the North Sea are currently managed as a single stock, and yet mounting empirical evidence supports the existence of a metapopulation of regionally variable, genetically distinct, sub-stocks. Applying the same management strategies to multiple stocks that differ in their resilience to exploitation inevitably results in the overfishing and likely collapse of the weaker components. Indeed, recent studies have identified two North Sea spawning stocks that have undergone disproportionally large collapses with very substantial reductions in egg production. Similarly affected cod stocks in the northwest Atlantic have shown little evidence of recovery, despite fishery closures. The possible implications of ignoring sub-structuring within management units for biocomplexity, local adaptation and ecosystem stability are considered.

  4. Spatio-temporal variability of the North Sea cod recruitment in relation to temperature and zooplankton.

    PubMed

    Nicolas, Delphine; Rochette, Sébastien; Llope, Marcos; Licandro, Priscilla

    2014-01-01

    The North Sea cod (Gadus morhua, L.) stock has continuously declined over the past four decades linked with overfishing and climate change. Changes in stock structure due to overfishing have made the stock largely dependent on its recruitment success, which greatly relies on environmental conditions. Here we focus on the spatio-temporal variability of cod recruitment in an effort to detect changes during the critical early life stages. Using International Bottom Trawl Survey (IBTS) data from 1974 to 2011, a major spatio-temporal change in the distribution of cod recruits was identified in the late 1990s, characterized by a pronounced decrease in the central and southeastern North Sea stock. Other minor spatial changes were also recorded in the mid-1980s and early 1990s. We tested whether the observed changes in recruits distribution could be related with direct (i.e. temperature) and/or indirect (i.e. changes in the quantity and quality of zooplankton prey) effects of climate variability. The analyses were based on spatially-resolved time series, i.e. sea surface temperature (SST) from the Hadley Center and zooplankton records from the Continuous Plankton Recorder Survey. We showed that spring SST increase was the main driver for the most recent decrease in cod recruitment. The late 1990s were also characterized by relatively low total zooplankton biomass, particularly of energy-rich zooplankton such as the copepod Calanus finmarchicus, which have further contributed to the decline of North Sea cod recruitment. Long-term spatially-resolved observations were used to produce regional distribution models that could further be used to predict the abundance of North Sea cod recruits based on temperature and zooplankton food availability. PMID:24551103

  5. Spatio-temporal variability of the North Sea cod recruitment in relation to temperature and zooplankton.

    PubMed

    Nicolas, Delphine; Rochette, Sébastien; Llope, Marcos; Licandro, Priscilla

    2014-01-01

    The North Sea cod (Gadus morhua, L.) stock has continuously declined over the past four decades linked with overfishing and climate change. Changes in stock structure due to overfishing have made the stock largely dependent on its recruitment success, which greatly relies on environmental conditions. Here we focus on the spatio-temporal variability of cod recruitment in an effort to detect changes during the critical early life stages. Using International Bottom Trawl Survey (IBTS) data from 1974 to 2011, a major spatio-temporal change in the distribution of cod recruits was identified in the late 1990s, characterized by a pronounced decrease in the central and southeastern North Sea stock. Other minor spatial changes were also recorded in the mid-1980s and early 1990s. We tested whether the observed changes in recruits distribution could be related with direct (i.e. temperature) and/or indirect (i.e. changes in the quantity and quality of zooplankton prey) effects of climate variability. The analyses were based on spatially-resolved time series, i.e. sea surface temperature (SST) from the Hadley Center and zooplankton records from the Continuous Plankton Recorder Survey. We showed that spring SST increase was the main driver for the most recent decrease in cod recruitment. The late 1990s were also characterized by relatively low total zooplankton biomass, particularly of energy-rich zooplankton such as the copepod Calanus finmarchicus, which have further contributed to the decline of North Sea cod recruitment. Long-term spatially-resolved observations were used to produce regional distribution models that could further be used to predict the abundance of North Sea cod recruits based on temperature and zooplankton food availability.

  6. Hierarchical modeling of bycatch rates of sea turtles in the western North Atlantic

    USGS Publications Warehouse

    Gardner, B.; Sullivan, P.J.; Epperly, S.; Morreale, S.J.

    2008-01-01

    Previous studies indicate that the locations of the endangered loggerhead Caretta caretta and critically endangered leatherback Dermochelys coriacea sea turtles are influenced by water temperatures, and that incidental catch rates in the pelagic longline fishery vary by region. We present a Bayesian hierarchical model to examine the effects of environmental variables, including water temperature, on the number of sea turtles captured in the US pelagic longline fishery in the western North Atlantic. The modeling structure is highly flexible, utilizes a Bayesian model selection technique, and is fully implemented in the software program WinBUGS. The number of sea turtles captured is modeled as a zero-inflated Poisson distribution and the model incorporates fixed effects to examine region-specific differences in the parameter estimates. Results indicate that water temperature, region, bottom depth, and target species are all significant predictors of the number of loggerhead sea turtles captured. For leatherback sea turtles, the model with only target species had the most posterior model weight, though a re-parameterization of the model indicates that temperature influences the zero-inflation parameter. The relationship between the number of sea turtles captured and the variables of interest all varied by region. This suggests that management decisions aimed at reducing sea turtle bycatch may be more effective if they are spatially explicit. ?? Inter-Research 2008.

  7. Post-glacial sea-level change along the Pacific coast of North America

    NASA Astrophysics Data System (ADS)

    Shugar, Dan H.; Walker, Ian J.; Lian, Olav B.; Eamer, Jordan B. R.; Neudorf, Christina; McLaren, Duncan; Fedje, Daryl

    2014-08-01

    Sea-level history since the Last Glacial Maximum on the Pacific margin of North America is complex and heterogeneous owing to regional differences in crustal deformation (neotectonics), changes in global ocean volumes (eustasy) and the depression and rebound of the Earth's crust in response to ice sheets on land (isostasy). At the Last Glacial Maximum, the Cordilleran Ice Sheet depressed the crust over which it formed and created a raised forebulge along peripheral areas offshore. This, combined with different tectonic settings along the coast, resulted in divergent relative sea-level responses during the Holocene. For example, sea level was up to 200 m higher than present in the lower Fraser Valley region of southwest British Columbia, due largely to isostatic depression. At the same time, sea level was 150 m lower than present in Haida Gwaii, on the northern coast of British Columbia, due to the combined effects of the forebulge raising the land and lower eustatic sea level. A forebulge also developed in parts of southeast Alaska resulting in post-glacial sea levels at least 122 m lower than present and possibly as low as 165 m. On the coasts of Washington and Oregon, as well as south-central Alaska, neotectonics and eustasy seem to have played larger roles than isostatic adjustments in controlling relative sea-level changes.

  8. Evolution and fluxes of 137Cs in the Black Sea/Turkish Straits System/North Aegean Sea

    NASA Astrophysics Data System (ADS)

    Delfanti, R.; Özsoy, E.; Kaberi, H.; Schirone, A.; Salvi, S.; Conte, F.; Tsabaris, C.; Papucci, C.

    2014-07-01

    The vertical profiles of 137Cs were determined in the North Aegean, Marmara and Black Seas, to assess inventories and fluxes of the radionuclide in these basins. The inventory of 137Cs in the Western Black Sea integrated from the surface down to 400 m water depth is 3.4 ± 0.1 kBq m- 2, which is surprisingly close to the amount determined in 1988, decay corrected to 2007 (2.9 ± 0.1 kBq m- 2). On the other hand, based on the comparison of profiles roughly 20 years apart, it is estimated that about 1 kBq m- 2 has been transferred from above the halocline to depths below the halocline, emphasizing the effective redistribution of tracers within the same period. We estimate that about 12 TBq y- 1 of 137Cs presently leaves the Black Sea with the upper layer flow through the Bosphorus and only 2 TBq y- 1 is returned with the lower layer inflow of Mediterranean water from the Marmara Sea. Accounting for river fluxes, estimated on the order of 2 TBq y- 1 few years after the Chernobyl accident, and possibly decreased by now, we can thus estimate a net rate of loss of about 8-10 TBq y- 1. Investigating the effective redistribution in the upper water column, the supply by the inflowing Mediterranean water alone does not explain the increase of 137Cs concentration and inventory at intermediate depths in the Western Black Sea. The most important mechanism transferring 137Cs and dissolved contaminants from the surface water to the sub-pycnocline layer appears to be the turbulent entrainment of a larger quantity of Black Sea water into the inflowing plume of Mediterranean water through mixing processes on the southwestern shelf and continental slope following its exit from the Bosphorus. This process produces an extra export of some10 TBq y- 1 of 137Cs from the surface to the sub-pycnocline depths of the Black Sea, a quantity comparable in magnitude to the total export out from the basin. It is the entrainment flux resulting from the mixing, and the further advection and

  9. Glacial North Atlantic: Sea-surface conditions reconstructed by GLAMAP 2000

    NASA Astrophysics Data System (ADS)

    Pflaumann, U.; Sarnthein, M.; Chapman, M.; D'Abreu, L.; Funnell, B.; Huels, M.; Kiefer, T.; Maslin, M.; Schulz, H.; Swallow, J.; van Kreveld, S.; Vautravers, M.; Vogelsang, E.; Weinelt, M.

    2003-09-01

    The response of the tropical ocean to global climate change and the extent of sea ice in the glacial nordic seas belong to the great controversies in paleoclimatology. Our new reconstruction of peak glacial sea surface temperatures (SSTs) in the Atlantic is based on census counts of planktic foraminifera, using the Maximum Similarity Technique Version 28 (SIMMAX-28) modern analog technique with 947 modern analog samples and 119 well-dated sediment cores. Our study compares two slightly different scenarios of the Last Glacial Maximum (LGM), the Environmental Processes of the Ice Age: Land, Oceans, Glaciers (EPILOG), and Glacial Atlantic Ocean Mapping (GLAMAP 2000) time slices. The comparison shows that the maximum LGM cooling in the Southern Hemisphere slightly preceeded that in the north. In both time slices sea ice was restricted to the north western margin of the nordic seas during glacial northern summer, while the central and eastern parts were ice-free. During northern glacial winter, sea ice advanced to the south of Iceland and Faeroe. In the central northern North Atlantic an anticyclonic gyre formed between 45° and 60°N, with a cool water mass centered west of Ireland, where glacial cooling reached a maximum of >12°C. In the subtropical ocean gyres the new reconstruction supports the glacial-to-interglacial stability of SST as shown by () [1981]. The zonal belt of minimum SST seasonality between 2° and 6°N suggests that the LGM caloric equator occupied the same latitude as today. In contrast to the CLIMAP reconstruction, the glacial cooling of the tropical east Atlantic upwelling belt reached up to 6°-8°C during Northern Hemisphere summer. Differences between these SIMMAX-based and published U37k- and Mg/Ca-based equatorial SST records are ascribed to strong SST seasonalities and SST signals that were produced by different planktic species groups during different seasons.

  10. Population trends of North American sea ducks as revealed by the Christmas Bird Count

    USGS Publications Warehouse

    Niven, D.K.; Sauer, J.R.; Butcher, G.S.

    2005-01-01

    Relative to other waterfowl, sea ducks are not well understood, yet evidence from a variety of analyses suggests that as many as 10 of the 15 species of North American sea ducks may be declining in population. However, because of the difficulty of conducting surveys of breeding populations and the lack of range-wide winter surveys, few data are available to assess the population trends of sea ducks with confidence. We analyze Audubon Christmas Bird Count data using hierarchical modeling methods that control for varying effort among circles and over time. These procedures allow us to assess early-winter relative density patterns among states and Bird Conservation Regions (BCRs) while also assessing trends in these regions and across the species North American range. Over the interval 1966 - 2003, continent-wide declines were observed in 1 of 11 species (the White-winged Scoter; -3.7%/yr). We compare CBC results to estimates of population change derived from the midwinter waterfowl survey conducted by the US Fish and Wildlife Service. The CBC does not effectively sample offshore populations of sea ducks; however, the CBC data can be used to assist in development of species-specific surveys, and CBC data can be used in combination with additional offshore sampling programs to better sample sea duck species.

  11. Seasonal differences in concentrations of particulate lipids, proteins and chitin in the North Sea

    NASA Astrophysics Data System (ADS)

    Lardinois, D.; Eisma, D.; Chen, S.

    The concentrations of particulate lipids, proteins and chitin were determined in the North Sea in January 1992, October 1992 and March 1993, with additional measurements of total suspended matter concentrations and organic matter contents in the suspended matter (POC) by ashing and wet-oxidation. During each of the three cruises, the proteins were by far the most important of the three components measured, followed by the lipids. The concentrations of chitin were always very low. The concentrations of these three components were highest in March and lowest in January; there was also a variation in the distribution over the North Sea between the three cruises. In January 1992, the suspended matter contained more organic matter in the northern North Sea than in the southern North Sea, but the higher concentrations of total suspended matter in the southern North Sea resulted in an inverse distribution for the concentrations of organic matter per volume of water. In March 1993, highest concentrations of the three organic compounds were observed in the Skagerrak and along the eastern side of the North Sea, decreasing towards the west. The suspended matter was richest in organic compounds in the Skagerrak and in the Norwegian Channel. In October 1992, the situation was very similar to that observed in January 1992, but the concentrations of organic compounds in the suspended matter and per volume of water were higher. The ratio of proteins to lipids was similar to this ratio in phytoplankton. The composition of the particulate organic matter became very close to that of phytoplankton if we assume that we missed a large amount of carbohydrates; the small differences persisting were probably due to the contributions of zooplankton, bacteria and terrestrial sources. The total contents of particulate lipids + proteins + chitin were low, but when estimated amounts of carbohydrates were added, the total particulate organic-matter concentrations found were very similar to the

  12. An application of a queuing model for sea states

    NASA Astrophysics Data System (ADS)

    Loffredo, L.; Monbaliu, J.; Anderson, C.

    2012-04-01

    Unimodal approaches in design practice have shown inconsistencies in terms of directionality and limitations for accurate sea states description. Spectral multimodality needs to be included in the description of the wave climate. It can provide information about the coexistence of different wave systems originating from different meteorological events, such as locally generated wind waves and swell systems from distant storms. A 20 years dataset (1989-2008) for a location on the North Sea (K13, 53.2°N 3.2°E) has been retrieved from the ECMWF ERA- Interim re-analysis data archive, providing a consistent and homogeneous dataset. The work focuses on the joint and conditional probability distributions of wind sea and swell systems. For marine operations and design applications, critical combinations of wave systems may exist. We define a critical sea state on the basis of a set of thresholds, which can be not necessarily extreme, the emphasis is given to the dangerous combination of different wave systems concerning certain operations (i.e. small vessels navigation, dredging). The distribution of non-operability windows is described by a point process model with random and independent events, whose occurrences and lengths can be described only probabilistically. These characteristics allow to treat the emerging patterns as a part of a queuing system. According to this theory, generally adopted for several applications including traffic flows and waiting lines, the input process describes the sequence of requests for a service and the service mechanism the length of time that these requests will occupy the facilities. For weather-driven processes at sea an alternating renewal process appears as a suitable model. It consists of a sequence of critical events (period of inoperability), each of random duration, separated by calms, also of random durations. Inoperability periods and calms are assumed independent. In this model it is not possible more than one critical

  13. Biweekly Sea Surface Temperature over the South China Sea and its association with the Western North Pacific Summer Monsoon

    NASA Astrophysics Data System (ADS)

    Vaid, B. H.

    2015-10-01

    The association of the biweekly intraseasonal (BWI) oscillation in the Sea Surface Temperature (SST) over the South China Sea (SCS) and the Western North Pacific Summer Monsoon is authenticated using version 4 the Tropical Rainfall Measuring Mission Microwave Imager data (SST and rain) and heat fluxes from Ocean Atmosphere Flux project data during 1998-2012. The results suggest that the SCS involves ocean-atmosphere coupling on biweekly timescales. The positive biweekly SST anomalies lead the rain anomalies over the SCS by 3 days, with a significant correlation coefficient (r = 0.6, at 99 % significance levels) between the SST-rain anomalies. It is evident from lead/lag correlation between biweekly SST and zonal wind shear that warm ocean surface induced by wind shear may contribute to a favorable condition of the convective activity over the SCS. The present study suggests that ocean-to-atmospheric processes induced by the BWI oscillation in the SCS SST results in enhanced sea level pressure and surface shortwave radiation flux during the summer monsoon. Besides, it is observed that the SCS BWI oscillation in the changes of SST causes a feedback in the atmosphere by modifying the atmospheric instability. This suggests that the active/break biweekly cycle of the SST over the SCS is related by sea level pressure, surface heat fluxes and atmospheric instability. The potential findings here indicate that the biweekly SST over the SCS play an important role in the eastward and the southward propagation of the biweekly anomalies in the Western North Pacific.

  14. Experience of cathodic protection, fabrication and installation of anodes for deep water pipelines in the North Sea and the Norwegian Sea

    SciTech Connect

    Eliassen, S.; Pettersen, N.H.

    1996-08-01

    Statoil is the major operator of the oil and gas pipelines in the North Sea and the Norwegian Sea. Different coating systems have been used for external corrosion protection of the pipelines. The paper presents the company`s experience regarding cathodic protection design and fabrication and installation of anodes for deep water pipelines.

  15. Strain migration during multiphase extension: Observations from the northern North Sea

    NASA Astrophysics Data System (ADS)

    Bell, Rebecca E.; Jackson, Christopher A.-L.; Whipp, Paul S.; Clements, Benjamin

    2014-10-01

    Many rifts develop through multiphase extension; it can be difficult, however, to determine how strain is distributed during reactivation because structural and stratigraphic evidence associated with earlier rifting is often deeply buried. Using 2-D and 3-D seismic reflection and borehole data from the northern North Sea, we examine the style, magnitude, and timing of reactivation of a preexisting, Permian-Triassic (Rift Phase 1) fault array during a subsequent period of Middle Jurassic to Early Cretaceous (Rift Phase 2) extension. We show that Rift Phase 2 led to the formation of new N-S striking faults close to the North Viking Graben but did not initially reactivate preexisting Rift Phase 1 structures on the Horda Platform. We suggest that at the beginning of Rift Phase 2, strain was focused in a zone of thermally weakened lithosphere associated with the Middle Jurassic North Sea thermal dome, rather than reactivating extant faults. Diachronous reactivation of the Permian-Triassic fault network eventually occurred, with those faults located closer to the Middle Jurassic to Early Cretaceous rift axis reactivating earlier than those toward the eastern margin. This diachroneity may have been related to flexural down bending as strain became focused within the North Viking Graben, and/or the shifting of the locus of rifting from the North Sea to the proto-North Atlantic. Our study shows that the geometry and evolution of multiphase rifts is not only controlled by the orientation of the underlying fault network but also by the thermal and rheological evolution of the lithosphere and variations in the regional stress field.

  16. The influence of Arctic sea ice variability on the summer North Atlantic Oscillation (SNAO)

    NASA Astrophysics Data System (ADS)

    Linderholm, H. W.; Folland, C. K.; Ou, T.; Jeong, J. H.; Wilson, R.; Rydval, M.; Chen, D.; Kim, B. M.

    2015-12-01

    The summer North Atlantic Oscillation (SNAO), which is strongly related to changes in Atlantic and European summer storm tracks and the latitudinal position of the jet stream, exerts a strong influence on rainfall, temperature, and cloudiness and is related to summer extremes, such as droughts and floods, mainly in Europe. Reconstructions suggest that the SNAO was mainly negative during the last several centuries until the mid-twentieth century when it entered a positive phase, and climate model projections have suggested a predominantly positive SNAO under future global warming. However, during the recent decade, the SNAO has mainly been in a negative phase, along with a southerly shift in the jet stream, accompanied by wet and cool summers in northwest Europe. Sea surface temperatures in the North Atlantic (related to the Atlantic Multidecadal Oscillation, AMO) strongly influence the SNAO, and the current positive phase of the AMO has likely played some role in the recent downturn of the SNAO. Additionally, we found a consistent association between winter/spring Arctic sea ice concentration (SIC), particularly in the Labrador and Nordic seas, and the SNAO over the last decades based on observations. However, since the 1990s the strength of the correlations with the regional SIC has changed, weakening over the Labrador Sea and strengthening over Barents Sea. This is particularly evident during the last decade. Possibly this is a response to the rapid changes in Arctic sea ice. To test this, a new tree-ring based reconstruction of the SNAO as well as CMIP5 model runs are used to examine the influence of Arctic sea ice on the summer atmospheric circulation over northwestern Europe in a long-term context.

  17. Correcting North Atlantic sea surface salinity biases in the Kiel Climate Model: influences on ocean circulation and Atlantic Multidecadal Variability

    NASA Astrophysics Data System (ADS)

    Park, T.; Park, W.; Latif, M.

    2016-10-01

    A long-standing problem in climate models is the large sea surface salinity (SSS) biases in the North Atlantic. In this study, we describe the influences of correcting these SSS biases on the circulation of the North Atlantic as well as on North Atlantic sector mean climate and decadal to multidecadal variability. We performed integrations of the Kiel Climate Model (KCM) with and without applying a freshwater flux correction over the North Atlantic. The quality of simulating the mean circulation of the North Atlantic Ocean, North Atlantic sector mean climate and decadal variability is greatly enhanced in the freshwater flux-corrected integration which, by definition, depicts relatively small North Atlantic SSS biases. In particular, a large reduction in the North Atlantic cold sea surface temperature bias is observed and a more realistic Atlantic Multidecadal Variability simulated. Improvements relative to the non-flux corrected integration also comprise a more realistic representation of deep convection sites, sea ice, gyre circulation and Atlantic Meridional Overturning Circulation. The results suggest that simulations of North Atlantic sector mean climate and decadal variability could strongly benefit from alleviating sea surface salinity biases in the North Atlantic, which may enhance the skill of decadal predictions in that region.

  18. Impacts of Sea Surface Salinity Bias Correction on North Atlantic Ocean Circulation and Climate Variability in the Kiel Climate Model

    NASA Astrophysics Data System (ADS)

    Park, Taewook; Park, Wonsun; Latif, Mojib

    2016-04-01

    We investigated impacts of correcting North Atlantic sea surface salinity (SSS) biases on the ocean circulation of the North Atlantic and on North Atlantic sector mean climate and climate variability in the Kiel Climate Model (KCM). Bias reduction was achieved by applying a freshwater flux correction over the North Atlantic to the model. The quality of simulating the mean circulation of the North Atlantic Ocean, North Atlantic sector mean climate and decadal variability is greatly enhanced in the freshwater flux-corrected integration which, by definition, depicts relatively small North Atlantic SSS biases. In particular, a large reduction in the North Atlantic cold sea surface temperature (SST) bias is observed and a more realistic Atlantic Multidecadal Variability (AMV) simulated. Improvements relative to the non-flux corrected integration also comprise a more realistic representation of deep convection sites, sea ice, gyre circulation and Atlantic Meridional Overturning Circulation (AMOC). The results suggest that simulations of North Atlantic sector mean climate and decadal variability could strongly benefit from alleviating sea surface salinity biases in the North Atlantic, which may enhance the skill of decadal predictions in that region.

  19. Dynamics of sea ice in the Baltic Sea and applications

    NASA Astrophysics Data System (ADS)

    Leppäranta, M.; Andrejev, O.; Oikkonen, A.

    2009-04-01

    Sea ice forms in the Baltic Sea annually. Coastal and archipelago areas are covered by landfast ice, while further offshore the ice drifts under the influence of winds and currents. The length scale of the Baltic Sea basins is 100 km and the scale of the ice thickness is ½ m, and the characteristics of the ice dynamics are similar to the ice dynamics in the polar seas. The drifting of the ice has major practical implications. First, the navigation conditions are determined by the ice extent, presence of leads and ice pressure, and therefore the dynamical behaviour of ice may cause rapid changes for them. Recent research has focused on ice kinematics scales, evolution of landfast ice zone, and downscaling of pressure from mesoscale models to ship scales. The length scale of dynamics depends on the ice thickness showing up in the stiffness of the ice and expansion of the landfast ice zone. Oil spills are in particular difficult in drift ice conditions, which has led to development of oil spill drift and dispersion models. This is most critical in the Gulf of Finland, a narrow and shallow basin with large oil terminals in the eastern side. The formation of sea ice ridges has important consequences in shallow basins since they ground to scour the bottom and form tie points for the expansion of the landfast ice.

  20. Space and time variability of satellite-derived sea surface temperatures and phytoplankton pigment concentrations in the eastern North Atlantic

    SciTech Connect

    Oliveira, P.B.; Peliz, A.R.; Fiuza, A.F.G.

    1994-12-31

    An analysis of NOAA/AVHRR II sea surface temperatures (SST) and NIMBUS-7/CZCS phytoplankton pigment concentrations was conducted in order to characterize their mean distributions and their space-time variability in the eastern North Atlantic, particularly in the vicinity of the western Iberian Peninsula. A 9-year long (1982--1990) SST set relative to a large part of the North Atlantic was extensively processed and analyzed to obtain the highest space-time resolution possible using only measured values. A good compromise led to a 9-year sequence of weekly averages of SST at 90 km x 90 km resolution. The first applications of these data were the preparation of yearly, seasonal and monthly mean surface temperature distributions with unprecedented resolution, as well as the construction of sequences of weekly SST charts for the whole 9-year period. The latter were used to construct a color video-loop which clearly shows the seasonal and interannual evolution of SST in a large region of the North Atlantic, in particular the meridional migration of the isotherms, the variability of large-scale thermal features associated with the Gulf Stream, the Labrador Current, the Azores Current, and the coastal upwelling along the North Atlantic eastern boundary.

  1. Investigating Sea-Level Acceleration Along the East Coast of North America

    NASA Astrophysics Data System (ADS)

    Davis, J. L.

    2015-12-01

    A number of researchers have reported on accelerated sea level along the east coast of North America, particularly in the northeast. We have previously modeled sea-level rates and accelerations from the last half of the 20th and early 21st centuries inferred from tide gauges in this region using steric sea-level changes, gravitationally self-consistent sea-level changes that includes self-attraction and loading (SAL), and glacial isostatic adjustment (GIA). We have found that, whereas the spatial variability of sea-level rates is dominated by GIA, the observed accelerations are not explained by these processes. In this talk, we first further investigate the observed accelerations, which we took to be constant during the study period. We have found, however, some evidence that the accelerations began in the timeframe 1990-2000. For example, the figure below shows the root-mean-square (rms) residual after removing a best-fit model wherein the acceleration was zero before the indicated year, for the Boston tide gauge, having one of the longest tide-gauge records. The minimimum rms residual occurs in the year 2000. A Monte Carlo simulation (red curve) shows that no time-dependence is expected from white noise. Evaluation of the statistical significance of these results has been difficult, since the postfit residuals are dominated by interannual variability. We will utilize time-dependent models for dynamic sea-level changes (including steric changes), GIA. For the Greenland ice mass, we will combine estimates of Greenland ice-mass variability obtained from recent analyses of GRACE data with long-term climate models for Greenland (from, e.g., RACMO) to calculate long-term sea-level impact. Comparing these models with tide-gauge data will yield insights into the nature and timing of accelerated sea level in this region. We will also discuss the implciations of these models for long-term global sea-level change.

  2. Pliocene sea surface temperatures of the north atlantic ocean at 3.0 Ma

    USGS Publications Warehouse

    Dowsett, H.J.; Poore, R.Z.

    1991-01-01

    Sea-surface temperature (SST) estimates based on quantitative analysis of planktic foraminifer faunas in North Atlantic deep sea cores suggest that high-frequency, low-amplitude variability related to orbital forcing was superimposed on long-term changes that delineate intervals within the Pliocene that were both warmer and cooler than today. SST estimates from several DSDP and ODP sites, as well as land sections, have been combined into a synoptic view of SST during a Pliocene warm interval centered at about 3.0 Ma. The Pliocene North Atlantic warm interval SST estimates show little evidence for warming in tropical regions whereas mid- to high-latitude areas show moderate to strong warming. SST estimates for the last interglacial (Isotope Stage 5e) show a similar pattern, but warming during the last interglacial was not as pronounced as the Middle Pliocene warming. The regional distribution of SST estimates during these past warm events suggests an increase in ocean circulation. ?? 1991.

  3. Identification of the first harbour porpoise ( Phocoena phocoena) calving ground in the North Sea

    NASA Astrophysics Data System (ADS)

    Sonntag, R. P.; Benke, H.; Hiby, A. R.; Lick, R.; Adelung, D.

    1999-05-01

    We investigated the occurrence of harbour porpoises in the North Sea off Schleswig-Holstein by conducting aerial surveys with emphasis on calves. Fourteen per cent of the sighted porpoises off the islands of Sylt, Amrum and southern Rømø were calves, whereas the average calf proportion for the whole North Sea as established during the 1994 SCANS survey was only 5.4%. The significantly higher proportion of calves off Sylt and Amrum indicates that these coastal waters are used as a preferred calving ground for harbour porpoises. Analysis of stranding data showed that the identified calving ground does not extend south of Amrum and that harbour porpoise calves are present off Sylt and Amrum all year round. The combination of sighting and stranding data demonstrates the special importance of the investigated area for harbour porpoises as a calving and nursing ground. The area should therefore be protected.

  4. Dimethylsulfoniopropionate (DMSP) cell quota of key Southern North Sea spring diatoms and Phaeocystis globosa.

    NASA Astrophysics Data System (ADS)

    Speeckaert, Gaëlle; Gypens, Nathalie; Lancelot, Christiane; Borges, Alberto V.

    2015-04-01

    Dimethylsulfide (DMS) in the ocean results of complex transformations of dimethylsulfoniopropionate (DMSP) produced by phytoplankton under different controls, including microbial transformation pathways. The phytoplankton composition is an important factor of variability due to the species dependence of the DMSP production and conversion to DMS. To better appraise the link between phytoplankton diversity and the DMS(P) cycling in the Southern North Sea we present measurements of the DMSP cell quota of key spring phytoplankton species (Skeletonema costatum, Thalassiosira rotula, Rhizosolenia delicatula, Asterionella glacialis, Nitzschia closterium, Chaetoceros debilis, Chaetoceros socialis and Phaeocystis globosa) isolated from the North Sea and maintained in non-limiting and axenic laboratory culture conditions. Results are discussed with regards to literature data and hypothesis currently used in DMS(P) biogeochemical models.

  5. Forecasting petroleum discoveries in sparsely drilled areas: Nigeria and the North Sea

    SciTech Connect

    Attanasi, E.D.; Root, D.H.

    1988-10-01

    Decline function methods for projecting future discoveries generally capture the crowding effects of wildcat wells on the discovery rate. However, these methods do not accommodate easily situations where exploration areas and horizons are expanding. In this paper, a method is presented that uses a mapping algorithm for separating these often countervailing influences. The method is applied to Nigeria and the North Sea. For an amount of future drilling equivalent to past drilling (825 wildcat wells), future discoveries (in resources found) for Nigeria are expected to decline by 68% per well but still amount to 8.5 billion barrels of oil equivalent (BOE). Similarly, for the total North Sea for an equivalent amount and mix among areas of past drilling (1322 wildcat wells), future discoveries are expected to amount to 17.9 billion BOE, whereas the average discovery rate per well is expected to decline by 71%.

  6. Effect of DGPS failures on dynamic positioning of mobile drilling units in the North Sea.

    PubMed

    Chen, Haibo; Moan, Torgeir; Verhoeven, Harry

    2009-11-01

    Basic features of differential global positioning system (DGPS), and its operational configuration on dynamically positioned (DP) mobile offshore drilling units in the North Sea are described. Generic failure modes of DGPS are discussed, and a critical DGPS failure which has the potential to cause drive-off for mobile drilling units is identified. It is the simultaneous erroneous position data from two DGPS's. Barrier method is used to analyze this critical DGPS failure. Barrier elements to prevent this failure are identified. Deficiencies of each barrier element are revealed based on the incidents and operational experiences in the North Sea. Recommendations to strengthen these barrier elements, i.e. to prevent erroneous position data from DGPS, are proposed. These recommendations contribute to the safety of DP operations of mobile offshore drilling units.

  7. Forecasting petroleum discoveries in sparsely drilled areas: Nigeria and the North Sea

    USGS Publications Warehouse

    Attanasi, E.D.; Root, D.H.

    1988-01-01

    Decline function methods for projecting future discoveries generally capture the crowding effects of wildcat wells on the discovery rate. However, these methods do not accommodate easily situations where exploration areas and horizons are expanding. In this paper, a method is presented that uses a mapping algorithm for separating these often countervailing influences. The method is applied to Nigeria and the North Sea. For an amount of future drilling equivalent to past drilling (825 wildcat wells), future discoveries (in resources found) for Nigeria are expected to decline by 68% per well but still amount to 8.5 billion barrels of oil equivalent (BOE). Similarly, for the total North Sea for an equivalent amount and mix among areas of past drilling (1322 wildcat wells), future discoveries are expected to amount to 17.9 billion BOE, whereas the average discovery rate per well is expected to decline by 71%. ?? 1988 International Association for Mathematical Geology.

  8. Effect of DGPS failures on dynamic positioning of mobile drilling units in the North Sea.

    PubMed

    Chen, Haibo; Moan, Torgeir; Verhoeven, Harry

    2009-11-01

    Basic features of differential global positioning system (DGPS), and its operational configuration on dynamically positioned (DP) mobile offshore drilling units in the North Sea are described. Generic failure modes of DGPS are discussed, and a critical DGPS failure which has the potential to cause drive-off for mobile drilling units is identified. It is the simultaneous erroneous position data from two DGPS's. Barrier method is used to analyze this critical DGPS failure. Barrier elements to prevent this failure are identified. Deficiencies of each barrier element are revealed based on the incidents and operational experiences in the North Sea. Recommendations to strengthen these barrier elements, i.e. to prevent erroneous position data from DGPS, are proposed. These recommendations contribute to the safety of DP operations of mobile offshore drilling units. PMID:19819364

  9. Lost and found: The identification process of human bodies recovered from the North Sea.

    PubMed

    Duijst, Wilma; Passier, Charlotte; Oude Grotebevelsborg, Bernice; de Kat, Dorothee; van Daalen, Marjolijn; Oostra, Roelof Jan

    2016-07-01

    Files of the Dutch bureau of missing persons at the North Sea (BVPN) were investigated to analyse the process that led to identification of human bodies recovered from the North Sea between 1980 and 2013. Of the 94 cases that were analysed 41.5% was identified by the family, 23.4% by the use of DNA and 17% by the use of the dental status. The linking pin for the identification was the place where the body was found (14.9%), the general appearance (12.8%), jewellery (11.6%) and media attention (9.6%). In only a few cases the DNA or fingerprint database was used for identification. When a person is not reported missing the identification is problematic because of the lack of antemortem data. National and international databases of people who have gone missing, can help solve this problem. PMID:27107563

  10. Primary Analysis of Shear-Wave Splitting Aroundbohai Sea Area in North China

    NASA Astrophysics Data System (ADS)

    Tai, L.; Gao, Y.; Shi, Y.; Sun, J.

    2012-12-01

    Bohai Sea area locates at eastern China, including 3 provinces ( Hebei, Liaoning and Shandong ) and 2 metropolitan cities ( Beijing and Tianjin ). There are 5 tectonic units (Yanshan uplift, Taihang uplift, Liaodong uplift, Luxi uplift and Jizhong depression), where is within North China (in short, NC). Zhangjiakou-Bohai seismic belt, an important seismotectonic zone in eastern China and Tanlu fault, the largest fault in eastern China, intersect in this zone, so that the tectonics are complicated. Earthquake activity is very strong in this zone, which is famous of earthquakes with large magnitude and high frequency. This study used a system analysis method of shear-wave splitting, namely SAM method (GAO et al, 2004). It includes mainly three aspects, i.e., calculation of cross-correlation function, elimination of time delay and check of polarization analysis. Preliminarily, we obtained the 378 seismic data within shear-wave window recorded by 27 stations around Bohai Sea area. The polarizations of fast shear-waves show different local features so that we divide the studied zone into 3 different areas, west of Bohai Sea gulf (including Beijing, Tianjin and Hebei province), north of Bohai Sea gulf (Liaoning province) and south of Bohai Sea gulf (Shandong province). In the west of Bohai Sea gulf, we divided the area into 3 parts. In south of Zhangjiakou-Bohai seismic belt, the predominant polarizations of fast shear-waves are a little scattered, lots of stations strike to nearly E-W, consistent with the direction of the in situ principal stress, consistent with the direction of regional tectonic stress in north part of NC, which strikes to nearly WNW or E-W, while some stations strike to NNE or NW, different from the direction of the regional principal stress field. It may be influenced by local tectonics or shallow crust structure. Within Zhangjiakou-Bohai seismic belt, the predominant polarizations of fast shear-waves are in direction of nearly E-W, consistent with

  11. Model calculates was deposition for North Sea oils

    SciTech Connect

    Majeed, A.; Bringedal, B.; Overa, S. )

    1990-06-18

    A model for calculation of wax formation and deposition in pipelines and process equipment has been developed along with a new method for wax-equilibrium calculations using input from TBP distillation cuts. Selected results from the wax formation and deposition model have been compared with laboratory data from wax equilibrium and deposition experiments, and there have been some field applications of the model.

  12. A comparison of two finite element models of tidal hydrodynamics using a North Sea data set

    USGS Publications Warehouse

    Walters, R.A.; Werner, F.E.

    1989-01-01

    Using the region of the English Channel and the southern bight of the North Sea, we systematically compare the results of two independent finite element models of tidal hydrodynamics. The model intercomparison provides a means for increasing our understanding of the relevant physical processes in the region in question as well as a means for the evaluation of certain algorithmic procedures of the two models. ?? 1989.

  13. Modelling climate change effects on benthos: Distributional shifts in the North Sea from 2001 to 2099

    NASA Astrophysics Data System (ADS)

    Weinert, Michael; Mathis, Moritz; Kröncke, Ingrid; Neumann, Hermann; Pohlmann, Thomas; Reiss, Henning

    2016-06-01

    In the marine realm, climate change can affect a variety of physico-chemical properties with wide-ranging biological effects, but the knowledge of how climate change affects benthic distributions is limited and mainly restricted to coastal environments. To project the response of benthic species of a shelf sea (North Sea) to the expected climate change, the distributions of 75 marine benthic species were modelled and the spatial changes in distribution were projected for 2099 based on modelled bottom temperature and salinity changes using the IPCC scenario A1B. Mean bottom temperature was projected to increase between 0.15 and 5.4 °C, while mean bottom salinity was projected to moderately increase by 1.7. The spatial changes in species distribution were modelled with Maxent and the direction and extent of these changes were assessed. The results showed a latitudinal northward shift for 64% of the species (maximum 109 km; brittle star Ophiothrix fragilis) and a southward shift for 36% (maximum 101 km; hermit crab Pagurus prideaux and the associated cloak anemone Adamsia carciniopados; 105 km). The relatively low rates of distributional shifts compared to fish or plankton species were probably influenced by the regional topography. The environmental gradients in the central North Sea along the 50 m depth contour might act as a 'barrier', possibly resulting in a compression of distribution range and hampering further shifts to the north. For 49 species this resulted in a habitat loss up to 100%, while only 11 species could benefit from the warming in terms of habitat gain. Particularly the benthic communities of the southern North Sea, where the strongest temperature increase was projected, would be strongly affected by the distributional changes, since key species showed northward shifts and high rates of habitat loss, with potential ramifications for the functioning of the ecosystem.

  14. Geological and operational summary, North Aleutian Shelf Coast No. 1 well, Bering Sea, Alaska. Final report

    SciTech Connect

    Turner, R.F.

    1988-11-01

    Discusses the first continental offshore stratigraphic test well drilled in the North Aleutian Basin Planning Area, Bering Sea, Alaska. The well was drilled to determine the hydrocarbon potential of the area. The report covers drilling operations; lithology and core data; velocity analysis; geologic setting and tectonic framework; seismic stratigraphy; well-log interpretation and lithostratigraphy; paleontology and biostratigraphy; geothermal gradient; organic geochemistry; abnormal formation pressure; geologic hazards and shallow geology; and environmental considerations.

  15. Management and protection protocols for nesting sea turtles on Cape Hatteras National Seashore, North Carolina

    USGS Publications Warehouse

    Cohen, J.B.

    2005-01-01

    Executive Summary 1. The southeast U.S. population of the loggerhead turtle (Caretta caretta) has increased since the species was listed as federally threatened in 1978. Since standardized monitoring began in North Carolina in 1995, the number of nests at Cape Hatteras National Seashore (CAHA) fluctuated from year to year, and was lowest in 1996 and 1997 (39 nests) and highest in 2003 (101 nests). Green turtles (Chelonia mydas) and leatherback turtles (Dermochelys coriacea) have nested in small numbers at CAHA, sporadically over time. 2. Hatching success of sea turtle nests typically approaches 80%. At CAHA hatching success from 1999-2003 was low when hurricanes hit during the nesting season (30%-38%), and ranged from 52%-70% otherwise. Hatching success at CAHA is usually correlated with hatching success in the surrounding subpopulation (north Florida to North Carolina). 3. Inclement weather, predation, and human recreation can negatively impact nesting rate and hatching success. 4. Currently there is little protection from recreation at CAHA for nesting females and nests that have not been found by monitors. We propose three management options to provide such protection, and to increase protection for known nests and hatchlings. We propose an adaptive management framework for assessing the effectiveness of these management options in improving sea turtle nesting rate and nest and hatchling survival. 5. We recommend continued efforts to trap and remove mammalian predators from all sea turtle habitat. We further recommend intensive monitoring and surveillance of protected areas to determine the extent and timing of threats to nests and broods, including nest overwash, predation, and disturbance or vandalism by humans. 6. Continue to relocate nests and assist stranded turtles according to North Carolina Wildlife Resources Commission guidelines. 7. Artificial light sources pose a serious threat to sea turtles in some parts of CAHA, which must be remedied immediately

  16. Concentrations of halogenated natural products versus PCB 153 in bivalves from the North and Baltic Seas.

    PubMed

    Hauler, Carolin; Rimkus, Gerhard; Risacher, Célia; Knölker, Hans-Joachim; Vetter, Walter

    2014-08-15

    Different halogenated natural products (HNPs) have been reported to occur in marine wildlife, particularly from regions with comparably little contamination with anthropogenic pollutants. The North Sea and the Baltic Sea have been known as a marine site heavily polluted with organohalogen compounds, and especially with polychlorinated biphenyls (PCBs). In this study we wished to determine the current abundance of HNPs in comparison with 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153), i.e. the major PCB congener in marine biota. For this purpose, forty blue mussels (Mytilus edulis) and oysters (Crassostrea gigas) from seven sites were analyzed on HNPs and PCB 153. Most of the samples contained HNPs in the form of polyhalogenated 1'-methyl-1,2'-bipyrroles (PMBPs including Q1) and the mixed halogenated compound MHC-1. In addition we determined several polyhalogenated 1,1'-dimethyl-2,2'-bipyrroles (PDBPs), 2,3,4,5-tetrabromo-N-methylpyrrole and several novel homologs, as well as polybrominated N-methylindoles. The occurrence of these HNP groups were considerably different in the samples from different regions with varying sum concentrations up to 1930 μg/kg lipids in blue mussels from Heligoland (North Sea) and much lower concentrations in samples from the Baltic Sea (up to 13 μg/kg lipids). The concentrations of HNPs varied by two orders of magnitude, compared to a factor of 10 for PCB 153, suggesting that HNPs are more spatially (and perhaps temporally) variant than POPs. In the North Sea region Heligoland, HNPs were more abundant than PCB 153.

  17. Sea-Level Acceleration Hotspot along the Atlantic Coast of North America

    NASA Astrophysics Data System (ADS)

    Sallenger, A. H.; Doran, K. J.; Howd, P.

    2012-12-01

    Spatial variations of sea level rise (SLR) can be forced by dynamic processes arising from circulation and variations in temperature and/or salinity, and by static equilibrium processes arising from mass re-distributions changing gravity and the earth's rotation and shape. The sea-level variations can form unique spatial patterns, yet there are very few field observations verifying predicted patterns, or fingerprints. We present evidence of SLR acceleration in a 1,000-km-long hotspot on the North American Atlantic coast north of Cape Hatteras, North Carolina to above Boston, Massachusetts. By using accelerations, or rate differences, sea level signals that are linear over sub-century records, like the relative sea level changes arising from vertical land movements of glacial isostatic adjustment, do not affect our results. For a 60-yr regression window (between 1950-1979 and 1980-2009), mean increase in the rate of SLR in the hotspot was 1.97 ± 0.64 mm/yr. (For a 40-yr window, the mean rate increase was 3.80 ± 1.06 mm/yr.) South of Cape Hatteras to Key West, Florida, rate differences for either 60 yr or 40 yr windows were not statistically different from zero (e.g. for 60 yr window: mean= 0.11 ± 0.92 mm/yr). This pattern is similar to a fingerprint of dynamic SLR established by sea-level projections in several climate model studies. Correlations were consistent with accelerated SLR associated with a slowdown of Atlantic Meridional Overturning Current.

  18. Modelling the seasonal occurrence and distribution of humanpathogenic bacteria within the German Bight, southern North Sea

    NASA Astrophysics Data System (ADS)

    Schakau, Vanessa; Lettmann, Karsten A.; Wolff, Jörg-Olaf

    2015-04-01

    In recent years, the occurrence of human-pathogenic bacteria of the genus Vibrio in the North Sea and the Baltic Sea has come into the focus of many marine research activities, as different Vibrio strains caused harmful infections, especially in summers 2003, 2006, 2010 and 2014. Furthermore, it is anticipated that under global warming conditions, the risk of the occurrence of human-pathogenic in summer season will increase very likely. To present knowledge temperature and salinity are the most powerful predictors of the occurrence of Vibrio spp. in coastal waters. However, studies support the interaction of human-pathogenic Vibrio spp. with different host and vector organisms like chitinous zooplankton or with predator organisms such as Vibrio-specific bacteriophages. A modeling system has been developed to understand and predict the occurrence and distribution of harmful Vibrio spp. within the North Sea with a special focus on the German Bight including the shallower Wadden Sea areas and the estuaries of Ems, Weser and Elbe. On the one hand, this modeling system is based on the unstructured-mesh hydrodynamic model FVCOM, which can predict the oceanic circulation and distributions of temperature and salinity within the German Bight for appropriate present and future climate conditions. On the other hand, a biological module has been attached, which can simulate the distribution and abundances of Vibrio spp.. In detail, apart from specific Vibrio strains, this biological module incorporates functional groups of phyto- and zooplankton and bacteriophages as potential host- and predator-organisms. In a first study, this modeling system has been applied to a hot summer season in 2006. It has been demonstrated that this system can reproduce the valid hydrodynamic conditions within the North Sea region of interest including temperature and salinity distribution patterns. In addition, reasonable temporal and spatial patterns of Vibrio abundances have been obtained.

  19. High-resolution IP25-based reconstruction of sea-ice variability in the western North Pacific and Bering Sea during the past 18,000 years

    NASA Astrophysics Data System (ADS)

    Méheust, Marie; Stein, Ruediger; Fahl, Kirsten; Max, Lars; Riethdorf, Jan-Rainer

    2016-04-01

    Due to its strong influence on heat and moisture exchange between the ocean and the atmosphere, sea ice is an essential component of the global climate system. In the context of its alarming decrease in terms of concentration, thickness and duration, understanding the processes controlling sea-ice variability and reconstructing paleo-sea-ice extent in polar regions have become of great interest for the scientific community. In this study, for the first time, IP25, a recently developed biomarker sea-ice proxy, was used for a high-resolution reconstruction of the sea-ice extent and its variability in the western North Pacific and western Bering Sea during the past 18,000 years. To identify mechanisms controlling the sea-ice variability, IP25 data were associated with published sea-surface temperature as well as diatom and biogenic opal data. The results indicate that a seasonal sea-ice cover existed during cold periods (Heinrich Stadial 1 and Younger Dryas), whereas during warmer intervals (Bølling-Allerød and Holocene) reduced sea ice or ice-free conditions prevailed in the study area. The variability in sea-ice extent seems to be linked to climate anomalies and sea-level changes controlling the oceanographic circulation between the subarctic Pacific and the Bering Sea, especially the Alaskan Stream injection though the Aleutian passes.

  20. Projections of Extreme Sea Level Rise Events along the Northeast Coast of North America

    NASA Astrophysics Data System (ADS)

    Goddard, P.; Yin, J.; Griffies, S. M.; Zhang, S.

    2014-12-01

    By analyzing long-term tide gauge (TG) records, we find an extreme sea level rise (SLR) event during 2009-10 along the Northeast Coast of North America. Within a two-year period, the coastal sea level north of New York City (NYC) jumped by up to 128 mm. Despite significant year-to-year fluctuation, this magnitude of SLR is unprecedented during the entire history of the TG records. We show that this extreme SLR event is a combined effect of two factors: an observed 30% downturn of the Atlantic meridional overturning circulation (AMOC) from April 2009 to March 2010, and an onshore/alongshore wind stress anomaly associated with the significant negative North Atlantic Oscillation (NAO) index. During the 21st century, state-of-the-art climate models project an increase in magnitude and frequency of extreme SLR events on the interannual time scale along this densely populated coast. An ensemble of 24 climate models demonstrates that AMOC strength is likely to decrease and extreme negative NAO indices are likely to increase over the next century. Our 2009-10 case study suggests that the combination of these two extreme dynamics causes exceptionally high sea levels from Cape Hatteras to the Southeast Coast of Canada.

  1. Recent advances in the compilation of holocene relative Sea-level database in North America

    NASA Astrophysics Data System (ADS)

    Horton, B.; Vacchi, M.; Engelhart, S. E.; Nikitina, D.

    2015-12-01

    Reconstruction of relative sea level (RSL) has implications for investigation of crustal movements, calibration of earth rheology models and the reconstruction of ice sheets. In recent years, efforts were made to create RSL databases following a standardized methodology. These regional databases provided a framework for developing our understanding of the primary mechanisms of RSL change since the Last Glacial Maximum and a long-term baseline against which to gauge changes in sea-level during the 20th century and forecasts for the 21st. Here we present two quality-controlled Holocene RSL database compiled for North America. Along the Pacific coast of North America (British Columbia, Canada to California, USA), our re-evaluation of sea-level indicators from geological and archaeological investigations yield 841 RSL data-points mainly from salt and freshwater wetlands or adjacent estuarine sediment as well as from isolation basin. Along the Atlantic coast of North America (Hudson Bay, Canada to South Carolina, USA), we are currently compiling a database including more than 2000 RSL data-points from isolation basin, salt and freshwater wetlands, beach ridges and intratidal deposits. We outline the difficulties and solutions we made to compile databases in such different depostional environment. We address complex tectonics and the framework to compare such large variability of RSL data-point. We discuss the implications of our results for the glacio-isostatic adjustment (GIA) models in the two studied regions.

  2. Subglacial Sediment Transport of a Marine Ice Stream During the Late Glacial Maximum, Northern North Sea

    NASA Astrophysics Data System (ADS)

    Nygard, A.; Sejrup, H. P.; Haflidason, H.; Lekens, W.; Clark, C.; Bigg, G.

    2006-12-01

    By means of high-resolution seismic and core data we have quantified the flux of sediment transported subglacially by the Norwegian Channel Ice Stream (NCIS) at the end of the Last Glacial Maximum (LGM). This was achieved by mapping the volume of sediment deposited during the last NCIS phase on the North Sea Fan, a glacial fan located on the continental slope at the outlet of the Norwegian Channel, northern North Sea. The North Sea Fan is dominated by glacigenic debris flows sourced from subglacial till brought to the shelf break by the NCIS, which drained a major part of the southwestern Fennoscandian Ice Sheet. 800 km3 of sediment was brought to the shelf edge by the NCIS between 20.0 and 19.0 cal. ka BP, which gives an annual flux of 8000 m3 pr. metre width of the ice stream front. This equates to a total of 1.1 Gt of sediment per year and is comparable to the present sediment flux from the worlds largest rivers. To explain the extreme sediment flux the NCIS must have flowed with high velocity (several kilometres/year) and/or the subglacial sediment transport must have occurred in a thick layer (several metres).

  3. Discarding of plaice (Pleuronectes platessa) in the Danish North Sea trawl fishery

    NASA Astrophysics Data System (ADS)

    Madsen, Niels; Feekings, Jordan; Lewy, Peter

    2013-01-01

    Plaice (Pleuronectes platessa) plays an important role in the North Sea benthic ecosystem and is by weight the most important commercial flatfish species in the North Sea demersal fishery. There is a high discarding of plaice in the active demersal fisheries in the North Sea. The change in fisheries management towards a more ecosystem based approach, together with a greater focus on sustainability, has caused a severe need for action. Subsequently, the European Commission is preparing regulations to reduce or even ban discards. The trawl fisheries are commercially the most important Danish fishery targeting plaice. Here we analyse discard data collected onboard Danish vessels in the period from 1998 to 2008. We describe the general patterns in these data by dividing them into three mesh size categories: 80-99 mm, 100-119 mm and ≥ 120 mm to reflect implemented technical measures of relevance. We analyse the landed and discarded portions in these mesh size categories and link the discarding to the minimum landing size. We employed a GAM model to assess how discarding of plaice below the minimum landing size is connected to relevant factors that could be of relevance from a management perspective. We identified a statistical significant effect of mesh size category and area. We discuss the results in relation to potential mitigation measures to be implemented in future fisheries management strategies.

  4. Aerosol climatology from ground-based measurements for the southern North Sea

    NASA Astrophysics Data System (ADS)

    Behnert, Irina; Matthias, Volker; Doerffer, Roland

    2007-05-01

    An aerosol climatology over the southern North Sea region has been set up using aerosol optical properties derived from regular sunphotometer (AERONET) and lidar (EARLINET) measurements between April and September for the years 2000-2003. Data from four AERONET sites in the North Sea coastal region (Helgoland Island, Oostende, Hamburg and Lille) and, for comparison purposes, also from two "maritime sites" (Rame Head and Azores Island) are selected. The variability of the aerosol optical depth τa(500) and the spatial distribution of aerosol optical depth τa(500), Ångström wavelength exponent α440-870 , as well as of retrieved microphysical aerosol parameters (single scattering albedo, index of refraction, particle size distribution) are studied. The 4 years of observations show great similarities between the North Sea coastal sites and Helgoland Island. Although 70 km separated from the coast, the aerosol optical properties found at the island are much closer to those at Hamburg, Oostende and Lille than at the maritime sites Rame Head and Azores. Compared to the standard aerosol models differences in the Ångström wavelength exponent α440-870 , the single scattering albedo and the refractive index are detected. Based on these observations a new aerosol model for the atmospheric correction of coastal water reflectance spectra of the imaging spectrometer MERIS/ENVISAT was set up, which meets in particular the higher Ångström wavelength exponent of the coastal sites compared to standard maritime conditions.

  5. Long-Term Trends in Calcifying Plankton and pH in the North Sea

    PubMed Central

    Beare, Doug; McQuatters-Gollop, Abigail; van der Hammen, Tessa; Machiels, Marcel; Teoh, Shwu Jiau; Hall-Spencer, Jason M.

    2013-01-01

    Relationships between six calcifying plankton groups and pH are explored in a highly biologically productive and data-rich area of the central North Sea using time-series datasets. The long-term trends show that abundances of foraminiferans, coccolithophores, and echinoderm larvae have risen over the last few decades while the abundances of bivalves and pteropods have declined. Despite good coverage of pH data for the study area there is uncertainty over the quality of this historical dataset; pH appears to have been declining since the mid 1990s but there was no statistical connection between the abundance of the calcifying plankton and the pH trends. If there are any effects of pH on calcifying plankton in the North Sea they appear to be masked by the combined effects of other climatic (e.g. temperature), chemical (nutrient concentrations) and biotic (predation) drivers. Certain calcified plankton have proliferated in the central North Sea, and are tolerant of changes in pH that have occurred since the 1950s but bivalve larvae and pteropods have declined. An improved monitoring programme is required as ocean acidification may be occurring at a rate that will exceed the environmental niches of numerous planktonic taxa, testing their capacities for acclimation and genetic adaptation. PMID:23658686

  6. Vertical distributions of autumn spawned larval herring ( Clupea harengus L.) in the North Sea

    NASA Astrophysics Data System (ADS)

    Heath, M.; Brander, K.; Munk, P.; Rankine, P.

    1991-12-01

    Vertical distributions of autumn spawned herring larvae were sampled at 10 sites in the North Sea between October 1987 and March 1988 during the Autumn Circulation Experiment (ACE). Several different patterns of vertical migrations occurred. Diel variations in the vertical distributions were found in all stages of development, from yolk-sac to pre-metamorphosis (35 mm). During diel migrations larvae were closer to the surface during daylight than at night. The amplitude of diel vertical migrations increased with the length of the larvae. Semi-diel cycles in the vertical distributions were rare, and appeared to be related to the tidal cycle rather than crepuscular periods. Diel cycles in vertical distribution could not be detected at sites in the southeastern North Sea, characterized by water depths less than 45 m, high vertical shear and high light attenuation coefficients. It is suggested that strong turbulence inhibits diel vertical migrations by herring larvae. This feature has important consequences for the advection of larvae in the North Sea.

  7. Wind farm induced changes in wind speed and surface fluxes over the North Sea

    NASA Astrophysics Data System (ADS)

    Chatterjee, Fabien; van Lipzig, Nicole; Meyers, Johan

    2016-04-01

    Offshore wind farm deployment in the North Sea is foreseen to expand dramatically in the coming years. The strong expansion of offshore wind parks is likely to affect the regional climatology on the North Sea. We assess this impact by conducting a regional climate model simulation over future wind farms built near the German coast. In order to achieve this, the wind farm parameterisation of Fitch et al. 2012, where wind farms are parameterised as elevated sources of turbulent kinetic energy and sinks of momentum ( Blahak et al 2010 and Fitch et al 2012) is implemented in COSMO-CLM at a 1.5 km resolution. As a first step, COSMO-CLM's ability to reproduce wind profiles over the North Sea is evaluated using wind speed data from the FINO1 meteorological mast, toghether with QuikScat scatterometer data, for a time period of 2000-2008. Subsequently, the impact of windfarms on the regional climate over a period of ten years (1999-2008) is assessed. A large scale wind farm can create wakes which depending on the wind direction could affect the power production of a neighbouring farm. Furthermore, wind farms decelerate the flow and create a vertical circulation in the inflow region. As a result, changes in vertical fluxes of moisture are observed. This leads to enhanced low level cloud cover which may trigger changes in precipitation.

  8. Two centuries of observed atmospheric variability and change over the North Sea region

    NASA Astrophysics Data System (ADS)

    Stendel, Martin; van den Besselaar, Else; Hannachi, Abdel; Kent, Elizabeth; Lefebvre, Christiana; van Oldenborgh, Geert Jan; Rosenhagen, Gudrun; Schenk, Frederik; van der Schrier, Gerard

    2015-04-01

    Situated in northwestern Europe, the North Sea region is under influence of air masses from subtropical to arctic origin, and thus exhibits significant natural climate variability. As the land areas surrounding the North Sea are densely populated, climate change is an important issue in terms of e.g. coastal protection, fishery and trade. This study is part of the NOSCCA initiative (North Sea Region Climate Change Assessment) and presents observed variability and changes in atmospheric parameters during the last roughly 200 years. Circulation patterns show considerable decadal variability. In recent decades, a northward shift of storm tracks and increased cyclonic activity has been observed. There is also an indication of increased persistence of weather types. The wind climate is dominated by large multidecadal variability, and no robust long-term trends can be identified in the available datasets. There is a clear positive trend in near-surface temperatures, in particular during spring and winter. Over the region as a whole, no clear long-term precipitation trends are visible, although regional indications exist for an increased risk of extreme precipitation events.

  9. The impact of shipping emissions on air pollution in the greater North Sea region - Part 2: Scenarios for 2030

    NASA Astrophysics Data System (ADS)

    Matthias, V.; Aulinger, A.; Backes, A.; Bieser, J.; Geyer, B.; Quante, M.; Zeretzke, M.

    2016-01-01

    Scenarios for future shipping emissions in the North Sea have been developed in the framework of the Clean North Sea Shipping project. The effects of changing NOx and SO2 emissions were investigated with the CMAQ chemistry transport model for the year 2030 in the North Sea area. It has been found that, compared to today, the contribution of shipping to the NO2 and O3 concentrations will increase due to the expected enhanced traffic by more than 20 and 5 %, respectively, by 2030 if no regulation for further emission reductions is implemented in the North Sea area. PM2.5 will decrease slightly because the sulfur contents in ship fuels will be reduced as international regulations foresee. The effects differ largely between regions, seasons and date of the implementation of stricter regulations for NOx emissions from newly built ships.

  10. Response of the Baltic and North Seas to river runoff from the Baltic watershed - Physical and biological changes

    NASA Astrophysics Data System (ADS)

    Hänninen, Jari; Vuorinen, Ilppo; Rajasilta, Marjut; Reid, Philip C.

    2015-11-01

    Selected Baltic Sea watershed River Runoff (BSRR) events during 1970-2000 were used as predictor in Generalised Linear Mixed Models (GLIMMIX) for evidence of simultaneous changes/chain of events (including possible time lags) in some chemical, physical and biological variables in the Baltic and North Sea ecosystems. Our aim was to explore for climatic-based explanation for ecological regime shifts that were documented semi-simultaneously in both ecosystems. Certain similarities were identified in the North Sea and the Baltic Sea salinity, oxygen concentration, temperature and phyto- and zooplankton parameters. These findings suggest that BSRR events which originate in the Baltic Sea catchment area modify and contribute to large scale ecosystem changes not only in the Baltic Sea, but also in the adjacent parts of the North Sea. However, the Baltic Sea inter-annual and inter-decadal variabilities of physical and biological parameters are driven by direct atmospheric forcing, typically with a relatively short lag. In contrast, such changes in the North Sea are influenced by both local and direct atmospheric forcing, typically with a longer lag than in the Baltic, and a more regional, indirect forcing from changes in the North Atlantic. We suggest that this interactive system partially is behind large scale ecosystem regime shifts found in both Seas. During our study period two such shifts have been identified independently from us in a study earlier in the Southern and Central Baltic in 1980s and 1990s and a later one in 2001/2002 in the North Sea. As a post hoc test we compared the 0+ year class strength of the North Sea herring with BSRR intensity, and found evidence for higher herring production in high BSRR periods, which further corroborates the idea of a remote effect from the large watershed area of the Baltic. Regime shifts as well as their semi-synchronous appearance in two neighbouring sea areas could be identified. GLIMMIX models provide opportunities for

  11. Exploring Linkages Between Gulf of Mexico Sea Surface Conditions and North American Hydroclimate during the Holocene

    NASA Astrophysics Data System (ADS)

    Richey, J. N.; Thirumalai, K.; Quinn, T. M.; Poore, R. Z.

    2015-12-01

    The Gulf of Mexico is part of the Atlantic Warm Pool, a feature that drives oceanic moisture flux to the surrounding continent. It is connected to the North Atlantic Ocean via the loop current, which transports salt and heat from the Caribbean and Gulf of Mexico poleward via the Gulf Stream. As such, variations in Gulf of Mexico sea surface temperature (SST) and salinity (SSS) are linked to changes in North Atlantic Ocean circulation and North American hydroclimate. Although SST and SSS variability in the Gulf of Mexico are well understood on inter-annual and glacial-interglacial timescales, little is known about centennial scale variability in these sea surface parameters through the Holocene. We present here the first continuous multi-decadal resolution time series of SST and SSS spanning the entire Holocene from the Gulf of Mexico. This proxy reconstruction is based on paired measurements of Mg/Ca and δ18O in the planktic foraminifer, Globigerinoides ruber (white variety) in the Garrison Basin. Using these data, in combination with additional Gulf of Mexico SST and SSS records from the late Holocene, we explore linkages between North American precipitation patterns and ocean circulation on centennial timescales.

  12. Genetic diversity of Saccharina latissima (Phaeophyceae) along a salinity gradient in the North Sea-Baltic Sea transition zone.

    PubMed

    Møller Nielsen, Mette; Paulino, Cristina; Neiva, João; Krause-Jensen, Dorte; Bruhn, Annette; Serrão, Ester A

    2016-08-01

    The North Sea-Baltic Sea transition zone constitutes a boundary area for the kelp species Saccharina latissima due to a strong salinity gradient operating in the area. Furthermore, the existence of S. latissima there, along Danish waters, is fairly patchy as hard bottom is scarce. In this study, patterns of genetic diversity of S. latissima populations were evaluated along the salinity gradient area of Danish waters (here designated brackish) and were compared to reference sites (here designated marine) outside the gradient area, using microsatellite markers. The results showed that the S. latissima populations were structured into two clusters corresponding to brackish versus marine sites, and that gene flow was reduced both between clusters and between populations within clusters. In addition, results provided empirical evidence that marginal populations of S. latissima in the salinity gradient area exhibited a distinct genetic structure when compared to marine ones. Brackish populations were less diverse, more related, and showed increased differentiation over distance compared to marine populations. The isolation of the brackish S. latissima populations within the salinity gradient area of Danish waters in conjunction with their general low genetic diversity makes these populations vulnerable to ongoing environmental and climate change, predicted to result in declining salinity in the Baltic Sea area that may alter the future distribution and performance of S. latissima in the area. PMID:27151230

  13. Is Ice-Rafted Sediment in a North Pole Marine Record Evidence for Perennial Sea-ice Cover?

    NASA Technical Reports Server (NTRS)

    Tremblay, L.B.; Schmidt, G.A.; Pfirman, S.; Newton, R.; DeRepentigny, P.

    2015-01-01

    Ice-rafted sediments of Eurasian and North American origin are found consistently in the upper part (13 Ma BP to present) of the Arctic Coring Expedition (ACEX) ocean core from the Lomonosov Ridge, near the North Pole (approximately 88 degrees N). Based on modern sea-ice drift trajectories and speeds, this has been taken as evidence of the presence of a perennial sea-ice cover in the Arctic Ocean from the middle Miocene onwards. However, other high latitude land and marine records indicate a long-term trend towards cooling broken by periods of extensive warming suggestive of a seasonally ice-free Arctic between the Miocene and the present. We use a coupled sea-ice slab-ocean model including sediment transport tracers to map the spatial distribution of ice-rafted deposits in the Arctic Ocean. We use 6 hourly wind forcing and surface heat fluxes for two different climates: one with a perennial sea-ice cover similar to that of the present day and one with seasonally ice-free conditions, similar to that simulated in future projections. Model results confirm that in the present-day climate, sea ice takes more than 1 year to transport sediment from all its peripheral seas to the North Pole. However, in a warmer climate, sea-ice speeds are significantly faster (for the same wind forcing) and can deposit sediments of Laptev, East Siberian and perhaps also Beaufort Sea origin at the North Pole. This is primarily because of the fact that sea-ice interactions are much weaker with a thinner ice cover and there is less resistance to drift. We conclude that the presence of ice-rafted sediment of Eurasian and North American origin at the North Pole does not imply a perennial sea-ice cover in the Arctic Ocean, reconciling the ACEX ocean core data with other land and marine records.

  14. Insight into the Pacific Sea Surface Temperature- North American Hydroclimate Connection from an Eastern Tropical North Pacific Coral Record

    NASA Astrophysics Data System (ADS)

    Svendsen, J. I.; Briner, J. P.; Mangerud, J.; Hughes, A. L. C.; Young, N. E.; Vasskog, K.

    2014-12-01

    The last few years of record-breaking climate anomalies across North America--a resilient atmospheric ridge and extreme drought over the West Coast, and severe winters across the Midwest and East Coast regions--have been linked to anomalous Pacific sea surface temperatures (Seager et al. 2014, Wang et al. 2014, Hartmann 2015). The synoptic associations prompt important questions on the relation between these unusual phenomena and extreme expressions of known Pacific decadal modes, such as the North Pacific Gyre Oscillation (NPGO). These questions motivate our pursuit to document multiple realizations of decadal variability in the Pacific-North American region through periods of varied radiative forcing. Here we introduce a 178 year, seasonally resolved Porites coral record from Clarion Island (18N, 115W), the westernmost island of the Revillagigedo Archipelago, a region both highly influenced by NPGO SST and SSS variability and critical for NPGO tropical-extratropical communication via the Seasonal Footprinting Mechanism (Vimont et al. 2003). When coupled with tree ring records from the western United States (Griffin and Anchukaitis 2014, MacDonald and Case 2005) and coral records from the central tropical Pacific (Cobb et al. 2001), the δ18O signal from the Clarion coral offers an extended framework of coherent continental hydroclimate and oceanic variability across the Pacific basin beyond the instrumental record. Over the last 200 years, we find clear commonality in the timing, magnitude and spatial expression of variability (illustrated through the NADA Atlas, Cook et al. 2004) amongst the proxy records. The strong relationship between Northeastern Pacific Clarion and the Central Pacific Palmyra record with the North American hydroclimate records can be viewed within the mechanistic framework of the NPGO; this framework is then explored over the last millennium across intervals of varied radiative forcing.

  15. Insight into the Pacific Sea Surface Temperature- North American Hydroclimate Connection from an Eastern Tropical North Pacific Coral Record

    NASA Astrophysics Data System (ADS)

    Sanchez, S. C.; Charles, C. D.; Carriquiry, J. D.

    2015-12-01

    The last few years of record-breaking climate anomalies across North America--a resilient atmospheric ridge and extreme drought over the West Coast, and severe winters across the Midwest and East Coast regions--have been linked to anomalous Pacific sea surface temperatures (Seager et al. 2014, Wang et al. 2014, Hartmann 2015). The synoptic associations prompt important questions on the relation between these unusual phenomena and extreme expressions of known Pacific decadal modes, such as the North Pacific Gyre Oscillation (NPGO). These questions motivate our pursuit to document multiple realizations of decadal variability in the Pacific-North American region through periods of varied radiative forcing. Here we introduce a 178 year, seasonally resolved Porites coral record from Clarion Island (18N, 115W), the westernmost island of the Revillagigedo Archipelago, a region both highly influenced by NPGO SST and SSS variability and critical for NPGO tropical-extratropical communication via the Seasonal Footprinting Mechanism (Vimont et al. 2003). When coupled with tree ring records from the western United States (Griffin and Anchukaitis 2014, MacDonald and Case 2005) and coral records from the central tropical Pacific (Cobb et al. 2001), the δ18O signal from the Clarion coral offers an extended framework of coherent continental hydroclimate and oceanic variability across the Pacific basin beyond the instrumental record. Over the last 200 years, we find clear commonality in the timing, magnitude and spatial expression of variability (illustrated through the NADA Atlas, Cook et al. 2004) amongst the proxy records. The strong relationship between Northeastern Pacific Clarion and the Central Pacific Palmyra record with the North American hydroclimate records can be viewed within the mechanistic framework of the NPGO; this framework is then explored over the last millennium across intervals of varied radiative forcing.

  16. Exchanges between the open Black Sea and its North West shelf

    NASA Astrophysics Data System (ADS)

    Shapiro, Georgy; Wobus, Fred; Zhou, Feng

    2014-05-01

    Exchanges between the vast NW shelf and the deep basin of the Black Sea play a significant role in maintaining the balance of nutrients, heat content and salinity of the shelf waters. Nearly 87 % of the Black Sea is entirely anoxic below 70 to 200m and contains high levels of hydrogen sulphide (Zaitsev et al, 2001), and this makes the shelf waters particularly valuable for maintaining the Black Sea ecosystem in good health. The increase in salinity of shelf waters occurs partially due to exchanges with more saline open sea waters and represents a threat to relics and endemic species. The shelf-break is commonly considered the bottle-neck of the shelf-deep sea exchanges (e.g. (Huthnance, 1995, Ivanov et al, 1997). Due to conservation of potential vorticity, the geostrophic currents flow along the contours of constant depth. However the ageostrophic flows (Ekman drift, mesoscale eddies, filaments, internal waves) are not subject to the same constraints. It has been shown that during the winter well mixed cold waters formed on the North West shelf propagate into the deep sea, providing an important mechanism for the replenishment of the Cold Intermediate Layer ( Staneva and Stanev, 1997). However, much less is known about exchanges in the warm season. In this study, the transports of water, heat and salt between the northwestern shelf and the adjacent deep basin of the Black Sea are investigated using a high-resolution three-dimensional primitive equation model, NEMO-SHELF-BLS (Shapiro et al, 2013). It is shown that during the period from April to August, 2005, both onshore and offshore cross-shelf break transports in the top 20 m were as high as 0.24 Sv on average, which was equivalent to the replacement of 60% of the volume of surface shelf waters (0 - 20 m) per month. Two main exchange mechanisms are studied: (i) Ekman transport, and (ii) transport by mesoscale eddies and associated meanders of the Rim Current. The Ekman drift causes nearly uniform onshore or

  17. Bio-optical characterization in an ultra-oligotrophic region: the North central Red Sea

    NASA Astrophysics Data System (ADS)

    Kheireddine, Malika; Jones, Burton

    2015-04-01

    Until recently, satellite-derived ocean color observations have been the only means of evaluating optical variability of the Red Sea. During a cruise in autumn 2014, we investigated the variability of Inherent Optical Properties (IOPs) in the North Central Red Sea (NCRS) with a particular focus on the particulate backscattering coefficient, bbp, and colored dissolved organic matter, CDOM, absorption. To our knowledge, these are some of the measurements of these properties in the Red Sea. The IOPs are derived from the concentration and physical properties of suspended particles in the ocean. They provide a simple description of the influence of these particles on the light within the water column. Bio-optical relationships found for ultra-oligotrophic waters of the six stations sampled significantly depart from the mean standard relationships provided for the global ocean, showing the peculiar character of the Red Sea. These optical anomalies relate to the specific biological and environmental conditions occurring in the Red Sea ecosystem. Specifically, the surface specific phytoplankton absorption coefficients are lower than the values predicted from the global relationships due to a high proportion of relatively large sized phytoplankton. Conversely, bbp values are much higher than the mean standard values for a given chlorophyll-a concentration, Chl a. This presumably results from the influence of highly refractive submicrometer particles of Saharan origin in the surface layer of the water column.

  18. Sea-level response to atmospheric forcing along the north coast of Persian Gulf

    NASA Astrophysics Data System (ADS)

    Hassanzadeh, S.; Kiasatpour, A.; Hosseinibalam, F.

    2007-02-01

    Data from tide gauges (1990-1999) at Bandar Abbas and Bushehr combined with atmospheric data at both stations are utilized to investigate the mean sea-level (MSL) response to meteorological forcing functions along the north coast of the Persian Gulf. The relations between MSL and forces due to air pressure, air temperature and local wind are examined. The characteristics of variability of each field are analyzed using the spectral analysis method. The annual cycle is dominant in the sea-level, atmospheric pressure, air temperature and wind spectra. The influence of local meteorological functions are quantified using forward stepwise regression techniques. The results suggest that 71.5% and 71.2% variations in the MSL of Bandar Abbas and Bushehr stations are due to meteorological forces at each stations. The model indicates that the most significant influence on the observed variation of MSL at Bandar Abbas is air pressure, while at Bushehr is air temperature. The results of multivariate and simple regression show that these parameters are highly intercorrelated. The sea-level is not significantly correlated with the monthly and winter NAO and Monsoon in the Persian Gulf. The remaining variations are due to density of sea water (steric effect), which has considerable influence on the sea-level variations, and coastal upwelling.

  19. Climatic forcing of Quaternary deep-sea benthic communities in the North Pacific Ocean

    USGS Publications Warehouse

    Yasuhara, Moriaki; Hunt, G.; Cronin, T. M.; Hokanishi, N.; Kawahata, H.; Tsujimoto, Akira; Ishitake, M.

    2012-01-01

    There is growing evidence that changes in deep-sea benthic ecosystems are modulated by climate changes, but most evidence to date comes from the North Atlantic Ocean. Here we analyze new ostracod and published foraminiferal records for the last 250,000 years on Shatsky Rise in the North Pacific Ocean. Using linear models, we evaluate statistically the ability of environmental drivers (temperature, productivity, and seasonality of productivity) to predict changes in faunal diversity, abundance, and composition. These microfossil data show glacial-interglacial shifts in overall abundances and species diversities that are low during glacial intervals and high during interglacials. These patterns replicate those previously documented in the North Atlantic Ocean, suggesting that the climatic forcing of the deep-sea ecosystem is widespread, and possibly global in nature. However, these results also reveal differences with prior studies that probably reflect the isolated nature of Shatsky Rise as a remote oceanic plateau. Ostracod assemblages on Shatsky Rise are highly endemic but of low diversity, consistent with the limited dispersal potential of these animals. Benthic foraminifera, by contrast, have much greater dispersal ability and their assemblages at Shatsky Rise show diversities typical for deep-sea faunas in other regions. Statistical analyses also reveal ostracod-foraminferal differences in relationships between environmental drivers and biotic change. Rarefied diversity is best explained as a hump-shaped function of surface productivity in ostracods, but as having a weak and positive relationship with temperature in foraminifera. Abundance shows a positive relationship with both productivity and seasonality of productivity in foraminifera, and a hump-shaped relationship with productivity in ostracods. Finally, species composition in ostracods is influenced by both temperature and productivity, but only a temperature effect is evident in foraminifera. Though

  20. Distribution of skates and sharks in the North Sea: 112 years of change.

    PubMed

    Sguotti, Camilla; Lynam, Christopher P; García-Carreras, Bernardo; Ellis, Jim R; Engelhard, Georg H

    2016-08-01

    How have North Sea skate and shark assemblages changed since the early 20th century when bottom trawling became widespread, whilst their environment became increasingly impacted by fishing, climate change, habitat degradation and other anthropogenic pressures? This article examines long-term changes in the distribution and occurrence of the elasmobranch assemblage of the southern North Sea, based on extensive historical time series (1902-2013) of fishery-independent survey data. In general, larger species (thornback ray, tope, spurdog) exhibited long-term declines, and the largest (common skate complex) became locally extirpated (as did angelshark). Smaller species increased (spotted and starry ray, lesser-spotted dogfish) as did smooth-hound, likely benefiting from greater resilience to fishing and/or climate change. This indicates a fundamental shift from historical dominance of larger, commercially valuable species to current prevalence of smaller, more productive species often of low commercial value. In recent years, however, some trends have reversed, with the (cold-water associated) starry ray now declining and thornback ray increasing. This shift may be attributed to (i) fishing, including mechanised beam trawling introduced in the 1960s-1970s, and historical target fisheries for elasmobranchs; (ii) climate change, currently favouring warm-water above cold-water species; and (iii) habitat loss, including potential degradation of coastal and outer estuarine nursery habitats. The same anthropogenic pressures, here documented to have impacted North Sea elasmobranchs over the past century, are likewise impacting shelf seas worldwide and may increase in the future; therefore, parallel changes in elasmobranch communities in other regions are to be expected.

  1. Distribution of skates and sharks in the North Sea: 112 years of change.

    PubMed

    Sguotti, Camilla; Lynam, Christopher P; García-Carreras, Bernardo; Ellis, Jim R; Engelhard, Georg H

    2016-08-01

    How have North Sea skate and shark assemblages changed since the early 20th century when bottom trawling became widespread, whilst their environment became increasingly impacted by fishing, climate change, habitat degradation and other anthropogenic pressures? This article examines long-term changes in the distribution and occurrence of the elasmobranch assemblage of the southern North Sea, based on extensive historical time series (1902-2013) of fishery-independent survey data. In general, larger species (thornback ray, tope, spurdog) exhibited long-term declines, and the largest (common skate complex) became locally extirpated (as did angelshark). Smaller species increased (spotted and starry ray, lesser-spotted dogfish) as did smooth-hound, likely benefiting from greater resilience to fishing and/or climate change. This indicates a fundamental shift from historical dominance of larger, commercially valuable species to current prevalence of smaller, more productive species often of low commercial value. In recent years, however, some trends have reversed, with the (cold-water associated) starry ray now declining and thornback ray increasing. This shift may be attributed to (i) fishing, including mechanised beam trawling introduced in the 1960s-1970s, and historical target fisheries for elasmobranchs; (ii) climate change, currently favouring warm-water above cold-water species; and (iii) habitat loss, including potential degradation of coastal and outer estuarine nursery habitats. The same anthropogenic pressures, here documented to have impacted North Sea elasmobranchs over the past century, are likewise impacting shelf seas worldwide and may increase in the future; therefore, parallel changes in elasmobranch communities in other regions are to be expected. PMID:27082729

  2. Bathymetric controls on Pliocene North Atlantic and Arctic sea surface temperature and deepwater production

    USGS Publications Warehouse

    Robinson, M.M.; Valdes, P.J.; Haywood, A.M.; Dowsett, H.J.; Hill, D.J.; Jones, S.M.

    2011-01-01

    The mid-Pliocene warm period (MPWP; ~. 3.3 to 3.0. Ma) is the most recent interval in Earth's history in which global temperatures reached and remained at levels similar to those projected for the near future. The distribution of global warmth, however, was different than today in that the high latitudes warmed more than the tropics. Multiple temperature proxies indicate significant sea surface warming in the North Atlantic and Arctic Oceans during the MPWP, but predictions from a fully coupled ocean-atmosphere model (HadCM3) have so far been unable to fully predict the large scale of sea surface warming in the high latitudes. If climate proxies accurately represent Pliocene conditions, and if no weakness exists in the physics of the model, then model boundary conditions may be in error. Here we alter a single boundary condition (bathymetry) to examine if Pliocene high latitude warming was aided by an increase in poleward heat transport due to changes in the subsidence of North Atlantic Ocean ridges. We find an increase in both Arctic sea surface temperature and deepwater production in model experiments that incorporate a deepened Greenland-Scotland Ridge. These results offer both a mechanism for the warming in the North Atlantic and Arctic Oceans indicated by numerous proxies and an explanation for the apparent disparity between proxy data and model simulations of Pliocene northern North Atlantic and Arctic Ocean conditions. Determining the causes of Pliocene warmth remains critical to fully understanding comparisons of the Pliocene warm period to possible future climate change scenarios. ?? 2011.

  3. Historical changes in carbon dioxide (CO2) and dimethyl sulphide (DMS) emissions in the eutrophied Southern North Sea

    NASA Astrophysics Data System (ADS)

    Gypens, N.; Borges, A. V.; Lancelot, C.

    2012-04-01

    Anthropogenic activities after the Second World War have severely increased river nutrient [nitrogen (N) and phosphorus (P)] loads to European coastal areas. The resulting N: P: Si imbalance (compared to phytoplankton requirements) stimulated in the Southern North Sea the growth of Phaeocystis colonies modifying the functioning of the ecosystem and, therefore, the carbon but also the biogenic sulphur cycles. Phaeocystis is a significant producer of DMSP (dimethylsulphide propionate), the precursor of DMS. When emitted to the atmosphere the DMS has a cooling effect on the climate contrarily to the CO2 greenhouse gas. Since the late 1990's specific nutrient reduction policies have however considerably reduced P loads while N is maintained. In this application we explore, with a mathematical tool, the effects of changing N and P loads on air-sea CO2 exchanges and DMS marine emissions. The chosen model is the MIRO-CO2-DMS, a complex biogeochemical model describing carbon, biogenic sulphur and nutrient cycles in the marine domain. Model simulations are performed for the contemporary period since 1950, using real forcing fields for sea surface temperature, wind speed and atmospheric CO2 and RIVERSTRAHLER model simulations for river carbon and nutrient loads. Results are discussing the importance of human activities and river inputs of carbon and nutrients on the eutrophication of coastal areas, their ability to absorb atmospheric CO2 and the importance of DMS emissions associated with phytoplankton blooms, especially Phaeocystis.

  4. A decade of sea ice thickness mapping by airborne lidar between Greenland and the North Pole

    NASA Astrophysics Data System (ADS)

    Hvidegaard, S. M.; Forsberg, R.; Skourup, H.; Stenseng, L.; Hanson, S.

    2007-12-01

    Airborne laser altimetry provides a direct measurement of sea ice freeboard, when combined with a precise geoid model and a lowest-level filtering algorithm to take into account residual errors in GPS-positioning, ocean dynamic topography, tides etc. Using swath laser scanning, the method additionally gives detailed information on the geometry of leads, ridges and the distribution of thin ice and open water. The conversion of sea ice freeboard heights to thickness is based on the assumption of equilibrium, with major errors sources relating to snow depth and density of sea ice. In the paper we describe results of measurements with airborne laser north of Greenland, Ellesmere Island and in the Fram Strait region, carried out on a yearly basis since 1998, in the first years using a single beam laser, and since 2001 using swath laser scanning giving a resolution of approximately 1 m in the ice features. The campaigns have mostly been done in the spring period, typically in connection with airborne gravity surveys or CryoSat calibration and validation activities. Observed secular changes in the sea ice freeboard heights are masked by limited spatial and temporal extent of campaigns, as well as interannual variability in the sea ice regime of the region. To address the error sources in the lidar thickness determination, a number of in-situ and helicopter EM comparisons have been carried out, e.g latest in April 2007 around the Tara drifting station beyond the North Pole, as part of the Damocles project. In cooperation with ESA and APL, coincident Ku-band radar and laser systems have also been flown, giving a unique opportunity for airborne measurement of snow depth as well.

  5. TOPAZ4: an ocean-sea ice data assimilation system for the North Atlantic and Arctic

    NASA Astrophysics Data System (ADS)

    Sakov, P.; Counillon, F.; Bertino, L.; Lisæter, K. A.; Oke, P. R.; Korablev, A.

    2012-08-01

    We present a detailed description of TOPAZ4, the latest version of TOPAZ - a coupled ocean-sea ice data assimilation system for the North Atlantic Ocean and Arctic. It is the only operational, large-scale ocean data assimilation system that uses the ensemble Kalman filter. This means that TOPAZ features a time-evolving, state-dependent estimate of the state error covariance. Based on results from the pilot MyOcean reanalysis for 2003-2008, we demonstrate that TOPAZ4 produces a realistic estimate of the ocean circulation in the North Atlantic and the sea-ice variability in the Arctic. We find that the ensemble spread for temperature and sea-level remains fairly constant throughout the reanalysis demonstrating that the data assimilation system is robust to ensemble collapse. Moreover, the ensemble spread for ice concentration is well correlated with the actual errors. This indicates that the ensemble statistics provide reliable state-dependent error estimates - a feature that is unique to ensemble-based data assimilation systems. We demonstrate that the quality of the reanalysis changes when different sea surface temperature products are assimilated, or when in-situ profiles below the ice in the Arctic Ocean are assimilated. We find that data assimilation improves the match to independent observations compared to a free model. Improvements are particularly noticeable for ice thickness, salinity in the Arctic, and temperature in the Fram Strait, but not for transport estimates or underwater temperature. At the same time, the pilot reanalysis has revealed several flaws in the system that have degraded its performance. Finally, we show that a simple bias estimation scheme can effectively detect the seasonal or constant bias in temperature and sea-level.

  6. Anthropogenic plutonium in the North Jiangsu tidal flats of the Yellow Sea in China.

    PubMed

    Liu, Zhiyong; Zheng, Jian; Pan, Shaoming; Gao, Jianhua

    2013-08-01

    The (239+240)Pu activities and (240)Pu/(239)Pu atom ratios were analyzed using a double-focusing SF-ICP-MS for sediment core samples obtained in 2007-2008 from the North Jiangsu tidal flats in the Yellow Sea in China. Particular attention was focused on the (240)Pu/(239)Pu atom ratios in the sediment to identify the origins of Pu isotopes. The profiles of (239+240)Pu activities in the sediment cores are similar to those of the (137)Cs activities. The (240)Pu/(239)Pu atom ratios in the tidal flats showed typical global fallout values, indicating that this area did not receive the possible early direct close-in fallout or oceanic current transported Pu from the Pacific Proving Grounds (PPG). If any, the contribution of the PPG source Pu to the total Pu inventory is negligible. This is different from the sediments in the Yangtze River estuary in the East China Sea, where the PPG source Pu contributed ca. 45 % to the total inventory. In addition, the observation of the global fallout origin Pu in the North Jiangsu tidal flats indicated that the nuclear power plant in the region was not causing any alteration/contamination to the (240)Pu/(239)Pu atom ratios. The (239+240)Pu and (137)Cs activities/inventories in the sediment cores showed correlation to the mean clay sediment compositions (fine particles) in the tidal flats. Therefore, mud deposits are served as sinks for the anthropogenic radionuclides in the tidal flats and the Yellow Sea. Integrated with the previously reported spatial distributions of (239+240)Pu and (137)Cs activities in the surface sediments of the Yellow Sea, the mechanism of Pu transport with the ocean currents and the scavenging characteristics in the Yellow Sea were discussed.

  7. Anthropogenic plutonium in the North Jiangsu tidal flats of the Yellow Sea in China.

    PubMed

    Liu, Zhiyong; Zheng, Jian; Pan, Shaoming; Gao, Jianhua

    2013-08-01

    The (239+240)Pu activities and (240)Pu/(239)Pu atom ratios were analyzed using a double-focusing SF-ICP-MS for sediment core samples obtained in 2007-2008 from the North Jiangsu tidal flats in the Yellow Sea in China. Particular attention was focused on the (240)Pu/(239)Pu atom ratios in the sediment to identify the origins of Pu isotopes. The profiles of (239+240)Pu activities in the sediment cores are similar to those of the (137)Cs activities. The (240)Pu/(239)Pu atom ratios in the tidal flats showed typical global fallout values, indicating that this area did not receive the possible early direct close-in fallout or oceanic current transported Pu from the Pacific Proving Grounds (PPG). If any, the contribution of the PPG source Pu to the total Pu inventory is negligible. This is different from the sediments in the Yangtze River estuary in the East China Sea, where the PPG source Pu contributed ca. 45 % to the total inventory. In addition, the observation of the global fallout origin Pu in the North Jiangsu tidal flats indicated that the nuclear power plant in the region was not causing any alteration/contamination to the (240)Pu/(239)Pu atom ratios. The (239+240)Pu and (137)Cs activities/inventories in the sediment cores showed correlation to the mean clay sediment compositions (fine particles) in the tidal flats. Therefore, mud deposits are served as sinks for the anthropogenic radionuclides in the tidal flats and the Yellow Sea. Integrated with the previously reported spatial distributions of (239+240)Pu and (137)Cs activities in the surface sediments of the Yellow Sea, the mechanism of Pu transport with the ocean currents and the scavenging characteristics in the Yellow Sea were discussed. PMID:23264060

  8. GPS-Constrained Microplate Kinematics and Plio-Pleistocene Tectonic Evolution of the North Anatolian Fault and North Aegean Sea

    NASA Astrophysics Data System (ADS)

    Thatcher, W.

    2004-12-01

    Emerging evidence from Global Position System (GPS) survey measurements in the Aegean and elsewhere suggests that present-day active continental deformation occurs largely due to the relative motions of a small number of rigid blocks or microplates. However, it is not universally agreed whether the continental microplate description of the GPS data is superior to other proposed models, nor is it clear whether present-day movement patterns can be usefully extrapolated into the geologic past. Here I examine the known deformation history of the North Aegean over the past ~10 Ma and compare it with predictions based on the present-day microplate model. Agreement provides independent support for the GPS-based model and demonstrates its value in bettering our understanding of Aegean tectonics. If we knew nothing about late Cenozoic North Aegean tectonics and provisionally assumed the correctness of the Aegean microplate model of Nyst & Thatcher [2004 JGR], we would predict several features of the tectonic evolution that accord with geologic evidence. First, the North Aegean Sea would be created by extension due to SSW motion of the South Aegean and concomitant CW rotation of central Greece during the past 10 Ma. The same kinematic process would cause extension to be succeeded by strike-slip motion as the `ridge-transform-ridge' triple junction migrates WSW 24 km/Ma and the North Anatolian fault propagates into the region. The Plio-Pleistocene history of the North Aegean shows these same general features. Drilling and seismic imaging document the existence of young (< 10 Ma) and thick (up to 6 km) sedimentary sequences attributed to crustal extension by a factor of 3-4. Seismic profiling and bathymetric mapping show a mesh of roughly orthogonal faults with dip-slip offsets. Structural studies of sub-aerial exposures of these faults suggest an earlier episode of extension was followed by predominantly strike-slip motions. The plate kinematic reconstruction of late Cenozoic

  9. Spatial and temporal patterns in oxygen and nutrient fluxes in sediment of German Bight (North Sea)

    NASA Astrophysics Data System (ADS)

    Neumann, Andreas; Friedrich, Jana; van Beusekom, Justus; Naderipour, Céline

    2016-04-01

    The German Bight in the southern North Sea is affected by intensive anthropogenic exploitation. Over a century of intensive use by shipping, fishery, and input by polluted rivers has pushed the coastal ecosystem far from its pristine state. The nutrient load reached a maximum in the early 1990s (Amann et al. 2012), and implementation of environmental protection policies substantially decreased the riverine nutrient load. While the riverine input of pollutants has constantly reduced since then, new forms of sea exploitation emerge. The most noticeable example is the installation of more than 600 wind turbines over the past few years in the German EEZ, and additionally 1,200 are already planned. The impact of these installations on hydrology and biogeochemical cycles is largely unclear. In a series of monitoring cruises we repeatedly sampled the sediment at a set of monitoring stations, which represent all typical habitats of the German Bight. We deployed benthic landers for in-situ chamber incubations and performed ex-situ whole-core incubations to investigate the benthic fluxes of oxygen and nutrients, and their spatial and temporal variability. Our first results indicate that benthic nutrient recycling is more intense during summer than during winter, which suggests that biological processes contribute substantially to the recycling of nutrients. The fluxes of reactive nitrogen appear lower than observations from 1992 (Lohse et al. 1993), when riverine N loads were at their maximum (Amann et al. 2012). The comparison of our recent measurements with observations from the past decades will enable us to assess the effect of decreasing nutrient discharge into the coastal North Sea. Our results will further set a baseline for elucidating the impact of the massive installation of wind turbines in the near future. This study contributes to the NOAH project (North Sea; Observation and Assessment of Habitats). References Amann T., A. Weiss, and J. Hartmann (2012): Carbon

  10. The impact of North Indian Ocean sea surface temperatures on the Indian summer monsoon

    NASA Astrophysics Data System (ADS)

    Levine, Richard; Turner, Andrew

    2010-05-01

    The relationship between sea surface temperature (SST) in the North Indian Ocean and Indian monsoon rainfall is investigated in both observational/re-analyses and climate model simulations. We focus on the partially land-enclosed Arabian Sea and Bay of Bengal, where SSTs are found to have significant correlations with All Indian Rainfall (AIR). This part of the Indian Ocean is therefore important for monsoon predictions, while this area tends to provide significant problems in coupled atmosphere-ocean model simulations. The observational variability of the SST-rainfall relationship is investigated on seasonal to decadal time-scales. This highlights a predominantly negative correlation over the monsoon trough area in North East India and a positive correlation over the rest of India, while these relationships are found to be weakened by the ENSO-monsoon teleconnection. Mechanisms are further investigated by performing a series of atmosphere-only model simulations using the Met Office Unified Model (MetUM). In these experiments we determine the response of the atmosphere to forced cold SST anomalies over isolated areas, which we also extend out into the equatorial Indian Ocean. The cold SSTs in the Arabian Sea and Bay of Bengal lead to a dramatic reduction in Indian rainfall, while cold biases in the equatorial Indian Ocean have the opposite effect, highlighting the competition between oceanic and continental Tropical Convergence Zones (TCZ). However, the impacts for the Arabian Sea and Bay of Bengal experiments are found to change between the pre-monsoon and post-monsoon onset periods.The impact on monsoon rainfall for cold SST biases in these regions is found to be the result of a balance between changes in regional low-level temperature gradients and the availability of moisture over the oceans, which determine the pathway of the monsoon jet and the moisture transport towards India. These experiments suggest that the intra-seasonal variability of the relationship

  11. Applicability of highly branched isoprenoids as a sea ice proxy in the Ross Sea

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Hyun; Lee, Jae Il; Belt, Simon T.; Gal, Jong-Ku; Smik, Lukas; Shin, Kyung-Hoon

    2016-04-01

    Sea ice is an integral component of the polar climate system, constraining the effect of changing surface albedo, ocean-atmosphere heat exchanges, the formation of deep and intermediate waters that participate in driving the meridional overturning circulation and thus global climate. In recent years, a mono-unsaturated highly branched isoprenoid (HBI) alkene which is biosynthesised by certain sea ice diatoms during the spring bloom and, upon ice melt, deposited into underlying sediments, has been uniquely observed in Arctic sea ice and in Arctic sediments. Hence, the term IP25 (ice proxy with 25 carbon atoms) was proposed to distinguish this compound from other HBI isomers and has become an established proxy for the reconstruction of Arctic sea ice. In contrast, a monounsaturated HBI alkene, i.e. IP25, has not been observed in sea ice or sediments from the Antarctic. Hence, the application of diene and triene HBI concentrations and the resulting diene/triene (D/T) ratio was alternatively introduced as sea ice/open water indicators in the Southern Ocean. However, there is still lack of data covering the wide areas around the Antarctic, especially from the Ross Sea. Hence, we investigated surface sediment samples from the Ross Sea (n=14) collected during the R/V ARAON cruise in 2015 as well as from the Antarctic Peninsula (n=17) collected during several R/V ARAON cruises between 2001 and 2013. We will present our preliminary results and will discuss the applicability of the HBI in the Ross Sea.

  12. Predation rates by North Sea cod (Gadus morhua) - Predictions from models on gastric evacuation and bioenergetics

    USGS Publications Warehouse

    Hansson, S.; Rudstam, L. G.; Kitchell, J.F.; Hilden, M.; Johnson, B.L.; Peppard, P.E.

    1996-01-01

    We compared four different methods for estimating predation rates by North Sea cod (Gadus moi hua). Three estimates, based on gastric evacuation rates, came from an ICES multispecies working group and the fourth from a bioenergetics model. The bioenergetics model was developed from a review of literature on cod physiology. The three gastric evacuation rate models produced very different prey consumption estimates for small (2 kg) fish. For most size and age classes, the bioenergetics model predicted food consumption rates intermediate to those predicted by the gastric evacuation models. Using the standard ICES model and the average population abundance and age structure for 1974-1989, annual, prey consumption by the North Sea cod population (age greater than or equal to 1) was 840 kilotons. The other two evacuation rate models produced estimates of 1020 and 1640 kilotons, respectively. The bioenergetics model estimate was 1420 kilotons. The major differences between models were due to consumption rate estimates for younger age groups of cod. (C) 1996 International Council for the Exploration of the Sea

  13. Temporal analysis of archived samples indicates marked genetic changes in declining North Sea cod (Gadus morhua).

    PubMed Central

    Hutchinson, William F; van Oosterhout, Cock; Rogers, Stuart I; Carvalho, Gary R

    2003-01-01

    Despite increasing evidence that current exploitation rates can contribute to shifts in life-history traits and the collapse of marine fish stocks, few empirical studies have investigated the likely evolutionary impacts. Here, we used DNA recovered from a temporal series of archived North Sea cod (Gadus morhua) otoliths, to investigate genetic diversity within the Flamborough Head population between 1954 and 1998, during which time the population underwent two successive declines. Microsatellite data indicated a significant reduction in genetic diversity between 1954 and 1970 (total number of alleles: 1954, 46; 1960, 42; 1970, 37), and a subsequent recovery between 1970 and 1998 (total number of alleles: 1970, 37; 1981, 42; 1998, 45). Furthermore, estimates of genetic differentiation (F(ST) and R(ST)) showed a significant divergence between 1998 and earlier samples. Data are consistent with a period of prolonged genetic drift, accompanied by a replacement of the Flamborough Head population through an increased effective migration rate that occurred during a period of high exploitation and appreciable demographic and phenotypic change. Other studies indicate that diversity at neutral microsatellite loci may be correlated with variability at selected genes, thus compromising a population's subsequent recovery and adaptive potential. Such effects are especially pertinent to North Sea cod, which are threatened by continuing exploitation and rising sea temperatures. PMID:14561275

  14. Differential recruitment of introduced Pacific oysters and native mussels at the North Sea coast: coexistence possible?

    NASA Astrophysics Data System (ADS)

    Diederich, Susanne

    2005-04-01

    Pacific oysters ( Crassostrea gigas Thunberg 1793) have been introduced into the Wadden Sea (North Sea), where they settle on native mussel beds ( Mytilus edulis L.), which represent the only extensive insular hard substrata in this soft-sediment environment. As abundances of C. gigas rose, some mussel beds became increasingly overgrown with oysters, whereas others did not. Field experiments revealed that recruitment of C. gigas was higher in the lower intertidal than in the upper subtidal zone, that it was higher on conspecifics than on mussels, and that it was not affected by barnacle epigrowth except when settling on mussels. Mussel recruitment is known from inter- and subtidal zones. It occurred equally on oyster and mussel shells but showed a clear preference for barnacle epigrowth over clean shells. Assuming that settlement and recruitment are key processes for species abundances on the North Sea coast, it is predicted that the positive feedback in oyster settlement will lead to rapid reef formation of this invader at the expense of mussel beds. Mussels, however, may escape competitive exclusion by settling between or on the larger oysters especially when barnacles are abundant. Experimental patches with mussels were more often covered by fucoid algae ( Fucus vesiculosus forma mytili Nienburg) than patches with oysters, and oyster recruitment was poor underneath such algal canopies. Thus, fucoids may provide the native mussels with a refuge from the invading oysters and the two bivalves may coexist, provided food is not limiting.

  15. Iceberg severity off eastern North America: Its relationship to sea ice variability and climate change

    SciTech Connect

    Marko, J.R.; Fissel, D.B. ); Wadhams, P. ); Kelly, P.M. ); Brown, R.D. )

    1994-09-01

    Iceberg trajectory, deterioration (mass loss), and sea ice data are reviewed to identify the sources of observed interannual and seasonal variations in the numbers of icebergs passing south of 48[degrees]N off eastern North America. The results show the dominant role of sea ice in the observed variations. Important mechanisms involved include both seasonal modulation of the southerly iceberg flow by ice cover control of probabilities for entrapment and decay in shallow water, and the suppression of iceberg melt/deterioration rates by high concentrations of sea ice. The Labrador spring ice extent, shown to be the critical parameter in interannual iceberg number variability, was found to be either determined by or closely correlated with midwinter Davis Strait ice extents. Agreement obtained between observed year-to-year and seasonal number variations with computations based upon a simple iceberg dissipation model suggests that downstream iceberg numbers are relatively insensitive to iceberg production rates and to fluctuations in southerly iceberg fluxes in areas north of Baffin Island. Past variations in the Davis Strait ice index and annual ice extents are studied to identify trends and relationships between regional and larger-scale global climate parameters. It was found that, on decadal timescales in the post-1960 period of reasonable data quality, regional climate parameters have varied, roughly, out of phase with corresponding global and hemispheric changes. These observations are compared with expectations in terms of model results to evaluate current GCM-based capabilities for simulating recent regional behavior. 64 refs., 11 figs., 3 tabs.

  16. Species assemblages of pelagic fish embryos in the southern North Sea between 1984 and 2000

    NASA Astrophysics Data System (ADS)

    von Westernhagen, Hein; Dethlefsen, Volkert; Bade, Tim; Wosniok, Werner

    2002-02-01

    The occurrence and abundance of the pelagic eggs of southern North Sea spring-spawning fish were analysed between 1984 and 2000. Species number varied between six (1986) and 14 (1999) and was positively correlated with sea surface temperature. With one exception, dab eggs were always the most abundant and usually highly dominant. Ranking of species depended on temperature, but no significant differences in ranking between years was discernible. Although with the increase in temperature in the 1990s a change in species assemblage was evident [species belonging to the boreal-Mediterranean (Lusitanian) group became more apparent in the species assemblage] this did not lead to an increased species diversity (Shannon Index) or a change in other community parameters. It appears that the recent developments regarding spawning stock biomass of commercial North Sea fish is reflected in the declining egg abundance of the respective commercial and larger species (i.e. cod, flounder, plaice) and an increase in abundance of the eggs of small species (i.e. long rough dab, rockling) over the years.

  17. Revisiting the Submerged Paleo Elbe Valley (S North Sea) with High-Resolution Shallow Seismics

    NASA Astrophysics Data System (ADS)

    Papenmeier, S.; Hass, H. C.

    2014-12-01

    The Elbe paleo valley is the most prominent subsurface structure in the southern North Sea (~10,000 km²) and constitutes an important part of Germany's largest marine Natura 2000-Reserve "Sylter Außenriff" (European environmental protection area). It is supposed that the valley was formed by epeirogenic movement during the Tertiary. The depression developed to its present form during the Weichselian sea-level lowstand (-130 m below present). Melt waters that discharged in north-westerly directions fed the paleo Elbe at that time. During the Holocene the valley drowned in the rising sea. A narrow raster of new shallow seismic data combined with high resolution sidescan sonar data is used to shed new light on the Holocene development of the paleo Elbe valley and its adjacent regions in detail. Cross sections distributed with transect distances of 400 and 800 m, respectively, over a length of 100 km (approximately one third of the total valley length) enable a good comprehensive analysis of the historical process of sedimentary valley infill and coastal evolution with the successive Holocene sea level rise. The eastern flank of the valley is characterized by a relatively steep slope with one or more terraces, representing moraine deposits which are today still present at the seafloor surface, partly covered with Holocene marine deposits. The western slip-off slope of the valley is much smoother than the eastern undercut slope. West of the valley, sediment cores show peat and tidal flat sediments. Shallow seismic data show the base of the valley. There are conspicuous internal seismic reflectors above the base, inclined in northeastern direction. They indicate a sedimentary infill of the valley from the southwest when the southern part of the Dogger Bank was flooded during the early Holocene sea-level rise. In this process the steeper eastern slope acted as a natural barrier towards the northeast, averted sediment transport beyond the eastern boundary of the paleo

  18. Trace element levels in fish from clean and polluted coastal marine sites in the Mediterranean Sea, Red Sea and North Sea

    NASA Astrophysics Data System (ADS)

    Kress, Nurit; Herut, Barak; Shefer, Edna; Hornung, Hava

    1999-12-01

    The bioaccumulation of Hg, Cd, Zn, Cu, Mn and Fe was evaluated in the muscle and liver tissue of four fish species (Siganus rivulatus, Diplodus sargus, Lithognatus mormyrus and Plathychtis flesus) from clean and polluted marine coastal sites in the Red Sea, Mediterranean Sea and North Sea within the framework of the MARS 1 program. Representative liver samples were screened for organic contaminants (DDE, PCBs and PAHs) which exhibited very low concentrations. The levels of Cd, Cu, Zn, Fe and Mn found in the muscle tissue in this study were similar among the four species and within the naturally occurring metal ranges. However, differences were found among the sites. In the Red Sea, Cu was higher in the muscle of S. rivulatus at Ardag and Zn at the Observatory (OBS). Cu, Zn and Mn were higher in the Red Sea than in the specimens from the Mediterranean. The differences were attributed to different diets derived from distinctively different natural environments. D. sargus from Haifa Bay (HB) had higher Cd, Cu and Mn values than specimens from Jaffa (JFA), and L. mormyrus higher Cd, Fe and Mn in HB, corresponding to the polluted environmental status of the Bay. No differences in metal levels were found among the North Sea sites, except for Fe that was lower at the Eider station. Hg was low in all the specimens, but the values varied with species and sites. The lowest Hg values were found in S. rivulatus, the herbivorous species, as expected from its trophic level. Hg in P. flesus was higher than in S. rivulatus but still low. Higher Hg values were found in the muscle tissue of L. mormyrus,with the highest values in D. sargus, both carnivorous species from the same family. Hg in D. sargus was higher in HB than in JFA, as expected, but in the larger specimens of L. mormyrus from JFA values were higher, while in the small specimens there were no differences in Hg values. The levels of all metals were higher in the liver than in the muscle, with enrichment factors ranging

  19. Climate change and fishing: a century of shifting distribution in North Sea cod.

    PubMed

    Engelhard, Georg H; Righton, David A; Pinnegar, John K

    2014-08-01

    Globally, spatial distributions of fish stocks are shifting but although the role of climate change in range shifts is increasingly appreciated, little remains known of the likely additional impact that high levels of fishing pressure might have on distribution. For North Sea cod, we show for the first time and in great spatial detail how the stock has shifted its distribution over the past 100 years. We digitized extensive historical fisheries data from paper charts in UK government archives and combined these with contemporary data to a time-series spanning 1913-2012 (excluding both World Wars). New analysis of old data revealed that the current distribution pattern of cod - mostly in the deeper, northern- and north-easternmost parts of the North Sea - is almost opposite to that during most of the Twentieth Century - mainly concentrated in the west, off England and Scotland. Statistical analysis revealed that the deepening, northward shift is likely attributable to warming; however, the eastward shift is best explained by fishing pressure, suggestive of significant depletion of the stock from its previous stronghold, off the coasts of England and Scotland. These spatial patterns were confirmed for the most recent 3 1/2 decades by data from fisheries-independent surveys, which go back to the 1970s. Our results demonstrate the fundamental importance of both climate change and fishing pressure for our understanding of changing distributions of commercially exploited fish.

  20. Looking beyond stratification: a model-based analysis of the biological drivers of oxygen deficiency in the North Sea

    NASA Astrophysics Data System (ADS)

    Große, Fabian; Greenwood, Naomi; Kreus, Markus; Lenhart, Hermann-Josef; Machoczek, Detlev; Pätsch, Johannes; Salt, Lesley; Thomas, Helmuth

    2016-04-01

    Low oxygen conditions, often referred to as oxygen deficiency, occur regularly in the North Sea, a temperate European shelf sea. Stratification represents a major process regulating the seasonal dynamics of bottom oxygen, yet, lowest oxygen conditions in the North Sea do not occur in the regions of strongest stratification. This suggests that stratification is an important prerequisite for oxygen deficiency, but that the complex interaction between hydrodynamics and the biological processes drives its evolution. In this study we use the ecosystem model HAMSOM-ECOHAM to provide a general characterisation of the different zones of the North Sea with respect to oxygen, and to quantify the impact of the different physical and biological factors driving the oxygen dynamics inside the entire sub-thermocline volume and directly above the bottom. With respect to oxygen dynamics, the North Sea can be subdivided into three different zones: (1) a highly productive, non-stratified coastal zone, (2) a productive, seasonally stratified zone with a small sub-thermocline volume, and (3) a productive, seasonally stratified zone with a large sub-thermocline volume. Type 2 reveals the highest susceptibility to oxygen deficiency due to sufficiently long stratification periods (> 60 days) accompanied by high surface productivity resulting in high biological consumption, and a small sub-thermocline volume implying both a small initial oxygen inventory and a strong influence of the biological consumption on the oxygen concentration. Year-to-year variations in the oxygen conditions are caused by variations in primary production, while spatial differences can be attributed to differences in stratification and water depth. The large sub-thermocline volume dominates the oxygen dynamics in the northern central and northern North Sea and makes this region insusceptible to oxygen deficiency. In the southern North Sea the strong tidal mixing inhibits the development of seasonal stratification

  1. Comparison of Chlorophyll-A Algorithms for the Transition Zone Between the North Sea and Baltic Sea

    NASA Astrophysics Data System (ADS)

    Huber, Silvia; Hansen, Lars B.; Rasmussen, Mads O.; Kaas, Hanne

    2015-12-01

    Monitoring water quality of the transition zone between the North Sea and Baltic Sea from space is still a challenge because of the optically complex waters. The presence of suspended sediments and dissolved substances often interfere with the phytoplankton signal and thus confound conventional case-1 algorithms developed for the open ocean. Specific calibration to case-2 waters may compensate for this. In this study we compared chlorophyll-a (chl-a) concentrations derived with three different case-2 algorithms: C2R, FUB/WeW and CoastColour using MERIS data as basis. Default C2R and FUB clearly underestimate higher chl-a concentrations. However, with local tuning we could significantly improve the fit with in-situ data. For instance, the root mean square error is reduced by roughly 50% from 3.06 to 1.6 μ g/L for the calibrated C2R processor as compared to the default C2R. This study is part of the FP7 project AQUA-USERS which has the overall goal to provide the aquaculture industry with timely information based on satellite data and optical in-situ measurements. One of the products is chlorophyll-a concentration.

  2. Sea-floor geology of Long Island Sound north of Duck Pond Point, New York

    USGS Publications Warehouse

    McMullen, K.Y.; Poppe, L.J.; Danforth, W.W.; Blackwood, D.S.; Schaer, J.D.; Glomb, K.A.; Doran, E.F.

    2012-01-01

    The U.S. Geological Survey, the National Oceanic and Atmospheric Administration (NOAA), and the Connecticut Department of Environmental Protection are mapping the sea floor in coastal areas of the northeastern United States. As part of the project, more than 100 square kilometers of multibeam-echosounder data, 23 sediment samples, bottom video, and 86 still photographs were obtained from an area in Long Island Sound north of Duck Pond Point, New York, in the study area of NOAA survey H11999. This report delineates the sediment types and sea-floor features found within this area in order to better understand the sea-floor processes occurring in this part of Long Island Sound. The sea floor in the study area is dominated by ubiquitous sand-wave fields and three northeast-southwest trending bathymetric depressions. Barchanoid and transverse sand waves, including sinusoidal, bifurcating, arced, and straight-crested morphologies, are variably present. Asymmetrical sand-wave profiles indicate a westward to southwestward direction of sediment transport in most of the study area; current ripples and megaripples on the stoss slopes of the sand waves indicate transport is ongoing. The majority of the sediment on the sea floor is sand, although bouldery, gravelly, and muddy sediments are also present. Gray, cohesive mud crops out on the walls of some of the scour depressions associated with the troughs of large sand waves. Clasts of the muddy sediment scattered on the sea floor around the depressions demonstrate the intensity of the scour and suggest erosion of the underlying distal deltaic sediments.

  3. New insights into the earliest Quaternary environments in the Central North Sea from 3D seismic

    NASA Astrophysics Data System (ADS)

    Lamb, Rachel; Huuse, Mads; Stewart, Margaret; Brocklehurst, Simon H.

    2014-05-01

    In the past the transition between an unconformable surface in the south to a conformable horizon towards the north has made identification and mapping the base-Quaternary in the central North Sea difficult (Sejrup et al 1991; Gatliff et al 1994). However recent integration of biostratigraphy, pollen analysis, paleomagnetism and amino acid analysis in the Dutch and Danish sectors (Rasmussen et al 2005; Kuhlmann et al 2006) has allowed greater confidence in the correlation to the region 3D seismic datasets and thus has allowed the base-Quaternary to be mapped across the entire basin. The base-Quaternary has been mapped using the PGS MegaSurvey dataset from wells in the Danish Sector along the initially unconformable horizon and down the delta front into the more conformable basin giving a high degree of confidence in the horizon pick. The revised base-Quaternary surface reaches a depth of 1248 ms TWT with an elongate basin shape which is significantly deeper than the traditionally mapped surface. Using RMS amplitudes and other seismic attributes the revised base-Quaternary has been investigated along the horizon and in time slice to interpret the environments of the earliest Quaternary prior to the onset of glaciation. Combined with analysis of aligned elongate furrows over 10 km long, 100 m wide and 100 m deep suggest a deep marine environment in an almost enclosed basin with persistent strong NW-SE bottom currents in the deepest parts. Pockmarks were formed by the escape of shallow gas on the sides of a small delta in the eastern part of the basin. The progradation of large deltas from both the north and south into the basin make up the majority of the deposition of sediment into the basin. Key Words: base-Quaternary; seismic interpretation; paleoenvironments References: Gatliff, R.W, Richards, P.C, Smith, K, Graham, C.C, McCormac, M, Smith, N.J.P, Long, D, Cameron, T.D.J, Evans, D, Stevenson, A.G, Bulat, J, Ritchie, J.D, (1994) 'United Kingdom offshore regional

  4. A model for tides and currents in the English Channel and southern North Sea

    USGS Publications Warehouse

    Walters, Roy A.

    1987-01-01

    The amplitude and phase of 11 tidal constituents for the English Channel and southern North Sea are calculated using a frequency domain, finite element model. The governing equations - the shallow water equations - are modifed such that sea level is calculated using an elliptic equation of the Helmholz type followed by a back-calculation of velocity using the primitive momentum equations. Triangular elements with linear basis functions are used. The modified form of the governing equations provides stable solutions with little numerical noise. In this field-scale test problem, the model was able to produce the details of the structure of 11 tidal constituents including O1, K1, M2, S2, N2, K2, M4, MS4, MN4, M6, and 2MS6.

  5. A comparison of the measured North Sea Andrea rogue wave with numerical simulations

    NASA Astrophysics Data System (ADS)

    Bitner-Gregersen, E. M.; Fernandez, L.; Lefèvre, J. M.; Monbaliu, J.; Toffoli, A.

    2013-09-01

    A coupling of a spectral wave model with a nonlinear phase resolving model is used to reconstruct the evolution of wave statistics during a storm crossing the North Sea on 8-9 November 2007. During this storm a rogue wave (named the Andrea wave) was recorded at the Ekofisk field. The wave has characteristics comparable to the well-known New Year wave measured by Statoil at the Draupner platform the 1 January 1995. Hindcast data of the storm are here applied as input to calculate random realizations of sea surface and evolution of its statistical properties associated with this specific wave event by solving the Euler equations with a Higher Order Spectral Method (HOSM). The numerical results are compared with the Andrea wave profile as well as characteristics of the Andrea wave record measured by the down-looking lasers at the Ekofisk field.

  6. Metabolism of Centropages species in the Mediterranean Sea and the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Gaudy, Raymond; Thibault-Botha, Delphine

    2007-02-01

    Information on the metabolism rates of Centropages typicus and congeneric species ( C. hamatus, C. furcatus, C. brachiatus and C. abdominalis) in neritic areas of the Mediterranean Sea, the North Atlantic Ocean and the Pacific Ocean are reported here. Respiration rates and excretion rates are strongly influenced by abiotic (i.e. temperature, salinity) and biotic factors (i.e. food availability and composition). Differences in the response of respiratory rates to temperature of acclimated, acclimatized and adapted individuals are clearly observed among regions of the Mediterranean Sea and the West and East shores of the Atlantic Ocean. Food supply also strongly affects respiration and excretion rates, as well as the size, sex and stage development of the individuals. The co-measurement of these two rates allows confirmation of the omnivory or carnivory oriented feeding habits of these species. The role of this neritic genus in coastal environment is also discussed.

  7. North Sea storminess from a novel storm surge record since AD 1843

    NASA Astrophysics Data System (ADS)

    Dangendorf, Sönke; Müller-Navarra, Sylvin; Jensen, Jürgen; Schenk, Frederik; Wahl, Thomas; Weisse, Ralf

    2014-05-01

    The detection of potential long-term changes in historical storm statistics and storm surges plays a vitally important role for protecting coastal communities. In the absence of long homogeneous wind records, we present a novel, independent and homogeneous storm surge record based on water level observations in the North Sea since AD 1843. Storm surges are characterized by considerable inter-annual to decadal variability linked to large-scale atmospheric circulation patterns. Time periods of increased storm surge levels prevailed in the late 19th and 20th centuries without any evidence for significant long-term trends. This contradicts with recent findings based on reanalysis data, which suggest increasing storminess in the region since the late 19th century. We compare the wind and pressure fields from the 20th century reanalysis (20CRv2) with the storm surge record by applying state of the art empirical wind surge formulas. The comparison reveals that the reanalysis is a valuable tool which leads to good results over the past 100 years; previously the statistical relationship fails, leaving significantly lower values in the upper percentiles of the predicted surge time series. These low values lead to significant upward trends over the entire investigation period, which are in turn neither supported by the storm surge record nor by an independent circulation index based on homogeneous pressure readings. We therefore suggest that these differences are related to higher uncertainties in the earlier years of the 20CRv2 over the North Sea region. Reference: Dangendorf, S., Müller-Navarra, S., Jensen, J., Schenk, F., Wahl, T., and Weisse, R. (revised after minor revision): North Sea storminess from a novel storm surge record since AD 1843, Journal of Climate.

  8. Temperature tracking by North Sea benthic invertebrates in response to climate change.

    PubMed

    Hiddink, Jan G; Burrows, Michael T; García Molinos, Jorge

    2015-01-01

    Climate change is a major threat to biodiversity and distributions shifts are one of the most significant threats to global warming, but the extent to which these shifts keep pace with a changing climate is yet uncertain. Understanding the factors governing range shifts is crucial for conservation management to anticipate patterns of biodiversity distribution under future anthropogenic climate change. Soft-sediment invertebrates are a key faunal group because of their role in marine biogeochemistry and as a food source for commercial fish species. However, little information exists on their response to climate change. Here, we evaluate changes in the distribution of 65 North Sea benthic invertebrate species between 1986 and 2000 by examining their geographic, bathymetric and thermal niche shifts and test whether species are tracking their thermal niche as defined by minimum, mean or maximum sea bottom (SBT) and surface (SST) temperatures. Temperatures increased in the whole North Sea with many benthic invertebrates showing north-westerly range shifts (leading/trailing edges as well as distribution centroids) and deepening. Nevertheless, distribution shifts for most species (3.8-7.3 km yr(-1) interquantile range) lagged behind shifts in both SBT and SST (mean 8.1 km yr(-1)), resulting in many species experiencing increasing temperatures. The velocity of climate change (VoCC) of mean SST accurately predicted both the direction and magnitude of distribution centroid shifts, while maximum SST did the same for contraction of the trailing edge. The VoCC of SBT was not a good predictor of range shifts. No good predictor of expansions of the leading edge was found. Our results show that invertebrates need to shift at different rates and directions to track the climate velocities of different temperature measures, and are therefore lagging behind most temperature measures. If these species cannot withstand a change in thermal habitat, this could ultimately lead to a drop in

  9. Quantification of tertiary exhumation in the United Kingdom southern North Sea using sonic velocity data

    SciTech Connect

    Hillis, R.R.

    1995-01-01

    Sonic velocities from the Upper and Middle Chalk (Upper Cretaceous), the Bunter Sandstone and the Bunter Shale (both Lower Triassic) were used to independently quantify apparent exhumation (height above maximum burial depth) in the United Kingdom (UK) southern North Sea. Apparent exhumation is the displacement, on the depth axis, of a given velocity/depth trend from the normal (unaffected by exhumation) trend. Apparent exhumation results derived from the Upper and Middle Chalk, the Bunter Sandstone, and the Bunter Shale are statistically similar. The consistency of results from carbonate and clastic units suggests that, at a formational and regional scale, over-compaction (i.e., anomalously high sonic velocity) in all three units analyzed reflects previously greater burial depth, rather than sedimentological and/or diagenetic processes, and validates the use of lithologies other than shale in maximum burial depth studies. The consistency of results from units of Early Triassic to Late Cretaceous age suggests that Tertiary exhumation was of sufficiently great magnitude to mask any earlier Mesozoic periods of exhumation, and the maximum Mesozoic-Cenozoic burial depth in the southern North Sea was attained prior to Tertiary exhumation. The proposed magnitudes of exhumation are generally greater than those previously published for the southern North Sea, but they are consistent with recent estimates from apatite fission track analysis. Cretaceous-Tertiary burial prior to exhumation must have been of great magnitude and more rapid than suggested by the preserved stratigraphy. The effect of this extra burial and subsequent exhumation on sedimentary rock decompaction procedure and thermal maturation modeling is illustrated for the Cleethorpes-1 and 44/7-1 wells, and must also be incorporated in modeling reservoir diagenesis. The regional, Tertiary tectonic uplift associated with exhumation must have had a thick-skinned origin.

  10. Characterization of Phaeocystis globosa (Prymnesiophyceae), the blooming species in the Southern North Sea

    NASA Astrophysics Data System (ADS)

    Rousseau, Véronique; Lantoine, François; Rodriguez, Francisco; LeGall, Florence; Chrétiennot-Dinet, Marie-Josèphe; Lancelot, Christiane

    2013-02-01

    Despite significant research dedicated to the marine genus Phaeocystis, which forms large blooms in the coastal waters of the Southern North Sea, some aspects of the taxonomy and biology of this species still suffer from a sketchy knowledge. It is currently admitted that P. globosa is the species that blooms in the Southern North Sea. This has however, never been confirmed by SSU rDNA sequencing which constitutes nowadays, together with the morphology of the haploid flagellate, a reliable taxonomic criterion to distinguish between Phaeocystis species. Also, although the fine morphology of the haploid scaly flagellate is well known, there is a lack of comparable and harmonized description of the other cell types, i.e. colonial cells and diploid flagellates, previously identified within the Phaeocystis life cycle. In this study, we used SSU rDNA sequencing, light and electron scanning microscopy and flow cytometry to identify and characterize three cell types produced in controlled and reproducible manner from two strains of Phaeocystis isolated from the Belgian coastal zone. Our morphometry and sequencing data confirm unambiguously that P. globosa is the species that blooms in the Southern North Sea, but suggest in addition that both strains are representative of the original P. globosa Scherffel. Our study compares, for the first time since the species description, the fine morphometry and ploidy features of diploid colonial cells, diploid and haploid flagellates originating from same strains, providing therefore unambiguous identification criteria for distinguishing them from each other. The diploid stage, colonial or flagellated cell, is thus characterized by a naked surface, has a size range nearly twice that of the haploid flagellate and do not produce the chitinous filaments specific of the haploid stage. Colonial cells lack flagella and haptonema but possess on their apical side two appendages, which elongate to form the flagella of the diploid flagellate.

  11. Developmental defects in pelagic embryos of several flatfish species in the Southern North sea

    NASA Astrophysics Data System (ADS)

    Cameron, P.; Berg, J.; Dethlefsen, V.; Von Westernhagen, H.

    In the spring of 1984 through and in the summer of 1987 pelagic flatfish eggs were collected in horizontal subsurface hauls with a 1-m ring net in the southern North Sea between 51°49' to 55°30'N and 2°30' to 8°00'E. The flatfish eggs were observed alive for their developmental stage and aberrations from normal development. Flatfish eggs occurring in the winter ichthyoplankton of the southern North Sea were dab, Limanda limanda; flounder. Platichthys flesus; plaice, Pleuronectes platessa, and long rough dab, Hippoglossoides platessoides. Summer samples contained dab, turbot, Psetta maxima; little sole, Buglossidium luteum; common sole, Solea solea; Norwegian topknot, Phrynorhombus norwegicus, and lemon sole, Microstomus kitt. In winter as well as in summer eggs of dab were the most abundant in the southern North Sea with up to 249 eggs·m -3 surface water in winter and 26 eggs·m -3 in summer. The investigations revealed considerable quantities of abnormally developed flatfish embryos in the plankton samples. Highest malformation rates were recorded for the early stages of dab (44.4%) followed by flounder (41.3%) and plaice (26.0%) in winter; in summer these rates were for dab 18.9%, for turbot 14.1% and for little sole 12.5%. Generally malformation rates decreased with development. Areas of high malformation rates were off the river estuaries and in near-shore areas along the Dutch and German coasts. Malformation rates decreased with the distance from the coast. Causes and effects of the occurrence of malformations during embryonic development are discussed.

  12. Benthic mineralization rates at two locations in the southern North Sea

    NASA Astrophysics Data System (ADS)

    Osinga, Ronald; Kop, Arjen J.; Duineveld, Gerard C. A.; Prins, Rudolf A.; Van Duyl, Fleur C.

    1996-12-01

    Benthic oxygen uptake, sulphate reduction and benthic bacterial production were measured at two contrasting locations in the southern North Sea: the shallow and turbulent Broad Fourteens area in the Southern Bight, and the deeper Oyster Grounds, a deposition area, where thermohaline stratification occurs during summer. Oxygen uptake and sulphate reduction showed a clear seasonal pattern in the Broad Fourteens area, indicating a supply of carbon to the benthic system that is closely related to the standing stock of carbon in the water column. This close benthic-pelagic coupling is probably due to the influence of the tide in this part of the North Sea, which keeps the water column permanently mixed. At the Oyster Grounds, no seasonal pattern was observed. Peaks in oxygen uptake and sulphate reduction were found in winter. Irregularly occurring events, such as storms and fishery-related activities, are likely to affect the benthic mineralization patterns in this area. Annual benthic carbon mineralization rates estimated from oxygen uptake rates were 44 gC·m -2 at the Broad Fourteens, and 131 gC·m -2 at the Oyster Grounds, of which 26 and 28%, respectively, could be attributed to sulphate reduction (assuming an annual sulphide reoxidation rate of 100%). Although sulphate reduction rates in the southern North Sea are higher than previously suggested, aerobic respiration is the most important pathway for benthic carbon mineralization at the stations visited. Production rates of benthic bacterial carbon measured with labelled leucine were much higher than carbon mineralization rates based on oxygen uptake or sulphate reduction. This may either imply a very high bacterial carbon conversion efficiency, or point to shortcomings in the accuracy of the techniques. A critical evaluation of the techniques is recommended.

  13. Contemporary radioecological state of the North-western Black Sea and the problems of environment conservation.

    PubMed

    Tereshchenko, N N; Mirzoyeva, N Yu; Gulin, S B; Milchakova, N A

    2014-04-15

    Review is devoted to the analysis of a radioecological situation in the North-western Black Sea and concerns the levels of contamination of the components of an ecosystem by the main artificial radioactive isotopes ((90)Sr, (137)Cs, (239,240)Pu). The long-term accumulation trends of these radionuclides were analyzed in components of the Black Sea ecosystem after the Chernobyl nuclear power plant accident. Zones that have an increased ability to accumulate these radioisotopes were revealed. The assessment of irradiation dose rates formed by (90)Sr, (137)Cs and (239,240)Pu in Black Sea hydrobionts was obtained. The strategy for biodiversity conservation and sustainable management of natural resources should include monitoring of the radioecological state of the marine ecosystems, and the formation of a complex of biogeochemical criteria for assessment of an ecological situation in the sea. This approach is important for marine protected areas, since it allows the formation of a basis for scientific and practical function. PMID:24461697

  14. Contemporary radioecological state of the North-western Black Sea and the problems of environment conservation.

    PubMed

    Tereshchenko, N N; Mirzoyeva, N Yu; Gulin, S B; Milchakova, N A

    2014-04-15

    Review is devoted to the analysis of a radioecological situation in the North-western Black Sea and concerns the levels of contamination of the components of an ecosystem by the main artificial radioactive isotopes ((90)Sr, (137)Cs, (239,240)Pu). The long-term accumulation trends of these radionuclides were analyzed in components of the Black Sea ecosystem after the Chernobyl nuclear power plant accident. Zones that have an increased ability to accumulate these radioisotopes were revealed. The assessment of irradiation dose rates formed by (90)Sr, (137)Cs and (239,240)Pu in Black Sea hydrobionts was obtained. The strategy for biodiversity conservation and sustainable management of natural resources should include monitoring of the radioecological state of the marine ecosystems, and the formation of a complex of biogeochemical criteria for assessment of an ecological situation in the sea. This approach is important for marine protected areas, since it allows the formation of a basis for scientific and practical function.

  15. Late Eocene sea surface cooling of the western North Atlantic (ODP Site 647A)

    NASA Astrophysics Data System (ADS)

    Sliwinska, Kasia K.; Coxall, Helen K.; Schouten, Stefan

    2016-04-01

    The initial shift out of the early Cenozoic greenhouse and into a glacial icehouse climate occurred during the middle to late Eocene and culminated in the abrupt growth of a continental-scale ice cap on Antarctica, during an episode known as the Oligocene Isotope Event 1 (Oi-1) ˜33.7 Ma. Documenting the patterns of global and regional cooling prior to Oi-1 is crucial for understanding the driving force and feedback behind the switch in climate mode. Well-dated high-resolution temperature records, however, remain sparse and the climatic response in some of the most climatically sensitive regions of the Earth, including the high latitude North Atlantic (NA), where today large amounts of ocean heat are exchanged, are poorly known. Here we present a sea surface palaeotemperature record from the late Eocene to the early Oligocene (32.5 Ma to 35 Ma) of ODP Hole 647A based on archaeal tetraether lipids (TEX86H). The site is located in the western North Atlantic (Southern Labrador Sea) and is the most northerly located (53° N) open ocean site with a complete Eocene-Oligocene sequence which yields both calcareous and organic microfossils suitable for detailed proxy reconstructions. Our record agrees with the magnitude of temperature decrease (˜3 ° C sea surface cooling) recorded by alkenones and pollen data from the Greenland Sea, but our higher resolution study reveals that the high latitude NA cooling step occurred about 500 kyrs prior to the Oi-1 Antarctic glaciation, at around ˜34.4 Ma. This cooling can be explained by regional effects related to local NA tectonics including ocean gateways, known to have changed at the time, with potential to effect NA overturning circulation due to adjustments in the thermohaline density balance. Alternatively, the cooling itself may be due to changes in NA circulation, suggesting that global ocean circulation played a role in pre-conditioning the Earth for Antarctic glaciation.

  16. Nd isotopes in deep-sea corals in the North-eastern Atlantic

    NASA Astrophysics Data System (ADS)

    Copard, Kevin; Colin, Christophe; Douville, Eric; Freiwald, Andre; Gudmundsson, Gudmundur; De Mol, Ben; Frank, Norbert

    2010-09-01

    Neodymium (Nd) concentrations and isotopic signatures of living and fossil deep-sea coral species Lophelia pertusa, Desmophyllum dianthus and Madrepora oculata from the northeast Atlantic Ocean have been investigated in order to test the ability of deep-sea corals to reconstruct the seawater Nd isotopic signature and past changes of ocean circulation in the eastern North Atlantic. Small quantities of Nd—less than 45 ng/g—are incorporated into the aragonite skeleton of living deep-sea corals that dwell at upper intermediate depths throughout the Northeast Atlantic. Rigorous cleaning techniques are needed in order to avoid Nd contamination from manganese-oxide and iron hydroxide coatings. Moreover, Nd isotopic compositions have been measured using thermal ionization mass spectrometry (TIMS) by Nd-oxide method. Our data indicate that the isotopic signatures of modern corals are similar to those of adjacent water masses, implying that deep-sea corals can serve as an archive of the seawater Nd isotopic compositions in the past. The first results from few fully-cleaned fossils corals collected within the Porcupine Seabight and the southwest Rockall Bank reveal significantly higher ɛNd for corals dated between 150 ± 40 and 3060 ± 90 yrs than those of the living corals located in similar areas. This suggests rapid hydrological variations along the eastern margin of the North Atlantic Ocean at intermediate water depth with higher contribution of the Mediterranean Overflow Waters (MOW) or other temperate Atlantic mid-depth water masses (ENACW or NAC) in the past.

  17. Shelf sheet-sand reservoir of the lower Cretaceous Greensand, North Celtic Sea Basin, offshore Ireland

    SciTech Connect

    Winn, R.D. Jr.

    1994-11-01

    Core and log data show that the marine, early to middle Albian {open_quotes}A{close_quotes} Sand of the Aptian to lower Cenomanian Greensand-Gault interval, North Celtic Sea Basin, offshore Ireland, was deposited as an approximately tabular sand body in shelf water depths. The {open_quotes}A{close_quotes} Sand is the major reservoir interval at Kinsale Head and Ballycotton gas fields. The reservoir sandstone is bioturbated, variably glauconitic, shell rich, and least muddy toward its provenance in a local area of the Irish massif and finer grained southeastward into the basin. Thickness and coarseness of the {open_quotes}A{close_quotes} Sand are related, in part, to distance from a narrow area of the paleoshore. Bathymetric control of sand thickness was superimposed on proximal-distal trends. Specifically, thick intervals are inferred to have been deposited in shelf lows, and thin zones were deposited over bathymetric highs. The {open_quotes}A{close_quotes} Sand was not deposited as a ridge sand, and positive relief on the depositional sand body appears to have been minor. Deposition of the Greensand occurred during thermal subsidence of the North Celtic Sea Basin following Early Cretaceous rifting. Overall late Early Cretaceous to Late Cretaceous transgression was interrupted by progradation of the {open_quotes}A{close_quotes} Sand, probably caused by a relative drop in sea level (forced regression). The {open_quotes}A{close_quotes} Sand sheet consists of several units within the central depositional basin. Three slightly coarsening-upward units up to 15 m thick probably are the consequence of high-frequency fluctuations in sea level during progradation. The top of the {open_quotes}A{close_quotes} Sand consists of a several-meter-thick, very glauconitic, muddy sandstone to sandy mudstone. The upper unit accumulated in deepening water following the maximum lowstand.

  18. Towards an integrated view of benthic and pelagic processes in the southern North Sea (German Bight)

    NASA Astrophysics Data System (ADS)

    Friedrich, Jana; van Beusekom, Justus; Neumann, Andreas; Naderipour, Celine

    2015-04-01

    The North Sea can be classified as a semi-enclosed shelf on the western-European continent. Atlantic influences are mainly through the Fair Isle current Channel in the North, and through the Strait of Dover in the South. An anti-clockwise circulation prevails, driven by mainly semi-diurnal tides and winds. The German Bight is located in the south-eastern part of the North Sea, and is strongly influenced by continental rivers. The outflow from the rivers Scheldt, Maas and Rhine is carried towards the German Bight with the residual currents. The German rivers Ems, Weser and Elbe directly debouche into the German Bight. On the shallow shelf, the water column is completely mixed by tidal forces and wind, largely preventing downward flux of particles and instead fostering temporary deposition and resuspension, which influences benthic mineralization. Hence, complex interactions between pelagic and benthic processes occur. Previous budget calculations indicate that the nutrient inventory has to be processed several times to support observed primary production, and, depending on water depth; only 10-20% remineralisation occurs in sediments of the German Bight whereas about 50% of organic matter is remineralised in the sediments of the shallow Wadden Sea. In this presentation, we use in-situ and ex-situ field data on pelagic and benthic oxygen respiration and benthic nutrient fluxes to assess the intense mineralization activity in the German Bight, the partitioning of benthic and pelagic processes and the factors influencing organic matter mineralization. Measurements of pelagic oxygen respiration based on Winkler titration, in-situ benthic oxygen uptake measurements based on flux-chamber landers and ex-situ incubations of intact sediment cores revealed that benthic remineralisation rates are about an order of magnitude smaller than pelagic rates, in agreement with previous budget estimates. Both benthic and pelagic oxygen respiration show a strong seasonality; with higher

  19. Mapping Underwater Sound in the Dutch Part of the North Sea.

    PubMed

    Sertlek, H Özkan; Aarts, Geert; Brasseur, Sophie; Slabbekoorn, Hans; ten Cate, Carel; von Benda-Beckmann, Alexander M; Ainslie, Michael A

    2016-01-01

    The European Union requires member states to achieve or maintain good environmental status for their marine territorial waters and explicitly mentions potentially adverse effects of underwater sound. In this study, we focused on producing maps of underwater sound from various natural and anthropogenic origins in the Dutch North Sea. The source properties and sound propagation are simulated by mathematical methods. These maps could be used to assess and predict large-scale effects on behavior and distribution of underwater marine life and therefore become a valuable tool in assessing and managing the impact of underwater sound on marine life. PMID:26611061

  20. Mapping Underwater Sound in the Dutch Part of the North Sea.

    PubMed

    Sertlek, H Özkan; Aarts, Geert; Brasseur, Sophie; Slabbekoorn, Hans; ten Cate, Carel; von Benda-Beckmann, Alexander M; Ainslie, Michael A

    2016-01-01

    The European Union requires member states to achieve or maintain good environmental status for their marine territorial waters and explicitly mentions potentially adverse effects of underwater sound. In this study, we focused on producing maps of underwater sound from various natural and anthropogenic origins in the Dutch North Sea. The source properties and sound propagation are simulated by mathematical methods. These maps could be used to assess and predict large-scale effects on behavior and distribution of underwater marine life and therefore become a valuable tool in assessing and managing the impact of underwater sound on marine life.

  1. Charging for port reception facilities in North Sea ports: putting theory into practice.

    PubMed

    Carpenter, A; Macgill, S

    2001-04-01

    The aim of this paper is to evaluate the charging systems for the use of port reception facilities for waste oil, and to examine the potential impact of the charging elements of the new (late 2000) EU Directive on port reception facilities for ship-generated waste and cargo residues. Experience to date with alternative models for charging is considered. Conclusions are drawn about the effectiveness of the EU Directive as a means of controlling pollution in the North Sea and producing a 'level playing field' between ports.

  2. The megaepifauna of the Dogger Bank (North Sea): species composition and faunal characteristics 1991-2008

    NASA Astrophysics Data System (ADS)

    Sonnewald, Moritz; Türkay, Michael

    2012-03-01

    During a long-term study in the summer months of the years 1991-2008, 176 megaepifaunal species were recorded through a series of beam trawl surveys on a grid of fixed stations on the Dogger Bank (central North Sea). This paper gives a qualitative overview on species composition throughout the research period, determined from samples collected during 15 cruises. In recent years, a number of species with more oceanic distribution patterns (e.g. species from SW British coasts) has been collected. In spite of these newcomers, there was a slight decrease in total species numbers during the research period.

  3. Assessing the Underwater Ship Noise Levels in the North Tyrrhenian Sea.

    PubMed

    Rossi, Eduardo; Licitra, Gaetano; Iacoponi, Andrea; Taburni, Daniele

    2016-01-01

    The purpose of this research was to assess the anthropic underwater noise caused by ships within the Cetacean Sanctuary, a wide area in the North Tyrrhenian Sea. Noise from low-frequency continuous sounds has been investigated within the 1/3-octave bands centered at 63 and 125 Hz. All the information about noise sources and sound attenuation have been organized in a database; a tool automatically extracts useful information from it and feeds a ray-tracing model to estimate noise levels. The results show average levels generally over the 100 dB re 1 μPa value. PMID:26611053

  4. Fate of a tritiated Ekofisk crude oil in a controlled ecosystem experiment with North Sea plankton

    SciTech Connect

    Laake, M.; Tjessem, K.; Rein, K.

    1984-09-01

    Flexible plastic enclosures were employed with the main intent of determining the fate of an Ekofisk crude oil exposed to North Sea spring conditions. By use of a tritium-labeled Ekofisk crude oil, a dynamic model was developed that allowed calculation of vertical mass fluxes with depth based on actual concentration profiles and measured sedimentation rates. It has been concluded that adsorption and subsequent sedimentation of plankton and organic detritus may cause a rapid sinking of petroleum hydrocarbons. Microbial mineralization seemed to be insignificant on a short-term scale.

  5. Assessing the Underwater Ship Noise Levels in the North Tyrrhenian Sea.

    PubMed

    Rossi, Eduardo; Licitra, Gaetano; Iacoponi, Andrea; Taburni, Daniele

    2016-01-01

    The purpose of this research was to assess the anthropic underwater noise caused by ships within the Cetacean Sanctuary, a wide area in the North Tyrrhenian Sea. Noise from low-frequency continuous sounds has been investigated within the 1/3-octave bands centered at 63 and 125 Hz. All the information about noise sources and sound attenuation have been organized in a database; a tool automatically extracts useful information from it and feeds a ray-tracing model to estimate noise levels. The results show average levels generally over the 100 dB re 1 μPa value.

  6. Multiple-stage deformation along the southern flank of the North Chukchi High, Chukchi Sea, Alaska

    SciTech Connect

    Johnson, P.P. )

    1990-05-01

    Structural and stratigraphic relations along the southern edge of the North Chukchi high provide insights into the timing and mechanics of Late Cretaceous and Cenozoic tectonic events in the northern Chukchi Sea. In this area, the easternmost strand of the north-trending Hanna wrench fault zone is deflected to the northeast and terminates in a series of reverse faults along the southern edge of the high. Areas east of the Hanna fault zone were characterized by tectonic stability during this period of time. Within the fault zone, east-west-trending box folds and reverse faults accompanied uplift of the North Chukchi high and erosion of the entire Ellesmerian sequence along its southern margin. Stratigraphic and structural relations indicate that this compressional deformation began during the Early Cretaceous (Albian ) but ceased prior to the Late( ) Cretaceous. During the early Cenozoic( ), the northern part of the Hanna fault zone was reactivated as an extensional systems which controlled the development of a local basin. Some faults which showed an early history of reverse displacement were reactivated as normal faults during this late-stage tectonic event. This data is consistent with a model for Early Cretaceous impingement of adjacent blocks at a constrained corner near the North Chukchi high during the rift opening of the North Chukchi basin. The compressional deformation ceased prior to the Cenozoic when the opposing blocks in the constrained corner finally escaped past each other. Continued rifting and subsidence of the North Chukchi basin resulted in late-stage extensional overprinting of earlier compressional structures.

  7. Sea-air of CO2 in the North Pacific using shipboard and satellite data

    NASA Technical Reports Server (NTRS)

    Stephens, Mark P.; Samuels, Geoffrey; Olson, Donald B.; Fine, Rana A.; Takahashi, Taro

    1995-01-01

    A method has been developed to produce high-resolution maps of pCO2 in surface water for the North Pacific using satellite sea surface temperature (SST) data and statistical relationships between measured pCO2 and temperature. In the subtropical North Pacific the pCO in seawater is controlled primarily by temperature. Accordingly, pCO2 values that are calculated from the satellite SST data have good agreement with the measured values (rms deviation of +/- microatm). In the northwestern subpolar region the pCO2 is controlled not only by temperature, but also by significant seasonal changes in the total CO2 concentration, which are caused by seasonal changes in primary production, mixing with subsurface waters and sea-air exchange. Consequently, the parameterization of oceanic p CO2 based on SST data alone is not totally successful in the northwestern region (rms deviation of +/- 40 microatm). The use of additional satellite products, such as wind and ocean color data, as planned for a future study, is considered necessary to account for the pCO2 variability caused by seasonal changes in the total CO2 concentration. The net CO2 flux for the area of the North Pacific included in this study (north of 10 deg N) has been calculated using the monthly pCO2 distributions computed, and monthly wind speeds from the European Centre for Medium-Range Weather Forecasts. The region is found to be a net source to the atmosphere of 1.9 x 10(exp 12) to 5.8 x 10(exp 12) moles of CO2 per year (or 0.02-0.07 Gt C/yr), most of the outflux occurring in the subtropics.

  8. On the Influence of North Pacific Sea Surface Temperature on the Arctic Winter Climate

    NASA Technical Reports Server (NTRS)

    Hurwitz, Margaret M.; Newman, P. A.; Garfinkel, C. I.

    2012-01-01

    Differences between two ensembles of Goddard Earth Observing System Chemistry-Climate Model simulations isolate the impact of North Pacific sea surface temperatures (SSTs) on the Arctic winter climate. One ensemble of extended winter season forecasts is forced by unusually high SSTs in the North Pacific, while in the second ensemble SSTs in the North Pacific are unusually low. High Low differences are consistent with a weakened Western Pacific atmospheric teleconnection pattern, and in particular, a weakening of the Aleutian low. This relative change in tropospheric circulation inhibits planetary wave propagation into the stratosphere, in turn reducing polar stratospheric temperature in mid- and late winter. The number of winters with sudden stratospheric warmings is approximately tripled in the Low ensemble as compared with the High ensemble. Enhanced North Pacific SSTs, and thus a more stable and persistent Arctic vortex, lead to a relative decrease in lower stratospheric ozone in late winter, affecting the April clear-sky UV index at Northern Hemisphere mid-latitudes.

  9. Prediction of interannual North Atlantic sea surface temperature and its remote influence over land

    NASA Astrophysics Data System (ADS)

    Lienert, Fabian; Doblas-Reyes, Francisco J.

    2016-07-01

    The quality of a multimodel of six coupled climate forecast systems initialized with observations—relative to the accompanying uninitialized system—to re-forecast the future annual-mean North Atlantic sea surface temperature (SST) departures is described. The study concludes that, measured by the anomaly correlation (AC) skill, the evolution of the leading two empirical orthogonal function modes of North Atlantic SSTs are skillfully forecast throughout the 9-year forecast range. This skill results in part from the predictions of the trend. The skill of the detrended modes, i.e., in absence of SST variability generated by the trend, is reduced, but still statistically distinguishable from zero throughout the 9-year forecast for the first mode and exclusively in the first two forecast years for the second mode. The initialization effect on the AC skill in the initialized system is statistically distinguishable from the one without initialization for the detrended first mode during the first three forecast years and the first forecast year only when the trend in North Atlantic SSTs is included. All six initialized systems of the multimodel are capable to skillfully forecast the shift of the full first mode of North Atlantic SST anomalies in the mid 1990s at all leads with HadCM 3 and EC-Earth 2.3 outperforming other systems. All systems share an intrinsic bias in simulating annual-mean SST variability in the North Atlantic. The study finds that the area-average AC skill (i.e., of a forecast containing regional information) of the North Atlantic influence on anomalous European temperature in the initialized multimodel is positive and statistically distinguishable from zero throughout the 9-year forecast for the full field case. On the other hand, a continent-wide forecast (i.e., without any regional information) of future European precipitation departures associated with North Atlantic SST variability is skillful throughout the 9-year forecast for the full field

  10. Speciation of 129I and 127I in seawater and implications for sources and transport pathways in the North Sea.

    PubMed

    Hou, Xiaolin; Aldahan, Ala; Nielsen, Sven P; Possnert, Göran; Nies, Hartmut; Hedfors, Jim

    2007-09-01

    Surface seawater samples collected from the North Sea and English Channel were analyzed for total 129I and 127I, as well as for iodide and iodate. Relatively high 129I concentrations (2-3 x 10(11) atoms/L) were observed in the northern part of the English Channel and in the southeastern North Sea. The atomic ratio of 129I/127I decreases from the eastern (1.0-1.9 x 10(-6)) to the western (4-6 x 10(-8)) parts of the North Sea and from the northeastern (1.5 x 10(-6)) to southwestern (1-5 x 10(-8)) parts of the English Channel. The ratios of iodide to iodate are 0.1-0.5 and 0.5-1.6 for 127I and 129I, respectively, in open seawaters, whereas these ratios range from 0.6 to 1.3 and 0.8 to 2.2, respectively, in coastal waters. The results suggest that (1) imprints of the La Hague facility dominates the 129I distribution in the surface water of the North Sea, (2) reduction of iodate to iodide is relatively fast during the transport to the European continental coast, (3) oxidation of newly produced 129I- to (129)IO3- is insignificant during water exchange between the coastal area and open sea, (4) reduction of iodate and oxidation of iodide in the open sea seems to be a slow process. PMID:17937272

  11. Modeling of turbulent dissipation and its validation in periodically stratified region in the Liverpool Bay and in the North Sea

    NASA Astrophysics Data System (ADS)

    Sasmal, Kaushik; Maity, Subhendu; Warrior, Hari V.

    2015-07-01

    The present work explores the applicability of an alternative eddy viscosity formulation in numerical models dealing with the dynamics of the coastal ocean. The formulation is based on the Reynolds stress anisotropy-anisotropy being an important tool for capturing turbulent mixing. Initially idealized entrainment scenarios are evaluated that are typical for shelf seas viz. entrainment in linearly stratified and two-layer fluids caused by surface wind stress or barotropic pressure gradient-driven bottom stress. An attempt is made to simulate the realistic semi-diurnal cycle of turbulent dissipation in Liverpool Bay Region of Freshwater Inflow (ROFI) in the Irish Sea characterized by strong horizontal gradients and interactions with tidal flow. Turbulent dissipation cycles with a 25-h period using free-falling light yo-yo (FLY) dissipation profiler exhibits a strong asymmetry between ebb and flood. The above dynamics involving tidal straining during the ebb and mixing during the flood has been simulated using k- and the alternative formulated turbulence scheme in a one-dimensional (1-D) dynamic model. The model is forced with observed tidal flow and horizontal gradients of temperature and salinity. Simulated dissipation cycles show good agreement with observation. The present work also involves a comparison of dissipation rate measurements in northern North Sea using the abovementioned turbulence schemes—the measurements being taken using free-falling shear probes and CTD (conductivity, temperature, and depth) sensors. The main forcing provided for the upper and bottom boundary layers are atmospheric forcing and tides, respectively. To compare the observations and model results, quantitative error measurements have also been studied which reveal the applicability of the alternative turbulence scheme.

  12. The developmental biogeography of hawksbill sea turtles in the North Pacific.

    PubMed

    Van Houtan, Kyle S; Francke, Devon L; Alessi, Sarah; Jones, T Todd; Martin, Summer L; Kurpita, Lauren; King, Cheryl S; Baird, Robin W

    2016-04-01

    High seas oceanic ecosystems are considered important habitat for juvenile sea turtles, yet much remains cryptic about this important life-history period. Recent progress on climate and fishery impacts in these so-called lost years is promising, but the developmental biogeography of hawksbill sea turtles (Eretmochelys imbricata) has not been widely described in the Pacific Ocean. This knowledge gap limits the effectiveness of conservation management for this globally endangered species. We address this with 30 years of stranding observations, 20 years of bycatch records, and recent simulations of natal dispersal trajectories in the Hawaiian Archipelago. We synthesize the analyses of these data in the context of direct empirical observations, anecdotal sightings, and historical commercial harvests from the insular Pacific. We find hawksbills 0-4 years of age, measuring 8-34 cm straight carapace length, are found predominantly in the coastal pelagic waters of Hawaii. Unlike other species, we find no direct evidence of a prolonged presence in oceanic habitats, yet satellite tracks of passive drifters (simulating natal dispersal) and our small sample sizes suggest that an oceanic phase for hawksbills cannot be dismissed. Importantly, despite over 600 million hooks deployed and nearly 6000 turtle interactions, longline fisheries have never recorded a single hawksbill take. We address whether the patterns we observe are due to population size and gear selectivity. Although most sea turtle species demonstrate clear patterns of oceanic development, hawksbills in the North Pacific may by contrast occupy a variety of ecosystems including coastal pelagic waters and shallow reefs in remote atolls. This focuses attention on hazards in these ecosystems - entanglement and ingestion of marine debris - and perhaps away from longline bycatch and decadal climate regimes that affect sea turtle development in oceanic regions. PMID:27110350

  13. TOPAZ4: an ocean-sea ice data assimilation system for the North Atlantic and Arctic

    NASA Astrophysics Data System (ADS)

    Sakov, P.; Counillon, F.; Bertino, L.; Lisæter, K. A.; Oke, P. R.; Korablev, A.

    2012-04-01

    We present a detailed description of TOPAZ4, the latest version of TOPAZ - a coupled ocean-sea ice data assimilation system for the North Atlantic Ocean and Arctic. It is the only operational, large-scale ocean data assimilation system that uses the ensemble Kalman filter. This means that TOPAZ features a time-evolving, state-dependent estimate of the state error covariance. Based on results from the pilot MyOcean reanalysis for 2003-2008, we demonstrate that TOPAZ4 produces a realistic estimate of the ocean circulation and the sea ice. We find that the ensemble spread for temperature and sea-level remains fairly constant throughout the reanalysis demonstrating that the data assimilation system is robust to ensemble collapse. Moreover, the ensemble spread for ice concentration is well correlated with the actual errors. This indicates that the ensemble statistics provide reliable state-dependent error estimates - a feature that is unique to ensemble-based data assimilation systems. We demonstrate that the quality of the reanalysis changes when different sea surface temperature products are assimilated, or when in situ profiles below the ice in the Arctic Ocean are assimilated. We find that data assimilation improves the match to independent observations compared to a free model. Improvements are particularly noticeable for ice thickness, salinity in the Arctic, and temperature in the Fram Strait, but not for transport estimates or underwater temperature. At the same time, the pilot reanalysis has revealed several flaws in the system that have degraded its performance. Finally, we show that a simple bias estimation scheme can effectively detect the seasonal or constant bias in temperature and sea-level.

  14. The developmental biogeography of hawksbill sea turtles in the North Pacific.

    PubMed

    Van Houtan, Kyle S; Francke, Devon L; Alessi, Sarah; Jones, T Todd; Martin, Summer L; Kurpita, Lauren; King, Cheryl S; Baird, Robin W

    2016-04-01

    High seas oceanic ecosystems are considered important habitat for juvenile sea turtles, yet much remains cryptic about this important life-history period. Recent progress on climate and fishery impacts in these so-called lost years is promising, but the developmental biogeography of hawksbill sea turtles (Eretmochelys imbricata) has not been widely described in the Pacific Ocean. This knowledge gap limits the effectiveness of conservation management for this globally endangered species. We address this with 30 years of stranding observations, 20 years of bycatch records, and recent simulations of natal dispersal trajectories in the Hawaiian Archipelago. We synthesize the analyses of these data in the context of direct empirical observations, anecdotal sightings, and historical commercial harvests from the insular Pacific. We find hawksbills 0-4 years of age, measuring 8-34 cm straight carapace length, are found predominantly in the coastal pelagic waters of Hawaii. Unlike other species, we find no direct evidence of a prolonged presence in oceanic habitats, yet satellite tracks of passive drifters (simulating natal dispersal) and our small sample sizes suggest that an oceanic phase for hawksbills cannot be dismissed. Importantly, despite over 600 million hooks deployed and nearly 6000 turtle interactions, longline fisheries have never recorded a single hawksbill take. We address whether the patterns we observe are due to population size and gear selectivity. Although most sea turtle species demonstrate clear patterns of oceanic development, hawksbills in the North Pacific may by contrast occupy a variety of ecosystems including coastal pelagic waters and shallow reefs in remote atolls. This focuses attention on hazards in these ecosystems - entanglement and ingestion of marine debris - and perhaps away from longline bycatch and decadal climate regimes that affect sea turtle development in oceanic regions.

  15. Distribution patterns of wintering sea ducks in relation to the North Atlantic Oscillation and local environmental characteristics

    USGS Publications Warehouse

    Zipkin, Elise F.; Gardner, Beth; Gilbert, Andrew T.; O'Connell, Allan F.; Royle, J. Andrew; Silverman, Emily D.

    2010-01-01

    Twelve species of North American sea ducks (Tribe Mergini) winter off the eastern coast of the United States and Canada. Yet, despite their seasonal proximity to urbanized areas in this region, there is limited information on patterns of wintering sea duck habitat use. It is difficult to gather information on sea ducks because of the relative inaccessibility of their offshore locations, their high degree of mobility, and their aggregated distributions. To characterize environmental conditions that affect wintering distributions, as well as their geographic ranges, we analyzed count data on five species of sea ducks (black scoters Melanitta nigra americana, surf scoters M. perspicillata, white-winged scoters M. fusca, common eiders Somateria mollissima, and long-tailed ducks Clangula hyemalis) that were collected during the Atlantic Flyway Sea Duck Survey for ten years starting in the early 1990s. We modeled count data for each species within ten-nautical-mile linear survey segments using a zero-inflated negative binomial model that included four local-scale habitat covariates (sea surface temperature, mean bottom depth, maximum bottom slope, and a variable to indicate if the segment was in a bay or not), one broad-scale covariate (the North Atlantic Oscillation), and a temporal correlation component. Our results indicate that species distributions have strong latitudinal gradients and consistency in local habitat use. The North Atlantic Oscillation was the only environmental covariate that had a significant (but variable) effect on the expected count for all five species, suggesting that broad-scale climatic conditions may be directly or indirectly important to the distributions of wintering sea ducks. Our results provide critical information on species-habitat associations, elucidate the complicated relationship between the North Atlantic Oscillation, sea surface temperature, and local sea duck abundances, and should be useful in assessing the impacts of climate

  16. Flexible dynamic riser for floating-production facility in the North Sea

    SciTech Connect

    Pettenati, C.; Dumay, J.M.

    1983-09-01

    When considering the production riser aspect of a floating-production facility project, two systems can be generally envisaged: - The rigid steel, tensioned multiple riser. - The flexible, dynamic riser. Although this last one was successfully introduced in Brazil as early as 1978, and since then has proved to be an extremely reliable solution in several other parts of the world as well, for other major operators, the industry in general was still recently expressing some concern about its introduction in an extreme-weather environment such as the North Sea. A more classic and well-known technique such as the steel tensioned riser was generally favoured by companies operating in this hostile context. (Ex: Argyll, Buchan). This paper describing what can be considered as a typical development involving flexible, dynamic risers in the North Sea, presents evidence that this concern, although understandable, is mostly unfounded and that on the contrary, the flexible, dynamic riser represents a very considerable improvement in the reliability and efficiency of a floating-facility offshore development.

  17. Merging ancient and modern DNA: extinct seabird taxon rediscovered in the North Tasman Sea.

    PubMed

    Steeves, Tammy E; Holdaway, Richard N; Hale, Marie L; McLay, Emma; McAllan, Ian A W; Christian, Margaret; Hauber, Mark E; Bunce, Michael

    2010-02-23

    Ancient DNA has revolutionized the way in which evolutionary biologists research both extinct and extant taxa, from the inference of evolutionary history to the resolution of taxonomy. Here, we present, to our knowledge, the first study to report the rediscovery of an 'extinct' avian taxon, the Tasman booby (Sula tasmani), using classical palaeontological data combined with ancient and modern DNA data. Contrary to earlier work, we show an overlap in size between fossil and modern birds in the North Tasman Sea (classified currently as S. tasmani and Sula dactylatra fullagari, respectively). In addition, we show that Holocene fossil birds have mitochondrial control region sequences that are identical to those found in modern birds. These results indicate that the Tasman booby is not an extinct taxon: S. dactylatra fullagari O'Brien & Davies, 1990 is therefore a junior synonym of Sula tasmani van Tets, Meredith, Fullagar & Davidson, 1988 and all North Tasman Sea boobies should be known as S. d. tasmani. In addition to reporting the rediscovery of an extinct avian taxon, our study highlights the need for researchers to be cognizant of multidisciplinary approaches to understanding taxonomy and past biodiversity.

  18. Are solar activity and sperm whale Physeter macrocephalus strandings around the North Sea related?

    NASA Astrophysics Data System (ADS)

    Vanselow, Klaus Heinrich; Ricklefs, Klaus

    2005-04-01

    In the final decades of the last century, an increasing number of strandings of male sperm whales ( Physeter macrocephalus) around the North Sea led to an increase in public interest. Anthropogenic influences (such as contaminants or intensive sound disturbances) are supposed to be the main causes, but natural environmental effects may also explain the disorientation of the animals. We compared the documented sperm whale strandings in the period from 1712 to 2003 with solar activity, especially with sun spot number periodicity and found that 90% of 97 sperm whale stranding events around the North Sea took place when the smoothed sun spot period length was below the mean value of 11 years, while only 10% happened during periods of longer sun spot cycles. The relation becomes even more pronounced (94% to 6%, n = 70) if a smaller time window from November to March is used (which seems to be the main southward migration period of male sperm whales). Adequate chi-square tests of the data give a significance of 1% error probability that sperm whale strandings can depend on solar activity. As an alternative explanation, we suggest that variations of the earth's magnetic field, due to variable energy fluxes from the sun to the earth, may cause a temporary disorientation of migrating animals.

  19. Protected areas in the North Sea: An absolute need for future marine research

    NASA Astrophysics Data System (ADS)

    Lindeboom, H. J.

    1995-03-01

    There are many signals that different human activities affect the marine ecosystem on local and sometimes regional scales. There is evidence that in the Dutch sector of the North Sea at least 25 species have decreased tremendously in numbers or have totally disappeared. But what has caused their disappearance: fisheries, pollution, eutrophication, climatic changes, or a combination of causes? On the Dutch Continental Shelf, the fisheries are now so intensive that every square metre is trawled, on an average, once to twice a year. Furthermore, it has been shown that trawling causes direct damage to the marine ecosystem. This indicates that the “natural” North Sea ecosystem we are studying is already a heavily influenced system. And what is the value of data on the diversity and production of benthic animals, if the research area has been raked by beamtrawl gear an unknown amount of times before sampling? To be able to study the natural trends in the marine ecosystem, or to answer the question which human activity has most influenced the ecosystem, there is an absolute and immediate need for protected areas to be established. The size of the protected areas must be determined by the behaviour of that species characteristic for the area. In such areas, where fisheries and local pollution would be forbidden or very limited, scientific research into the species composition and age distribution of different populations should be carried out and trends should be established.

  20. Resolving the abundance and air-sea fluxes of airborne microorganisms in the North Atlantic Ocean.

    PubMed

    Mayol, Eva; Jiménez, María A; Herndl, Gerhard J; Duarte, Carlos M; Arrieta, Jesús M

    2014-01-01

    Airborne transport of microbes may play a central role in microbial dispersal, the maintenance of diversity in aquatic systems and in meteorological processes such as cloud formation. Yet, there is almost no information about the abundance and fate of microbes over the oceans, which cover >70% of the Earth's surface and are the likely source and final destination of a large fraction of airborne microbes. We measured the abundance of microbes in the lower atmosphere over a transect covering 17° of latitude in the North Atlantic Ocean and derived estimates of air-sea exchange of microorganisms from meteorological data. The estimated load of microorganisms in the atmospheric boundary layer ranged between 6 × 10(4) and 1.6 × 10(7) microbes per m(2) of ocean, indicating a very dynamic air-sea exchange with millions of microbes leaving and entering the ocean per m(2) every day. Our results show that about 10% of the microbes detected in the boundary layer were still airborne 4 days later and that they could travel up to 11,000 km before they entered the ocean again. The size of the microbial pool hovering over the North Atlantic indicates that it could play a central role in the maintenance of microbial diversity in the surface ocean and contribute significantly to atmospheric processes.

  1. Host-specific microbial communities in three sympatric North Sea sponges.

    PubMed

    Naim, Mohd Azrul; Morillo, Jose A; Sørensen, Søren J; Waleed, Abu Al-Soud; Smidt, Hauke; Sipkema, Detmer

    2014-11-01

    The establishment of next-generation technology sequencing has deepened our knowledge of marine sponge-associated microbiota with the identification of at least 32 phyla of Bacteria and Archaea from a large number of sponge species. In this study, we assessed the diversity of the microbial communities hosted by three sympatric sponges living in a semi-enclosed North Sea environment using pyrosequencing of bacterial and archaeal 16S ribosomal RNA gene fragments. The three sponges harbor species-specific communities each dominated by a different class of Proteobacteria. An α-proteobacterial Rhodobacter-like phylotype was confirmed as the predominant symbiont of Halichondria panicea. The microbial communities of Haliclona xena and H. oculata are described for the first time in this study and are dominated by Gammaproteobacteria and Betaproteobacteria, respectively. Several common phylotypes belonging to Chlamydiae, TM6, Actinobacteria, and Betaproteobacteria were detected in all sponge samples. A number of phylotypes of the phylum Chlamydiae were present at an unprecedentedly high relative abundance of up to 14.4 ± 1.4% of the total reads, which suggests an important ecological role in North Sea sponges. These Chlamydiae-affiliated operational taxonomic units may represent novel lineages at least at the genus level as they are only 86-92% similar to known sequences.

  2. Survey of Anisakis sp. and Hysterothylacium sp. in sardines and anchovies from the North Adriatic Sea.

    PubMed

    Cavallero, S; Magnabosco, C; Civettini, M; Boffo, L; Mingarelli, G; Buratti, P; Giovanardi, O; Fortuna, C M; Arcangeli, G

    2015-05-01

    The occurrence of larval Anisakidae and Raphidascarididae in anchovies and sardines from the North Adriatic Sea has been estimated. Anisakis pegreffii and Hysterothylacium aduncum were reported, with low prevalence values. In brief, a total amount of 7650 fish specimens collected between September 2011 and 2012 were analysed using three different inspection analyses: a visual inspection of the coelomic cavity, an examination of the viscera exploiting the positive hydro-tropism of the larvae (modified Baermann technique) and enzymatic digestion of muscular tissue pools. Low level of infestation was reported for Anisakis sp. in both in anchovies and sardines, while higher values were reported for Hysterothylacium sp. Subsamples of nematodes collected were characterized at species level using the molecular diagnostic key based on ITS nuclear ribosomal region, and A. pegreffii and H. aduncum were identified. The low prevalence of Anisakis sp. in sardines and anchovies from the North Adriatic Sea could be related to the peculiar distribution of cetaceans and carnivorous zooplankton in the investigated region and could be used as a potential tag to define oily fishes from this specific fishing area as at low-risk for anisakiasis.

  3. Health status of seabirds and coastal birds found at the German North Sea coast

    PubMed Central

    2012-01-01

    Background Systematic pathological investigations to assess the health status of seabirds and coastal birds in Germany were performed. The investigation was conducted to obtain data on possible causes of decline in seabird and coastal bird populations. Methods 48 individuals of 11 different species of seabirds and coastal birds were collected by the stranding network along the entire German North Sea coast from 1997 to 2008, including mainly waders such as Eurasian oystercatchers (Haematopus ostralegus) and red knots (Calidris canutus) as well as seabirds such as northern fulmars (Fulmaris glacialis) and common scoters (Melanitta nigra). For most birds (n = 31) found dead along the shore no obvious cause of death was evident, while 17 individuals were killed by collisions with lighthouses. Results Overall, the nutritional status of the investigated birds was very poor, and the body mass in most cases was significantly lower compared to masses of living birds caught during the same periods of the year. This is partly linked to chronic parasitic or bacterial infections in different organs or to septicaemia. In some cases infections with zoonotic tuberculosis caused by Mycobacterium spp. were found. Avian influenza was not found in any of the collected birds. Conclusion The presented data contribute to the evaluation of the health status of birds in the German North Sea. Moreover, they present an important tool for the assessment of potential pathogens with an impact on the health status of seabirds and coastal birds. PMID:22812640

  4. Merging ancient and modern DNA: extinct seabird taxon rediscovered in the North Tasman Sea.

    PubMed

    Steeves, Tammy E; Holdaway, Richard N; Hale, Marie L; McLay, Emma; McAllan, Ian A W; Christian, Margaret; Hauber, Mark E; Bunce, Michael

    2010-02-23

    Ancient DNA has revolutionized the way in which evolutionary biologists research both extinct and extant taxa, from the inference of evolutionary history to the resolution of taxonomy. Here, we present, to our knowledge, the first study to report the rediscovery of an 'extinct' avian taxon, the Tasman booby (Sula tasmani), using classical palaeontological data combined with ancient and modern DNA data. Contrary to earlier work, we show an overlap in size between fossil and modern birds in the North Tasman Sea (classified currently as S. tasmani and Sula dactylatra fullagari, respectively). In addition, we show that Holocene fossil birds have mitochondrial control region sequences that are identical to those found in modern birds. These results indicate that the Tasman booby is not an extinct taxon: S. dactylatra fullagari O'Brien & Davies, 1990 is therefore a junior synonym of Sula tasmani van Tets, Meredith, Fullagar & Davidson, 1988 and all North Tasman Sea boobies should be known as S. d. tasmani. In addition to reporting the rediscovery of an extinct avian taxon, our study highlights the need for researchers to be cognizant of multidisciplinary approaches to understanding taxonomy and past biodiversity. PMID:19675005

  5. Offshore Windfarm Impact on Pelagic Primary Production in the Southern North Sea

    NASA Astrophysics Data System (ADS)

    Slavik, Kaela; Zhang, Wenyan; Lemmen, Carsten; Wirtz, Kai

    2016-04-01

    As society struggles to find solutions to mitigate global warming, the demand for renewable energy technology has increased. Especially investment in offshore wind energy has proliferated in the European Union, with projections over the next 15 years estimating an over 40 fold increase in total offshore wind electricity. Though built with the goal of reducing the environmental impacts associated with traditional energy production, the long-term ecological impacts of offshore windfarm structures is not yet well understood. The consequences are of particular importance in the southern North Sea, where the expansion of offshore windfarms is focused. Our study investigates how the gradual accumulation of epifaunal biomass on submerged substrate at offshore windfarms impacts ecosystem services in the southern North Sea. Biofouling is governed predominately by the filter feeder Mytilus edulis, which, as an ecological engineer, will further alter the surrounding benthic and pelagic environment. We reconstruct the distribution of benthic filter feeders in the SNS and generate scenarios of increased potential distribution based on available information of Mytilus edulis settlement at turbines and of turbine locations. These maps are coupled through the MOSSCO (Modular Coupling System for Shelves and Coasts) to state-of-the-art and high resolution hydrodynamic and ecosystem models. We find a substantial change in pelagic primary production as a result of additional Mytilus edulis growth at offshore windfarms.

  6. Hotspot of accelerated sea-level rise on the Atlantic coast of North America

    USGS Publications Warehouse

    Sallenger,, Asbury H.; Doran, Kara S.; Howd, Peter A.

    2012-01-01

    Climate warming does not force sea-level rise (SLR) at the same rate everywhere. Rather, there are spatial variations of SLR superimposed on a global average rise. These variations are forced by dynamic processes, arising from circulation and variations in temperature and/or salinity, and by static equilibrium processes, arising from mass redistributions changing gravity and the Earth's rotation and shape. These sea-level variations form unique spatial patterns, yet there are very few observations verifying predicted patterns or fingerprints. Here, we present evidence of recently accelerated SLR in a unique 1,000-km-long hotspot on the highly populated North American Atlantic coast north of Cape Hatteras and show that it is consistent with a modelled fingerprint of dynamic SLR. Between 1950–1979 and 1980–2009, SLR rate increases in this northeast hotspot were ~ 3–4 times higher than the global average. Modelled dynamic plus steric SLR by 2100 at New York City ranges with Intergovernmental Panel on Climate Change scenario from 36 to 51 cm (ref. 3); lower emission scenarios project 24–36 cm (ref. 7). Extrapolations from data herein range from 20 to 29 cm. SLR superimposed on storm surge, wave run-up and set-up will increase the vulnerability of coastal cities to flooding, and beaches and wetlands to deterioration.

  7. Survey of Anisakis sp. and Hysterothylacium sp. in sardines and anchovies from the North Adriatic Sea.

    PubMed

    Cavallero, S; Magnabosco, C; Civettini, M; Boffo, L; Mingarelli, G; Buratti, P; Giovanardi, O; Fortuna, C M; Arcangeli, G

    2015-05-01

    The occurrence of larval Anisakidae and Raphidascarididae in anchovies and sardines from the North Adriatic Sea has been estimated. Anisakis pegreffii and Hysterothylacium aduncum were reported, with low prevalence values. In brief, a total amount of 7650 fish specimens collected between September 2011 and 2012 were analysed using three different inspection analyses: a visual inspection of the coelomic cavity, an examination of the viscera exploiting the positive hydro-tropism of the larvae (modified Baermann technique) and enzymatic digestion of muscular tissue pools. Low level of infestation was reported for Anisakis sp. in both in anchovies and sardines, while higher values were reported for Hysterothylacium sp. Subsamples of nematodes collected were characterized at species level using the molecular diagnostic key based on ITS nuclear ribosomal region, and A. pegreffii and H. aduncum were identified. The low prevalence of Anisakis sp. in sardines and anchovies from the North Adriatic Sea could be related to the peculiar distribution of cetaceans and carnivorous zooplankton in the investigated region and could be used as a potential tag to define oily fishes from this specific fishing area as at low-risk for anisakiasis. PMID:25662709

  8. Resolving the abundance and air-sea fluxes of airborne microorganisms in the North Atlantic Ocean

    PubMed Central

    Mayol, Eva; Jiménez, María A.; Herndl, Gerhard J.; Duarte, Carlos M.; Arrieta, Jesús M.

    2014-01-01

    Airborne transport of microbes may play a central role in microbial dispersal, the maintenance of diversity in aquatic systems and in meteorological processes such as cloud formation. Yet, there is almost no information about the abundance and fate of microbes over the oceans, which cover >70% of the Earth's surface and are the likely source and final destination of a large fraction of airborne microbes. We measured the abundance of microbes in the lower atmosphere over a transect covering 17° of latitude in the North Atlantic Ocean and derived estimates of air-sea exchange of microorganisms from meteorological data. The estimated load of microorganisms in the atmospheric boundary layer ranged between 6 × 104 and 1.6 × 107 microbes per m2 of ocean, indicating a very dynamic air-sea exchange with millions of microbes leaving and entering the ocean per m2 every day. Our results show that about 10% of the microbes detected in the boundary layer were still airborne 4 days later and that they could travel up to 11,000 km before they entered the ocean again. The size of the microbial pool hovering over the North Atlantic indicates that it could play a central role in the maintenance of microbial diversity in the surface ocean and contribute significantly to atmospheric processes. PMID:25400625

  9. Interannual sedimentary effluxes of alkalinity in the southern North Sea: Model results compared with summer observations.

    NASA Astrophysics Data System (ADS)

    Paetsch, Johannes; Kuehn, Wilfried; Six, Katharina

    2016-04-01

    Alkalinity generation in the sediment of the southern North Sea is the focus of several recent studies. One motivation for these efforts is the potentially enhanced buffering capacity of anthropogenic CO2 invasion into the corresponding pelagic system. An adaptation of a global multilayer sediment model (Heinze et al., 1999) in combination with a pelagic ecosystem model for shelf sea dynamics was used to study the benthic reactions on very different annual cycles (2001 - 2009) including the River Elbe summer flooding in 2002. The focus of this study is the efflux of alkalinity, their different contributors (aerobic respiration, denitrification, net sulfate reduction, calcite dissolution, nitrification) and their seasonal and interannual cycles. Similar to the observations covering the southern North Sea (Brenner et al., 2015) the model results show large horizontal gradients from the near-shore high productive areas with benthic remineralization up to Rmin = 10.6 mol C m-2 yr-1 and TA generation RTA = 2 mol C m-2 yr-1 to off-shore moderate productive areas with mean Rmin = 2.5 mol C m-2 yr-1 and mean TA generation RTA = 0.4 mol C m-2 yr-1. Beside calcite dissolution, aerobic respiration (producing ammonium) and denitrification are the largest contributors to alkalinity generation. Nitrification is reducing alkalinity in the sediment. Due to low regenerated primary production in summer, the year 2001 exhibits the lowest input of particulate organic matter into the sediment (POCexp=2.3 mol C m-2 yr-1), while the year 2003 exhibits the highest export production (POCexp=2.6 mol C m-2 yr-1). The biogeochemical reactions and the effluxes from the sediment follow these pelagic amplitudes with a time lag of about one year with damped amplitudes. References Brenner, H., Braeckman, U., Le Guitton, M., Meysman, F.J.R., 2015. The impact of sedimentary alkalinity release on the water column CO2 system in the North Sea. Biogeosiences Discussion, 12(15): 12395-12453. Heinze, C

  10. Benthic remineralisation rates in southern North Sea - from point measurements to areal estimates

    NASA Astrophysics Data System (ADS)

    Neumann, Andreas; Friedrich, Jana; van Beusekom, Justus; Naderipour, Céline

    2015-04-01

    The southern North Sea is enclosed by densely populated hinterland with intensive use by agriculture and industry and thus substantially affected by anthropogenic influences. As a coastal subsystem, this applies especially to the German Wadden Sea, a system of back-barrier tidal flats along the whole German Bight. Ongoing efforts to implement environmental protection policies during the last decades changed the significance of various pollutants such as reactive nitrogen or phosphate, which raises the desire for constant monitoring of the coastal ecosystem to assess the efficiency of the employed environmental protection measures. Environmental monitoring is limited to point measurements which thus have to be interpolated with appropriate models. However, existing models to estimate various sediment characteristics for the interpolation of point measurements appear insufficient when compared with actual field measurements in the southern North Sea. We therefore seek to improve these models by identifying and quantifying key variables of benthic solute fluxes by comprehensive measurements which cover the complete spatial and seasonal variability. We employ in-situ measurements with the eddy-correlation technique and flux chambers in combination with ex-situ incubations of sediment cores to establish benthic fluxes of oxygen and nutrients. Additional ex-situ measurements determine basic sediment characteristics such as permeability, volumetric reaction rates, and substrate concentration. With our first results we mapped the distribution of measured sediment permeability, which suggest that areas with water depth greater than 30 m are impervious whereas sediment in shallower water at the Dogger Bank and along the coast is substantially permeable with permeability between 10-12 m2 and 10-10 m2. This implies that benthic fluxes can be estimated with simple diffusion-type models for water depths >30 m, whereas estimates especially for coastal sediments require

  11. Interannual sedimentary effluxes of alkalinity in the southern North Sea: Model results compared with summer observations.

    NASA Astrophysics Data System (ADS)

    Paetsch, Johannes; Kuehn, Wilfried; Six, Katharina

    2016-04-01

    Alkalinity generation in the sediment of the southern North Sea is the focus of several recent studies. One motivation for these efforts is the potentially enhanced buffering capacity of anthropogenic CO2 invasion into the corresponding pelagic system. An adaptation of a global multilayer sediment model (Heinze et al., 1999) in combination with a pelagic ecosystem model for shelf sea dynamics was used to study the benthic reactions on very different annual cycles (2001 - 2009) including the River Elbe summer flooding in 2002. The focus of this study is the efflux of alkalinity, their different contributors (aerobic respiration, denitrification, net sulfate reduction, calcite dissolution, nitrification) and their seasonal and interannual cycles. Similar to the observations covering the southern North Sea (Brenner et al., 2015) the model results show large horizontal gradients from the near-shore high productive areas with benthic remineralization up to Rmin = 10.6 mol C m‑2 yr‑1 and TA generation RTA = 2 mol C m‑2 yr‑1 to off-shore moderate productive areas with mean Rmin = 2.5 mol C m‑2 yr‑1 and mean TA generation RTA = 0.4 mol C m‑2 yr‑1. Beside calcite dissolution, aerobic respiration (producing ammonium) and denitrification are the largest contributors to alkalinity generation. Nitrification is reducing alkalinity in the sediment. Due to low regenerated primary production in summer, the year 2001 exhibits the lowest input of particulate organic matter into the sediment (POCexp=2.3 mol C m‑2 yr‑1), while the year 2003 exhibits the highest export production (POCexp=2.6 mol C m‑2 yr‑1). The biogeochemical reactions and the effluxes from the sediment follow these pelagic amplitudes with a time lag of about one year with damped amplitudes. References Brenner, H., Braeckman, U., Le Guitton, M., Meysman, F.J.R., 2015. The impact of sedimentary alkalinity release on the water column CO2 system in the North Sea. Biogeosiences Discussion, 12

  12. Numerical modelling of climate change impacts on freshwater lenses on the North Sea Island of Borkum

    NASA Astrophysics Data System (ADS)

    Sulzbacher, H.; Wiederhold, H.; Siemon, B.; Grinat, M.; Igel, J.; Burschil, T.; Günther, T.; Hinsby, K.

    2012-03-01

    A numerical variable-density groundwater model is set up for the North Sea Island of Borkum to estimate climate change impacts on coastal aquifers and especially the situation of barrier islands in the Wadden Sea. The database includes information from boreholes, a seismic survey, a helicopter-borne electromagnetic survey (HEM), monitoring of the freshwater-saltwater boundary by vertical electrode chains in two boreholes, measurements of groundwater table, pumping and slug tests, as well as water samples. Based on a statistical analysis of borehole columns, seismic sections and HEM, a hydrogeological model is set up. The groundwater model is developed using the finite-element programme FEFLOW. The variable-density groundwater model is calibrated on the basis of hydraulic, hydrological and geophysical data, in particular spatial HEM and local monitoring data. Verification runs with the calibrated model show good agreement between measured and computed hydraulic heads. A good agreement is also obtained between measured and computed density or total dissolved solids data for both the entire freshwater lens on a large scale and in the area of the well fields on a small scale. For simulating future changes in this coastal groundwater system until the end of the current century we use the climate scenario A2, specified by the Intergovernmental Panel on Climate Change and in particular the data for the German North Sea coast. Simulation runs show proceeding salinization with time beneath the well fields of the two waterworks Waterdelle and Ostland. The modelling study shows that spreading of well fields is an appropriate protection measure against excessive salinization of the water supply until the end of the current century.

  13. Evolution of physical and biological characteristics of mesoscale eddy in north-central Red Sea

    NASA Astrophysics Data System (ADS)

    Zarokanellos, Nikolaos; Jones, Burton

    2015-04-01

    Eddies appear to be important to both the physical and biogeochemical dynamics of the Red Sea. Numerical simulations of physical dynamics and remote sensing studies of chlorophyll concentration and sea surface height in the Red Sea indicate their importance to the upper portions of the sea (Raitsos et al., 2013; Yao et al., 2014; Zhan et al., 2014). Despite their apparent importance, process studies of these eddies have been lacking. In March 2013 we began an extended observational study of the north-central Red Sea (NCRS) where anticyclonic eddies have been observed. The study began with a ship-based characterization of the eddy and was followed by a three-month observational time series using an autonomous glider equipped with a CTD, oxygen sensor, and optical sensors for chlorophyll, CDOM and optical backscatter. The ship-based study captured an initial snapshot of an anticyclonic eddy and it's associated biological and bio-optical distributions. Initially, chlorophyll distributions tended to mirror the density distribution, with deeper isopycnals and chlorophyll maximum depth in the anticyclonic eddy center. The anticyclone eddy in March had an along basin diameter of 150 km, penetrated vertically less than 150 m and elevated near surface chlorophyll concentrations appeared along its outer boundary. The shallowing of the pycnocline of the outer boundaries of the anticyclone eddy on March may elevate nutrients into the lower euphotic zone, contributing to phytoplankton productivity and biomass within the eddy. This eddy contains most of the kinetic energy of the region with the maximum velocities up to 30 - 35 cm/s. The eddy appeared to interact with the coastal reefs where exchange particulate and dissolved matter may occur. The autonomous glider provided the spring-to-summer progression of the system with increasing stratification, shallowing of the subsurface chlorophyll maximum, and fluctuations in the position and intensity of the eddy. Our glider effort

  14. Obliquity-driven expansion of North Atlantic sea ice controls structure of the last glacial

    NASA Astrophysics Data System (ADS)

    Turney, Chris; Thomas, Zoe; Hutchinson, David; Bradshaw, Corey; Brook, Barry; England, Matthew; Fogwill, Christopher; Jones, Richard; Palmer, Jonathan; Hughen, Konrad; Cooper, Alan

    2015-04-01

    North Atlantic late-Pleistocene climate was characterised by a series of abrupt climate changes, the most extreme of which were the Dansgaard-Oeschger (D-O) events; millennial-scale oscillations that switched rapidly between cold and warm atmospheric conditions of up to Δ16°C, most strongly expressed during the period 60-30 ka. Time series analysis of palaeoclimate ice core records is one of the best ways to detect threshold behaviour in the climate system; however, some of these techniques can be age model dependent. Spectral analysis of a new Greenland-Cariaco GICC05 age model (GICC05-CB), generated by combining the GICC05 and Cariaco ∂18O chronologies, reveals a change in the dominant periodicities at ~31 ka, consistent with the cessation of the D-O events. While the GICC05-CB has the same ∂18O structure as GICC05, the different periodicity profile reveals a change in the climate system at 31 ka. Stability analysis of the ∂18O time series over the last 60 ka determines the number of states the climate experienced over time, and reveals a bifurcation in the climate system at 31 ka, switching from a bistable to a monostable state. Early warning signals of this bifurcation are also detected starting 10,000 years before the shift in the form of increasing autocorrelation and variance. This is consistent with the climate system experiencing a slow forcing towards a critical threshold. These signals are found in both the GICC05-CB and GICC05 chronologies, though the timing of the bifurcation point varies slightly. We suggest that this bifurcation is linked to a minima in obliquity, causing greatly expanded sea ice in the Labrador sea. Modelling runs from the CSIRO Mk3L Earth-system model indicates that extensive sea ice cover is established in the Labrador Sea and North Pacific at the obliquity minima centred on 28.5 ka. This expanded sea ice is thus responsible for shifting the Northern Hemisphere westerlies southwards and reducing the strength of the AMOC

  15. Methane in the Baltic and North Seas and a reassessment of the marine emissions of methane

    SciTech Connect

    Bange, H.W.; Bartell, U.H.; Rapsomanikis, S.

    1994-12-01

    During three measurement campaigns on the Baltic and North Seas, atmospheric and dissolved methane was determined with an automated gas chromatographic system. Area-weighted mean saturation values in the sea surface waters were 113{+-}5% and 395{+-}82% and 126{+-}8%. On the bases of our data and a compilation of literature data the global oceanic emissions of methane were reassessed by introducing a concept of regional gas transfer coefficients. Our estimates computed with two different air-sea exchange models lie in the range of 11-18 Tg CH{sub 4} yr{sup -1}. Despite the fact that shelf areas and estuaries only represent a small part of the world`s ocean they contribute about 75% to the global oceanic emissions. We applied a simple, coupled, three-layer model to evaluate the time dependent variation of the oceanic flux to the atmosphere. The model calculations indicate that even with increasing tropospheric methane concentration, the ocean will remain a source of atmospheric methane. 72 refs., 7 figs., 7 tabs.

  16. Decrease in water clarity of the southern and central North Sea during the 20th century.

    PubMed

    Capuzzo, Elisa; Stephens, David; Silva, Tiago; Barry, Jon; Forster, Rodney M

    2015-06-01

    Light in the marine environment is a key environmental variable coupling physics to marine biogeochemistry and ecology. Weak light penetration reduces light available for photosynthesis, changing energy fluxes through the marine food web. Based on published and unpublished data, this study shows that the central and southern North Sea has become significantly less clear over the second half of the 20th century. In particular, in the different regions and seasons investigated, the average Secchi depth pre-1950 decreased between 25% and 75% compared to the average Secchi depth post-1950. Consequently, in summer pre-1950, most (74%) of the sea floor in the permanently mixed area off East Anglia was within the photic zone. For the last 25+ years, changes in water clarity were more likely driven by an increase in the concentration of suspended sediments, rather than phytoplankton. We suggest that a combination of causes have contributed to this increase in suspended sediments such as changes in sea-bed communities and in weather patterns, decreased sink of sediments in estuaries, and increased coastal erosion. A predicted future increase in storminess (Beniston et al., 2007; Kovats et al., 2014) could enhance the concentration of suspended sediments in the water column and consequently lead to a further decrease in clarity, with potential impacts on phytoplankton production, CO2 fluxes, and fishery production.

  17. The North Pacific Acoustic Laboratory deep-water acoustic propagation experiments in the Philippine Sea.

    PubMed

    Worcester, Peter F; Dzieciuch, Matthew A; Mercer, James A; Andrew, Rex K; Dushaw, Brian D; Baggeroer, Arthur B; Heaney, Kevin D; D'Spain, Gerald L; Colosi, John A; Stephen, Ralph A; Kemp, John N; Howe, Bruce M; Van Uffelen, Lora J; Wage, Kathleen E

    2013-10-01

    A series of experiments conducted in the Philippine Sea during 2009-2011 investigated deep-water acoustic propagation and ambient noise in this oceanographically and geologically complex region: (i) the 2009 North Pacific Acoustic Laboratory (NPAL) Pilot Study/Engineering Test, (ii) the 2010-2011 NPAL Philippine Sea Experiment, and (iii) the Ocean Bottom Seismometer Augmentation of the 2010-2011 NPAL Philippine Sea Experiment. The experimental goals included (a) understanding the impacts of fronts, eddies, and internal tides on acoustic propagation, (b) determining whether acoustic methods, together with other measurements and ocean modeling, can yield estimates of the time-evolving ocean state useful for making improved acoustic predictions, (c) improving our understanding of the physics of scattering by internal waves and spice, (d) characterizing the depth dependence and temporal variability of ambient noise, and (e) understanding the relationship between the acoustic field in the water column and the seismic field in the seafloor. In these experiments, moored and ship-suspended low-frequency acoustic sources transmitted to a newly developed distributed vertical line array receiver capable of spanning the water column in the deep ocean. The acoustic transmissions and ambient noise were also recorded by a towed hydrophone array, by acoustic Seagliders, and by ocean bottom seismometers.

  18. Middle Jurassic Oseberg delta, northern North Sea: A sedimentological and sequence stratigraphic interpretation

    SciTech Connect

    Muto, T.; Steel R.J.

    1997-07-01

    The Aalenian Oseberg Formation (0-80 m thick) is an important reservoir unit in the Middle Jurassic Brent Group in the northern North Sea, consisting of multiple sets of sandy Gilbert-type deltas. Small-scale (1.5-10 m) fining-upward units seen in the gamma-ray log correspond with individual delta sets, as independently confirmed by steepening-upward trends seen in the dip log. Within each set, the steep foreset slopes typically show thinly bedded sandstone facies (avalanche grain flows), whereas the lower foreset slopes, toesets, and bottomsets are formed largely by massive sandstone facies (sandy debris flows). On an intermediate scale (up to 40 m), the gamma-ray logs show both fining-upward and coarsening-upward trends through stacked delta sets, and these trends, traceable between wells, are interpreted in terms of decelerating and accelerating rates of relative sea level rise, respectively. The relative abundance of the sandy debris-flow deposits reflects a periodic and significant instability of the delta`s upper foreset slope, probably during times of increased water depth in front of the delta. The normal progradation of individual Gilbert-type sets, however, is likely to have been along a subhorizontal topography during periods of little or no change in water depth. The long-term change to produce the observed vertical stacking of deltaic sets was one of a generally rising relative sea level.

  19. Distribution, partitioning and sources of dissolved and particulate nitrogen and phosphorus in the north Yellow Sea

    NASA Astrophysics Data System (ADS)

    Duan, Li-Qin; Song, Jin-Ming; Yuan, Hua-Mao; Li, Xue-Gang; Li, Ning

    2016-11-01

    Little is known about characteristics of dissolved and particulate N and P forms in the north Yellow Sea (NYS). In this study, water and particulate samples were collected from the NYS to understand the biogeochemical behaviors, interactions and sources of dissolved and particulate N and P. Among the various N and P forms, dissolved organic N (DON) and P (DOP) were the predominant forms, accounting for 64% and 65% of total N (TN) and P (TP). Dissolved and particulate inorganic N and P displayed a decreasing trend from northwest region to the middle region, which was mainly influenced by riverine input along the Liaodong Peninsula coast. However, dissolved and particulate organic N and P showed higher values at northwest region and southern region, which were dominantly affected by biological activities and the Bohai Sea input. Vertical distribution patterns of dissolved and particulate N and P generally displayed the higher values at surface and bottom waters, which was the combined result of the influences by thermocline, the Yellow Sea Cold Water Mass (YC), biological activities and sediment resuspension. There were significant correlations between dissolved and particulate pools and between inorganic and organic forms, indicating their transformations through phytoplankton and bacteria activities and adsorption/desorption processes. Budgets suggested that net sink of dissolved inorganic N and P in the NYS could be mainly removed from water column. Particulate N and P were mainly from phytoplankton productivity, contributing to 84% and 74% of total particulate N (TPN) and P (TPP) influx.

  20. The North Pacific Acoustic Laboratory deep-water acoustic propagation experiments in the Philippine Sea.

    PubMed

    Worcester, Peter F; Dzieciuch, Matthew A; Mercer, James A; Andrew, Rex K; Dushaw, Brian D; Baggeroer, Arthur B; Heaney, Kevin D; D'Spain, Gerald L; Colosi, John A; Stephen, Ralph A; Kemp, John N; Howe, Bruce M; Van Uffelen, Lora J; Wage, Kathleen E

    2013-10-01

    A series of experiments conducted in the Philippine Sea during 2009-2011 investigated deep-water acoustic propagation and ambient noise in this oceanographically and geologically complex region: (i) the 2009 North Pacific Acoustic Laboratory (NPAL) Pilot Study/Engineering Test, (ii) the 2010-2011 NPAL Philippine Sea Experiment, and (iii) the Ocean Bottom Seismometer Augmentation of the 2010-2011 NPAL Philippine Sea Experiment. The experimental goals included (a) understanding the impacts of fronts, eddies, and internal tides on acoustic propagation, (b) determining whether acoustic methods, together with other measurements and ocean modeling, can yield estimates of the time-evolving ocean state useful for making improved acoustic predictions, (c) improving our understanding of the physics of scattering by internal waves and spice, (d) characterizing the depth dependence and temporal variability of ambient noise, and (e) understanding the relationship between the acoustic field in the water column and the seismic field in the seafloor. In these experiments, moored and ship-suspended low-frequency acoustic sources transmitted to a newly developed distributed vertical line array receiver capable of spanning the water column in the deep ocean. The acoustic transmissions and ambient noise were also recorded by a towed hydrophone array, by acoustic Seagliders, and by ocean bottom seismometers. PMID:24116529

  1. Isolation and Screening of Lipolytic Fungi From Coastal Waters of the Southern Caspian Sea (North of Iran)

    PubMed Central

    Sadati, Razieh; Barghi, Amin; Abbasi Larki, Reza

    2015-01-01

    Background: Lipases (acylglycerol acylhydrolase, E. C. 3. 1. 1. 3) are widely distributed among microorganisms, animals and plants, catalyzing the hydrolysis of triglycerides to free fatty acids and glycerol. Their commercial application includes pharmaceutical, chemical, and paper industries. Objectives: This study aimed to isolate and screen lipolytic fungi from coastal waters of the southern Caspian Sea by Internal Transcribed Spacer-Polymerase Chain Reaction (ITS-PCR), and to optimize their lipolytic activity, pH and temperature. The ITS regions possess a high variation among taxonomically distinct fungal species and even within species. Materials and Methods: All fungal were tested to determine their lipolytic activity by the Tributyrin agar plate assay. After DNA extraction, lipase-producing fungi were identified via ITS-PCR of rDNA region with ITS1 and ITS4 primers. Results: Four fungal species were isolated from water samples of the Caspian Sea (north of Iran) between February and June 2011. The nucleotide sequences reported for three of these isolates have been assigned accession numbers from NCBI Gene Bank database. Among these species, Cladosporium langeronii showed maximum lipolytic activity (34 U/mL) and maximum clear zone formation (6 mm) on the Tributyrin agar plates. The optimum pH and temperature for activity were 8.0 and 35°C, respectively. Conclusions: The findings of this study indicated that these isolates were plant pathogenic fungi, which entered seawater from the environment, and were likely to have a suitable lipase activity on plant oils. PMID:26034538

  2. The distribution of deep-sea sponge aggregations in the North Atlantic and implications for their effective spatial management

    NASA Astrophysics Data System (ADS)

    Howell, Kerry-Louise; Piechaud, Nils; Downie, Anna-Leena; Kenny, Andrew

    2016-09-01

    Sponge aggregations have been recognised as key component of shallow benthic ecosystems providing several important functional roles including habitat building and nutrient recycling. Within the deep-sea ecosystem, sponge aggregations may be extensive and available evidence suggests they may also play important functional roles, however data on their ecology, extent and distribution in the North Atlantic is lacking, hampering conservation efforts. In this study, we used Maximum Entropy Modelling and presence data for two deep-sea sponge aggregation types, Pheronema carpenteri aggregations and ostur aggregations dominated by geodid sponges, to address the following questions: 1) What environmental factors drive the broad-scale distribution of these selected sponge grounds? 2) What is the predicted distribution of these grounds in the northern North Atlantic, Norwegian and Barents Sea? 3) How are these sponge grounds distributed between Exclusive Economic Zones (EEZs) and High Seas areas? 4) What percentage of these grounds in High Seas areas are protected by the current High Seas MPA network? Our results suggest that silicate concentration, temperature, depth and amount of particulate organic carbon are the most important drivers of sponge distribution. Most of the sponge grounds are located within national EEZs rather than in the High Seas. Coordinated conservation planning between nations with significant areas of sponge grounds such as Iceland, Greenland and Faroes (Denmark), Norway (coastal Norway and Svalbard), Portugal and the UK, should be implemented in order to effectively manage these communities in view of the increasing level of human activity within the deep-sea environment.

  3. Influence of prolonged Anomalies in North Atlantic Sea Surface Temperature on Winter Windstorms

    NASA Astrophysics Data System (ADS)

    Höschel, Ines; Schuster, Mareike; Grieger, Jens; Ulbrich, Uwe

    2016-04-01

    The focus of this presentation is on decadal scale variations in the frequency and in the intensity of mid-latitude winter windstorms. Projections for the end of the next century are often beyond the time horizon of business, thus there is an increasing interest on decadal prediction, especially for infrastructural planning and in the insurance industry. One source of decadal predictability is the Atlantic multidecadal variability (AMV), a change in the sea surface temperature of the North Atlantic, strongly linked to the meridional overturning circulation. Correlation patterns between annual AMV-indices and annual mean of geopotential height at 500 hPa in reanalysis data show an anti-correlation in the North Atlantic. That is, during AMV warm phases the North Atlantic Oscillation (NAO) is more negative. Consequently, AMV should influence the characteristics of winter windstorms at multi-year scales. For the presented investigations a 10-member ensemble of 38-year-long idealized simulations with the atmosphere model ECHAM6 with lower boundary conditions, representing warm and cool phases of the AMV, is used. In the idealized simulations, the anti-correlation between AMV and NAO is well represented. For the identification of winter windstorms an objective wind tracking algorithm based on the exceedance of the local 98th percentile of 10m wind speed is applied. Storms under AMV-warm and AMV-cool conditions will be compared in terms of storm track density and probability distribution of storm characteristics.

  4. Variability in Sea Surface Height: A Qualitative Measure for the Meridional Overturning in the North Atlantic

    NASA Technical Reports Server (NTRS)

    Hakkinen, Sirpa

    1999-01-01

    Sea surface height (SSH) from altimeter observations from 1992 on and from modeling results is investigated to determine the modes of variability and the linkages to the state of oceanic circulation in the North Atlantic. First the altimeter and model simulated SSH are analyzed using the empirical orthogonal function (EOF) analysis. They are found to share a similar leading mode where the center of action is along the Gulf Stream and North Atlantic Current with opposite sign anomalies in the subpolar gyre and in the slope waters along the Eastern Seaboard. The time series of the leading EOF mode from the altimeter data shows that between winters of 1995 and 1996, SSH over the Gulf Stream decreased by about 12cm which change is reproduced by the model simulation. Based on the relationship from the model simulations between the time series of the SSH EOF1 and meridional heat transport, it is suggested that associated with this SSH change in 1995-96, the overturning has slowed down from its heights in the early 90's. Furthermore, it is shown that decadal variability in the leading SSH mode originates from the thermal forcing component. This adds confidence to the qualitative relationship between the state of overturning/meridional heat transport and SSH in the limited area described by the EOF1. SSH variability in the eastern side of the North Atlantic basin, outside the western boundary current region, is determined by local and remote (Rossby waves) wind stress curl forcing.

  5. A model of loggerhead sea turtle (Caretta caretta) habitat and movement in the oceanic North Pacific.

    PubMed

    Abecassis, Melanie; Senina, Inna; Lehodey, Patrick; Gaspar, Philippe; Parker, Denise; Balazs, George; Polovina, Jeffrey

    2013-01-01

    Habitat preferences for juvenile loggerhead turtles in the North Pacific were investigated with data from two several-year long tagging programs, using 224 satellite transmitters deployed on wild and captive-reared turtles. Animals ranged between 23 and 81 cm in straight carapace length. Tracks were used to investigate changes in temperature preferences and speed of the animals with size. Average sea surface temperatures along the tracks ranged from 18 to 23 °C. Bigger turtles generally experienced larger temperature ranges and were encountered in warmer surface waters. Seasonal differences between small and big turtles suggest that the larger ones dive deeper than the mixed layer and subsequently target warmer surface waters to rewarm. Average swimming speeds were under 1 km/h and increased with size for turtles bigger than 30 cm. However, when expressed in body lengths per second (bl s(-1)), smaller turtles showed much higher swimming speeds (>1 bl s (-1) ) than bigger ones (0.5 bl s(-1)). Temperature and speed values at size estimated from the tracks were used to parameterize a habitat-based Eulerian model to predict areas of highest probability of presence in the North Pacific. The model-generated habitat index generally matched the tracks closely, capturing the north-south movements of tracked animals, but the model failed to replicate observed east-west movements, suggesting temperature and foraging preferences are not the only factors driving large-scale loggerhead movements. Model outputs could inform potential bycatch reduction strategies.

  6. Seasonal Storminess in the North Pacific, Bering Sea, and Alaskan Regions

    NASA Astrophysics Data System (ADS)

    Shippee, N. J.; Atkinson, D. E.; Walsh, J. E.; Partain, J.; Gottschalck, J.; Marra, J.

    2012-12-01

    Annually, extra-tropical cyclones present a high impact natural hazard to the North Pacific, Bering Sea, and Alaskan regions. In these regions, extensive subsistence and commercial fishing, new oil and gas field development, tourism, growing interest in and exploitation of new commercial shipping potential, and increasing military and Coast Guard activity, all represent potential parties impacted by storms in these waters. It is of interest to many parties to begin developing capacity to provide some indication of storm activity at a monthly- to seasonal-outlook (30 to 90 days) timeframe. Using storm track data from NOAA's Climate Prediction Center for the North Pacific and Alaskan region, an experimental seasonal storminess outlook product, using eigen-based methods similar to the operational seasonal temperature and precipitation products currently produced at NOAA CPC, has been created and tested in hindcast mode using predicted states of ENSO, the Pacific Decadal Oscillation (PDO), the Pacific-North American Pattern (PNA), and the Arctic Oscillation (AO). A sample of the seasonal storminess outlook product will be shown along with a discussion of the utility of individual teleconnection patterns in the generation of the product.

  7. A Model of Loggerhead Sea Turtle (Caretta caretta) Habitat and Movement in the Oceanic North Pacific

    PubMed Central

    Abecassis, Melanie; Senina, Inna; Lehodey, Patrick; Gaspar, Philippe; Parker, Denise; Balazs, George; Polovina, Jeffrey

    2013-01-01

    Habitat preferences for juvenile loggerhead turtles in the North Pacific were investigated with data from two several-year long tagging programs, using 224 satellite transmitters deployed on wild and captive-reared turtles. Animals ranged between 23 and 81 cm in straight carapace length. Tracks were used to investigate changes in temperature preferences and speed of the animals with size. Average sea surface temperatures along the tracks ranged from 18 to 23 °C. Bigger turtles generally experienced larger temperature ranges and were encountered in warmer surface waters. Seasonal differences between small and big turtles suggest that the larger ones dive deeper than the mixed layer and subsequently target warmer surface waters to rewarm. Average swimming speeds were under 1 km/h and increased with size for turtles bigger than 30 cm. However, when expressed in body lengths per second (bl s−1), smaller turtles showed much higher swimming speeds (>1 bl s−1) than bigger ones (0.5 bl s−1). Temperature and speed values at size estimated from the tracks were used to parameterize a habitat-based Eulerian model to predict areas of highest probability of presence in the North Pacific. The model-generated habitat index generally matched the tracks closely, capturing the north-south movements of tracked animals, but the model failed to replicate observed east-west movements, suggesting temperature and foraging preferences are not the only factors driving large-scale loggerhead movements. Model outputs could inform potential bycatch reduction strategies. PMID:24039901

  8. Marine downscaling of a future climate scenario in the North Sea and possible effects on dinoflagellate harmful algal blooms.

    PubMed

    Friocourt, Y F; Skogen, M; Stolte, W; Albretsen, J

    2012-01-01

    Two hydrodynamic and ecological models were used to investigate the effects of climate change-according to the IPCC A1b emission scenario - on the primary productivity of the North Sea and on harmful algal blooms. Both models were forced with atmospheric fields from a regional downscaling of General Circulation Models to compare two sets of 20-year simulations representative of present climate (1984-2004) conditions and of the 2040s. Both models indicated a general warming of the North Sea by up to 0.8°C and a slight freshening by the 2040s. The models suggested that the eastern North Sea would be subjected to more temperature and salinity changes than the western part. In addition, the ecological modules of the models indicated that the warming up of the sea would result in a slightly earlier spring bloom. The one model that also computes the distribution of four different phytoplankton groups suggests an increase in the abundance of dinoflagellates, whereas the abundance of diatoms, flagellates and Phaeocystis sp. remains comparable to current levels, or decrease. Assuming that Dinophysis spp. would experience a similar increase in abundance as the modelled group of dinoflagellates, it is hypothesised that blooms of Dinophysis spp. may occur more frequently in the North Sea by 2040. However, implications for shellfish toxicity remain unclear.

  9. The application of ERTS imagery to monitoring Arctic sea ice. [mapping ice in Bering Sea, Beaufort Sea, Canadian Archipelago, and Greenland Sea

    NASA Technical Reports Server (NTRS)

    Barnes, J. C. (Principal Investigator); Bowley, C. J.

    1974-01-01

    The author has identified the following significant results. Because of the effect of sea ice on the heat balance of the Arctic and because of the expanding economic interest in arctic oil and minerals, extensive monitoring and further study of sea ice is required. The application of ERTS data for mapping ice is evaluated for several arctic areas, including the Bering Sea, the eastern Beaufort Sea, parts of the Canadian Archipelago, and the Greenland Sea. Interpretive techniques are discussed, and the scales and types of ice features that can be detected are described. For the Bering Sea, a sample of ERTS-1 imagery is compared with visual ice reports and aerial photography from the NASA CV-990 aircraft. The results of the investigation demonstrate that ERTS-1 imagery has substantial practical application for monitoring arctic sea ice. Ice features as small as 80-100 m in width can be detected, and the combined use of the visible and near-IR imagery is a powerful tool for identifying ice types. Sequential ERTS-1 observations at high latitudes enable ice deformations and movements to be mapped. Ice conditions in the Bering Sea during early March depicted in ERTS-1 images are in close agreement with aerial ice observations and photographs.

  10. Is ice-rafted sediment in a North Pole marine record evidence for perennial sea-ice cover?

    PubMed

    Tremblay, L B; Schmidt, G A; Pfirman, S; Newton, R; DeRepentigny, P

    2015-10-13

    Ice-rafted sediments of Eurasian and North American origin are found consistently in the upper part (13 Ma BP to present) of the Arctic Coring Expedition (ACEX) ocean core from the Lomonosov Ridge, near the North Pole (≈88° N). Based on modern sea-ice drift trajectories and speeds, this has been taken as evidence of the presence of a perennial sea-ice cover in the Arctic Ocean from the middle Miocene onwards (Krylov et al. 2008 Paleoceanography 23, PA1S06. (doi:10.1029/2007PA001497); Darby 2008 Paleoceanography 23, PA1S07. (doi:10.1029/2007PA001479)). However, other high latitude land and marine records indicate a long-term trend towards cooling broken by periods of extensive warming suggestive of a seasonally ice-free Arctic between the Miocene and the present (Polyak et al. 2010 Quaternary Science Reviews 29, 1757-1778. (doi:10.1016/j.quascirev.2010.02.010)). We use a coupled sea-ice slab-ocean model including sediment transport tracers to map the spatial distribution of ice-rafted deposits in the Arctic Ocean. We use 6 hourly wind forcing and surface heat fluxes for two different climates: one with a perennial sea-ice cover similar to that of the present day and one with seasonally ice-free conditions, similar to that simulated in future projections. Model results confirm that in the present-day climate, sea ice takes more than 1 year to transport sediment from all its peripheral seas to the North Pole. However, in a warmer climate, sea-ice speeds are significantly faster (for the same wind forcing) and can deposit sediments of Laptev, East Siberian and perhaps also Beaufort Sea origin at the North Pole. This is primarily because of the fact that sea-ice interactions are much weaker with a thinner ice cover and there is less resistance to drift. We conclude that the presence of ice-rafted sediment of Eurasian and North American origin at the North Pole does not imply a perennial sea-ice cover in the Arctic Ocean, reconciling the ACEX ocean core data with

  11. Anthropogenic 129I in the North Pacific, Bering and Chukchi Seas, and Arctic Ocean in 2012-2013

    NASA Astrophysics Data System (ADS)

    Nagai, H.; Hasegawa, A.; Yamagata, T.; Kumamoto, Y.; Nishino, S.; Matsuzaki, H.

    2015-10-01

    Most of anthropogenic 129I in marine environment are due to discharge from the nuclear fuel reprocessing facilities at Sellafield (U.K.) and La Hague (France) for past few decades. The discharge raised 129I concentration in seawaters in the North Atlantic and Arctic Oceans to more than 109 atoms L-1, which is two orders of magnitude higher than that in other region. Recently, in March 2011, a large quantity of 129I was released into the western North Pacific due to the Fukushima Daiichi Nuclear Power Plant (F1NPP) accident. To evaluate the influence of these events, we have measured 129I concentration in seawaters in the northern North Pacific Ocean, Bering and Chukchi Seas, and Arctic Ocean in 2012-2013. The 129I concentrations were 1.0-1.8 × 107 atoms L-1 in the surface waters in the vicinity of 47°N 150°E-130°W North Pacific Ocean, Bering Sea, and Chukchi Sea (<74°N), which are equal to or lower than the 129I concentration level in surface water in the North Pacific Ocean before the F1NPP accident. The vertical profiles in the North Pacific were almost same as that observed in the western North Pacific before the F1NPP accident. The 129I distribution in seawater in the North Pacific to the Chukchi Sea revealed no significant increase of 129I concentration caused by the F1NPP accident. The 129I concentrations were 13-14 × 107 atoms L-1 in surface waters and 80 × 107 atoms L-1 at depths of 300 and 800 m in the Arctic Ocean.

  12. Unusual forest growth decline in boreal North America covaries with the retreat of Arctic sea ice.

    PubMed

    Girardin, Martin P; Guo, Xiao Jing; De Jong, Rogier; Kinnard, Christophe; Bernier, Pierre; Raulier, Frédéric

    2014-03-01

    The 20th century was a pivotal period at high northern latitudes as it marked the onset of rapid climatic warming brought on by major anthropogenic changes in global atmospheric composition. In parallel, Arctic sea ice extent has been decreasing over the period of available satellite data records. Here, we document how these changes influenced vegetation productivity in adjacent eastern boreal North America. To do this, we used normalized difference vegetation index (NDVI) data, model simulations of net primary productivity (NPP) and tree-ring width measurements covering the last 300 years. Climatic and proxy-climatic data sets were used to explore the relationships between vegetation productivity and Arctic sea ice concentration and extent, and temperatures. Results indicate that an unusually large number of black spruce (Picea mariana) trees entered into a period of growth decline during the late-20th century (62% of sampled trees; n = 724 cross sections of age >70 years). This finding is coherent with evidence encoded in NDVI and simulated NPP data. Analyses of climatic and vegetation productivity relationships indicate that the influence of recent climatic changes in the studied forests has been via the enhanced moisture stress (i.e. greater water demands) and autotrophic respiration amplified by the declining sea ice concentration in Hudson Bay and Hudson Strait. The recent decline strongly contrasts with other growth reduction events that occurred during the 19th century, which were associated with cooling and high sea ice severity. The recent decline of vegetation productivity is the first one to occur under circumstances related to excess heat in a 300-year period, and further culminates with an intensifying wildfire regime in the region. Our results concur with observations from other forest ecosystems about intensifying temperature-driven drought stress and tree mortality with ongoing climatic changes.

  13. Organic Carbon Geochemistry in the North-western Black Sea Danube River System

    NASA Astrophysics Data System (ADS)

    Galimov, E. M.; Kodina, L. A.; Zhiltsova, L. I.; Tokarev, V. G.; Vlasova, L. N.; Bogacheva, M. P.; Korobeinik, G. S.; Vaisman, T. I.

    2002-03-01

    The isotopic and chemical composition of organic matter from sediments collected on the north-western shelf of the Black Sea and the Danube River are discussed. The δ 13C distribution pattern in organic carbon from surface sediments (0-1 cm) of the western part of the Black Sea has been established. It reveals a rather complicated picture, reflecting the superposition of several factors: local marine primary productivity, terrestrial input to the Danube River discharge and possible contribution from anaerobic microbial activity. The analysis of organic carbon by a pyrolysis-chromatography technique showed that the H/O indices of organic matter from marine sediments are in correlation with δ 13C values. This is an indication of the mixed origin of the organic carbon in the littoral sediments. However, samples from the zone where H 2S conditions prevail deviate from the correlation line of δ 13C vs H/O indices. We believe that this is due to the contribution of the biomass of chemosynthetic bacteria in the sediments. Thus, we argue that in the Danube-Black Sea system several consecutive zones are distinguished. River discharge delivers organic carbon with δ 13C values from -28 to -26 (PSU is used). Mixing of the land-derived material with autochtonous marine primary production gives δ 13C values of about -26 to -23 for the organic carbon in coastal sediments. On the shelf area, beyond significant influence of both terrestrial and sulphide regime factors, plankton material dominates as a source of organic carbon in sediments. In the hydrogen sulphide zone, chemosynthetic bacteria produce additional amounts of organic matter with hydrogen to oxygen indices similar to those of plankton, but with different isotopic composition, which results in the appearance of relatively isotopically light organic carbon in the deep-sea sediments.

  14. Sequence stratigraphy and stratigraphic simulation of the Brent Group, Norwegian North Sea

    SciTech Connect

    Prueser, R.E.; Levine, P.A.; Baum, G.R.; Kendall, G.S.C.

    1996-12-31

    Sequence stratigraphic analysis of a well log data base from the Norwegian North Sea has established that the Brent Group is a deltaic complex consisting of four third-order depositional sequences. Sequence 1 was deposited first during northwestern progradation of the delta from the Horda Platform, while sequences 2 and 3 were primarily aggradational. Sequence 4 is characterized by backslapping geometries and a basin wide drowning event which resulted from variably increasing subsidence rates across the basin. The stratigraphic events interpreted in this study are based on the identification of unconformities (sequence boundaries), transgressive surfaces, and maximum flooding surfaces. Dates for these events were established using biostratigraphy from 12 wells. Unlike earlier interpretations, the Oseberg Formation is considered to be part of Sequence 1 and is an incised-valley fill which is genetically related to the distal Rannoch and Etive formations. Also in this study, a new sea level curve is proposed for the Aalenian - Bathonian which has similar frequencies to the Exxon sea level chart, but much smaller amplitudes. This interpretation was simulated in order to estimate the sea level, subsidence, and sediment supply parameters involved in deposition of these sequences. Simulation results indicate that the main deposition of the Brent Group occurred during uniform subsidence, while drowning of the depositional system resulted from a sharp, but variable increase in subsidence rates across the basin. Quantitative comparisons between the lithologic percentages in each sequence at well locations and at representative points in the simulation confirm that the simulation presents a unique and reasonable answer.

  15. Sequence stratigraphy and stratigraphic simulation of the Brent Group, Norwegian North Sea

    SciTech Connect

    Prueser, R.E.; Levine, P.A.; Baum, G.R.; Kendall, G.S.C. )

    1996-01-01

    Sequence stratigraphic analysis of a well log data base from the Norwegian North Sea has established that the Brent Group is a deltaic complex consisting of four third-order depositional sequences. Sequence 1 was deposited first during northwestern progradation of the delta from the Horda Platform, while sequences 2 and 3 were primarily aggradational. Sequence 4 is characterized by backslapping geometries and a basin wide drowning event which resulted from variably increasing subsidence rates across the basin. The stratigraphic events interpreted in this study are based on the identification of unconformities (sequence boundaries), transgressive surfaces, and maximum flooding surfaces. Dates for these events were established using biostratigraphy from 12 wells. Unlike earlier interpretations, the Oseberg Formation is considered to be part of Sequence 1 and is an incised-valley fill which is genetically related to the distal Rannoch and Etive formations. Also in this study, a new sea level curve is proposed for the Aalenian - Bathonian which has similar frequencies to the Exxon sea level chart, but much smaller amplitudes. This interpretation was simulated in order to estimate the sea level, subsidence, and sediment supply parameters involved in deposition of these sequences. Simulation results indicate that the main deposition of the Brent Group occurred during uniform subsidence, while drowning of the depositional system resulted from a sharp, but variable increase in subsidence rates across the basin. Quantitative comparisons between the lithologic percentages in each sequence at well locations and at representative points in the simulation confirm that the simulation presents a unique and reasonable answer.

  16. Environmental factors affecting methane distribution and bacterial methane oxidation in the German Bight (North Sea)

    NASA Astrophysics Data System (ADS)

    Osudar, Roman; Matoušů, Anna; Alawi, Mashal; Wagner, Dirk; Bussmann, Ingeborg

    2015-07-01

    River estuaries are responsible for high rates of methane emissions to the atmosphere. The complexity and diversity of estuaries require detailed investigation of methane sources and sinks, as well as of their spatial and seasonal variations. The Elbe river estuary and the adjacent North Sea were chosen as the study site for this survey, which was conducted from October 2010 to June 2012. Using gas chromatography and radiotracer techniques, we measured methane concentrations and methane oxidation (MOX) rates along a 60 km long transect from Cuxhaven to Helgoland. Methane distribution was influenced by input from the methane-rich mouth of the Elbe and gradual dilution by methane-depleted sea water. Methane concentrations near the coast were on average 30 ± 13 nmol L-1, while in the open sea, they were 14 ± 6 nmol L-1. Interestingly, the highest methane concentrations were repeatedly detected near Cuxhaven, not in the Elbe River freshwater end-member as previously reported. Though, we did not find clear seasonality we observed temporal methane variations, which depended on temperature and presumably on water discharge from the Elbe River. The highest MOX rates generally coincided with the highest methane concentrations, and varied from 2.6 ± 2.7 near the coast to 0.417 ± 0.529 nmol L-1 d-1 in the open sea. Turnover times varied from 3 to >1000 days. MOX rates were strongly affected by methane concentration, temperature and salinity. We ruled out the supposition that MOX is not an important methane sink in most of the Elbe estuary and adjacent German Bight.

  17. Barrier island response to an elevated sea-level anomaly: Onslow Beach, North Carolina, USA

    NASA Astrophysics Data System (ADS)

    Theuerkauf, E. J.; Rodriguez, A. B.; Fegley, S. R.; Luettich, R.

    2012-12-01

    Variations in sea level over time scales ranging from hours to millennia influence coastal processes and evolution. At annual time scales, elevated sea-level anomalies produce coastal flooding and promote beach erosion. This study examines the coastal response of Onslow Beach, North Carolina to the summer 2009 East Coast sea-level anomaly. Onslow Beach is a 12-km-long wave-dominated barrier island with highly variable along-barrier morphology. The transgressive southern portion of the island is characterized by a narrow beach, low dunes, and multiple washover fans, while the regressive northern portion is characterized by a wide beach and continuous tall dunes. Hourly tide gauge data from adjacent NOAA stations (Beaufort and Wrightsville Beach) are used to determine the timing and extent of elevated water levels. The seasonal and longer term trends (relative sea level rise) are removed from both of the water level series and the sea-level anomaly is represented by a large residual between the observed and predicted water levels. Beach response is quantified using terrestrial laser scanning for morphology and from geoprobe cores to determine the maximum depth of erosion (MDOE). The mean high water (MHW) shoreline and dune toe are digitized from digital elevation models derived from the laser scans and analyzed using the Digital Shoreline Analysis System (DSAS). Landward (negative) movement of these contacts indicates erosion. Wave data collected from an Acoustic Wave and Current Meter (AWAC) located offshore of the southern end of Onslow Beach is used to characterize the wave regime throughout the study. Water level is elevated in the tide gauge data from June 2009 to March 2010. This sea-level anomaly corresponds with an increase in the maximum depth of erosion between 2009 and 2010. Landward movement of the MHW shoreline and the dunetoe increased during the period between September 2009 and May 2010 indicating an increase in beach erosion during the sea

  18. Distribution of total mercury in surface sediments of the western Jade Bay, Lower Saxonian Wadden Sea, southern North Sea.

    PubMed

    Jin, Huafang; Liebezeit, Gerd; Ziehe, Daniel

    2012-04-01

    A total of 114 surface sediment samples was equidistantly collected in the western part of the Jade Bay, southern North Sea, to analyse total mercury contents as well as grain size distribution and total organic carbon (TOC) contents. Total mercury was determined by oxygen combustion-gold amalgamation. Validation, precision and accuracy of the method were evaluated and controlled with two certified reference materials (HISS-1 and MESS-3). Total mercury contents varied between 8 and 243 ng/g dry sediment with a mean value of 103 ng/g dw. The mercury levels in surface sediments showed an inhomogeneous spatial distribution with higher contents in near-dike areas. The values are mostly in the range of natural background values (50–100 ng/g dw) and positively related to TOC and clay/silt contents (<63 μm). The present total mercury contents are compared to those of previous studies, in order to estimate possible temporal trends of mercury contents in the study area over the last decades. Moreover, the comparison to sediment quality guidelines indicated that the surface sediments of the Jade Bay are not mercury contaminated. These results also suggested that the current mercury contents of Jade Bay surficial sediments are mostly affected by atmospheric deposition and re-emission.

  19. Nitrification and growth of autotrophic nitrifying bacteria and Thaumarchaeota in the coastal North Sea

    NASA Astrophysics Data System (ADS)

    Veuger, Bart; Pitcher, Angela; Schouten, Stefan; Sinninghe Damsté, Jaap S.; Middelburg, Jack J.

    2013-04-01

    A dual stable isotope (15N and 13C) tracer approach in combination with compound-specific stable isotope analysis of bacterial and Thaumarchaeotal lipid biomarkers was used to investigate nitrification and the associated growth of autotrophic nitrifiers in the Dutch coastal North Sea. This study focusses on the stoichiometry between nitrification and DIC fixation by autotrophic nitrifiers as well as on the contributions of bacteria versus Thaumarchaeota to total autotrophic DIC-fixation by nitrifiers. Water from the dutch coastal North Sea was collected at weekly to biweekly intervals during the winter of 2007-2008. Watersamples were incubated with 15N-labeled ammonium and 15N was traced into nitrate and suspended material to quantify rates of nitrification and ammonium assimilation respectively. Growth of autotrophic nitrifiers was measured by incubating water samples with 13C-DIC in the presence and absence of nitrification inhibitors (nitrapyrin and chlorate) and subsequent analysis of 13C in bacterial phospholipid-derived fatty acids (PLFAs) and the Thaumarchaeotal biomarker crenarchaeol. Results revealed high nitrification rates with nitrification being the primary sink for ammonium. 13C-DIC fixation into bacterial and Thaumarchaeotal lipids was strongly reduced by the nitrification inhibitors (27-95%). The ratio between rates of nitrification versus DIC fixation by nitrifiers was higher or even much higher than typical values for autotrophic nitrifiers, indicating that little DIC was fixed relative to the amount of energy that was generated by nitrification, and hence that other other processes for C acquisition may have been relevant as well. The inhibitor-sensitive 13C-PLFA pool was dominated by the common PLFAs 16:0, 16:1ω7c and 18:1ω7c throughout the whole sampling period and occasionally also included the polyunsaturated fatty acids 18:2ω6c and 18:3ω3. Cell-specific 13C-DIC fixation activity of the nitrifying bacteria was much higher than that of the

  20. Bioavailability of Metals in Sediments of the Dogger Bank (Central North Sea): A Mesocosm Study

    NASA Astrophysics Data System (ADS)

    Langston, W. J.; Burt, G. R.; Pope, N. D.

    1999-05-01

    There are conflicting arguments surrounding the nature and origins of metal enrichment in sediments from the Dogger Bank (central North Sea) and much speculation as to its biological significance. To help resolve this controversy, a mesocosm approach was evaluated to test whether metal loadings in sediments from the Dogger Bank region display enhanced bioavailability, relative to reference sites off south-west England. This involved the combination of physicochemical characterization of sediments (including porewaters) with bioaccumulation studies, using sediment cores seeded with benthic organisms (bivalves Spisula solida and Venus striatula, the gastropod Turritella communis and the polychaete Melinna palmata). There was little evidence of As, Cu, Hg or Pb bioaccumulation from Dogger cores. In contrast, all species accumulated Cd; Ag concentrations rose by up to fourfold in most bioindicators; and Ni, Cr and Mn burdens also increased, occasionally by as much as 10-fold. Variable, but generally smaller increases in Fe and Zn were observed. Physiological variations in metal bioaccumulation processes, including the ability to regulate essential elements, were responsible for species differences in response—a feature which may contribute to uncertainty in the interpretation and comparison of biomonitoring data. Mesocosm results nevertheless complement earlier field reports of unexpectedly enriched levels of certain metals (notably Cd) in biota from this part of the central North Sea. Characterization of sediments provided some physicochemical explanations for enhanced metal uptake in biota and helped, partly, to define bioavailable and anthropogenic fractions. Thus, whilst total sediment-metal concentrations were not exceptional in Dogger samples, for some metals there was a significant proportion in non-refractory (readily extractable) form, together with relatively high concentrations in interstitial waters—both presumably available for assimilation

  1. Distribution and abundance of pelagic tunicates in the North Yellow Sea

    NASA Astrophysics Data System (ADS)

    Franco, Pietro; Chen, Hongju; Liu, Guangxing

    2014-10-01

    In this paper, the distribution patterns and abundance of pelagic tunicates in the North Yellow Sea of China during the period 2006-2007 were analyzed. Zooplankton samples were obtained with vertical towing from bottom to surface using a WP2 plankton net (200 μm mesh size; mouth area: 0.25 m2). Five species belonging to two classes were identified: Oikopleura dioica, O. longicauda and Fritillaria borealis belonging to class Appendicularia; Salpa fusiformis and Doliolum denticulatum of class Thaliacea. O. dioica and O. longicauda were the dominant species, occurring in the samples of all four seasons, with different distribution patterns. Their maximum abundance were 1664.7 ind. m-3 (spring) and 1031.7 ind. m-3 (spring) respectively. Following Oikopleura spp. were D. denticulatum, which was found only in autumn with an average abundance of 149.6 ind. m-3, and S. fusiformis, which was detected all the year long except for autumn with low abundance (max. abundance 289.4 ind. m-3 in summer). Only a very small amount of F. borealis was detected in summer samples, with an average abundance of 2.7 ind. m-3. The relationship between tunicates abundances and the environmental factors was analyzed using the stepwise regression model for each species. The variation of appendicularian abundance showed a significant correlation with the surface water temperature and with the concentration of Chl- a. No relationship was found between tunicates abundance and salinity, likely due to the slight changes in surface salinity of the studied area during the four seasons. Salps abundance and that of doliolids were significantly correlated to bottom water temperature, indicating that these two species ( S. fusiformis and D. denticulatum) migrate vertically in the water column. In particular D. denticulatum, known to be a warm water species, showed not only an important correlation with water temperature, but also a spatial distribution connected to the warm currents in the North Yellow

  2. Marine habitat mapping, classification and monitoring in the coastal North Sea: Scientific vs. stakeholder interests

    NASA Astrophysics Data System (ADS)

    Hass, H. Christian; Mielck, Finn; Papenmeier, Svenja; Fiorentino, Dario

    2016-04-01

    Producing detailed maps of the seafloor that include both, water depth and simple textural characteristics has always been a challenge to scientists. In this context, marine habitat maps are an essential tool to comprehend the complexity, the spatial distribution and the ecological status of different seafloor types. The increasing need for more detail demands additional information on the texture of the sediment, bedforms and information on benthic sessile life. For long time, taking samples and videos/photographs followed by interpolation over larger distances was the only feasible way to gain information about sedimentary features such as grain-size distribution and bedforms. While ground truthing is still necessary, swath systems such as multibeam echo sounders (MBES) and sidescan sonars (SSS), as well as single beam acoustic ground discrimination systems (AGDS) became available to map the seafloor area-wide (MBES, SSS), fast and in great detail. Where area-wide measurements are impossible or unavailable point measurements are interpolated, classified and modeled. To keep pace with environmental change in the highly dynamic coastal areas of the North Sea (here: German Bight) monitoring that utilizes all of the mentioned techniques is a necessity. Since monitoring of larger areas is quite expensive, concepts for monitoring strategies were developed in scientific projects such as "WIMO" ("Scientific monitoring concepts for the German Bight, SE North Sea"). While instrumentation becomes better and better and interdisciplinary methods are being developed, the gap between basic scientific interests and stakeholder needs often seem to move in opposite directions. There are two main tendencies: the need to better understand nature systems (for theoretical purposes) and the one to simplify nature (for applied purposes). Science trends to resolve the most detail in highest precision employing soft gradients and/or fuzzy borders instead of crisp demarcations and

  3. Using very high resolution satellite images to identify coastal zone dynamics at North Western Black Sea

    NASA Astrophysics Data System (ADS)

    Florin Zoran, Liviu; Ionescu Golovanov, Carmen; Zoran, Maria

    2010-05-01

    The availability of updated information about the extension and characteristics of land cover is a crucial issue in the perspective of a correct landscape planning and management of marine coastal zones. Satellite remote sensing data can provide accurate information about land coverage at different scales and the recent availability of very high resolution images definitely improved the precision of coastal zone spatio-temporal changes. The Romanian North Western coastal and shelf zones of the Black Sea and Danube delta are a mosaic of complex, interacting ecosystems, rich natural resources and socio-economic activity. Dramatic changes in the Black Sea's ecosystem and resources are due to natural and anthropogenic causes (increase in the nutrient and pollutant load of rivers input, industrial and municipal wastewater pollution along the coast, and dumping on the open sea). A scientific management system for protection, conservation and restoration must be based on reliable information on bio-geophysical and geomorphologic processes, coastal erosion, sedimentation dynamics, mapping of macrophyte fields, water quality, and climatic change effects. Use of satellite images is of great help for coastal zone monitoring and environmental impact assessment. Synergetic use of in situ measurements with multisensors satellite data could provide a complex assessment of spatio-temporal changes. In this study was developed a method for extracting coastal zone features information as well as landcover dynamics from IKONOS, very high resolution images for North-Western Black Sea marine coastal zone. The main objective was obtaining reliable data about the spatio-temporal coastal zone changes in two study areas located in Constanta urban area and Danube Delta area. We used an object-oriented approach based on preliminary segmentation and classification of the resulting object. First of all, segmentation parameters were tested and selected comparing segmented polygons with

  4. Holocene relative sea-level changes from North America and the Caribbean

    NASA Astrophysics Data System (ADS)

    Horton, Benjamin; Engelhart, Simon; Vacchi, Matteo; Khan, Nicole; Peltier, Dick; Roy, Keven

    2014-05-01

    Reconstructions of Holocene relative sea level (RSL) are important for identifying the ice equivalent meltwater contribution to sea-level change during deglaciation. Holocene RSL reconstructions from near, intermediate and far field regions enable the assessment of earth and ice parameters of Glacial Isostatic Adjustment (GIA) models. RSL reconstructions provide data for estimating rates of spatially variable and ongoing vertical land motion; a requirement for understanding the variation in modern and late Holocene sea level as recorded by instrumental and proxy records. Here we explain the methodology employed to reconstruct former sea levels, which follows the practice of the International Geoscience Programme (IGCP). We produce sea level index points from the Pacific and Atlantic coasts of North America and the Caribbean. Index points are defined as the most reliable observations of former sea levels. They consist of an estimate of X (age) and Y (the position of former RSL). Where a suite of index points are developed for a locality or region, they describe changes in RSL through time and estimate rates of change. A valid index point must meet the following four criteria; (1) location of the sample is known; (2) the altitude of the sample (and the error associated with measuring that altitude) is known; (3) the indicative meaning (the relationship between the sample and a tide level) is estimated; and (4) the age of the sample, which is commonly radiocarbon dated is calibrated to sidereal years using the latest calibration curves. In total databases have over 2000 sea-level index points from formerly ice covered, uplifting regions of Canada, to the region of forebulge collapse along the subsiding mid-Atlantic and mid-Pacific coastlines of the United States, to the tropical regions of the Caribbean. Recent analyses of these new published databases have led to a further refinement of the most recent of the ICE-NG (VMX) series of global models of GIA. The records

  5. Middle and Late Weichselian (Devensian) glaciation history of south-western Norway, North Sea and eastern UK

    NASA Astrophysics Data System (ADS)

    Sejrup, H. P.; Nygård, A.; Hall, A. M.; Haflidason, H.

    2009-02-01

    Data from eastern England, Scotland, the northern North Sea and western Norway have been compiled in order to outline our current knowledge of the Middle and Late Weichselian glacial history of this region. Radiometric dates and their geological context from key sites in the region are presented and discussed. Based on the available information the following conclusions can be made: (i) Prior to 39 cal ka and most likely after ca 50 cal ka Scotland and southern Norway were extensively glaciated. Most likely the central North Sea was not glaciated at this time and grounded ice did not reach the shelf edge. (ii) During the time interval between 29 and 39 ka periods with ameliorated climate (including the Ålesund, Sandnes and Tolsta Interstadials) alternated with periods of restricted glaciation in Scotland and western Norway. (iii) Between 29 and 25 ka maximum Weichselian glaciation of the region occurred, with the Fennoscandian and British ice sheets coalescing in the central North Sea. (iv) Decoupling of the ice sheets had occurred at 25 ka, with development of a marine embayment in the northern North Sea (v) Between 22 and 19 ka glacial ice expanded westwards from Scandinavia onto the North Sea Plateau in the Tampen readvance. (vi) The last major expansion of glacial ice in the offshore areas was between 17.5 and 15.5 ka. At this time ice expanded in the north-western part of the region onto the Måløy Plateau from Norway and across Caithness and Orkney and to east of Shetland from the Moray Firth. The Norwegian Channel Ice Stream (NCIS), which drained major parts of the south-western Fennoscandian Ice Sheet, was active at several occasions between 29 and 18 ka.

  6. Local adaptation and oceanographic connectivity patterns explain genetic differentiation of a marine diatom across the North Sea–Baltic Sea salinity gradient

    PubMed Central

    Sjöqvist, C; Godhe, A; Jonsson, P R; Sundqvist, L; Kremp, A

    2015-01-01

    Drivers of population genetic structure are still poorly understood in marine micro-organisms. We exploited the North Sea–Baltic Sea transition for investigating the seascape genetics of a marine diatom, Skeletonema marinoi. Eight polymorphic microsatellite loci were analysed in 354 individuals from ten locations to analyse population structure of the species along a 1500-km-long salinity gradient ranging from 3 to 30 psu. To test for salinity adaptation, salinity reaction norms were determined for sets of strains originating from three different salinity regimes of the gradient. Modelled oceanographic connectivity was compared to directional relative migration by correlation analyses to examine oceanographic drivers. Population genetic analyses showed distinct genetic divergence of a low-salinity Baltic Sea population and a high-salinity North Sea population, coinciding with the most evident physical dispersal barrier in the area, the Danish Straits. Baltic Sea populations displayed reduced genetic diversity compared to North Sea populations. Growth optima of low salinity isolates were significantly lower than those of strains from higher native salinities, indicating local salinity adaptation. Although the North Sea–Baltic Sea transition was identified as a barrier to gene flow, migration between Baltic Sea and North Sea populations occurred. However, the presence of differentiated neutral markers on each side of the transition zone suggests that migrants are maladapted. It is concluded that local salinity adaptation, supported by oceanographic connectivity patterns creating an asymmetric migration pattern between the Baltic Sea and the North Sea, determines genetic differentiation patterns in the transition zone. PMID:25892181

  7. Denali Ice Core Record of North Pacific Sea Surface Temperatures and the Pacific Decadal Oscillation

    NASA Astrophysics Data System (ADS)

    Polashenski, D.; Osterberg, E. C.; Winski, D.; Ferris, D. G.; Kreutz, K. J.; Wake, C. P.; Introne, D.

    2015-12-01

    Ice cores collected from high elevation alpine glaciers in the Alaska Range provide a unique opportunity to investigate changes in the regional climate of southern Alaska and the north Pacific over the past millennium. In this study, we seek to investigate changes in sea surface temperature (SST) in the north-central Pacific Ocean using the deuterium excess (d-excess) record from the Mt. Hunter ice cores collected in Denali National Park, Alaska. A collaborative research team from Dartmouth College and the Universities of Maine and New Hampshire collected two parallel ice cores to bedrock (208 m long) in May-June 2013 from the Mt. Hunter summit plateau (63º N, 151º W, 4,000 m above sea level). The cores were melted on a continuous melter system in the Dartmouth ice core lab and then analyzed for concentrations of major ions and trace elements, as well as stable water isotope ratios. The depth-age scale of the cores was determined using annual layer counting of δ18O and the concentrations of Mg, NH4, and Methanesulfonic acid (MSA) obtained by ion chromatography. The depth-age scale was validated using large, well-dated volcanic eruptions and the spike in 137Cs concentrations associated with nuclear weapons testing in 1963. Preliminary analyses indicate that the full record spans the past millennium. Analysis of the isotope data set extending back to 1938 using reanalysis data shows a positive correlation (p<0.05) between d-excess at the core site and the north-central Pacific SST. The north-central Pacific region of positive SST-d-excess correlation occurs at one node of the Pacific Decadal Oscillation (PDO), and thus the Denali cores are sensitive to PDO variability with low (high) d-excess associated with positive (negative) PDO index values. We also note a significant (p<0.05) declining trend in d-excess from 1938-2012, which we hypothesize to represent a rising proportion of Arctic moisture sources influencing Denali as Arctic temperatures and evaporation

  8. Productivity, ventilation and oxygenation in the north-central Bering Sea during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Cook, M. S.; Ravelo, A. C.; Caissie, B.; Addison, J. A.; Kusler, J. E.

    2013-12-01

    During the last deglaciation, the oxygen minimum zone (OMZ) in the North Pacific intensified, resulting in laminated and dysoxic continental margin sediments at intermediate depths from the Gulf of California to Japan. The ventilation of North Pacific Intermediate Water can cause basin-wide changes in OMZ intensity, but increased export productivity near intermediate-water formation areas can also affect the North Pacific OMZ by decreasing oxygen concentrations of recently-formed water, decoupling ventilation from oxygenation. There is evidence that both productivity and ventilation of the subarctic Pacific changed at millennial time scales during the deglaciation. Both processes could have impacted the oxygenation of subsurface water originating in the North Pacific and the basin-wide OMZ. We studied IODP Site U1345, from 1000 meters water depth on the continental slope of the Bering Sea, and a nearby piston core, HLY02-02-3JPC. High terrigenous sediment fluxes result in an expanded deglacial sequence, with millimeter-scale annual laminations during the Bolling-Allerod (BA) and early Holocene. We measured benthic and planktonic foraminiferal radiocarbon, paleoproductivity proxies, and bulk sediment δ15N to reconstruct the local production and ventilation history in this marginal sea. During the early deglaciation, there is a convergence of benthic and planktonic radiocarbon ages, accompanied by a minimum of d15N and increasing productivity. This suggests there were episodes of convection to at least 1000 m, accompanied by greater major nutrient supply to the surface ocean and lower utilization. During the BA, the water column at 1000 m was enriched in radiocarbon compared to today, but with no evidence of local convection. From the BA through the early Holocene, laminated, high productivity, high δ15N sediments alternate with massive, lower productivity, low δ15N sediments, but the benthic-planktonic radiocarbon age differences are stationary. If we assume that

  9. 76 FR 16612 - Proposed Information Collection; Comment Request; Sea Grant Program Application Requirements for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-24

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration Proposed Information Collection; Comment Request; Sea Grant Program Application Requirements for Grants, for Sea Grant Fellowships, and for Designation as a Sea...

  10. Trace metal contamination of Beaufort's Dyke, North Channel, Irish Sea: a legacy of ordnance disposal.

    PubMed

    Callaway, Alexander; Quinn, Rory; Brown, Craig J; Service, Matthew; Benetti, Sara

    2011-11-01

    Beaufort's Dyke is a disused ordnance disposal ground within the North Channel of the Irish Sea. Over 1 million tonnes of ordnance were disposed of in the dyke over a 40 year period representing a substantial volume of trace metal pollutants introduced to the seabed. Utilising particle transport modelling software we simulated the potential transport of metal particles from Beaufort's Dyke over a 3 month period. This demonstrated that Beaufort's Dyke has the potential to act as a source for trace metal contamination to areas beyond the submarine valley. Trace metal analysis of sediments from the Dyke and surrounding National Marine Monitoring Programme areas demonstrate that the Dyke is not the most contaminated site in the region. Particle transport modelling enables the transport pathways of trace metal contaminants to be predicted. Implementation of the technique in other munitions disposal grounds will provide valuable information for the selection of monitoring stations.

  11. Seabirds as monitor organisms of contaminants along the German North Sea coast

    NASA Astrophysics Data System (ADS)

    Becker, Peter H.

    1989-09-01

    In the 1980s, significant regional, interspecific and annual differences in contamination with toxic chemicals were found in eggs of breeding birds along the German North Sea coast. In some regions residue levels approached a range endangering breeding success, especially in terns. In 1987, a three-year monitoring-program for common tern Sterna hirundo and oystercatcher Haematopus ostralegus was started, in order to recognize such contamination trends. Eggs from 9 14 areas along the coast are now being analysed for chlororganic residues and mercury. First results on geographical and year-to-year variation are presented here, and the advantages of seabird eggs as spatial and temporal monitors of marine pollution are discussed. The suggestion is made to include a shore-breeding bird species in the European monitoring programs.

  12. Direct pore-scale computation of material and transport properties for North Sea reservoir rocks

    NASA Astrophysics Data System (ADS)

    Øren, P.-E.; Bakke, S.; Held, R.

    2007-12-01

    This work investigates two complex, heterogeneous sandstone lithofacies in a North Sea petroleum reservoir field. We compare samples acquired by X-ray microtomography with numerically reconstructed lithofacies, obtained from a geological process based reconstruction technique. Effective material and transport properties of these digitized rocks, such as electrical resistivity, elastic moduli, fluid permeability, and magnetic resonance (NMR), are computed. The comparison largely reveals an excellent agreement of calculated effective properties between the actual and reconstructed pore structures. A dependence of the effective properties on the specific mineralogy could be investigated in case of the reconstructed rocks. Our results allow for an interpretation of trends in effective medium properties and facilitate the construction of cross-property relations for the investigated lithofacies. The present study demonstrates the potential and feasibility of combining computer generated rocks with numerical calculations to derive material and transport properties for reservoir rocks.

  13. Oxfordian-Kimmeridgian (Late Jurassic) reservoir sandstones in the Witch Ground Graben, U. K. North Sea

    SciTech Connect

    Harker, S.D. Ltd., Aberdeen ); Mantel, K.A. ); Morton, D.J. ); Riley, L.A. )

    1991-03-01

    Oil-bearing Late Jurassic Oxfordian-Kimmeridgian sandstones of the Sgiath and Piper formations are of major economic importance in the Witch Ground Graben. They form the reservoirs in Scott, which in 1993 will be the largest producing North Sea oil field to come on stream for more than a decade. Together with Scott, the Piper, Saltire, Tartan, Highlander, Petronella, Rob Roy, and Ivanhoe fields contained almost 2 Bbbl of recoverable reserves in these formations. The Sgiath and Piper represent two phases of Late Jurassic transgression and regression, initially represented by paralic deposited sand culminating in a wave-dominated delta sequence. The history of the Sgiath and Piper formations is reviewed and lithostratigraphic and biostratigraphic correlations presented to illustrate the distribution of the reservoir sandstones.

  14. Inverted barometer contributions to recent sea level changes along the northeast coast of North America

    NASA Astrophysics Data System (ADS)

    Piecuch, Christopher G.; Ponte, Rui M.

    2015-07-01

    Regional sea level (SL) changes reflect dynamic and isostatic ocean effects. Recent works have interpreted accelerated and extreme SL changes along the northeast coast of North America primarily in terms of dynamic changes; however, dedicated study of isostatic changes related to surface atmospheric pressure loading—the inverted barometer (IB) effect—has been lacking. This investigation uses five different atmospheric pressure products to analyze the influence of the IB effect on annual mean SL from tide gauge records. The IB effect explains ˜25% of interannual SL variance and accounts for ˜50% of the magnitude of a recent extreme event of SL rise along Atlantic Canada and New England. Estimated IB effects also amount to ˜10-30% of recent multidecadal SL accelerations over the Mid-Atlantic Bight and Southern New England. These findings reiterate the need for careful estimation and removal of isostatic effects for studies of dynamic SL.

  15. Kimmeridgian Shales Total Petroleum System of the North Sea Graben Province

    USGS Publications Warehouse

    Gautier, Donald L.

    2005-01-01

    The North Sea Graben of northwestern Europe, World Energy Project Province 4025, is entirely offshore within the territorial waters of Denmark, Germany, the Netherlands, Norway, and the United Kingdom. Extensional tectonics and failed rifting are fundamental to the distribution of oil and gas in the province. Accordingly, the geologic history and reser-voir rocks of the province are considered in the context of their temporal relationship to the principal extension and rifting events. The oil and gas accumulations of the province are considered part of a single petroleum system: the Kimmeridg-ian Shales Total Petroleum System (TPS). Source rocks of the Kimmeridgian Shales TPS were deposited in Late Jurassic to earliest Cretaceous time during the period of intensive exten-sion and rifting. The Kimmeridgian Shales contain typical 'type II' mixed kerogen. Oil and gas generation began locally in the North Sea Graben Province by Cretaceous time and has continued in various places ever since. Reservoirs are found in strata with ages ranging from Devonian to Eocene. Pre-rift reservoirs are found in fault-block structures activated during rifting and can be of any age prior to the Late Jurassic. Syn-rift reservoirs are restricted to strata actually deposited during maximum extension and include rocks of Late Jurassic to earliest Cretaceous age. Post-rift reservoirs formed after rifting and range in age from Early Cretaceous to Eocene. Seals are diverse, depending upon the structural setting and reservoir age. Pre-rift reservoirs com-monly have seals formed by fine-grained, post-rift sedimentary sequences that drape the Late Jurassic to earliest Cretaceous structures. Contemporaneous shales such as the Kimmeridge Clay seal many syn-rift reservoirs. Fields with post-rift res-ervoirs generally require seals in fine-grained Tertiary rocks. In most of the North Sea Graben, source rocks have been continuously buried since deposition. Structural trap forma-tion has also taken

  16. North Sea pipeline and riser loss of containment study -- Continuing improvements

    SciTech Connect

    Al-Hassan, T.; Robertson, J.L.M.; Wickham, A.; Ellinas, C.

    1996-12-01

    The PARLOC Pipeline and Incident Databases provide the most complete information available on North Sea pipelines and risers from 1975. The database information enables the frequency of incidents which either result, or have a potential to result, in loss of containment to be related to the pipeline population as a whole or expressed as a function of particular pipeline characteristics. The importance of the PARLOC study in risk assessments of offshore pipelines is acknowledged worldwide and it is recognized as having contributed positively to their safer operation. Continuing improvements ensure that it remains a key reference in risk assessment studies. This paper describes the improvements which are being made to the study and shows how PARLOC is being used by the offshore industry in the consideration of pipeline safety. The rationalization of current arrangements for regulating pipeline safety presented in the new UK Pipeline Safety Regulations offer an important role for PARLOC regarding both offshore and onshore pipelines.

  17. Artificial neural networks for modeling time series of beach litter in the southern North Sea.

    PubMed

    Schulz, Marcus; Matthies, Michael

    2014-07-01

    In European marine waters, existing monitoring programs of beach litter need to be improved concerning litter items used as indicators of pollution levels, efficiency, and effectiveness. In order to ease and focus future monitoring of beach litter on few important litter items, feed-forward neural networks consisting of three layers were developed to relate single litter items to general categories of marine litter. The neural networks developed were applied to seven beaches in the southern North Sea and modeled time series of five general categories of marine litter, such as litter from fishing, shipping, and tourism. Results of regression analyses show that general categories were predicted significantly moderately to well. Measured and modeled data were in the same order of magnitude, and minima and maxima overlapped well. Neural networks were found to be eligible tools to deliver reliable predictions of marine litter with low computational effort and little input of information. PMID:24836642

  18. Influence of oil aromaticity on N sub 2 -flooding in North Sea fields; Preliminary thermodynamic analysis

    SciTech Connect

    de Leeuw, V.V.; Bekkering, P.E.; Runde, H.; de Loos, T.W.; de Swaan Avons, J. )

    1990-01-01

    A synthetic oil has been defined, typical for crudes found in the North Sea. It consists of 65 mole % methane, 15 mole % n-butane and 20 mole % n-tetradecane. Aromaticity has been varied by replacing n-tetradecane by n-octyl-benzene. Minimum miscibility pressures (MMP's) and vapor-liquid equilibria (VLE) of these synthetic oils have been calculated for adding nitrogen. The Peng-Robinson equation of state has been used in conjunction with binary interaction parameters, either experimentally determined or from independent correlations. It appeared that aromaticity hardly influences MMP's but that it has a significant impact on the mutual miscibility of equilibrium phases at 373.15 K and 400 bar. The MMP-calculation shows to be very sensitive to the (methane + n-octyl-benzene) interaction parameter.

  19. Intermodel variations in projected precipitation change over the North Atlantic: Sea surface temperature effect

    NASA Astrophysics Data System (ADS)

    Long, Shang-Min; Xie, Shang-Ping

    2015-05-01

    Intermodel variations in future precipitation projection in the North Atlantic are studied using 23 state-of-art models from Phase 5 of the Coupled Model Intercomparison Project. Model uncertainty in annual mean rainfall change is locally enhanced along the Gulf Stream. The moisture budget analysis reveals that much of the model uncertainty in rainfall change can be traced back to the discrepancies in surface evaporation change and transient eddy effect among models. Results of the intermodel Singular Value Decomposition (SVD) analysis show that intermodel variations in local sea surface temperature (SST) pattern exert a strong control over the spread of rainfall projection among models through the modulation of evaporation change. The first three SVD modes explain more than 60% of the intermodel variance of rainfall projection and show distinct SST patterns with mode water-induced banded structures, reduced subpolar warming due to ocean dynamical cooling, and the Gulf Stream shift, respectively.

  20. Drivers of sea-level change - using relative sea level records from the North and South Atlantic to fingerprint sources of mid-Holocene ice melt

    NASA Astrophysics Data System (ADS)

    Horton, B.; Khan, N.; Ashe, E.; Kopp, R. E.; Long, A. J.; Gehrels, W. R.

    2015-12-01

    Many factors give rise to relative sea-level (RSL) changes that are far from globally uniform. For example, spatially variable sea-level responses arise because of the exchange of mass between ice sheets and oceans. Gravitational, flexural, and rotational processes generate a distinct spatial pattern - or "fingerprint" - of sea-level change associated with each shrinking land ice mass. As a land ice mass shrinks, sea-level rise is greater in areas geographically distal to the ice mass than in areas proximal to it, in large part because the gravitational attraction between the ice mass and the ocean is reduced. Thus, the U.S. mid-Atlantic coastline experiences about 50% of the global average sea-level-rise due to Greenland Ice Sheet melt, but about 120% of the global average due to West Antarctic Ice Sheet melt. Separating the Greenland and Antarctic ice sheet contributions during the past 7,000 years requires analysis of sea-level changes from sites in the northern and southern hemisphere. Accordingly we present sea-level records within a hierarchical statistical modeling to: (1) quantify rates of change; (2) compare rates of change among sites, including full quantification of the uncertainty in their differences; and (3) test hypotheses about the sources of meltwater through their sea-level fingerprints. Preliminary analysis of three sites within our North and South Atlantic sea-level database indicates sea-level gradient in the rate of RSL rise during the mid Holocene between 6000 and 4000 years BP; a greater change in rate is found in Brazil than St Croix than New Jersey, consistent with an increase and then decrease in Greenland Ice Sheet mass.

  1. Bioaccumulation and effects of PCBs and heavy metals in sea stars (Asterias rubens, L.) from the North Sea: a small scale perspective.

    PubMed

    Danis, B; Wantier, P; Flammang, R; Pernet, Ph; Chambost-Manciet, Y; Coteur, G; Warnau, M; Dubois, Ph

    2006-03-01

    Sea stars (Asterias rubens L.) were collected in different stations distributed in the Southern Bight of the North Sea. Concentrations of four heavy metals and six PCB congeners were measured in two body compartments (body wall and pyloric caeca). In order to assess the potential harm of these contaminants, two biochemical parameters were measured in sea stars, viz. reactive oxygen species (ROS) production by amoebocytes and cytochrome P450 immunopositive protein (CYP1A IPP) induction in pyloric caeca. Sea stars from stations located in the plume of the Scheldt river showed the highest contamination levels. Other stations, similarly located, displayed lower levels. No simple relationship could be established between ROS production by sea star amoebocytes and contaminant levels measured in sea star tissues. CYP1A IPP induction displayed more contrasted responses, and highly significant regressions were found between PCB concentrations measured in pyloric caeca and CYP1A IPP. Both biological parameters were found to vary significantly over the study area. On the whole, data indicated that contamination levels and subsequent effects in sea stars were comparable to those described in previous large-scale studies, but that working at a smaller scale highlighted the existence of patterns of contamination which can blur general trends due to major contamination sources like contaminated rivers.

  2. Disentangling Middle Paleozoic sea level and tectonic events in cratonic margins and cratonic basins of North America

    NASA Astrophysics Data System (ADS)

    Bond, Gerard C.; Kominz, Michelle A.

    1991-04-01

    The cratonic margins and basins of North America contain evidence of distinct changes in relative sea level, one of the most intriguing of which occurred in middle Paleozoic time. The change in relative sea level began in Frasnian time (Late Devonian) and continued through Visean time (Middle Mississippian) in the Cordilleran miogeocline, in the Southern Oklahoma Aulacogen, in the Appalachian miogeocline and in the Michigan, Illinois, and Williston basins. The synchroneity and wide geographic distribution of this event are striking and would seem to argue for an eustatic mechanism. An estimate of the middle Paleozoic sea level rise relative to the stable craton in Iowa suggests that while a large sea level rise occurred, it is smaller than the magnitude of subsidence in the cratonic basins and margins. Flexural foreland basin models do not appear to account for the all of the events in the cratonic margins, and thermal subsidence mechanisms do not seem appropriate for the subsidence in the cratonic basins. The middle Paleozoic stratigraphic record from the North American craton and its margins, therefore, poses a basic problem of identifying a mechanism for producing a large-amplitude rise in sea level relative to the stable craton at the same time as a synchronous onset of tectonic subsidence in widespread basinal and marginal settings of diverse tectonic origin. One plausible mechanism for the tectonic subsidence in the basins and margins is a pulse of intraplate compressive stress. The origin of the large sea level rise relative to the stable craton could reflect an unusually large eustatic sea level change, but we cannot eliminate the possibility of a small component of subsidence or change in dynamic topography of the North American craton. The synchroneity of the sea level rise relative to the craton with the subsidence of basins and margins may be fortuitous, but it is also predicted by recent mantle convection models for the early stages of accretion of

  3. Basaltic magmatism in the North Sea and its relationship to lithospheric extension

    NASA Astrophysics Data System (ADS)

    Latin, Dave; Waters, Frances G.

    1992-07-01

    Mesozoic magmatism in the North Sea rift system varies from mildly to strongly alkaline in character. In the 'triple-junction', which occurs at the intersection of the Viking Graben-Moray Firth-Central Graben, large volumes of alkali basalt erupted to form the Forties volcanic province. These basalts are located in the most extended region of the rift which underwent lithospheric stretching by a factor of two. Much smaller volumes of distinctive undersaturated volatile-rich ultrapotassic and nephelinitic rocks were erupted and intruded in off-axis regions in which β is generally less than 1.2. The average thickness (~ 1 km) and composition of the Forties basalts is most easily explained in terms of mixing of melt components derived from the asthenosphere and the more easily fusible volatile-enriched parts of the continental lithosphere. Using recent work by McKenzie and O'Nions (1991) we show that asthenosphere of normal potential temperature will melt if it is brought rapidly to depths of less than 80 km. The asthenosphere rose to ~ 60 km during rifting in the Forties region of the North Sea. The thickness (0.66 km) and composition of melt produced from the asthenosphere is calculated using the results of a REE inversion scheme (McKenzie and O'Nions, 1991). The composition of the lithospheric melt component appears to be some mixture of nephelinite and ultrapotassic melt. Mixing asthenospheric and lithospheric melts in approximately equal proportions appears to be able to produce ~ 1.2 km of melt whose elemental and isotopic composition is very similar to that of the Forties basalts.

  4. Incidental catch of marine birds in the north pacific high seas driftnet fisheries in 1990

    USGS Publications Warehouse

    Johnson, D.H.; Shaffer, T.L.; Gould, P.J.

    1993-01-01

    The incidental take of marine birds was estimated for the following North Pacific driftnet fisheries in 1990: Japanese squid, Japanese large-mesh, Korean squid, and Taiwanese squid and large-mesh combined. The take was estimated by assuming that the data represented a random sample from an unstratified population of all driftnet fisheries in the North Pacific. Estimates for 13 species or species groups are presented, along with some discussion of inadequacies of the design. About 416,000 marine birds were estimated to be taken incidentally during the 1990 season; 80% of these were in the Japanese squid fishery. Sooty Shearwaters, Short-tailed Shearwaters, and Laysan Albatrosses were the most common species in the bycatch.Regression models were also developed to explore the relations between bycatch rate of three groups--Black-footed Albatross, Laysan Albatross, and 'dark' shearwaters--and various explanatory variables, such as latitude, longitude, month, vessel, sea surface temperature, and net soak time (length of time nets were in the water). This was done for only the Japanese squid fishery, for which the most complete information was available. For modelling purposes, fishing operations for each vessel were grouped into 5-degree blocks of latitude and longitude.Results of model building indicated that vessel had a significant influence on bycatch rates of all three groups. This finding emphasizes the importance of the sample of vessels being representative of the entire fleet. In addition, bycatch rates of all three groups varied spatially and temporally. Bycatch rates for Laysan Albatrosses tended to decline during the fishing season, whereas those for Black-footed Albatrosses and dark shearwaters tended to increase as the season progressed. Bycatch rates were positively related to net soak time for Laysan Albatrosses and dark shearwaters. Bycatch rates of dark shearwaters were lower for higher sea surface temperatures.

  5. Combining rock physics and sedimentology for seismic reservoir characterization of North Sea turbidite systems

    NASA Astrophysics Data System (ADS)

    Avseth, Per Age

    The petroleum industry is increasing its focus on the exploration of reservoirs in turbidite systems. However, these sedimentary environments are often characterized by very complex sand distributions. Hence, reservoir description based on conventional seismic and well-log interpretation may be very uncertain. There is a need to employ more quantitative seismic techniques to reveal reservoirs units in these complex systems from seismic amplitude data. In this study we focus on North Sea turbidite systems. Our goal is to improve the ability to use 3D seismic data to map reservoirs in these systems. A cross-disciplinary methodology for seismic reservoir characterization is presented that combines rock physics, sedimentology, and statistical techniques. We apply this methodology to two turbidite systems of Paleocene age located in the South Viking Graben of the North Sea. First, we investigate the relationship between sedimentary petrography and rock physics properties. Next, we define seismic scale sedimentary units, referred to as seismic lithofacies. These facies represent populations of data that have characteristic geologic and seismic properties. We establish a statistically representative training database by identifying seismic lithofacies from thin-sections, cores, and well-log data. This procedure is guided by diagnostic rock physics modeling. Based on the training data, we perform multivariate classification of data from several wells in the area. Next, we assess uncertainties in amplitude versus offset (AVO) response related to the inherent natural variability of each seismic lithofacies. We generate bivariate probability density functions (pdfs) of two AVO parameters for different facies combinations. By combining the bivariate pdfs estimated from well-logs with the AVO parameters estimated from seismic data, we use both quadratic discriminant analysis and Bayesian classification to predict lithofacies and pore fluids from seismic amplitudes. The final

  6. Biogeochemical processes and microbial diversity of the Gullfaks and Tommeliten methane seeps (Northern North Sea)

    NASA Astrophysics Data System (ADS)

    Wegener, G.; Shovitri, M.; Knittel, K.; Niemann, H.; Hovland, M.; Boetius, A.

    2008-02-01

    Fluid-flow related seafloor structures and gas seeps were detected in the North Sea in the 1970s and 1980s by acoustic sub-bottom profiling and oil rig surveys. A variety of features like pockmarks, gas vents and authigenic carbonate cements were found to be associated with sites of oil and gas exploration, indicating a link between these surface structures and underlying deep hydrocarbon reservoirs. In this study we performed acoustic surveys and videographic observation at Gullfaks, Holene Trench, Tommeliten, Witch's Hole and the giant pockmarks of the UK Block 15/25, to investigate the occurrence and distribution of cold seep ecosystems in the Northern North Sea. The most active gas seep sites, i.e. Gullfaks and Tommeliten, were investigated in detail: at both sites gas bubbles escaped continuously from small holes in the seabed to the water column, reaching the upper mixed surface layer as indicated by acoustic images of the gas flares. At Gullfaks a 0.1 km2 large gas emission site was detected on a flat sandy seabed, covered by filamentous sulfide-oxidizing bacteria. At Tommeliten we found a patchy distribution of small bacterial mats indicating sites of gas seepage. Here the seafloor consists of layers of sand and stiff clay, and gas emission was observed from small cracks in the seafloor. At both sites the anaerobic oxidation of methane (AOM) coupled to sulfate reduction is the major source of sulfide. Molecular analyses targeting specific lipid biomarkers and 16 S rRNA gene sequences identified an active microbial community dominated by sulfide-oxidizing and sulfate-reducing bacteria (SRB) as well as methanotrophic bacteria and archaea. Carbon isotope values of specific microbial fatty acids and alcohols were highly depleted, indicating that the microbial community at both gas seeps incorporates methane or its metabolites. The microbial community composition of both shallow seeps show high similarities to the deep water seeps associated with gas hydrates

  7. Biogeochemical processes and microbial diversity of the Gullfaks and Tommeliten methane seeps (Northern North Sea)

    NASA Astrophysics Data System (ADS)

    Wegener, G.; Shovitri, M.; Knittel, K.; Niemann, H.; Hovland, M.; Boetius, A.

    2008-08-01

    Fluid flow related seafloor structures and gas seeps were detected in the North Sea in the 1970s and 1980s by acoustic sub-bottom profiling and oil rig surveys. A variety of features like pockmarks, gas vents and authigenic carbonate cements were found to be associated with sites of oil and gas exploration, indicating a link between these surface structures and the underlying, deep hydrocarbon reservoirs. In this study we performed acoustic surveys and videographic observation at Gullfaks, Holene Trench, Tommeliten, Witch's Hole and the giant pockmarks of the UK Block 15/25, to investigate the occurrence and distribution of cold seep ecosystems in the Northern North Sea. The most active gas seep sites, i.e. Gullfaks and Tommeliten, were investigated in detail. At both sites, gas bubbles escaped continuously from small holes in the seabed to the water column, reaching the upper mixed surface layer. At Gullfaks a gas emitting, flat area of 0.1 km2 of sandy seabed covered by filamentous sulfur-oxidizing bacteria was detected. At Tommeliten, we found a patchy distribution of small bacterial mats indicating sites of gas seepage. Below the patches the seafloor consisted of sand from which gas emissions were observed. At both sites, the anaerobic oxidation of methane (AOM) coupled to sulfate reduction (SR) was the major source of sulfide. Molecular analyses targeting specific lipid biomarkers and 16S rRNA gene sequences identified an active microbial community dominated by sulfur-oxidizing and sulfate-reducing bacteria (SRB) as well as methanotrophic bacteria and archaea. Stable carbon isotope values of specific, microbial fatty acids and alcohols from both sites were highly depleted in the heavy isotope 13C, indicating that the microbial community incorporates methane or its metabolites. The microbial community composition of both shallow seeps shows high similarities to the deep water seeps associated with gas hydrates such as Hydrate Ridge or the Eel River basin.

  8. Sedimentation history of the northern North Sea Margin during the last 150 ka

    NASA Astrophysics Data System (ADS)

    Lekens, W. A. H.; Haflidason, H.; Sejrup, H. P.; Nygard, A.; Richter, T.; Vogt, C.; Frederichs, T.

    2009-03-01

    The Norwegian Channel Ice Stream (NCIS) is one the defining features of the Fennoscandian icesheet. Still little is known of the detailed dynamics of this ice stream in relation to regional changes in ice cover, paleoceanographic and climatic changes. Sedimentological data from core MD99-2283 in combination with seismic data allow a detailed chronological reconstruction of the outbuilding of the margin and the ice extent in southern Scandinavia through the last 150 ka. An integrated stratigraphy of the margin is presented and compared to the glacial history. Changes in the regional ice cover are reflected in the accumulation rates, the clay mineralogy, the coarse chalk fraction and the number of IRD >2 mm in core MD99-2283, while the sedimentation on the North Sea Fan as derived from seismic data provides direct evidence for the glacial activity at the shelf edge. Tentative evidence was found for two Early Weichselian glacial advances in southern Scandinavia and possibly Scotland at around 110 and 80 ka BP. From 42 cal ka BP the ice cover expanded in southern Fennoscandia and led to increased deposition on the margin and the occurrence of local melt water outbursts. Significantly increased accumulation rates, coarse chalk, local meltwater output and smectite occur during the ice expansion in the North Sea from around 34 cal ka BP. The main outbuilding phase of the NSF during the last glacial cycle occurred after 30 cal ka BP. From around 24 cal ka BP the NCIS became highly active and advanced at least three times prior to the final retreat from the shelf edge around 19.0 cal ka BP.

  9. Diversity and seasonality of Pseudo- nitzschia (Peragallo) at two North Sea time-series monitoring sites

    NASA Astrophysics Data System (ADS)

    Bresnan, Eileen; Kraberg, Alexandra; Fraser, Sheila; Brown, Lyndsay; Hughes, Sarah; Wiltshire, Karen H.

    2015-06-01

    Species within the diatom genus Pseudo- nitzschia (Peragallo) have been identified as producers of domoic acid, the toxin responsible for amnesic shellfish poisoning. Toxin- and non-toxin-producing species of Pseudo- nitzschia have been reported globally; however, as Pseudo- nitzschia species cannot be routinely identified to species level using light microscopy, cells are rarely recorded to species level during long-term monitoring studies. Here, we report the results of a comparative survey of Pseudo- nitzschia species at two monitoring sites in the North Sea: Stonehaven on the east coast of Scotland and Helgoland Roads in the German Bight. A difference in the seasonality of this genus was observed between the sites with Pseudo- nitzschia cells playing a major role in the spring bloom as well at the summer and autumn diatom community at Stonehaven. In contrast, Pseudo- nitzschia was abundant only during the summer months at Helgoland. Pseudo- nitzschia cells constitute a higher proportion of the diatom community at Stonehaven than at Helgoland, particularly during the late summer, autumn and winter and thus may be considered more `ecologically important' at this site. A total of eight different species were recorded during this survey with five Pseudo- nitzschia species observed at the Helgoland site: P. pungens, P. fraudulenta, P. americana, P. cf. delicatissima and the potentially toxic species P. multiseries. Six species were also recorded at Stonehaven; P. australis, P cf. delicatissima, P. pungens, P. cf. pseudodelicatissima, P. subpacifica and P. seriata. This study represents the first examination of the seasonality of Pseudo-nitzschia species around Helgoland and the first comparison between two long-term monitoring sites in the North Sea. P. americana and P. multiseries are also recorded at the Helgoland Roads time-series site for the first time.

  10. Ecoregional Analysis of Nearshore Sea-Surface Temperature in the North Pacific

    PubMed Central

    Payne, Meredith C.; Brown, Cheryl A.; Reusser, Deborah A.; Lee, Henry

    2012-01-01

    The quantification and description of sea surface temperature (SST) is critically important because it can influence the distribution, migration, and invasion of marine species; furthermore, SSTs are expected to be affected by climate change. To better understand present temperature regimes, we assembled a 29-year nearshore time series of mean monthly SSTs along the North Pacific coastline using remotely-sensed satellite data collected with the Advanced Very High Resolution Radiometer (AVHRR) instrument. We then used the dataset to describe nearshore (<20 km offshore) SST patterns of 16 North Pacific ecoregions delineated by the Marine Ecoregions of the World (MEOW) hierarchical schema. Annual mean temperature varied from 3.8°C along the Kamchatka ecoregion to 24.8°C in the Cortezian ecoregion. There are smaller annual ranges and less variability in SST in the Northeast Pacific relative to the Northwest Pacific. Within the 16 ecoregions, 31–94% of the variance in SST is explained by the annual cycle, with the annual cycle explaining the least variation in the Northern California ecoregion and the most variation in the Yellow Sea ecoregion. Clustering on mean monthly SSTs of each ecoregion showed a clear break between the ecoregions within the Warm and Cold Temperate provinces of the MEOW schema, though several of the ecoregions contained within the provinces did not show a significant difference in mean seasonal temperature patterns. Comparison of these temperature patterns shared some similarities and differences with previous biogeographic classifications and the Large Marine Ecosystems (LMEs). Finally, we provide a web link to the processed data for use by other researchers. PMID:22253893

  11. Exchanges between the open Black Sea and its North West shelf

    NASA Astrophysics Data System (ADS)

    Shapiro, Georgy; Wobus, Fred; Zhou, Feng

    2014-05-01

    Exchanges between the vast NW shelf and the deep basin of the Black Sea play a significant role in maintaining the balance of nutrients, heat content and salinity of the shelf waters. Nearly 87 % of the Black Sea is entirely anoxic below 70 to 200m and contains high levels of hydrogen sulphide (Zaitsev et al, 2001), and this makes the shelf waters particularly valuable for maintaining the Black Sea ecosystem in good health. The increase in salinity of shelf waters occurs partially due to exchanges with more saline open sea waters and represents a threat to relics and endemic species. The shelf-break is commonly considered the bottle-neck of the shelf-deep sea exchanges (e.g. (Huthnance, 1995, Ivanov et al, 1997). Due to conservation of potential vorticity, the geostrophic currents flow along the contours of constant depth. However the ageostrophic flows (Ekman drift, mesoscale eddies, filaments, internal waves) are not subject to the same constraints. It has been shown that during the winter well mixed cold waters formed on the North West shelf propagate into the deep sea, providing an important mechanism for the replenishment of the Cold Intermediate Layer ( Staneva and Stanev, 1997). However, much less is known about exchanges in the warm season. In this study, the transports of water, heat and salt between the northwestern shelf and the adjacent deep basin of the Black Sea are investigated using a high-resolution three-dimensional primitive equation model, NEMO-SHELF-BLS (Shapiro et al, 2013). It is shown that during the period from April to August, 2005, both onshore and offshore cross-shelf break transports in the top 20 m were as high as 0.24 Sv on average, which was equivalent to the replacement of 60% of the volume of surface shelf waters (0 - 20 m) per month. Two main exchange mechanisms are studied: (i) Ekman transport, and (ii) transport by mesoscale eddies and associated meanders of the Rim Current. The Ekman drift causes nearly uniform onshore or

  12. An Evaluation of the Use by Teachers of British Petroleum's Multi-Media Resource Pack, A North Sea Adventure.

    ERIC Educational Resources Information Center

    Scott, Jean; Lloyd, Gerald

    Presented is an evaluation of a multi-media resource pack, available from British Petroleum Corporation, which details the discovery and extraction of North Sea oil. The evaluation presented includes three thrusts: (1) a determination of the areas where the packs were distributed; (2) personal interviews with teachers who had used the packs; and…

  13. Stratified and nonstratified areas in the North Sea: Long-term variability and biological and policy implications

    NASA Astrophysics Data System (ADS)

    van Leeuwen, Sonja; Tett, Paul; Mills, David; van der Molen, Johan

    2015-07-01

    The European Unions' Marine Strategy Framework Directive aims to limit anthropogenic influences in the marine environment. But marine ecosystems are characterized by high variability, and it is not trivial to define its natural state. Here, we use the physical environment as a basis for marine classification, as it determines the conditions in which organisms must operate to survive and thrive locally. We present a delineation of the North Sea into five distinct regimes, based on multidecadal stratification characteristics. Results are based on a 51 year simulation of the region using the coupled hydrobiogeochemical model GETM-ERSEM-BFM. The five identified regimes are: permanently stratified, seasonally stratified, intermittently stratified, permanently mixed, and Region Of Freshwater Influence (ROFI). The areas characterized by these regimes show some interannual variation in geographical coverage, but are overall remarkable stable features within the North Sea. Results also show that 29% of North Sea waters fail to classify as one of the defined stratification regimes, due to high interannual variability. Biological characteristics of these regimes differ from diatom-based food webs in areas with prolonged stratification to Phaeocystis-dominated food webs in areas experiencing short-lived or no stratification. The spatial stability of the identified regimes indicates that carefully selected monitoring locations can be used to represent a substantive area of the North Sea.

  14. The impact of sedimentary alkalinity release on the water column CO2 system in the North Sea

    NASA Astrophysics Data System (ADS)

    Brenner, H.; Braeckman, U.; Le Guitton, M.; Meysman, F. J. R.

    2016-02-01

    It has been previously proposed that alkalinity release from sediments can play an important role in the carbonate dynamics on continental shelves, lowering the pCO2 of seawater and hence increasing the CO2 uptake from the atmosphere. To test this hypothesis, sedimentary alkalinity generation was quantified within cohesive and permeable sediments across the North Sea during two cruises in September 2011 (basin-wide) and June 2012 (Dutch coastal zone). Benthic fluxes of oxygen (O2), alkalinity (AT) and dissolved inorganic carbon (DIC) were determined using shipboard closed sediment incubations. Our results show that sediments can form an important source of alkalinity for the overlying water, particularly in the shallow southern North Sea, where high AT and DIC fluxes were recorded in near-shore sediments of the Belgian, Dutch and German coastal zone. In contrast, fluxes of AT and DIC are substantially lower in the deeper, seasonally stratified, northern part of the North Sea. Based on the data collected, we performed a model analysis to constrain the main pathways of alkalinity generation in the sediment, and to quantify how sedimentary alkalinity drives atmospheric CO2 uptake in the southern North Sea. Overall, our results show that sedimentary alkalinity generation should be regarded as a key component in the CO2 dynamics of shallow coastal systems.

  15. Reprint of: The ecophysiology of Sprattus sprattus in the Baltic and North Seas

    NASA Astrophysics Data System (ADS)

    Peck, Myron A.; Baumann, Hannes; Bernreuther, Matthias; Clemmesen, Catriona; Herrmann, Jens-Peter; Haslob, Holger; Huwer, Bastian; Kanstinger, Philipp; Köster, Fritz W.; Petereit, Christoph; Temming, Axel; Voss, Rudi

    2012-12-01

    The European sprat (Sprattus sprattus) was a main target species of the German GLOBEC program that investigated the trophodynamic structure and function of the Baltic and North Seas under the influence of physical forcing. This review summarizes literature on the ecophysiology of sprat with an emphasis on describing how environmental factors influence the life-history strategy of this small pelagic fish. Ontogenetic changes in feeding and growth, and the impacts of abiotic and biotic factors on vital rates are discussed with particular emphasis on the role of temperature as a constraint to life-history scheduling of this species in the Baltic Sea. A combination of field and laboratory data suggests that optimal thermal windows for growth and survival change during early life and are wider for eggs (5-17 °C) than in young (8- to 12-mm) early feeding larvae (5-12 °C). As larvae become able to successfully capture larger prey, thermal windows expand to include warmer waters. For example, 12- to 16-mm larvae can grow well at 16 °C and larger, transitional-larvae and early juveniles display the highest rates of feeding and growth at ∼18-22 °C. Gaps in knowledge are identified including the need for additional laboratory studies on the physiology and behavior of larvae (studies that will be particularly critical for biophysical modeling activities) and research addressing the role of overwinter survival as a factor shaping phenology and setting limits on the productivity of this species in areas located at the northern limits of its latitudinal range (such as the Baltic Sea). Based on stage- and temperature-specific mortality and growth potential of early life stages, our analysis suggests that young-of-the year sprat would benefit from inhabiting warmer, near-shore environments rather than the deeper-water spawning grounds such as the Bornholm Basin (central Baltic Sea). Utilization of warmer, nearshore waters (or a general increase in Baltic Sea temperatures) is

  16. The ecophysiology of Sprattus sprattus in the Baltic and North Seas

    NASA Astrophysics Data System (ADS)

    Peck, Myron A.; Baumann, Hannes; Bernreuther, Matthias; Clemmesen, Catriona; Herrmann, Jens-Peter; Haslob, Holger; Huwer, Bastian; Kanstinger, Philipp; Köster, Fritz W.; Petereit, Christoph; Temming, Axel; Voss, Rudi

    2012-09-01

    The European sprat (Sprattus sprattus) was a main target species of the German GLOBEC program that investigated the trophodynamic structure and function of the Baltic and North Seas under the influence of physical forcing. This review summarizes literature on the ecophysiology of sprat with an emphasis on describing how environmental factors influence the life-history strategy of this small pelagic fish. Ontogenetic changes in feeding and growth, and the impacts of abiotic and biotic factors on vital rates are discussed with particular emphasis on the role of temperature as a constraint to life-history scheduling of this species in the Baltic Sea. A combination of field and laboratory data suggests that optimal thermal windows for growth and survival change during early life and are wider for eggs (5-17 °C) than in young (8- to 12-mm) early feeding larvae (5-12 °C). As larvae become able to successfully capture larger prey, thermal windows expand to include warmer waters. For example, 12- to 16-mm larvae can grow well at 16 °C and larger, transitional-larvae and early juveniles display the highest rates of feeding and growth at ∼18-22 °C. Gaps in knowledge are identified including the need for additional laboratory studies on the physiology and behavior of larvae (studies that will be particularly critical for biophysical modeling activities) and research addressing the role of overwinter survival as a factor shaping phenology and setting limits on the productivity of this species in areas located at the northern limits of its latitudinal range (such as the Baltic Sea). Based on stage- and temperature-specific mortality and growth potential of early life stages, our analysis suggests that young-of-the year sprat would benefit from inhabiting warmer, near-shore environments rather than the deeper-water spawning grounds such as the Bornholm Basin (central Baltic Sea). Utilization of warmer, nearshore waters (or a general increase in Baltic Sea temperatures) is

  17. Summertime atmosphere-ocean preconditionings for the Bering Sea ice retreat and the following severe winters in the North America

    NASA Astrophysics Data System (ADS)

    Nakanowatari, T.; Inoue, J.; Sato, K.; Kikuchi, T.

    2015-12-01

    Atmospheric responses to sea ice retreat in the Bering Sea have been linked to recent extreme winters in North America. We investigate the leading factor for the interannual variability of Bering sea ice concentration (SIC) in early winter (November-December), using canonical correlation analysis based on seasonally resolved atmosphere and ocean data for 1980-2014. We found that the 3-month leading (August-September) geopotential height at 500 hPa (Z500) in the Northern Hemisphere explains 29% of SIC variability. The spatial pattern of Z500 for positive sea ice anomalies is associated with negative anomalies over the Gulf of Alaska related to the Pacific Transition (PT) pattern. The heat budget analysis indicates that summertime atmospheric conditions influence SIC through the ocean temperature anomalies of the Alaskan Coastal Current forced by atmospheric turbulent heat fluxes. The PT pattern highly correlates with convective precipitation in the western subtropical Pacific, implying that tropical forcing is the likely cause for the recent extreme winters in North America. Our results present a major factor for interannual variability in the Bering Sea ice area, and further would contribute to the improvement of forecast skill for winter climate in North America.

  18. Deformation bands in chalk, examples from the Shetland Group of the Oseberg Field, North Sea, Norway

    NASA Astrophysics Data System (ADS)

    Wennberg, Ole Petter; Casini, Giulio; Jahanpanah, Ali; Lapponi, Fabio; Ineson, Jon; Wall, Brita Graham; Gillespie, Paul

    2013-11-01

    Deformation bands are described in detail for the first time in carbonate rock from the subsurface and in chalk from the North Sea. The samples are from 2200 to 2300 m below sea level, in upper Maastrichtian to Danian chalk in the Oseberg Field. The deformation bands were investigated using thin-section analysis, SEM and computed tomography (CT). There is a reduction in porosity from 30 to 40% in the matrix to ca. 10% or less inside the deformation bands. They have apparent thicknesses ranging from less than 0.05-0.5 mm and have previously often been referred to as hairline fractures. Their narrowness is probably the reason why these features have not previously been recognised as deformation bands. The deformation bands in chalk are very thin compared to deformation bands in sandstone and carbonate grainstones which have mm to cm widths. This is suggested to be due to the fine grain size of the chalk matrix (2-10 μm), and it appears to be a positive correlation between grain-size and width of deformation bands. The deformation bands are suggested to have been formed as compactional shear bands during mechanical compaction, and also related to faulting.

  19. Benthos and demersal fish habitats in the German Exclusive Economic Zone (EEZ) of the North Sea

    NASA Astrophysics Data System (ADS)

    Neumann, Hermann; Reiss, Henning; Ehrich, Siegfried; Sell, Anne; Panten, Kay; Kloppmann, Matthias; Wilhelms, Ingo; Kröncke, Ingrid

    2013-09-01

    We compiled data from different monitoring surveys to analyse and compare community and diversity patterns of fish, epi- and infauna in the German Exclusive Economic Zone (EEZ) of the North Sea in order to identify benthic habitats common to all faunal components. We found congruent community patterns of fish, epi- and infauna for the coastal waters, the Oysterground and the area called "Duck's Bill", which coincided with specific abiotic characteristics of these regions. The three regions were defined as special habitats for fish, epi- and infauna species in the German EEZ. The differences in the seasonal variability of abiotic factors seem to be the most important discriminating abiotic characteristic for the three habitats. The spatial distribution of fish, epifauna and infauna communities remained stable over time although habitat characteristics such as sea surface temperature increased due to climate change. However, it is expected that the coastal habitat will be more sensitive to future climate change effects in contrast to the Oysterground and Duck's Bill habitat.

  20. Sea cliff erosion in the eastern part of the North Aegean coastline, Northern Greece.

    PubMed

    Xeidakis, George S; Delimani, P K; Skias, S G

    2006-01-01

    The coastal zone is an area where many human activities are taking place. Erosion of the coast obstructs, in various ways, these activities creating occasionally serious socioeconomic and environmental problems. In this paper the coastal erosion problems encountered in the eastern Greek part of the North Aegean Sea Coast, a stretch of about 51 km long adjacent to the city of Alexandroupolis, are discussed. Given the observed type and location of erosion and other sea-action phenomena, the coast under study is divided in two parts/stretches. The western stretch, where the city of Alexandroupolis is presently extending, presents, mainly, cliff erosion problems and retreat of the coastline, very serious in some sections; whereas, the eastern stretch (to the east of the city) exhibits deposition and progression seawards due to the abundance of sediments supplied by Evros river delta. A classification of the coastline according to its relief, geologic material, erosion characteristics and rate, slope failure phenomena as well as the wave energy potential, is presented together with suggestions for case-appropriate mitigation and protection measures regarding the coastal erosion problems. The paper is focusing on the cliff erosion phenomena, since varying in height coastal cliffs made of soft rocks, cover the major part of the investigated coastline (western stretch).

  1. Wind waves simulation in the north area of the South China Sea

    NASA Astrophysics Data System (ADS)

    Wang, Wenzhi; Chen, Junchang; Li, Manqiu; Li, Yuxiang; Li, Zhiwei

    1992-06-01

    A third generation wave model was developed to simulate wind waves in the South China Sea near Hong Kong. The model solves the energy conservation equation of the two dimensional wave spectrum by directly computing the nonlinear energy interaction among waves of different frequencies, thus avoiding the imposition of restrictions on the shape of the predicted spectra. The use of an upwind difference scheme in the advective terms produces an artificial diffusion which partly compensates the dispersive effect due to the phase velocity differences among various wave components. The use of a semi-implicit scheme for the source terms together with a special treatment of the high frequency tail of the spectrum allows a large time integration step. Verification of the model was done for wave hindcasting studies under conditions of two typhoons and two cold fronts in the north part of the South China Sea near Hong Kong. The model results agree well with the field measurements except that the presence of a distant swell could not be accounted for, and indicate that an accurate modelling of the wind field is essential.

  2. The Body Size-Dependent Diet Composition of North American Sea Ducks in Winter

    PubMed Central

    Ouellet, Jean-François; Vanpé, Cécile; Guillemette, Magella

    2013-01-01

    Daily food requirements scale with body mass and activity in animals. While small species of birds have higher mass-specific field metabolic rates than larger species, larger species have higher absolute energy costs. Under energy balance, we thus expect the small species to have a higher energy value diet. Also the weight and time constraints for flighted and diurnal foragers should set a maximum to the amount of prey items taken in one meal and to the daily number of meals, respectively. Further, avoidance of competition causes the species to reduce the amount of shared prey in their diet. Some diet segregation is therefore to be expected between species. We tested these hypotheses and investigated the role of body mass in the diet composition of 12 sea duck species (Somateria mollissima, Somateria spectabilis, Somateria fischeri, Polysticta stelleri, Bucephala clangula, Bucephala islandica, Bucephala albeola, Melanitta nigra, Melanitta perspicillata, Melanitta deglandi, Histrionicus histrionicus and Clangula hyemalis) wintering in North America. This study was based on a literature survey with special emphasis given to the diet data from the former US Bureau of Biological Survey. The data supported our hypothesis that the energy value of winter diet of sea ducks scales negatively with body mass. Diet diversity also scaled negatively with body mass. Our results suggest the existence of a minimum for the energy value of avian diets. PMID:23755266

  3. Fiber optic well monitoring for Shell`s North Sea field

    SciTech Connect

    1995-12-01

    After eight years of development work, Alcatel Kabel Norge has reached an agreement with Shell U.K. Exploration and Production to install Alcatel`s first commercial Sub-Sea Fiber Optic Well Monitoring (FOWM) system in Shell`s Guillemot A-OP2 well on its completion in August 1996. The FOWM project was started in 1988 by Norske Shell and Alcatel. BP Norway joined the project in 1991, and additional support has been contributed by Norsk Hydro and the Norwegian Research Council. The first Alcatel FOWM system was installed in onshore gas Well 7 in NAM`s Sleen field in the Netherlands in October 1993. The final offshore test took place in late 1994, in BP Norway`s Well 2/1 A-32 in Gyda field, in the Norwegian North Sea. FOWM is a new type of permanently installed downhole monitoring system based on an optical sensor system integrating simple passive silicon resonator sensors with optical communication. The system tolerates high pressure and high temperatures (HPHT). Main elements that contribute to its high reliability are discussed.

  4. The Spatial and Temporal Variability of Sea Level Change along the North American East Coast

    NASA Astrophysics Data System (ADS)

    Davis, J. L.; Han, D.; Oh, B.; Chen, C.

    2014-12-01

    Understanding the nature of sea-level change (SLC) is of paramount importance to, and a significant aspect of the future well being of, coastal towns and ecosystems. The east coast of North America is particularly susceptible to the impacts of SLC because its high economic productivity and population density compound the possible damage that could occur to the region. Moreover, predictions regarding the near-term and long-term future effects of SLC in this region are inconclusive because there is uncertainty regarding its long-term causes. As a result, the findings of a study of the various components of sea-level change on the U.S. East Coast will be presented. A model for SLC on the East Coast will be developed consisting of SLC due to thermosteric changes, glacial isostatic adjustment, and gravitationally self-consistent calculations for SLC due to present-day melting from Greenland and other areas from GRACE data. Tide gauges along the coast will be used to provide observational constraints on SLC. The models will include scenarios for the time-dependence of SLC. The comparison between data and models will be used to assess the current level of understanding of SLC in this region on a wide range of timescales.

  5. Mya arenaria — an ancient invader of the North Sea coast

    NASA Astrophysics Data System (ADS)

    Strasser, Matthias

    1998-09-01

    Mya arenaria currently occupies a wide geographical range in the northern hemisphere, on both coasts of the Atlantic as well as on the Pacific east coast. Some authors claim it also occurs on the Pacific west coast. The species originated in the Pacific during the Miocene and was already present on both Atlantic coasts in the Pliocene. However, it died out on the east coasts of the Pacific and the Atlantic during glaciation of the Pleistocene. With the aid of man it was reintroduced to the North Sea some 400-700 years ago and to the East Pacific last century. In the 1960s it was also introduced to the Black Sea. M. arenaria invaded new habitats by different modes: (1) natural range expansion (2) intentional as plantings, (3) unintentional as a ballast species and (4) unintentional as a byproduct of oyster transplants. Properties that may favor its wide range of distribution and invading success are: high fecundity; planktonic dispersal stages and life stages that lend itself to unintentional transport by humans; a broad spectrum of habitat and food preference; tolerance of a wide range of environmental conditions such as salinity and temperature; longevity, and perhaps relatively large size.

  6. Northern North Atlantic Sea Surface Height and Ocean Heat Content Variability

    NASA Technical Reports Server (NTRS)

    Hakkinen, Sirpa; Rhines, Peter; Worthen, Denise L.

    2013-01-01

    The evolution of nearly 20 years of altimetric sea surface height (SSH) is investigated to understand its association with decadal to multidecadal variability of the North Atlantic heat content. Altimetric SSH is dominated by an increase of about 14 cm in the Labrador and Irminger seas from 1993 to 2011, while the opposite has occurred over the Gulf Stream region over the same time period. During the altimeter period the observed 0-700 m ocean heat content (OHC) in the subpolar gyre mirrors the increased SSH by its dominantly positive trend. Over a longer period, 1955-2011, fluctuations in the subpolar OHC reflect Atlantic multidecadal variability (AMV) and can be attributed to advection driven by the wind stress ''gyre mode'' bringing more subtropical waters into the subpolar gyre. The extended subpolar warming evident in SSH and OHC during the altimeter period represents transition of the AMV from cold to warm phase. In addition to the dominant trend, the first empirical orthogonal function SSH time series shows an abrupt change 2009-2010 reaching a new minimum in 2010. The change coincides with the change in the meridional overturning circulation at 26.5N as observed by the RAPID (Rapid Climate Change) project, and with extreme behavior of the wind stress gyre mode and of atmospheric blocking. While the general relationship between northern warming and Atlantic meridional overturning circulation (AMOC) volume transport remains undetermined, the meridional heat and salt transport carried by AMOC's arteries are rich with decade-to-century timescale variability.

  7. Holocene climate variability in the North-Western Mediterranean Sea (Gulf of Lions)

    NASA Astrophysics Data System (ADS)

    Jalali, B.; Sicre, M.-A.; Bassetti, M.-A.; Kallel, N.

    2016-01-01

    Sea surface temperatures (SSTs) and land-derived input time series were generated from the Gulf of Lions inner-shelf sediments (NW Mediterranean Sea) using alkenones and high-molecular-weight odd-carbon numbered n-alkanes (TERR-alkanes), respectively. The SST record depicts three main phases: a warm Early Holocene ( ˜ 18 ± 0.4 °C) followed by a cooling of ˜ 3 °C between 7000 and 1000 BP, and rapid warming from ˜ 1850 AD onwards. Several superimposed multi-decadal to centennial-scale cold events of ˜ 1 °C amplitude were also identified. TERR-alkanes were quantified in the same sedimentary horizons to identify periods of high Rhone River discharge and compare them with regional flood reconstructions. Concentrations show a broad increase from the Early Holocene towards the present with a pronounced minimum around 2500 BP and large fluctuations during the Late Holocene. Comparison with Holocene flood activity reconstructions across the Alps region suggests that sediments of the inner shelf originate mainly from the Upper Rhone River catchment basin and that they are primarily delivered during positive North Atlantic Oscillation (NAO).

  8. Future increase in harmful algal blooms in the North Sea due to climate change.

    PubMed

    Peperzak, L

    2005-01-01

    In temperate seas such as the North Sea harmful (toxic) algal blooms will probably increase as a result of climate change. This conclusion was reached after investigating the projected effect of climate change for the year 2100 in Dutch coastal waters (4 degrees C temperature rise and increased water column stratification) on the growth rates of six harmful and two non-harmful phytoplankton species. Micro algae form the basis of the marine food chain. However, toxin-producing species may seriously disrupt the food web and lead to fish kills and human intoxication. Two species with estimated doubled growth rates in 2100, F. japonica and C. antiqua, entered Europe via ship's ballast water or shellfish imports. This stresses the need to legally regulate such invasion routes in order to prevent the import of novel species. Future toxic phytoplankton blooms may further devaluate ecosystem deliverables such as fish production or recreational use. This devaluation can be estimated by monetary value assessments that are needed in cost-benefit analyses for policy guidance. The lack of understanding of future climate, ecosystem functioning and its response to climate change calls for a scientific effort to improve our knowledge on present day coastal ecosystem functioning and its resilience. PMID:15918356

  9. Experimental sea slicks: Their practical applications and utilization for basic studies of air-sea interactions

    NASA Astrophysics Data System (ADS)

    Hühnerfuss, Heinrich; Garrett, W. D.

    1981-01-01

    Practical applications of organic surface films added to the sea surface date back to ancient times. Aristotle, Plutarch, and Pliny the Elder describe the seaman's practice of calming waves in a storm by pouring oil onto the sea [Scott, 1977]. It was also noted that divers released oil beneath the water surface so that it could rise and spread over the sea surface, thereby suppressing the irritating flicker associated with the passage of light through a rippled surface. From a scientific point of view, Benjamin Franklin was the first to perform experiments with oils on natural waters. His experiment with a `teaspoonful of oil' on Clapham pond in 1773 inspired many investigators to consider sea surface phenomena or to conduct experiments with oil films. This early research has been reviewed by Giles [1969], Giles and Forrester [1970], and Scott [1977]. Franklin's studies with experimental slicks can be regarded as the beginning of surface film chemistry. His speculations on the wave damping influence of oil induced him to perform the first qualitative experiment with artificial sea slicks at Portsmouth (England) in October of 1773. Although the sea was calmed and very few white caps appeared in the oil-covered area, the swell continued through the oiled area to Franklin's great disappointment.

  10. An overview of chemosynthetic symbioses in bivalves from the North Atlantic and Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Duperron, S.; Gaudron, S. M.; Rodrigues, C. F.; Cunha, M. R.; Decker, C.; Olu, K.

    2012-11-01

    Deep-sea bivalves found at hydrothermal vents, cold seeps and organic falls are sustained by chemosynthetic bacteria which ensure part or all of their carbon nutrition. These symbioses are of prime importance for the functioning of the ecosystems. Similar symbioses occur in other bivalve species living in shallow and coastal reduced habitats worldwide. In recent years, several deep-sea species have been investigated from continental margins around Europe, West Africa, East America, the Gulf of Mexico, and from hydrothermal vents on the Mid-Atlantic Ridge. In parallel, numerous more easily accessible shallow marine species were studied. We here provide a summary of the current knowledge available on chemosymbiotic bivalves in the area ranging west-to-east from the Gulf of Mexico to Marmara Sea, and north-to-south from the Arctic to the Gulf of Guinea. Characteristics of symbioses in 51 species from the area are summarized for each of the five bivalve families documented to harbor chemosynthetic symbionts (Mytilidae, Vesicomyidae, Solemyidae, Thyasiridae and Lucinidae), and compared among families with special emphasis on ecology, life cycle, and connectivity. Chemosynthetic symbioses are a major adaptation to ecosystems and habitats exposed to reducing conditions, yet relatively little is known regarding their diversity and functioning apart from a few "model species" on which effort has focused over the last 30 yr. In the context of increasing concern about biodiversity and ecosystems, and increasing anthropogenic pressure on Oceans, we advocate for a better assessment of bivalve symbioses diversity in order to evaluate the capacities of these remarkable ecological and evolutionary units to withstand environmental change

  11. An overview of chemosynthetic symbioses in bivalves from the North Atlantic and Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Duperron, S.; Gaudron, S. M.; Rodrigues, C. F.; Cunha, M. R.; Decker, C.; Olu, K.

    2013-05-01

    Deep-sea bivalves found at hydrothermal vents, cold seeps and organic falls are sustained by chemosynthetic bacteria that ensure part or all of their carbon nutrition. These symbioses are of prime importance for the functioning of the ecosystems. Similar symbioses occur in other bivalve species living in shallow and coastal reduced habitats worldwide. In recent years, several deep-sea species have been investigated from continental margins around Europe, West Africa, eastern Americas, the Gulf of Mexico, and from hydrothermal vents on the Mid-Atlantic Ridge. In parallel, numerous, more easily accessible shallow marine species have been studied. Herein we provide a summary of the current knowledge available on chemosymbiotic bivalves in the area ranging west-to-east from the Gulf of Mexico to the Sea of Marmara, and north-to-south from the Arctic to the Gulf of Guinea. Characteristics of symbioses in 53 species from the area are summarized for each of the five bivalve families documented to harbor chemosynthetic symbionts (Mytilidae, Vesicomyidae, Solemyidae, Thyasiridae and Lucinidae). Comparisons are made between the families, with special emphasis on ecology, life cycle, and connectivity. Chemosynthetic symbioses are a major adaptation to ecosystems and habitats exposed to reducing conditions. However, relatively little is known regarding their diversity and functioning, apart from a few "model species" on which effort has focused over the last 30 yr. In the context of increasing concern about biodiversity and ecosystems, and increasing anthropogenic pressure on oceans, we advocate a better assessment of the diversity of bivalve symbioses in order to evaluate the capacities of these remarkable ecological and evolutionary units to withstand environmental change.

  12. A chemical and toxicological profile of Dutch North Sea surface sediments.

    PubMed

    Klamer, Hans J C; Leonards, Pim E G; Lamoree, Marja H; Villerius, Leen A; Åkerman, Johan E; Bakker, Joop F

    2005-03-01

    Chemical and toxicological profiles were assessed in surface sediments (fraction <63 microm) from the southern North Sea. In extracts of freeze-dried samples, polybrominated biphenyl (PBB), Irgarol 1051 and phthalate concentrations were below the respective detection limits (except di(2-ethylhexyl)phthalate, which was between 170 and 3300 microg kg(-1) dry weight (dw)). Hexabromocyclododecane (HBCD) concentrations were between 0.8 and 6.9 microg kg(-1)dw, with highest concentrations at river mouths. Polybrominated diphenylethers (PBDE) concentrations were 0.4-0.6 microg kg(-1)dw, decabromodiphenylether (BDE209) 1-32 microg kg(-1)dw. The ratio BDE209/PCB153 was used as a tracer for recent emissions, and pointed towards a BDE209 source in the Western Scheldt's upper estuary. PCBs and PAHs were between 0.19-4.7 and 2.6-200 microg kg(-1)dw respectively and generally had highest concentrations at near-shore locations and river mouths. Responses in the Microtox broad-spectrum and the Mutatox genotoxicity assays were generally low, with near-shore locations giving higher responses. The umu-C genotoxicity and the ER-CALUX assay for estrogenicity showed no response, with the exception of one near-shore location (IJmuiden outer harbour, ER-CALUX). Highest dioxin-like toxicity (DR-CALUX) was found at near-shore locations, in the outflow of the Rhine/Meuse estuary including a dumping site of harbour sludge. At the Oyster Grounds, DR-CALUX responses appeared to be linked to the occurrence of larger PAHs (4-6 rings). A new, non-destructive clean up procedure resulted in significantly higher DR-CALUX responses than the current protocol. The Dutch legislation on disposal of harbour sludge at sea, dictates the use of the conventional clean up procedure. Our results therefore indicate that probably more dioxin-like toxicity associated with harbour sludge is disposed off at sea than assumed.

  13. Relating Cenozoic North Sea sediments to topography in southern Norway: The interplay between tectonics and climate

    NASA Astrophysics Data System (ADS)

    Anell, Ingrid; Thybo, Hans; Stratford, Wanda

    2010-11-01

    About 482 000 km 3 of sediment (ca 24 m/Ma) accumulated in the North Sea during the Cenozoic. Early Cenozoic sedimentation was likely due to uplift of the circum North Atlantic landmasses related to continental break-up. Kilometre-scale transient uplift, and in some areas permanent uplift, generated sources for progradational influx of clastic sediments from Scotland, the Shetland platform and, to a lesser degree, southwestern Norway. The Eocene sedimentation pattern was similar to the Palaeocene, with lower rates of accumulation associated with flooding and tectonic quiescence. Sediment influx from the Shetland platform continued throughout the Cenozoic while supply from southern Norway increased markedly around the Eocene-Oligocene, coeval with the greenhouse-icehouse transition. Mass balance calculations of sediment and eroded rock volumes suggest that while some topography along the western margin of Norway may be pre-Cenozoic, significant uplift of the main Paleic surface in southern Norway occurred around the early Oligocene. Sedimentation rates were almost ten-fold higher than the Cenozoic average in the Plio-Pleistocene, slightly higher than the global average. Mass balance calculations indicate that Plio-Pleistocene erosion over-deepened a pre-existing topography.

  14. Changes in North Atlantic Sea Surface Temperatures and Tropical Cyclones Activity

    NASA Astrophysics Data System (ADS)

    Andronache, C.; Phillips, V.

    2009-12-01

    The variability in the activity of North Atlantic tropical cyclones at seasonal scales, and beyond, has been linked to significant changes in the ocean - atmosphere system. The dominant factors affecting the development of North Atlantic tropical cyclones are: sea surface temperature (SST), surface pressure, atmospheric instability, humidity, and vertical shear of the mean flow. Changes in such factors at climate time-scales modulate the frequency of tropical cyclones and their most destructive manifestation, namely the hurricanes. Some of these changes have been observed to be linked to large-scale perturbations, such as ENSO, and other ocean - atmosphere oscillations and teleconnections. This study reports findings on changes in SST anomalies and their possible links to tropical cyclones. Using SST data over the last six decades, we illustrate statistical connections by applying novel mathematical techniques between the Atlantic Multi-decadal Oscillation (AMO) and tropical cyclones. Possible interactions between AMO, climate change and the fate of tropical cyclones are discussed in the context of recent advances in climate research.

  15. Atlantic meridional overturning circulation and the prediction of North Atlantic sea surface temperature

    NASA Astrophysics Data System (ADS)

    Klöwer, M.; Latif, M.; Ding, H.; Greatbatch, R. J.; Park, W.

    2014-11-01

    The Atlantic Meridional Overturning Circulation (AMOC), a major current system in the Atlantic Ocean, is thought to be an important driver of climate variability, both regionally and globally and on a large range of time scales from decadal to centennial and even longer. Measurements to monitor the AMOC strength have only started in 2004, which is too short to investigate its link to long-term climate variability. Here the surface heat flux-driven part of the AMOC during 1900-2010 is reconstructed from the history of the North Atlantic Oscillation, the most energetic mode of internal atmospheric variability in the Atlantic sector. The decadal variations of the AMOC obtained in that way are shown to precede the observed decadal variations in basin-wide North Atlantic sea surface temperature (SST), known as the Atlantic Multidecadal Oscillation (AMO) which strongly impacts societally important quantities such as Atlantic hurricane activity and Sahel rainfall. The future evolution of the AMO is forecast using the AMOC reconstructed up to 2010. The present warm phase of the AMO is predicted to continue until the end of the next decade, but with a negative tendency.

  16. From the Sea to the Mountains: A Soils and Geomorphology Field Tour of North Carolina USA

    NASA Astrophysics Data System (ADS)

    Lindbo, David L.; Vepraskas, Michael; Kleiss, Joseph

    2015-04-01

    During the course of this tour students are introduced to the wide variety of soils and landscapes found across the state of North Carolina. These soils will be representative of the land regions of the southeastern United States. The soils in parts of this region are some of the oldest in the U.S. and are among the least fertile. North Carolina is divided into three distinct land regions: Coastal Plain, Piedmont, and Blue Ridge Belt (mountains). This tour includes sites in all three of these regions. The book entitled Soil Systems of North Carolina gives complete information about the soils across North Carolina and serves as a reference about soils as well as the types of parent materials encountered on the tour. North Carolina soils vary in elevation from sea level near the coast to approximately 2000 m at Mt. Mitchell which is the highest peak in the eastern U.S. The soils and landscapes in this region are not static, but change in response to natural and human forces. The natural forces center around climatic factors such as hurricanes that bring high wind velocities and exceptionally large rainfall amounts (>50 cm/day). These cause erosion of our coast, massive flooding, migration of sand dunes, and contribute to landslides in the western portion of the state. All of these make living here a challenge. The state contains soils in the thermic, mesic, and frigid temperature regimes. You will examine soils in all three temperature regimes on this trip. The diversity of soils also affects land use. Issues with drainage, septic systems, compaction, landslides and urbanization are highlighted at appropriate sites throughout the tour. At each of the stops soil profile and landscape are examined. Detailed profile descriptions and analytical data are provided for each pedon to assist in classification. Selected objectives and discussion points for each stop are likewise provided in order to promote discussion and identify the principle reasons for making a site visit

  17. Tidal cycles of total particulate mercury in the Jade Bay, lower Saxonian Wadden Sea, southern North Sea.

    PubMed

    Jin, Huafang; Liebezeit, Gerd

    2013-01-01

    In this study, we evaluate the nature of the relationship between particulate matter and total mercury concentrations. For this purpose, we estimate both of the two values in water column over 12-h tidal cycles of the Jade Bay, southern North Sea. Total particulate mercury in 250 mL water samples was determined by oxygen combustion-gold amalgamation. Mercury contents varied from 63 to 259 ng/g suspended particulate matter (SPM) or 3.5-52.8 ng/L in surface waters. Total particulate mercury content (THg(p)) was positively correlated with (SPM), indicating that mercury in tidal waters is mostly associated with (SPM), and that tidal variations of total particulate mercury are mainly due to changes in (SPM) content throughout the tidal cycle. Maximum values for THg(p) were observed during mid-flood and mid-ebb, while the lowest values were determined at low tide and high tide. These data suggest that there are no mercury point sources in the Jade Bay. Moreover, the THg(p) content at low tide and high tide were significantly lower than the values recorded in the bottom sediment of the sampling site (>200 ng/g DW), while THg(p) content during the mid-flood and mid-ebb were comparable to the THg content in the surface bottom sediments. Therefore, changes in THg(p) content in the water column due to tidal forcing may have resulted from re-suspension of underlying surface sediments with relatively high mercury content.

  18. Invertebrate bioassays with North Sea water samples. I. Structural effects on embryos and larvae of serpulids, oysters and sea urchins

    NASA Astrophysics Data System (ADS)

    Klöckner, K.; Rosenthal, H.; Willführ, J.

    1985-03-01

    Structural effects of bottom and surface water samples from two dumping grounds in the inner German Bight on the development of three meroplanktonic organisms (Pomatoceros triqueter: Polychaeta, Psammechinus miliaris: Echinodermata and Crassostrea gigas, Mollusca) were investigated. The titaniumdioxide dumping site was sampled immediately after dumping (within the visible waste trail 1 km behind the vessel), and 10 h after dumping. Samples were taken in the sewage sludge deposition area in the intervals between the usual dumping activities, regardless of the exact dumping schedule. The preserved bioassay test organisms were inspected microscopically to count percentages of “normal” larval hatch in test water samples, reference water samples and laboratory aged control water samples (5 to 10 replicates). The relative water quality at various dumping sites was expressed in terms of “net risk”-values (Woelke, 1972) compared to hatching rates observed in the controls. Larval development of P. triqueter was significantly suppressed (up to -22 % “net risk”) in trail water of the titanium dioxide dump site while the development of sea urchin larvae was still affected in the 10 h surface samples. Hatching of all test organisms in bottom-water samples from the centre of the sewage sludge dump site was affected to different degrees when compared to reference areas about 4 km north or 6 km northwest of the dumping area. The general usefulness of standardized bioassay procedures in pollution monitoring programmes is discussed. The results presented here call for further verification to minimize experimental background variability and to enlarge the catalogue of suitable effects criteria.

  19. Different responses of Sea Surface Temperature in the North Pacific to greenhouse gas and aerosol forcing

    NASA Astrophysics Data System (ADS)

    Wang, Liyi; Liu, Qinyu

    2015-12-01

    The responses of Sea Surface Temperature (SST) to greenhouse gas (GHG) and anthropogenic aerosol in the North Pacific are compared based on the historical single and all-forcing simulations with Geophysical Fluid Dynamics Laboratory Climate Model version 3 (GFDL CM3). During 1860-2005, the effect of GHG forcing on the North Pacific SST is opposite to that of the aerosol forcing. Specifically, the aerosol cooling effect exceeds the GHG warming effect in the Kuroshio Extension (KE) region during 1950-2004 in the CM3 single forcing. The mid-latitude response of ocean circulation to the GHG (aerosol) forcing is to enhance (weaken) the Subtropical Gyre. Then the SST warming (cooling) lies on the zonal band of 40°N because of the increased (reduced) KE warm advection effect in the GHG (aerosol) forcing simulations, and the cooling effect to SST will surpass the warming effect in the KE region in the historical all-forcing simulations. Besides, the positive feedback between cold SST and cloud can also strengthen the aerosol cooling effect in the KE region during boreal summer, when the mixed layer depth is shallow. In the GHG (aerosol) forcing simulations, corresponding to warming (cooling) SST in the KE region, the weakened (enhanced) Aleutian Low appears in the Northeast Pacific. Consequently, the SST responses to all-forcing in the historical simulations are similar to the responses to aerosol forcing in sign and spatial pattern, hence the aerosol effect is quite important to the SST cooling in the mid-latitude North Pacific during the past 55 years.

  20. GPS and Relative Sea-level Constraints on Glacial Isostatic Adjustment in North America

    NASA Astrophysics Data System (ADS)

    James, T. S.; Simon, K.; Henton, J. A.; Craymer, M.

    2015-12-01

    Recently, new GIA models have been developed for the Innuitian Ice Sheet and for the north-central portion of the Laurentide Ice Sheet (Simon, 2014; Simon et al., 2015). This new combined model, herein called Innu-Laur15, was developed from the ICE-5G model and load adjustments were made to improve the fit to relative sea-level observations and to GPS-constrained vertical crustal motion in the Canadian Arctic Archipelago and around Hudson Bay. Here, the predictions of Innu-Laur15 are compared to observations and other GIA models over an extended region comprising much of North America east of the Rocky Mountains. GIA predictions are made using compressible Maxwell Earth models with gravitationally self-consistent ocean loading, changing coastlines, and ocean-water inundation where marine ice retreats or floats. For this study, GPS time series are the NA12 solution (Blewitt et al., 2013) downloaded from http://geodesy.unr.edu/NGLStationPages/GlobalStationList and fit with a linear trend, annual and semi-annual terms, and offsets as indicated by station logs and by inspection of the time series. For example, a comparison of GPS observations of vertical crustal motion from the NA12 solution at 360 sites gives root-mean-square (RMS) residuals of 3.2 mm/yr (null hypothesis), 1.8 mm/yr (Innu-Laur15), and 2.9 mm/yr (ICE-5G) for the VM5a Earth model. Preliminary comparisons with other Earth models give similar patterns where Innu-Laur15 provides a better fit than ICE-5G. Further adjustments to the Innu-Laur15 ice sheet history could improve the fit to GPS rates in other regions of North America.

  1. Seafloor classification using hydroacoustic methods in the shallow coastal North Sea

    NASA Astrophysics Data System (ADS)

    Mielck, F.; Hass, H.

    2012-12-01

    Seabed environments reveal important insights into marine ecosystems and hydrodynamics. However, the knowledge regarding their distribution in the North Sea is still fragmentary since data interpretation and mapping is very time consuming. Hydroacoustic devices are able to provide rapid and reliable information on the acoustic characteristics of the seafloor that are instrumental for seafloor discrimination. In this study we compare data of two different hydroacoustic devices: Sidescan sonar data provide acoustic images of the seafloor including bedforms and grain-size distribution. The acoustic ground discrimination system RoxAnn (200 kHz) was used to measure backscatter intensities which indicate roughness (first echo return) and hardness (second echo return) parameters of the seafloor. The data were acquired in an exclusively sandy and relatively shallow investigation area in the Sylt-Rømø Basin (SE North Sea) which is typical for the European Wadden Sea. For ground-truthing surface-sediment samples were taken. The results reveal surficial sediments ranging from fine to coarse sand. Finer material is rather restricted to the shallow areas while coarser sediments characterize the deeper tidal channels. The determined roughness and hardness parameters also strongly increase within these inlets following the change in grain size. The sidescan sonar imagery shows flow-transverse subaqueous dunes of different sizes (0.7 to 35 m from crest to crest). Both, ebb- and flood-dominated structures occur. Altogether six physically different environmental units were defined using grain-size data of the grab samples as well as bedform and backscatter data provided by the sidescan sonar. Not all of these units can be discriminated by the RoxAnn. In particular those showing similar grain sizes or superimposed bedforms yield no clear signature in the hardness vs. roughness scatter plots. However, there are some areas characterized by fine sand that reveal completely different

  2. Impact of trematode parasitism on the fauna of a North Sea tidal flat

    NASA Astrophysics Data System (ADS)

    Lauckner, G.

    1984-03-01

    The impact of larval trematodes on the fauna of a North Sea tidal flat is considered at the individual and at the population level, depicting the digenean parasites of the common periwinkle, Littorina littorea, and their life cycles, as an example. On the German North Sea coast, L. littorea is first intermediate host for 6 larval trematodes representing 6 digenean families — Cryptocotyle lingua (Heterophyidae), Himasthla elongata (Echinostomatidae), Renicola roscovita (Renicolidae), Microphallus pygmaeus (Microphallidae), Podocotyle atomon (Opecoelidae) and Cercaria lebouri (Notocotylidae). All except P. atomon utilize shore birds as final hosts; adult P. atomon parasitize in the intestine of teleosts, mainly pleuronectid flatfish. Second intermediate hosts of C. lingua are various species of fish; the cercariae of H. elongata encyst in molluscs and polychaetes, those of R. roscovita in molluscs; M. pygmaeus has an abbreviated life cycle; C. lebouri encysts free on solid surfaces; and the fish trematode P. atomon utilizes benthic crustaceans, mainly amphipods, as second intermediate hosts. On the tidal flats of the Königshafen (Sylt), up to 77% of the periwinkles have been found to be infested by larval trematodes. Maximum infestations in individual samples were 23% for C. lingua, 47% for H. elongata and 44% for R. roscovita. The digeneans cause complete ‘parasitic castration’ of their carriers and hence exclude a considerable proportion of the snails from the breeding population. Infestation reduces the longevity of affected hosts, and size-related, trematode-induced differential mortality causes changes in the normal size-frequency distribution of individual snail-age classes. Young flatfish Pleuronectes platessa from the Königshafen are 100% infested with metacercariae of C. lingua. Heavy infestation of the gills causes obstruction of blood vessels and respiratory impairment; metacercariae in the eyes and optic nerves cause visual and neurological

  3. Methane emission and consumption at a North Sea gas seep (Tommeliten area)

    NASA Astrophysics Data System (ADS)

    Niemann, H.; Elvert, M.; Hovland, M.; Orcutt, B.; Judd, A.; Suck, I.; Gutt, J.; Joye, S.; Damm, E.; Finster, K.; Boetius, A.

    2005-11-01

    The North Sea hosts large coal, oil and gas reservoirs of commercial value. Natural leakage pathways of subsurface gas to the hydrosphere have been recognized during geological surveys (Hovland and Judd, 1988). The Tommeliten seepage area is part of the Greater Ekofisk area, which is situated above the Tommeliten Delta salt diapir in the central North Sea. In this study, we report of an active seep site (56°29.90'N, 2°59.80'E) located in the Tommeliten area, Norwegian Block 1/9, at 75 m water depth. Here, cracks in a buried marl horizon allow methane to migrate into overlying clay-silt and sandy sediments. Hydroacoustic sediment echosounding showed several venting spots coinciding with the apex of marl domes where methane is released into the water column and potentially to the atmosphere during deep mixing situations. In the vicinity of the gas seeps, sea floor observations showed small mats of giant sulphide-oxidizing bacteria above patches of black sediments and carbonate crusts, which are exposed 10 to 50 cm above seafloor forming small reefs. These Methane-Derived Authigenic Carbonates (MDACs) contain 13C-depleted, archaeal lipids indicating previous gas seepage and AOM activity. High amounts of sn2-hydroxyarchaeol relative to archaeol and low abundances of biphytanes in the crusts give evidence that ANaerobic MEthane-oxidising archaea (ANME) of the phylogenetic cluster ANME-2 were the potential mediators of Anaerobic Oxidation of Methane (AOM) at the time of carbonate formation. Small pieces of MDACs were also found subsurface at about 1.7 m sediment depth, associated with the Sulphate-Methane Transition Zone (SMTZ). The SMTZ of Tommeliten is characterized by elevated AOM and Sulphate Reduction (SR) rates, increased concentrations of 13C-depleted tetraether derived biphytanes, and specific bacterial Fatty Acids (FA). Further biomarker and 16S rDNA based analyses give evidence that AOM at the Tommeliten SMTZ is mediated by archaea belonging to the ANME-1b

  4. PBB levels in fish from the Baltic and North seas and in selected food products from Poland.

    PubMed

    Gieroń, Joanna; Grochowalski, Adam; Chrzaszcz, Ryszard

    2010-03-01

    Recently, a significant amount of attention has been devoted to the determination of polybrominated biphenyls in food and the environment. In this study, PBB contamination of fish from the North and Baltic Seas, with a special focus on samples from Poland and France, was investigated. North Sea fish like salmon, herring, scarp, gilthead seabream and grey gurnard were collected from a French fish market. Baltic Sea fish like salmon, tunny, trout, herring, and freshwater fish such as carp were purchased from a Polish fish market. Cod livers in oil were also analyzed in this study. As additional food samples, butter, pork fat and beef fat were tested. Concentrations of PBBs in North Sea fish (except herring) were higher than in fish from the Baltic Sea. The highest total PBB concentration was measured in scarp muscle tissue (635+/-107 pg g(-1) wet weight), and the lowest was in carp samples (0.567+/-0.245 pg g(-1) wet weight). The PBB content in tunny oil samples was below the detection limits (0.45-1.05 pg g(-1)fat). Our study also demonstrated that PBBs may bioaccumulate in the liver, where PBB concentrations were 2116+/-351 pg g(-1) wet weight and 841+/-147 pg g(-1) wet weight. In fish species from Poland, the most dominant congeners were tetrabromobiphenyls, followed by pentabromobiphenyls and hexabromobiphenyls. In some species of fish from the North Sea, the most dominant groups were hexabromobiphenyls and tetrabromobiphenyls. Although the relative abundances of structurally known and unknown isomers varied from species to species, all fish (except tunny) were contaminated with PBBs. PMID:20060998

  5. Study on Precipitation Anomalies of North of China in April and Its relationship to Sea Surface Temperature Evolvement

    NASA Astrophysics Data System (ADS)

    Song, Y.; Li, Z.; Guan, Y.

    2012-04-01

    Using monthly precipitation data in North of China for 1960-2007, American NCEP/NCAR monthly reanalysis data and NOAA SST (sea surface temperature) data, and SST indices data in Climate System Monitoring Bulletin collected by National Climate Center, this paper studied the general circulation, large-scale weather system anomalous characteristics and SSTA evolvement with more rainfall of North of China in April. The results showed that precipitation differences between months in spring in North of China were quite obvious, and the correlation coefficients between precipitation of North of China in April and that in March and in May were not significant respectively. The linear trend of precipitation in April was out of phase with that in spring. It was meaningful to study precipitation in April solely. The space pattern of first leading mode of EOF analysis for precipitation of North of China in April indicated that rainfall changed synchronously. In years of more rainfall in April showed negative phase of EU pattern in 500hPa geopotential height field