Sample records for central north sea

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

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


    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 (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 rates to be used in the development of ecosystem models.

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

    Kheireddine, Malika


    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.

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

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


    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. The economics of CO2-EOR cluster developments in the UK Central North Sea

    Studies to date have generally shown that individual CO2-EOR offshore projects are uneconomic except under questionable assumptions. The present study is based on an interconnected cluster of nine oilfields in the Central North Sea linked to an onshore CO2 collection hub by a set of existing and new pipelines. Monte Carlo simulation modelling was undertaken of the prospective returns to investments in CO2-EOR in the fields. Relatively high oil prices were employed for the study period (2020–2050) and two contrasting CO2 transfer price scenarios, the first being the Carbon Price Floor (CPF) introduced by the UK Government and the second being relatively low negotiated prices reflecting recent and prospective levels under the EU-ETS. At CPF prices the investment returns were all found to be negative, but at prices averaging £10 per tonne positive returns were generally achieved. The study emphasises the importance of CO2 prices and the taxation system in determining the viability of the investments. - Highlights: • Detailed modelling of CO2 EOR in nine North Sea oil fields. • Overall investment risks are demonstrated to be very high. • Sharing of pipelines in network and cluster of CO2-EOR fields significantly reduces investment costs. • Range of plausible CO2 prices paid by investor results in very wide range of returns from CO2-EOR. • CO2 pricing and tax arrangements for EOR need further attention by policy makers

  5. Controls on the structural, stratigraphic and climatic development of the Central North Sea

    Jamieson, Rachel


    The North Sea is a marginal, epeirogenic sea lying in an intra-plate setting on the NW European continental shelf in the northern hemisphere at about 54 degrees north. It is a shallow, elongate, saucer-shaped depression that is more than 970 km long and 560 km wide; with an area of around 570,000 km2 and connected with the Atlantic Ocean both to the north through the Norwegian Sea, and to the south through the Dover Straits and English Channel. However, it has not always had...

  6. Evolution of physical and biological characteristics of mesoscale eddy in north-central Red Sea

    Zarokanellos, Nikolaos


    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

  7. Roadmap to the deployment of offshore wind energy in the Central and Southern North Sea (2020-2030)

    This Roadmap represents the final deliverable of the WINDSPEED project. It has a dual objective. Firstly, it aims to present an ambitious but realistic target for offshore wind with minimum negative impacts on other sea functions present in the Central and Southern North Sea basin in the time frame to 2030. Secondly, it aims to identify actions and milestones required to achieve this target. The North Sea countries - Belgium, Denmark, Germany, the Netherlands, Norway and the UK - are facing a number of challenges and opportunities in their quest for rapid expansion of offshore wind energy in the Central and Southern North Sea basin. The WINDSPEED project has carried out an assessment of (ambitious but realistic) deployment potentials under different scenarios to gain better insight into how key uncertainties can impact on OWE developments. An early understanding of how different development perspectives influence challenges and opportunities, as well as uncertainties, will allow for better adaptation of policies and approaches to promote large scale offshore wind energy (OWE). This is particularly important at a time when OWE is strongly driven by EU and national policy needs in attempting to reach overall policy goals of a competitive, secure and sustainable energy system. There is ample space in the Central and Southern North Sea. But many attractive areas for developing OWE within reasonable cost ranges are already occupied by other sea users. Moving OWE further from shore and into deeper waters not only drives costs up, but also raises the issue of the availability of deep sea technology components and the need for an offshore grid. To date, the North Sea countries will have developed a capacity of around 2 GW in the North Sea. It has taken a decade to get this far. Important lessons are being learnt and these must be taken into account in the development of OWE towards 2030. The WINDSPEED project concludes that a capacity of 135 GW of OWE in the Central and

  8. 137Cs vertical distribution at the deep basins of the North and Central Aegean Sea, Greece

    Large volume seawater samples were collected for the determination of 137Cs concentration along with depth in the deep basins of North and Central Aegean Sea. The vertical 137Cs distribution showed maximum concentration at the bottom of the basins, while the minimum values corresponded to the intermediate layer, where Levantine water exists. The surface 137Cs activity is found to lie between the two limits and is originated from the Black Sea waters. The typical oceanographic advection–diffusion balance model is modified to a diffusion-settling-decay balance model to better understand the vertical distribution and variation of the 137Cs concentration in the deep basins. In addition, the diffusivity of each basin, as well as the settling speed of particulate 137Cs is also estimated. The results are compared with theoretical approach as well as with previous data. - Highlights: • Three deep basins were studied using 137Cs as a tracer. • Deep waters constitute 137Cs repositories due to deep water formation followed Chernobyl accident. • Diffusivities, as well as particulate 137Cs settling speeds are estimated

  9. Pleistocene pollen stratigraphy from borehole 81/34, devil's hole area, central north sea

    Ekman, Sten R.


    Twelve pollen assemblage zones are identified in a 229 m deep borehole (BH 81/34) from the Devil's Hole area in the central North Sea (British sector). The sediment from this borehole is Early to Late Pleistocene in age and the observation of massulae from Azolla filiculoides in sediment with reversed polarity indicates an age younger than the Olduvai geomagnetic event for the entire sequence. The Early Pleistocene sediments were at least partly deposited in the vicinity of a river outlet and can be correlated either with the Eburonian or the Menapian cold stage and with the Bavel interglacial and the Linge glacial within the Bavelian stage in the Dutch stratigraphy. The Middle Pleistocene sequence contains an interval rich in Abies, Picea and Pinus, probably deposited during the end of either Cromerian Complex interglacial IV (Noordbergum) or possibly the Holsteinian. The uppermost 80 m of the core contains high frequencies of pre-Quaternary and deteriorated palynomorphs indicating extensive glacial or glaciofluvially reworked sediment.

  10. Electrifying reviews of the central North Sea area; Elektrisifiseringsvurderinger for midtre Nordsjoe

    Husdal, Geir


    We conducted a site evaluation of power from land to several fields in the central North Sea. The findings are included Dagny, Edvard Grieg, Draupne and Johan Sverdrup. In addition, an unidentified future field is included in the evaluation. Unclassified cost estimates have been prepared and measures cost is calculated for a main concept based on a set of assumptions and suppositions. To check the robustness of the results and to identify which parameters the results are most sensitive to, we conducted sensitivity analyzes in which key assumptions are changed. The study shows a cost of Nok 412 Nok / tonne reduction in Co2 emissions. This is slightly higher than the sum of the current Co2 tax and quota price, but lower than the Co2 cost proposed in the white paper. Sensitivity calculations show that the cost of measures is very sensitive to investment costs, future energy demand and the price difference between gas sold on the continent and electricity from the grid in Norway. (eb)

  11. Thermocline mixing and vertical oxygen fluxes in the stratified central North Sea

    Rovelli, Lorenzo; Dengler, Marcus; Schmidt, Mark; Sommer, Stefan; Linke, Peter; McGinnis, Daniel F.


    In recent decades, the central North Sea has been experiencing a general trend of decreasing dissolved oxygen (O2) levels during summer. To understand potential causes driving lower O2, we investigated a 3-day period of summertime turbulence and O2 dynamics in the thermocline and bottom boundary layer (BBL). The study focuses on coupling biogeochemical with physical transport processes to identify key drivers of the O2 and organic carbon turnover within the BBL. Combining our flux observations with an analytical process-oriented approach, we resolve drivers that ultimately contribute to determining the BBL O2 levels. We report substantial turbulent O2 fluxes from the thermocline into the otherwise isolated bottom water attributed to the presence of a baroclinic near-inertial wave. This contribution to the local bottom water O2 and carbon budgets has been largely overlooked and is shown to play a role in promoting high carbon turnover in the bottom water while simultaneously maintaining high O2 concentrations. This process may become suppressed with warming climate and stronger stratification, conditions which could promote migrating algal species that potentially shift the O2 production zone higher up within the thermocline.

  12. Seasonal methane accumulation and release from a gas emission site in the central North Sea

    Mau, S.; Gentz, T.; Körber, J.-H.; Torres, M. E.; Römer, M.; Sahling, H.; Wintersteller, P.; Martinez, R.; Schlüter, M.; Helmke, E.


    We investigated dissolved methane distributions along a 6 km transect crossing active seep sites at 40 m water depth in the central North Sea. These investigations were done under conditions of thermal stratification in summer (July 2013) and homogenous water column in winter (January 2014). Dissolved methane accumulated below the seasonal thermocline in summer with a median concentration of 390 nM, whereas during winter, methane concentrations were typically much lower (median concentration of 22 nM). High-resolution methane analysis using an underwater mass-spectrometer confirmed our summer results and was used to document prevailing stratification over the tidal cycle. We contrast estimates of methane oxidation rates (from 0.1 to 4.0 nM day-1) using the traditional approach scaled to methane concentrations with microbial turnover time values and suggest that the scaling to concentration may obscure the ecosystem microbial activity when comparing systems with different methane concentrations. Our measured and averaged rate constants (k') were on the order of 0.01 day-1, equivalent to a turnover time of 100 days, even when summer stratification led to enhanced methane concentrations in the bottom water. Consistent with these observations, we could not detect known methanotrophs and pmoA genes in water samples collected during both seasons. Estimated methane fluxes indicate that horizontal transport is the dominant process dispersing the methane plume. During periods of high wind speed (winter), more methane is lost to the atmosphere than oxidized in the water. Microbial oxidation seems of minor importance throughout the year.

  13. The Cenozoic geological evolution of the Central and Northern North Sea based on seismic sequence stratigraphy

    Jordt, Henrik


    This thesis represents scientific results from seismic sequence stratigraphic investigations. These investigations and results are integrated into an ongoing mineralogical study of the Cenozoic deposits. the main results from this mineralogical study are presented and discussed. The seismic investigations have provided boundary conditions for a forward modelling study of the Cenozoic depositional history. Results from the forward modelling are presented as they emphasise the influence of tectonics on sequence development. The tectonic motions described were important for the formation of the large oil and gas fields in the North Sea.

  14. North Sea update

    The article deals with the offshore activity in the North Sea bringing together a special update feature for the petroleum industries in the United Kingdom, Norway, Denmark and the Netherlands. The total capital expenditure required for the period from 1995 to 1998 for the North Sea area which includes exploration, development projects and well abandoning, are discussed and presented. 20 figs., 5 tabs

  15. Food of Flesh-footed shearwaters Puffinus carneipes associated with high-seas driftnets in the central North Pacific Ocean

    Gould, P.; Ostrom, P.; Walker, W.


    We examined digestive tract contents and stable nitrogen isotope ratios in breast muscles of Flesh-footed Shearwaters Puffinus carneipes associated with high-seas driftnet fisheries in the central North Pacific Ocean. Small fish, Lanternfish (Myctophidae) and Pacific Saury Cololabis saira, were the principal prey found in the digestive tracts. Pieces of unidentified fish, possibly Pacific Pomfret Brama japonica, and shredded squid tissue, mostly Neon Flying Squid Ommastrephes bartrami, in the digestive tracts indicate scavenging at driftnet fishing operations. Although softbodied animals such as Velella sp. were rare in the digestive tracts, low stable nitrogen isotope values (??15N) suggest Flesh-footed Shearwaters feed heavily on such low trophic level animals.

  16. Sup(14)C activity of dissolved organic carbon fractions in the north-central Pacific and Sargasso Sea

    Radiocarbon measurements of dissolved organic carbon (DOC) oxidizable by ultraviolet irradiation (DOCuv) yielded apparent ages of ∼6,000 yr in the deep waters of the oligotrophic north-central Pacific gyre. Recent reports of a potentially larger pool of DOC as measured by high-temperature catalytic combustion (DOChtc) using discrete injections of sea water have led to speculation that 'younger', more recently produced DOC could contribute significantly to overall oceanic organic carbon fluxes, owing to its suspected greater biological lability. Here we present a comparison of Δ14C (the deviation in parts per thousand from the 14C activity of nineteenth-century wood) of the DOChtc, DOCuv and humic substances in profiles from the oligotrophic north-central Pacific and Sargasso Sea. For each ocean, the Δ14C values of all three fractions are remarkably similar, yielding no evidence for a component of DOC that is cycled through the system on timescales shorter than several thousands of years. We observe an age difference between the two oceans of ∼2,000 yr for the deepest DOC, which can largely be accounted for by differences in the Δ14C of the DOC sources to the deep basins, and by the different deep-water circulation patterns and transit times in the two oceans. (author)

  17. Absolute sea levels and isostatic changes of the eastern North Sea to central Baltic region during the last 900 years

    Hansen, Jens Morten; Aagaard, Troels; Binderup, Merete


    confirms that ice-cap growth can be faster than ice-cap melting. By comparison with 29 long-term tide gauge measurements of the region we show that the isostatic implications of the sea-level curve are in nearly perfect agreement with Peltier's global isostatic VM2 model (applied by IPCC and PSMSL) and...

  18. Pollution of the North Sea

    This is the first modern review on the fate, distribution and effects of pollutants in the North Sea. The reader will find general information on the North Sea system and details on the behavior of pollutants and their impact on selected areas and organisms. (orig.) With 238 figs

  19. Mass-transport deposits and reservoir quality of Upper Cretaceous Chalk within the German Central Graben, North Sea

    Arfai, Jashar; Lutz, Rüdiger; Franke, Dieter; Gaedicke, Christoph; Kley, Jonas


    The architecture of intra-chalk deposits in the `Entenschnabel' area of the German North Sea is studied based on 3D seismic data. Adapted from seismic reflection characteristics, four types of mass-transport deposits (MTDs) are distinguished, i.e. slumps, slides, channels and frontal splay deposits. The development of these systems can be linked to inversion tectonics and halotectonic movements of Zechstein salt. Tectonic uplift is interpreted to have caused repeated tilting of the sea floor. This triggered large-scale slump deposition during Turonian-Santonian times. Slump deposits are characterised by chaotic reflection patterns interpreted to result from significant stratal distortion. The south-eastern study area is characterised by a large-scale frontal splay complex. This comprises a network of shallow channel systems arranged in a distributive pattern. Several slide complexes are observed near the Top Chalk in Maastrichtian and Danian sediments. These slides are commonly associated with large incisions into the sediments below. Best reservoir properties with high producible porosities are found in the reworked chalk strata, e.g. Danish North Sea, therefore MTDs detected in the study area are regarded as potential hydrocarbon reservoirs and considered as exploration targets.

  20. Pseudocollapse and rebuilding of North Sea mackerel (Scomber scombrus)

    Jansen, Teunis


    The largest observed change in mackerel (Scomber scombrus) abundance in the North Atlantic happened when the so-called “North Sea mackerel” collapsed due to overfishing. Despite protection, it has remained in a depleted state. Central to this interpretation was that the “North Sea mackerel...

  1. Advantages of North Sea Assets

    The North Sea is a significant hydrocarbon province and any large multinational will need to maintain North Sea assets within their portfolio - as indeed they do. The general feeling that pervades the oil industry that the North Sea is ''mature'' can be demonstrated by reference to the facts. The result is a potential fall-off in activity and a serious threat to the future levels of profitability in the region. Notwithstanding the continuing development of large fields, such as Troll, of or multi-field developments, for example BP's recent announcement on ETAPs, activity is beginning to fall, most noticeably at the front end of the development cycle, in exploration. (author)

  2. Assessment of sea surface temperature variations in the central North Atlantic using the alkenone unsaturation index (U 37k')

    Villanueva, Joan; Grimalt, Joan O.; Cortijo, Elsa; Vidal, Laurence; Labeyrie, Laurent


    A high resolution record of U 37k' -derived SST estimations has been obtained in a core from the central North Atlantic Ocean (SU90/08, 43°30'N, 30°24'W) spanning a time period of 280 ky. The general trend of the U 37k' profile parallels closely the δ 180 signal and represent an independent confirmation that the SST variations in the glacial-interglacial time scales are correlated with the northern ice sheets evolution. In contrast to the CLIMAP (1984) conclusions based on the foraminiferal transfer function technique, the SST during the last interglacial period (LIP, isotopic stage 5.5) are 2-3°C warmer than during the Holocene. This result is in good agreement with many studies based in coastal and continental records that strongly suggest warmer climatic conditions over North America and Europe. Finally, the SST estimates during the last glacial maximum (LGM, 18 ky BP) where 4.5°C cooler than during the previous glacial period (PGP, stage 6). We argue that this difference is caused by a northward position of the polar front during the PGP in the Central North Atlantic.

  3. Geology of the North Sea and Skagerrak

    Michelsen, O. [ed.


    The Marine Geology Unit of the Department of Earth Sciences organized the second Marine Geology symposium at Aarhus University, 7-8 October 1993. The intention was to bring together people working especially with the geology of the North Sea and Skagerrak. Approximately 60 people from different Danish and Norwegian institutions attended the symposium. 28 oral presentations were given and 2 posters presented. A large range of geological topics was covered, embracing biostratigraphy, sequence stratigraphy, sedimentology and structural geology. The majority of the presentations dealt with Quaternary geology and Cenozoic sequence stratigraphy, but also Jurassic and Lower Cretaceous stratigraphy was treated. Studies from the major part of the Danish sector were presented, spanning from Bornholm to the central North Sea, and further into the Norwegian North Sea sector. (au)

  4. Distribution of chroococcoid cyanobacteria and size-fractionated chlorophyll a biomass in the central and southern north sea waters during June/July 1989

    Iriarte, Arantza; Purdie, Duncan A.

    The spatial and vertical distribution of phycoerythrin(PE)-containing chroococcoid cyanobacteria and the contribution of the <3 μm size fraction to overall phytoplankton chlorophyll a biomass were investigated in the central and southern North Sea during June and July 1989. PE-containing chroococcoid cyanobacteria cell numbers ranged between 6×10 5 and 4.4×10 7 cells·dm -3 and was typically between 0.5×10 7 and 3×10 7 cells·dm -3, lowest numbers being recorded near the British coast in central North Sea waters. The vertical distribution of these cyanobacteria showed no evidence to suggest a preferential accumulation deep in the euphotic zone. The <3 μm size fraction accounted for 6.6 to 57.5% of the total phytoplankton chlorophyll a biomass (mean 19.7%). In general, the relative significance of the <3 μm size fraction decreased with increasing total chlorophyll a biomass.

  5. North Central Thailand


    This radar image shows the dramatic landscape in the Phang Hoei Range of north central Thailand, about 40 kilometers (25 miles) northeast of the city of Lom Sak. The plateau, shown in green to the left of center, is the area of Phu Kradung National Park. This plateau is a remnant of a once larger plateau, another portion of which is seen along the right side of the image. The plateaus have been dissected by water erosion over thousands of years. Forest areas appear green on the image; agricultural areas and settlements appear as red and blue. North is toward the lower right. The area shown is 38 by 50 kilometers (24 by 31 miles) and is centered at 16.96 degrees north latitude, 101.67 degrees east longitude. Colors are assigned to different radar frequencies and polarizations as follows: red is L-band horizontally transmitted and horizontally received; green is L-band horizontally transmitted and vertically received; blue is C-band horizontally transmitted and vertically received. The image was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture (SIR-C/X-SAR) imaging radar on October 3, 1994, when it flew aboard the space shuttle Endeavour. SIR-C/X-SAR is a joint mission of the U.S./German and Italian space agencies.Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA

  6. Radioactivity in the North Sea

    This chapter lists the main sources of radioactivity in the North Sea and explains the units used. The main source is naturally occuring long-lived radionuclides. Other significant sources are the Sellafield reprocessing plant, atmospheric atomic weapons testing, fallout from the Chernobyl reactor accident, the French nuclear reprocessing plant at Cap la Hague and oilfield production water brines. However, currently these are not significant compared with the natural background. If this is to continue, lower levels of discharge into the sea, strict control of new discharges and the cessation of atmospheric nuclear tests will be needed. There is a map showing the concentration of Cs137 in filtered water from the North Sea in 1985. (UK)

  7. Mesozoic Rifting in the German North Sea

    Lutz, R.; Jähne, F.; Arfai, J.


    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

  8. Spatio-temporal changes of Munida Rutllanti Zariquiey-Alvarez, 1952 (Decapoda: Galatheidae in the North-Western Ionian Sea (Central Mediterranean



    Full Text Available The spatio-temporal pattern of Munida rutllanti distribution in the north-western Ionian Sea has been studied. Data were collected during 14 experimental trawl surveys conducted from 1997 to 2010 as part of the international MEDITS project. The hauls were carried out during day-light hours between depths of 10 and 800 m in the spring season. A progressive increase in the abundance index (N/km2 of M. rutllanti was observed from 2000 to 2008, then a sharp decrease was shown in the last two years. The greatest and lowest abundance indices were observed in the Apulian and central Calabrian sub-areas, respectively. The species was collected between 107 and 795 m in depth, with a significant increase and decrease over time in the maximum and minimum depth of finding, respectively. A highly significant increase over time in the mean carapace length was also observed in the whole study area. The widespread occurrence and increasing abundance of this species in the Ionian Sea could be related to the increase in temperature and the variation in hydrographic conditions which occurred in the Ionian basin during the EMT-BiOS phenomenon.

  9. Artificial radioactivity in the North Sea

    The question of radioactive contamination of the environment is a problem of world-wide importance. The North Sea is an important example of a sea region heavily used by man and therefore polluted by different contaminants including radionuclides. A review of the present knowledge of the radiological situation of the North Sea and adjacent sea regions is given. The sources of artificial radionuclides and their distribution, behaviour and fate in this shallow sea area are discussed. (author)

  10. The North Sea field development guide. V.1: Northern North Sea. V.2: Southern North Sea. 6. ed.

    The 1997/8, sixth edition is the first to be divided into two volumes. Volume 1 covers the central and northern North Sea areas; volume 2 contains the southern North Sea as well as the Irish and German sectors. The pages are numbered consecutively over the two volumes, with page numbers greater than 702 contained in the second volume. There are three index sections. Main index. Arranged by national sector (UK, Norway etc.) Within each sector the entries are alphabetical by operator name. This index contains page numbers for the book entries: the other two index sections should be used with the main index to find the exact location of an entry; Index by field. If the reader knows a field name (e.g. Kittiwake) but not the operator or the national sector, this index will reference them; Index by installation. Each installation (''Fulmar SALM'', ''Togi'') is named, giving the operator, field and national sector where it is located. This index is also useful for locating particular kinds of installations, such as subsea completions; The book is intended to provide a factual overview of field development activity in the North Sea (a term loosely used to include the Irish Sea and the Baltic Sea). The aim is therefore to provide some background, specifications and history on every offshore installation in that area. Speculative or evaluative commentary is avoided where possible. No attempt has been made to forecast the form or probability of future developments, except in those few instances where announcements have been made by the oil company itself, and these are, clearly indicated. (UK)

  11. Vulnerability in north- central Vietnam

    Casse, Thorkil; Milhøj, Anders; Nguyen, Thao Phuong


    This article examines changes in livelihood strategies in response to flooding. It does so on the basis of a household survey which was undertaken in three provinces in north central Vietnam. All households in the survey were regularly affected by flooding, but only poor households experience...

  12. The carbon budget of the North Sea

    A. Vieira Borges


    Full Text Available A carbon budget has been established for the North Sea, a shelf sea of the NW European continental shelf. The air-sea exchange of CO2 has been assessed as closing term of the budget. The carbon exchange fluxes with the North Atlantic Ocean dominate the gross carbon budget. The net carbon budget – more relevant to the issue of the contribution of the coastal ocean to the marine carbon cycle – is dominated by the carbon inputs from rivers, the Baltic Sea and the atmosphere. The dominant carbon sink is the final export to the North Atlantic Ocean. The North Sea acts as a sink for organic carbon. More than 90% of the CO2 taken up from the atmosphere is exported to the North Atlantic Ocean making the North Sea a highly efficient continental shelf pump for carbon.

  13. The North Sea: Satellite colour atlas

    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.

  14. The North Sea Bird Club

    This paper reports that the creation of a club for the purpose of encouraging oil and gas workers to watch birds may not at first seem a viable proposition. To the layperson, birds offshore conjures up an image of hundreds of seagulls following fishing boats, and very little else. Also, the act of birdwatching is not seen as a typical offshore worker's activity. Anyone who has worked on an installation offshore and who has any interest in wildlife will be aware of the occasional presence of land-birds. Two decades ago, prompted by some keen offshore workers, a single oil company set up a monitoring program, which quickly became popular with a number of its employees. Birds seem offshore were recorded on data forms and collected together. At this stage the club was purely another recreation facility; however, when the data were collated it was soon realized that installations offshore were being used as staging posts by birds on migration, and that the information being collected would be of great interest in the study of bird movements. All over Britain, at strategic points on the coastline, there are bird observatories which record the arrival and departure of migrating birds. The presence of several hundred solid structures up and down the North Sea, which are used by birds en route, represents a huge, unique bird observatory, capable of uncovering facts about bird migration which have long eluded land-based scientists. Eleven years ago, the North Sea Bird Club began, composed of eight member companies, a recorder from Aberdeen University and a representative from the Nature Conservancy Council. The club received data from 41 installations, and the recorder collated these on Aberdeen University's computer and produced an annual report of sightings

  15. The Jurassic of Denmark and Greenland: Volgian–Ryazanian ‘hot shales’ of the Bo Member (Farsund Formation) in the Danish Central Graben, North Sea: stratigraphy, facies and geochemistry

    Dybkjær, Karen; Bojesen-Koefoed, Jørgen A.; Ineson, Jon I.; Nielsen, Lars Henrik


    Upper Jurassic – lowermost Cretaceous marine mudstones represent the most significant source of hydrocarbons in the Central and Northern North Sea. Of particular importance in the Danish sector of the Central Graben is a succession of radioactive ‘hot shales’ referred to the Bo Member, in the upper levels of the Farsund Formation (Kimmeridge Clay Formation equivalent). This mudstone-dominated succession is typically 15–30 m thick and has a total organic carbon (TOC) content of 3–8%, though lo...

  16. Radioactive inputs to the North Sea and the Channel

    The subject is covered in sections: introduction (radioactivity; radioisotopes; discharges from nuclear establishments); data sources (statutory requirements); sources of liquid radioactive waste (figure showing location of principal sources of radioactive discharges; tables listing principal discharges by activity and by nature of radioisotope); Central Electricity Generating Board nuclear power stations; research and industrial establishments; Ministy of Defence establishments; other UK inputs of radioactive waste; total inputs to the North Sea and the Channel (direct inputs; river inputs; adjacent sea areas); conclusions. (U.K.)

  17. The pollution of the North Sea

    The subject is covered in chapters entitled: the North Sea and its rivers; the uses of the North Sea (shipping; exploitation of oil and gas; fishing; recreation; land reclamation; industrial islands; waste dumping); the nature of the dumping problem (nuclear waste; organic chemicals; inorganic chemicals; oil; sewage; rubble and dredged spoils; ash); pollution legislation; Greenpeace activities in the North Sea (the nuclear campaigns (Windscale; Cap de la Hague; Atlantic waste dumping); the chemical campaigns); what is needed in the future; references; the Oslo Convention. (U.K.)

  18. Methane leakage during the evolution of petroleum systems in the Western Canada Sedimentary Basin and the Central Graben area of the North Sea

    Berbesi, L. A.; di Primio, R.; Anka, Z.; Horsfield, B.


    Around 500 to 600 Tg (1 Tg = 1012 g) of methane enter the atmosphere every year, mainly as product of microbial processes and combustion of fossil fuels and burning biomass. The importance of another source, the geologic emissions of methane, is up to now only loosely constrained. In this study, we addressed the potential methane emissions during the geological evolution of the Western Canada sedimentary basin (WCSB), which holds the largest oil sand accumulations in the world, and the Central Graben area of the North Sea. In the case of the WCSB, thermogenic gas generation and leakage at the sediment surface were addressed through 3D petroleum systems modeling. In this basin, the accumulated oil experienced intense biodegradation that resulted in large masses of biogenic methane. We quantified this latter mass though a two-step mass balance approach. Firstly, we estimated the rate of petroleum degradation and the magnitude of petroleum loss. After this, we calculated the mass of biogenic methane generated using a model that assumes hexadecane (C16H34) as representative of the saturated compounds (Zengler et al., 1999). Our 3D model suggests that 90000-150000 Tg of dry gas (mostly methane) could have leaked during the interval from 80 Ma to 60 Ma. Therefore, uniform leakage rates would have been in the order of 10-3-10-2 Tg yr-1. Biogenic methane generation could have taken place at rates of 10-4 to 10-2 Tg yr-1. However, the effective mass of thermogenic and biogenic methane reaching the atmosphere might have been up to 90% lower than calculated here due to methanotrophic consumption in soils (Etiope and Klusman, 2002). We addressed the thermogenic gas generation and leakage in the Central Graben through two different methods. The first is based on a previous 3D petroleum system modeling of the region (Neumann, 2006). The second consisted of calculating the mass of generated petroleum based on source rock extension and properties (Schmoker, 1994), and then

  19. Spatio-temporal changes of Munida Rutllanti Zariquiey-Alvarez, 1952 (Decapoda: Galatheidae) in the North-Western Ionian Sea (Central Mediterranean)

    Maiorano, P.; Capezzuto, F.; G. D'ONGHIA; TURSI, A.


    The spatio-temporal pattern of Munida rutllanti distribution in the north-western Ionian Sea has been studied. Data were collected during 14 experimental trawl surveys conducted from 1997 to 2010 as part of the international MEDITS project. The hauls were carried out during day-light hours between depths of 10 and 800 m in the spring season. A progressive increase in the abundance index (N/km2) of M. rutllanti was observed from 2000 to 2008, then a sharp decrease was shown in the last two yea...

  20. North Sea Forum report: March 1987

    The North Sea forum includes voluntary and statutory organisations interested in many aspects of the marine environment and its management. Thirty 'topic briefs' have been compiled to make recommendations on a variety of subjects. These have been consolidated in the Statement of the North Sea Forum which is included. The thirty topic briefs include the oceanography of the North Sea, reports on imputs of inorganic and organic contaminants from rivers, direct discharges, the atmosphere, dumping ships and platforms. One of this group, on the radioactivity in the North Sea, is indexed separately. (9 papers) The ecological effects of man's activities on plankton, benthos, fishes, shellfish, mammals, seabirds, waders, wildfowl, seaducks and plants are covered. (11 papers). The effects of other human uses on the marine environment are covered in 9 papers -military activities, recreation etc. (UK)

  1. The importance of North Sea gas to European energy supply

    Natural gas can, of course, be transported over very long distances but, because of the economics of gas transmission, its impact is most often local. This has certainly been the case with North Sea gas, which has clearly contributed significantly to European energy supply and will continue to do so for some time to come. The historical importance of the discovery of gas in the North Sea has been that it has enabled natural gas industries to grow rapidly in North West Europe. Without North Sea gas and Dutch gas it is difficult to see how town gas would have been replaced in North West Europe. Certainly, a much smaller natural gas industry would have emerged. North Sea gas has inevitably had the greatest impact on gas markets in the countries of the European Community and this will remain the case in future. Nevertheless, it is inevitable that gas will, in future, flow across more national boundaries than in the past, and that North Sea gas will have an important part to play in meeting the Central European demand for competitively priced, secure supplies. This paper discusses the United Kingdom market for gas and future demand both in the United Kingdom and more widely in Europe. An examination of the availability of gas supplies from the North Sea suggests that it is unlikely that there will be a surplus of gas for export from the United Kingdom continental shelf. Norway will remain the main source of exports, with the Netherlands also in a strong position. Transportation and political aspects are also considered. (author)

  2. Influence of pelagic invertebrate predators on the zooplankton in the Baltic Sea and the North Sea

    Barz, Kristina


    Pelagic invertebrates have a wide prey spectrum and may constitute important predators in marine ecosystems. This study analyses the impact of pelagic invertebrate predators in the two connected ecosystems Baltic Sea and North Sea. Both ecosystems have different hydrographic conditions, but also show similarities in their reaction on changing ocean conditions (synchronous regime shifts) and were object of comparative studies in the framework of the German GLOBEC Project. In the central Baltic...

  3. Euthanasia across the North Sea

    Rigter, Henk; Borst-Eilers, Els; Leenen, H J J


    The United Kingdom and The Netherlands are separated by a narrow stretch of sea but in terms of an understanding of euthanasia they seem to be light years apart. An attempt to bridge the information gap seems in order.

  4. Elastic behaviour of North Sea chalk

    Gommesen, Lars; Fabricius, Ida Lykke; Mukerji, T.;


    We present two different elastic models for, respectively, cemented and uncemented North Sea chalk well-log data. We find that low Biot coefficients correlate with anomalously low cementation factors from resistivity measurements at low porosity and we interpret this as an indication of cementation......-saturated North Sea reservoir chalk. In the acoustic impedance–Poisson's ratio plane, we forecast variations in porosity and hydrocarbon saturation from their influence on the elastic behaviour of the chalk. The Gassmann model and the self-consistent approximation give roughly similar predictions of the effect of...... filtrate. The amplitude-versus-angle (AVA) response for the general North Sea sequence of shale overlying chalk is predicted as a function of porosity and pore-fill. The AVA response of both cemented and uncemented chalk generally shows a declining reflectivity coefficient versus offset and a decreasing...

  5. North Sea sensitivity to atmospheric forcing

    Skogen, Morten D.; Drinkwater, Ken; Solfrid S. Hjøllo; Schrum, Corinna


    The sensitivity of North Sea physics and phytoplankton production to atmospheric forcing has been studied by performing perturbations of the atmospheric forcing fields through a number of model simulations. The perturbations are kept in the range of expected climate change, to give a first indication of the climate change impacts on regional systems. The model simulations suggest that an increase in air temperature and short wave radiation will increase sea surface temperature, while an incre...

  6. Tender moments in the North Sea

    Fox, C.


    Described is tender-assisted drilling (TAD) on the UK North Sea Gannet field. The Gannet field is developed by Shell UK Exploration and Production (Shell Expro). In March 1990, Shell Expro awarded Sedco Forex the design and engineering contract to convert the semisubmersible drilling rig Sedco 704 into the Gannet TSV (Tender Support Vessel). The only semisubmersible TSV operation so far to have completed drilling in the North Sea has been in the Norwegian sector. The Odin field, operated by Esso Norge a/s, was developed using the converted drilling rig Treasure Hunter. 1 fig., 1 ill., 3 refs.

  7. CZCS imagery of the North Sea

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


    A major series of CZCS satellite images of the North Sea has been processed to obtain information on the distribution of optical properties of chlorophyll, suspended sediments and coccolithophore blooms. The atmospheric correction of the scenes has been carried out after the method suggested by Gordon et al. (1983) and also by the interactive aerosol removal technique suggested by Arnone and LaViolette (1984). The processing techniques are described in relation to problems encountered in a case II water area such as the North Sea. Examples of atmospherically corrected CZCS images are presented and compared with available in situ chlorophyll.

  8. The North Sea region taken as an example for the behaviour of artificial radioisotopes in nearshore sea areas

    Different radioisotopes entering the sea with the waste waters from nuclear fuel reprocessing plants are used as tracers to observe transport processes in the sea. It could be stated that primarily the transport of water masses occurs within narrow regions along the coast. Virtually the whole water mass leaving the Irish Sea to the North flows along the Scottish coast into the North Sea and crosses her central region to the East. The water entering the southern North Sea through the English Channel analogously moves along the coast to the North. The two water masses meet in the region of the Skagerrak. One can follow them in a narrow strip along the Norwegian coast up to the Barents Sea

  9. Expensive tidying up in the North Sea

    The Norwegian government has decided that the scrapped offshore installations in the North Sea must be removed and brought to land for material recovery. This decision comprises fourteen steel platforms and the superstructure of the Ekofisk tank. By 2013, eleven platforms and waste material derived from drilling as well as rubbish on the sea floor around the installations must be removed. Until now platforms have been removed by first being dismounted at sea and then transported to land in pieces. The article describes a new transportation method proposed by a Norwegian company in which the removal is done in one operation

  10. Wind fluctuations over the North Sea

    Vincent, Claire Louise; Pinson, Pierre; Giebel, Gregor


    Climatological patterns in wind speed fluctuations with periods of 1 min to 10 h are analysed using data from a meteorological mast in the Danish North Sea. Fluctuations on these time scales are of particular relevance to the effective management of the power supply from large wind farms. The...

  11. Gas deliveries from Haltenbanken/North Sea

    The conference paper relates to the development and delivery of natural gas from the Haltenbanken area and the North Sea on the Norwegian continental shelf. Alternatives of field developments and pipelines together with the allocation of contracts for securing the contractual delivery of natural gas to the European continent in future and an alternative delivery to the Scandinavian countries, are discussed. 2 figs

  12. North Sea Elasmobranchs: distribution, abundance and biodiversity

    Daan, N.; Heessen, H.J.L.; Hofstede, ter R.


    Based on data from various international and national surveys, an overview is given of the fine-scale distribution (resolution of 20¿longitude * 10¿ latitude; ¿ 10*10 nm) and trends in abundance of elasmobranch species reported from the North Sea. Presence-absence maps are produced based on 4 survey

  13. Molecular techniques for identifying North Sea fauna

    Knebelsberger, Thomas; Ditzler, Sandra; Laakmann, Silke; Mohrbeck, Inga; Raupach, Michael J.


    Accelerated biodiversity assessment is the key to understanding the relationship between biodiversity and ecosystem functioning, especially in times of rapid climate change and habitat destruction. For the marine fauna of the North Sea, morphological species identification is impaired by the small size of many taxa, morphological convergence, intraspecific variation and larval stages which often elude morphological identification. Accordingly, the use of molecular methods...

  14. Opportunities for suppliers in the North Sea

    If European suppliers to the offshore industry are to prosper, it has to be on the basis of a single internationally competitive North Sea market. If we continue to talk and think in terms of a British sector, a Norwegian sector, Dutch and Danish sectors, then we will inhibit the full development of contractors and suppliers. The long term future in oilfield supplies lies in a mixed portfolio of international projects. Oil and gas exploration and development, particularly offshore, is notoriously cyclical. To survive the downturns in one market supply, companies need to have access to the upswing in others. The significance of a single North Sea market is that it presents an international arena for the best companies to demonstrate their technical and commercial abilities. Individual national sectors do not - cannot - provide that opportunity to anything like the same extent. Taking then the North Sea as a single competitive market, it represents the most important offshore area in the world at the present time, and this is likely to continue during the 1990s. The prospects of achieving a single North Sea market are discussed. (author)

  15. Extreme wind mapping over the North Sea

    Larsén, Xiaoli Guo

    Atlases of the 50-year wind over the North Sea have been created for two heights, 10 m and 100 m. The atlases have also been made for a range of temporal resolutions, from the original time resolution of the NCEP/NCAR reanalysis of 6 hours to 1 hour and further to 10 min. Two methods were used for...

  16. How attractive is the North Sea to the financial community?

    How attractive is the North Sea to the financial community? This question is answered by discussing the type of investment opportunity that the North Sea offers the investor. It is shown how North Sea investments have performed and some of the methods used to measure that performance are discussed. Finally, some thoughts on the future importance of the North Sea to the financial community reach the conclusion that it will remain important for some years to come. (author)

  17. Immunohistochemical localization of CYP1A, vitellogenin and Zona radiata proteins in the liver of swordfish (Xiphias gladius L.) taken from the Mediterranean Sea, South Atlantic, South Western Indian and Central North Pacific Oceans

    Cytochrome P4501A (CYP1A) monoxygenase, vitellogenin (Vtg) and Zona radiata proteins (Zrp) are frequently used as biomarkers of fish exposure to organic contaminants. In this work, swordfish liver sections obtained from the Mediterranean Sea, the South African coasts (South Atlantic and South Western Indian Oceans) and the Central North Pacific Ocean were immunostained with antisera against CYP1A, Zrp, and Vtg. CYP1A induction was found in hepatocytes, epithelium of the biliary ductus and the endothelium of large blood vessels of fish from the Mediterranean Sea and South African waters, but not from the Pacific Ocean. Zrp and Vtg were immunolocalized in hepatocytes of male swordfish from the Mediterranean Sea and from South African waters. Plasma Dot-Blot analysis, performed in Mediterranean and Pacific specimens, revealed the presence of Zrp and Vtg in males from Mediterranean but not from Pacific. These results confirm previous findings about the potential exposure of Mediterranean swordfish to endocrine, disrupting chemicals and raise questions concerning the possible presence of xenobiotic contaminants off the Southern coasts of South Africa in both the South Atlantic and South Western Indian Oceans

  18. Bioavailability of lead in North Sea sediments

    Kersten, M.; Kröncke, I.


    As part of an interdisciplinary research programme, lead contents were measured in the polychaete Nephtys spp. and in the sea-urchin Echinocardium cordatum as well as in the respective sediment fractions <20 μm taken from the Dogger Bank proper and the eastern coastal North Sea. A lower lead content was generally observed in the organisms taken from the German Bight than in those from the Dogger Bank, especially from its northeastern part. It is possible to divide both areas according to the slope found in the linear regression of lead versus total organic carbon contents in sediments, which is twice as steep for the Dogger Bank as for the eastern North Sea. This criterium points to a difference in sediment quality with regard to toxic metal contamination. The sediment quality of the Dogger Bank seems to be twice as bad compared with that of the eastern North Sea. This is in good agreement with the differences found in lead contamination of the sediment-dwelling polychaetes from both areas. The results indicate that lead is primarily accumulated by food ingestion.

  19. The Big Flood: North Sea storm surge.

    McRobie, Allan; Spencer, Tom; Gerritsen, Herman


    In the 50 years since the catastrophic southern North Sea storm surge of 31 January-1 February 1953, there have been technological advances in the engineering of flood protection, increased understanding of physical processes in shallow seas and estuaries, and developments in the mathematical statistics of extreme events. This introductory paper reviews how the scientific understanding of surge events, their impacts and the human responses to them is evolving on many fronts, often across disciplinary boundaries. The question of how the long-term nature of the problem itself will be influenced by possible climate, land use and policy changes is addressed, along with their associated uncertainties. PMID:16191649

  20. North Sea oil: fuel for the economy?

    The feverish hunt for the black gold that exerts such a potent influence on the world economy and world politics, is moving on. A giant semi-submersible oil drilling rig owned by Diamond Offshore Drilling, of Houston, Texas, is being towed from the North Sea to Australia, a voyage that takes three months. Another of the company's rigs has already been shifted from UK waters to the Black Sea, and the possibility of dismantling it and transporting the pieces overland to the Caspian, to drill off the coast of Azerbaijan, is being looked at. The emphasis in exploration and appraisal drilling is definitely shifting away from the UK continental shelf. (author)

  1. A brief analysis of North Sea physics

    Jürgen Sündermann


    Full Text Available The current state of understanding the North Sea's physical system is presented. First, basic phenomena like astronomical tides and general circulation will be described and analysed with respect to their physical nature and respective interactions. There will be special focus on fundamental dynamic balances. Next, some specific topics relevant to the marine ecosystem, the economy and society will be considered: among them, spreading and transport processes, the fresh water budget, the heat budget and storm surges. A separate section is dedicated to the North Sea of Tomorrow, i.e. the prospective variations of the physical environment resulting from global changes in future decades. The statements are based on the long experience of the authors and their groups and include findings that are little known if at all. The review finishes with a list of open questions and the corresponding research demands.

  2. Elastic behaviour of North Sea chalk

    Gommesen, Lars; Fabricius, Ida Lykke; Mukerji, T.;


    We present two different elastic models for, respectively, cemented and uncemented North Sea chalk well-log data. We find that low Biot coefficients correlate with anomalously low cementation factors from resistivity measurements at low porosity and we interpret this as an indication of cementation...... self-consistent approximation, which here represents the unrelaxed scenario where the pore spaces of the rock are assumed to be isolated, and the Gassmann theory, which assumes that pore spaces are connected, as tools for predicting the effect of hydrocarbons from the elastic properties of brine......-saturated North Sea reservoir chalk. In the acoustic impedance–Poisson's ratio plane, we forecast variations in porosity and hydrocarbon saturation from their influence on the elastic behaviour of the chalk. The Gassmann model and the self-consistent approximation give roughly similar predictions of the effect of...

  3. A tax reprieve for the North Sea?

    The United Kingdom government has for the time being put to one side its intended review of the fiscal regime in the North Sea. Consistently low oil prices over the last year and the consequent effect on production have given rise to this decision. The ongoing debate on oil taxation in the UK over the past 18 months since the advent of a new government is examined. It has its roots in the last major changes to the oil tax regime which were made in 1993. It has been made clear by the government that the taxation review has not been abandoned and could come to the fore again should there be a substantial increase in oil and gas prices or if companies sought premature decommissioning of North Sea fields. (UK)

  4. Radioactivity concentrations in the North Sea

    The following nuclides can be detected in the North Sea: 90Sr, 106Ru, 137Cs, 134Cs, 241Am and 244Cm. The water in the channel east of Cherbourg still contains low quantities up to 0.5 pCi/l of the fission product 125Sb (t 1/2=2.77 a). The activity of T is not exactly known, for the german Bay it is estimated to 50 pCi/l. In comparison of these artificial radioactivies with the natural radioactivity of the North Sea, which mainly depends on 40K, 87Rb as well as uranium and decay products, it has to be taken into account that the activity of α- and β-active substances from nuclear weapons tests before 1962 and by controlled discharge from nuclear power plants, amounts to a range of 1%. (HP)

  5. The North Sea reservoir chalk characterization

    Kallesten, Emanuela


    A significant amount of the hydrocarbon production in the North Sea is related to chalk reservoirs. Since 1969, the chalk play remains one of the most important oil sources in Norway. With the initial expected recovery factor 17%, development in technologies and methods contributed to a substantial increase in oil recovery to an approximately 40%. Much of the reserves in place are yet to be extracted, and secondary and tertiary recovery methods need to advance in order to mobilize the remaini...

  6. Extreme Storm Surges in the North Sea

    Goennert, G.; Buß, Th.; Mueller, O.; Thumm, S.


    Extreme Storm Surges in the North Sea Gabriele Gönnert, Olaf Müller, Thomas Buß and Sigrid Thumm Climate Change will cause a rise of the sea level and probably more frequent and more violent storm surges. This has serious consequences for the safety of people as well as for their values and assets behind the dikes. It is therefore inevitable to first assess how sea level rise and an extreme storm surge event designes. In a second step it is possible to determine the risk for specific locations and develop strategies. The Project XtremRisk - Extreme Storm Surges at the North Sea Coast and in Estuaries. Risk calculation and risk strategies, funded by the German Federal Government will help answering these questions. The „Source-Pathway-Receptor" Concept will be used as a basis for risk analysis and development of new strategies. The Project offers methods to assess the development of extreme events under the conditions of today. Under conditions reflecting the climate change it will be tried to design an extreme event. For these three main points will be considered: a) Analysis and calculation of each factor, which produce a storm surge and its maximum level occurring in the last 100 years. These are: - maximum surge level: surge (due to the wind), - influence of the tide and the interaction between surge and tide, - influence of external surges , b) The hydrodynamics of a storm surge cause nonlinear effects in the interaction of the named factors. These factors and effects will both be taken into account to calculate the magnitude of the extreme storm surge. This step is very complex and need additional examination by numerical models. c) Analysis of the different scenarios to mean sea level rise and to the increase of wind speed due to the climate change. The presentation will introduce methods and show first results of the analysis of extreme events and the mean sea level rise.

  7. Role of bacteria in the North Sea ecosystem

    Billen, Gilles; Joiris, Claude; Meyer-Reil, Lutz; Linderboom, Han

    Since about 15 years methods available to assess the role of bacteria in organic matter cycling of aquatic ecosystems have been considerably improved. Their application to the North Sea deeply modified the vision of the ecological structure of this ecosystem which prevailed in the early seventies, as summarized e.g. by STEELE (1974). A critical examination of the methodology utilized for measuring standing stock and activities of bacteria in the water column and the sediments of the North Sea is presented and the results of these measurements summarized. Measurements of planktonic bacterial biomass show important seasonal and geographical variations, related, with a delay of about 10 days, to phytoplanktonic development. Assessment of the standing stock and turnover rate of high molecular weight dissolved organic matter and monomeric substrates provides data consistent with the view that extracellular enzymatic hydrolysis of polymers is limiting the rate of organic matter utilization, while uptake of direct substrates is rapid and maintains their concentration at a near constant level. The flux of organic matter flowing through the planktonic bacterial compartment is evaluated to about 110gC/m 2.yr in the coastal continental zone, i.e. 57% of net primary production. Bacterial production rates show a growth yield in the range 0.1 to 0.4. In the Central North Sea data are lacking to allow accurate estimation of planktonic bacterial activity on annual basis. The available information suggests that a lower percentage of primary production is used by bacteria there. Data concerning bacterial biomass and activity in the benthos are even less numerous than for the planktonic phase. A crude estimate of the flux of organic matter sedimentation based on sediment traps measurements on the one hand, and of organic matter utilization rates by benthic organisms (including both bacteria and meiofauna) derived from oxidant or nutrient budgets on the other hand, yield values in the

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

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


    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.

  9. The Jurassic of Denmark and Greenland: Volgian–Ryazanian ‘hot shales’ of the Bo Member (Farsund Formation in the Danish Central Graben, North Sea: stratigraphy, facies and geochemistry

    Dybkjær, Karen


    Full Text Available Upper Jurassic – lowermost Cretaceous marine mudstones represent the most significant source of hydrocarbons in the Central and Northern North Sea. Of particular importance in the Danish sector of the Central Graben is a succession of radioactive ‘hot shales’ referred to the Bo Member, in the upper levels of the Farsund Formation (Kimmeridge Clay Formation equivalent. This mudstone-dominated succession is typically 15–30 m thick and has a total organic carbon (TOC content of 3–8%, though locally exceeding 15%. Although truncated on some structural highs, the Bo Member is a persistent feature of the Danish Central Graben. Lateral variation in boththickness and organic richness is attributed to intrabasinal structural topography and to the location of sediment input centres.Detailed study of the dinoflagellate cyst biostratigraphy of 10 wells indicates that the onset of enhanced organic carbon burial began in the middle–late Middle Volgian in this portion of theCentral Graben. The Bo Member, representing the peak of organic carbon enrichment, is largely of Early Ryazanian age. Core data (Jeppe-1, E-1 wells indicate that the organic-rich shales of theBo Member are not wholly of hemipelagic origin, as commonly assumed, but may locally be dominated by fine-grained turbidites. Absence of bioturbation, well-preserved lamination and high TOC values suggest that bottom waters were predominantly anoxic although the presenceof in-situ benthic bivalves at discrete horizons in the E-1 well suggests that suboxic conditions prevailed on occasion. The Bo Member is a good to very good source rock, showing very highpyrolysis yields (10–100 kg HC/ton rock and Hydrogen Index (HI values in the range 200–600. In particular, the Bo Member is characterised by an abundance of 28,30 bisnorhopane (H28, acompound that is indicative of anoxic environments. These new data from the Danish sector of the Central Graben are compatible with the model of Tyson et

  10. Phytoplankton Bloom in North Sea off Scotland


    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.

  11. Atmospheric concentrations and air-sea exchanges of nonylphenol, tertiary octylphenol and nonylphenol monoethoxylate in the North Sea

    Concentrations of nonylphenol isomers (NP), tertiary octylphenol (t-OP) and nonylphenol monoethoxylate isomers (NP1EO) have been simultaneously determined in the sea water and atmosphere of the North Sea. A decreasing concentration profile appeared following the distance increasing from the coast to the central part of the North Sea. Air-sea exchanges of t-OP and NP were estimated using the two-film resistance model based upon relative air-water concentrations and experimentally derived Henry's law constant. The average of air-sea exchange fluxes was -12 ± 6 ng m-2 day-1 for t-OP and -39 ± 19 ng m-2 day-1 for NP, which indicates a net deposition is occurring. These results suggest that the air-sea vapour exchange is an important process that intervenes in the mass balance of alkylphenols in the North Sea. - Air-sea vapour exchanges of estrogenic alkylphenols are studied in the North Sea and it is shown that a net deposition is occurring

  12. A synthesis of Cenozoic sedimentation in the North Sea

    Anell, Ingrid Anna Margareta; Thybo, Hans; Rasmussen, E.S.


    sediment influx into the North Sea during the Cenozoic is more complex than previously suggested clockwise rotation from early northwestern to late southern sources. The Shetland Platform supplied sediment continuously, although at varying rates, until the latest Cenozoic. Sedimentation around Norway...... changed from early Cenozoic influx from the southwestern margin, to almost exclusively from the southern margin in the Oligocene and from all of southern Norway in the latest Cenozoic. Thick Eocene deposits in the Central Graben are sourced mainly from a western and a likely southern source, indicating...

  13. Emerald oil field on production in North Sea

    This paper reports that Midland and Scottish Energy Ltd. (MSE) has placed Emerald oil field on stream in the U.K. North Sea with a floating production unit. Initial production, from two satellite wells, will be used to commission facilities. Three water injection wells have been unplugged and are ready for start-up. MSE will place a central cluster of wells-five producers and one water injector-on stream during the next few weeks. Production will build to an expected 25,000 b/d from 35 million bbl of reserves. Field development has undergone an unusually large number of setbacks and changes

  14. North Sea oil and the environment

    This book, which is arranged in five sections, provides an historical record of the development of North Sea oil and gas over the past twenty years and records the lessons learnt from this experience. This first section provides an introductory framework to the three main themes, namely resources, environment and development. Section 2 is primarily concerned with the economic and social consequences of oil related development at two levels; firstly on the national economy and secondly the impact on local communities. Section 3 deals with impacts upon the physical environment and introduces the statutory land use planning system in Scotland. The Scottish approach to environmental assessment is reviewed and the need for mitigation by design explored. Section 4 examines specific field developments, and reviews the statutory controls and international initiatives regulating the extent of environmental disturbance and pollution from offshore operations. The effects of oil spillage and submarine pipelines on the environment and their impact on the fishing industry is followed by a discussion on the decommissioning and abandonment of offshore installations. Section 5 deals with the role and value of hazard and risk analysis in the siting, layout and safety zoning of onshore facilities and develops a case study on a major fractionation facility. The means of mitigating acute and chronic environmental risks are considered. A postscript provides a range of past comments and criticisms and finally draws some conclusions on the performance of environmental management and North Sea oil development. The North Sea oil and gas development experience proves that with wisdom, forethought and goodwill, industrial exploiters of natural resources can operate economically within legislative, policy, scientific, technical and design parameters without causing long-term irreversible environmental damage. (author)

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

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


    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

  16. North Sea Elasmobranchs: distribution, abundance and biodiversity

    Daan, N.; Heessen, H.J.L.; Hofstede, ter, AHM Arthur


    Based on data from various international and national surveys, an overview is given of the fine-scale distribution (resolution of 20¿longitude * 10¿ latitude; ¿ 10*10 nm) and trends in abundance of elasmobranch species reported from the North Sea. Presence-absence maps are produced based on 4 surveys, which help to delineate distribution limits of the less common species, while maps in terms of catch rates (International Bottom Trawl Survey data only) are given for the seven most common shark...

  17. Petroleum Economist's 1993 North Sea survey

    A survey is presented for 51 oil fields in the North Sea belonging to the United Kingdom, 17 belonging to Norway, 4 belonging to the Netherlands and 7 belonging to Denmark. Similarly data is presented for 32 gas fields belonging to the United Kingdom, 5 belonging to Norway, 42 belonging to the Netherlands, and 1 belonging to Denmark. The information given in the surveys includes the original recoverable reserves, remaining reserves, water depth, gravity, sulphur content, discovery date, start-up date, participants and production. (U.K.)

  18. Migration of western mackerel to the North Sea 1973 - 1988

    Iversen, Svein A.; Skagen, Dankert W.


    The latest years, it is evident that most of the mackerel present in the North Sea belongs to the Western stock, since the yearly catches by far exceed the presumed size of the North Sea stock. The Norwegian tagging data have been revised to obtain estimates of the percentage of Western mackerel in the catches in the North Sea. By combining these data with the distribution of catches, a reasonable estimate of the migration of the Western mackerel to the North Sea may be o...

  19. Sea surface temperatures and salinities from platforms in the Barents Sea, Sea of Japan, North Atlantic Ocean, Philippine Sea, Red Sea, and the South China Sea (Nan Hai) from 1896-1950 (NODC Accession 0000506)

    National Oceanic and Atmospheric Administration, Department of Commerce — Surface temperatures and salinities were collected in the Barents Sea, Sea of Japan, North Atlantic Ocean, Philippine Sea, Red Sea, and South China Sea (Nan Hai)...

  20. North Sea focus on radwaste disposal

    At the recent North Sea Conference in the Netherlands possible future strategies for managing radioactive waste (radwaste) proved to be a contentious issue. Several of its North Sea littoral neighbours sought a categorical assurance that the UK would forego the option of constructing a subterranean radwaste repository which though accessed from land, extends under the coastline, or a sub-seabed facility reached from an offshore structure. It was pointed out that the UK has no present plans for such a radwaste repository. However, sub-seabed designs as a possibility for future repositories were not ruled out. NIREX has decided to concentrate its exploration work at two sites -Sellafield and Dounreay. Both sites are coastal locations and the government is aware that detailed geological exploration may favour extension of a radwaste repository beyond the shoreline, even if initially developed entirely on land. The design of such a radioactive waste repository is outlined. The position of NIREX and the Radioactive Waste Management Advisory Committee is discussed. (author)

  1. Diversity and community structure of epibenthic invertebrates and fish in the North Sea

    Callaway, R.; Alsväg, J.; de Boois, I.;


    The structure of North Sea benthic invertebrate and fish communities is an important indicator of anthropogenic and environmental impacts. Although North Sea fish stocks are monitored regularly, benthic fauna are not. Here, we report the results of a survey carried out in 2000, in which five...... nations sampled the epibenthic and fish fauna at 270 stations throughout the North Sea. The aim of the survey was to investigate the diversity and community structure of epibenthic and fish communities and to identify relationships with environmental factors, including the frequency of commercial otter...... and beam trawling disturbance. Epibenthic species diversity was lower in the southern North Sea than in central and northern areas. Fish, conversely, were more diverse in the south. The 50 m, 100 m and 200 m depth contours broadly defined the boundaries of benthic and fish communities. The abundance...

  2. The contamination of the North Sea by artificial radionuclides during the year 1987

    The activity concentrations of the caesium isotopes 137Cs and 134Cs and of the radionuclide strontium-90 in the seawater of the North Sea during the year 1987 are presented. Isotopes originating from the reactor disaster at Chernobyl are detectable in the water of the North Sea only at very low activities. At some positions in the North Sea, plutonium isotopes, americium and curium have been determined. The main source of these artificial nuclides are the preprocessing plants at Sellafield (UK) and La Hague (France). Due to the installation of new reprocessing facilities at Sellafield, a constant downward trend of contamination from 137Cs in the central North Sea can be established. (author)

  3. Combining sea state and land subsidence rates in an assessment of flooding hazards at the Danish North Sea coast

    Sørensen, Carlo Sass; Broge, Niels; Knudsen, Per; Andersen, Ole Baltazar

    Sand nourishments (2-3 M3/y) counteract erosion on the central North Sea coast of Denmark and dikes and artificial dunes protect the low-lying hinterland from flooding. The fisheries towns of Thyboron, Thorsminde and Hvide Sande are all liable to flooding during storm surges. Tide gauge series from...

  4. [Evacuation of patients from the North Sea].

    Freund, K G


    In 1986 and 1987 the department of orthopaedic surgery at the Central Hospital of Esbjerg dealt with 135 medical problems by radio-telephone contacts to persons at sea. Of these, 28% needed a chartered helicopter. This eguals one third of all chartered helicopter evacuations from Danish waters. 77% of the evacuations were from fishing boats and the rest from offshore structures or other kinds of ships. The mechanism of trauma and the diagnosis agreed with the findings in an earlier Danish publication. PMID:2749648

  5. Regional cenozoic uplift and subsidence events in the southeastern North Sea

    Jordt, H.


    The Paleocene topography of the Fennoscandian Shield is indicated by outbuilding towards the Central Trough and the Ringkoebing-Fyn High. From Eocene until Pliocene time three events of relative vertical movements are indicated by changes in outbuilding directions and reflection termination patterns in the central North Sea. The firs event of uplift was in the Eocene and resulted in relative uplift of the Mid North Sea High and contemporary subsidence east of it, indicated by a change in outbuilding from north to west. A second event of uplift is indicated to the north of the study area at the Eocene-Oligocene boundary by renewed southward outbuilding in the Norwegian-Danish Basin. In Miocene until Early Pliocene time a relatively stationary, almost east-west striking, basin margin was probably located to the north along the Tornquist Zone as indicated by the continued outbuilding towards the Ringkoebing-Fyn High. A third event of relative uplift is indicated east of the study area by changes in the Pliocene outbuilding pattern. After the first event of uplift it appears that the deepest parts of the Eocene North Sea Basin was located more easterly than the deepest part are today. Apparently the two latest uplift events north and east of the study area were related to movements of, or along the Tornquist Zone or to regional uplift of the Fennoscandian Shield finally resulting in the present-day configuration of the North Sea. (au) 11 refs.

  6. Scientific symposium on the North Sea quality status report 1993

    The Scientific Symposium on the 1993 North Sea quality Status Report took place in Ebeltoft, Denmark from 18 to 21 April 1994. The aim was to bring together scientists, researchers and administrators from governments, industries and environmental organizations from the countries around the North Sea in order to review new information which may supplements the 1993 North Sea Quality Status Report and to discuss the Quality Status Report and its possible implications. The 1993 North Sea Quality Status Report has been prepared by the North Sea Task force as a comprehensive statement of circulation patterns, inputs and dispersion of contaminants, ecological conditions and effects of human activities in the North Sea including the Skagerrak and the Kattegat. The programme of the Scientific Symposium on the 1993 North Sea Quality Status Report included 8 sessions for oral presentations, a poster session presenting the North Sea Task Force subregional reports and a poster session presenting individual posters. The headings of the sessions were as follows: Oceanography, Models and Remote Sensing; Ecosystem Structure; Contaminants -Distribution and Effects; Nutrients and Eutrophication Problems; Effects of Fishery; Habitats and Species; Management Implications; Conclusions and Recommendations. The proceedings includes a total of 45 contributed papers. (EG)

  7. Submarine pipelines and the North Sea environment

    The function and design of pipelines for use on the United Kingdom continental shelf are described. Environmental influences which can threaten the integrity of seabed pipelines in the North Sea include hydrodynamic forces due to residual, tidal and wave currents, the nature of seabed sediments and corrosion by seawater. Damage may be caused to pipelines by interaction with vessel anchors and with fishing gear. Special care has to be taken over the selection of the general area for the landfall of a pipeline and the engineering of the installation where the pipeline comes ashore. Trenching and other protection techniques for pipelines are discussed together with hydrostatic testing and commissioning and subsequent inspection, maintenance and repair. (UK)

  8. Compaction of North-sea chalk

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


    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

  9. Power production via North Sea Hot Brines

    Traditionally the power demand of offshore oil platforms is delivered by on-platform gas turbines. Natural gas to fuel these turbines is usually separated from the produced oil. However, in ageing fields as oil production declines so does the associated gas. Ultimately gas supply becomes insufficient; in order to continue producing fuel is imported at great expense. This study proposes the power demand of a platform could be met or supplemented by an on-platform ORC (organic Rankine cycle ) fuelled by coproduced hot brines. This could extend the operating life of oil platforms and reduce both cost and emissions. The potential power output of an ORC is modelled for fields in the North Sea's Brent Province. Results show 6 fields have the potential to generate more than 10 MW via an organic Rankine cycle fuelled by hot brines, with a maximum of 31 MW predicted for the Ninian field. Analysis of simulations for the Eider field shows that ORC plants can scale to size constraints. The cost of a 10 MW ORC is compared to cost of continued use of gas turbines. Payback times of between 3.09 and 4.53 years are predicted for an ORC, without accounting for greenhouse gas emissions levies. - Highlights: • We model organic Rankine cycles fuelled by hot brines produced in the North Sea. • Organic Rankine cycles could provide all an off-shore platform's power demand. • 6 fields in the Brent province have the potential to produce >10 MW via an ORC system. • Payback time calculated for a 10 MW organic Rankine cycle is 3.09–4.53 years

  10. Sea Surface Temperature Climate Data Record for the North Sea and Baltic Sea

    Høyer, Jacob L.; Karagali, Ioanna


    A 30-yr climate data record (CDR) of sea surface temperature (SST) has been produced with daily gap-free analysis fields for the North Sea and the Baltic Sea region from 1982 to 2012 by combining the Pathfinder AVHRR satellite data record with the Along-Track Scanning Radiometer (ATSR) Reprocessing...... ARC observations on average. Validation against independent in situ observations shows a very stable performance of the data record, with a mean difference of -0.06 °C compared to moored buoys and a 0.46 °C standard deviation of the differences. The mean annual biases of the SST CDR are small for all...

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

    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

  12. Well data summary sheets. Vol. 21. Danish North Sea



    This twenty first volume of the `Well Data Summary sheets` together with volumes twenty and twenty two which have been prepared concurrently, includes data from wells in the Danish North Sea with Jurassic sections. With the exception of Falk-1 well in volume 20, all the included wells have been released and can be found in the previous volumes (1-16). The primary purpose of producing these three volumes (20-22) has been to update the previously released wells and produce them in our new format. Additionally, this compilation brings together wells from the same geographic region (Central Graben area) with Jurassic sections. An exception to this is the Ibenholt-1 well (this volume) and the Felicia-1/1A well (volume 20). Minor corrections have been made since the first edition. The `Complete index of released wells` had been updated. Volume 27, 28 and 29 are regional volumes; volume 27 includes well data from Southern Jutland; volumes 28 and 29 cover well data from Northern Jutland. All data from released Danish North Sea wells are included in volumes 17-26 and 30. Data references are made to the revised volumes and not to the original published reference. (au)

  13. Space Radar Image of North Sea, Germany


    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

  14. More North Sea oil flowing despite stormy disruptions

    North Sea operations this year have been plagued by storms, a perennial problem off Northwest Europe. Even so, operators continued to log progress in placing new fields on stream. Seventeen U.K. offshore fields have gone on stream during 1993, compared with Norway's four, Netherlands' three, and Denmark's two. Although the boom days are over for the North Sea, some operators are convinced that reduction of development and operational costs could yield opportunities in the region for years to come. The paper discusses selected highlights of the year's operations in the North Sea

  15. Tectonic and thermal reconstruction by joint inversion of many wells in the North Sea area

    Nielsen, S.B.


    This report develops and applies a method for joint inverse tectonic and thermal analysis of many wells in the central and Easten North Sea area. The model simultaneously considers the thermal and topographic effects from a number of processes on widely differing length and time scales. The processes are: 1) changing asthenospheric temperatures coupled with changing rates of material up- or down-welling in asthenosphere and lithosphere, 2) tectonic processes in the form of pure shear extension or compression, 3) sediment compaction, 4) halokinetics, 5) all loading effects, 6) global sea level variations, 7) surface temperature variations and 8) lateral variations of the crustal contribution to heat flow. Data for the model were obtained from compilation of many North Sea wells, 40 of which were used in the present study. The model results give for the first time a quantitative indication of the relationship between the general geological evolution of the North Sea over 300 Ma and the regional and more localised geodynamic processes, which set the scene for this evolution. Thus the Permo-Triassic post-rift sequence is accommodated by thermal relaxation of the lithosphere-asthenosphere system, enhanced by a decreasing rate of material upwelling and a falling asthenospheric temperature. The rise of the Middle Jurassic dome, which led to the North Sea wide mid-Kimmerian inconformity, is related to an increasing rate of material upwelling and increasing asthenospheric temperature. The demise of the dome and the associated reduction in upwelling rate and cooling of the lithosphere-asthenosphere system provided accommodation space for the post-mid Cretaceous sedimentary succession. It cannot be explained in terms of Late Jurassic lithospheric extension. Heat flow shows a smooth decline over 300 Ma. Neither rifting nor doming episodes appear to have influenced the overall heat flow significantly in the study area. In the case of rifting this is partly due to thermal

  16. Rock-physics modelling of the North Sea greensand

    Hossain, Zakir

    glauconitic greensand may have similar seismic response to oil saturated quartzitic sandstone and that strongly cemented greensand with oil saturation can have similar AVO response to brine saturated weakly cemented greensand. The third rock-physical model predicts pore fluid effects on elastic properties of...... homogeneous. The central part of this study is rock-physics modelling of greensand. The first of the models is a grain contact model of the North Sea Paleocene greensand. First a Hertz-Mindlin contact model is developed for a mixture of quartz and glauconite. Next step is to use the moduli predicted from this...... Hertz-Mindlin contact model of two types of grains as the initial moduli for a soft-sand model and a stiff-sand model. Results of rock-physics modelling and thin section observations indicate that variations in the elastic properties of greensand can be explained by two main diagenetic phases: silica...

  17. Quantification of seep-related methane gas emissions at Tommeliten, North Sea

    Schneider von Deimling, J.S.; Rehder, G.; Greinert, J.; McGinnnis, D.F.; Boetius, A.; Linke, P.


    Tommeliten is a prominent methane seep area in the Central North Sea. Previous surveys revealed shallow gas-bearing sediments and methane gas ebullition into the water column. In this study, the in situ methane flux at Tommeliten is re-assessed and the potential methane transport to the atmosphere i

  18. The microbiome of North Sea copepods

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


    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.

  19. Radioactive contamination of the North Sea and the Baltic Sea - a status report (September 1986)

    The author examines different inputs of North and Baltic Sea by fallout of nuclear weapons, reprocessing plants and Chernobyl. The reprocessing plants Sellafield and La Hague are the most important sources of radioactive contamination, especially for the North Sea. After Chernobyl all radionuclides of the fallout were demonstrable. (CW)

  20. Temperature, Salinity, Oxygen, Phosphate, pH and Alkalinity data collected in the North Atlantic Ocean, Baltic Sea, Barents Sea, Greenland Sea, North Sea, Norwegian Sea and White Sea from R/Vs Artemovsk, Atlantida, Okeanograf, Professor Rudovits, and ice observations, 1957 - 1995 (NODC Accession 0073674)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature, Salinity, Oxygen, Phosphate, pH and Alkalinity data collected in the North Atlantic Ocean, Baltic Sea, Barents Sea, Greenland Sea, North Sea, Norwegian...

  1. Soil indigenous knowledge in North Central Namibia

    Prudat, Brice; Bloemertz, Lena; Kuhn, Nikolaus J.


    Mapping and classifying soils is part of an important learning process to improve soil management practices, soil quality and increase productivity. In order to assess soil quality improvement related to an ongoing land reform in North-Central Namibia, the characteristics that determine soil quality in the local land use context were determined in this study. To do so, we collated the indigenous soil knowledge in North-Central Namibia where the Ovakwanyama cultivate pearl millet for centuries. Local soil groups are defined mostly based on their productivity potential, which varies depending on the rainfall pattern. The morphological criteria used by the farmers to differentiate the soil groups (colour, consistence) were supported by a conventional analysis of soil physical and chemical properties. Now, they can be used to develop a soil quality assessment toolbox adapted to the regional use. The characteristics of the tool box do not directly indicate soil quality, but refer to local soils groups. The quality of these groups is relatively homogenous at the local scale. Our results show that understanding of indigenous soil knowledge has great potential to improve soil quality assessment with regards to land use. The integration of this knowledge with the conventional soil analysis improves the local meaning of such a "scientific" assessment and thus facilitates dialog between farmers and agronomists, but also scientists working in different regions of the world, but in similar conditions. Overall, the integration of indigenous knowledge in international classification systems (e.g. WRB) as attempted in this study has thus a major potential to improve soil mapping in the local context.

  2. The North Sea: perspectives on regional environmental co-operation

    The North Sea is important to many countries. Its well-being depends on even more. Representatives of many of these countries meet at the North Sea Conferences to discuss current and future issues on all aspects of the North Sea environment. In this issue a perspective view of the Conferences is taken in the first part (7 papers). This includes the history of the Conference, the legal status of the North Sea declarations and problems of their implantation. Existing frameworks are considered in the second part (11 papers). Outstanding issues on specific problems such as marine life are discussed in the final part (8 papers). This includes an article on radiological discharges, which come mostly from the Sellafield Reprocessing plant, which is indexed separately. (U.K.)

  3. North Central Project: Environment act proposal

    Manitoba Hydro proposes to construct a power transmission and distribution line system to connect 12 northern Manitoba communities to the utility's central power grid. The purpose of this North Central Project (NCP) is to provide reliable and unrestricted electric service to remote communities now largely receiving limited diesel-generated power. The NCP is composed of a 138-kV transmission line running ca 350 km from the Kelsey Generating Station, ca 160 km of 25-kV distribution lines, new transformer stations at four communities, upgraded internal distribution systems within the communities, removal of existing diesel stations and restoration of the sites, modifications and additions to the Kelsey switchyard, and a communications system. The NCP is described in detail, including proposed line routes and transformer station locations, rationales for site and route selection, projected impacts on the environment and local societies, and consultations with the communities to be affected. Potential impacts are expected to be modest, with few unmitigable adverse impacts and a number of potentially significant positive benefits. Impact management measures are proposed to prevent or mitigate adverse effects and to create or enhance positive impacts such as local employment of native peoples. 49 figs., 1 tab

  4. Recruitment of meroplanktonic larvae in the Southern Bight of the North Sea

    Belgrano, A.; Vincx, M.; Dewarumez, J.-M.; A. Richard; Craeymeersch, J.A.; Heip, C. H. R.


    The density distribution of meroplanktonic larvae is compared with the density distribution of adults in the benthos, at five coastal stations in the Southern Bight of the North Sea (Abra alba community). Plankton communities were sampled during one tidal cycle, along a buoy traject or at a fixed point; southern and northern locations, 250 m from each central sampling point, have been investigated too. Benthos samples were taken only at the central points of this traject. Meroplankton consist...

  5. North sea water mass cartography, with radiotracer technologies

    The radionuclide study was the root of important improvements in recent oceanography; indeed their environment future may be followed. The artificial radioisotopes, which are soluble in sea water, allowed to identify accurately water masses, penetrating in North Sea. Those water cartographies give essential informations on the release impact evaluation, accidental or controlled, in a very active economical european region. 6 figs. 1 tab

  6. Assessment of the North-East Arctic and North Sea Stocks of Saithe Taking Into Account Migration

    Jakobsen, Tore


    Tagging experiments have shown that there is a substantial migration of young saithe from the Norwegian coast north of 62°N to the North Sea. Assessments of the North-East Arctic and North Sea Stocks of saithe were made assuming that all 1-4 year old saithe caught between 62° and 64°N would have recruited to the North Sea stock. The new assessments give a decrease in the level of recruitment to the North-East Arctic stock and an increase to the North Sea stock. he exploitation of the NorthEa...

  7. Lifestyle survey amongst North Sea oil workers

    Horsley, Harry [RGIT Ltd., Research Unit, Aberdeen (United Kingdom); MacKenzie, I.G. [Robert Gordon Univ., School of Computer and Mathematical Sciences, Aberdeen (United Kingdom)


    Recognition is growing of the influence of the workplace on lifestyle, and its consequent effect on health. This relation between work, lifestyle and health is highly relevant to the North Sea oil and gas industry where employment often demands the adoption of, and exposure to, a lifestyle far removed from that of comparable onshore occupations. This risk factors for Coronary Heart Disease (CHD) which is the largest single cause of premature adult death in Great Britain can be classified according to those that are immodifiable (eg gender), and those that result from lifestyle choices (eg smoking, diet). The demographic profile (predominant gender, age group and nationality) of the offshore workforce is thought to place it in an inherently high risk group for CHD. Anecdotal evidence further suggests that the offshore lifestyle may expose the workforce to increased CHD risk factors, particularly in terms of diet, tobacco consumption and exercise habits. The lifestyle of offshore workers may be considered as a form of occupational hazard, comparable with recognised occupational risks. A sample of 500 offshore workers undertaking survival training were surveyed using a structured questionnaire to investigate aspects of their lifestyle. Subjects compared their smoking, dietary and exercise habits between periods onshore and offshore. Analysis of results pointed to some significant differences in lifestyle between these two periods. Additional factors such as occupation status (whether directly employed or contracted), onshore alcohol consumption, and subjects` perception of job and family satisfaction were also analysed in relation to lifestyle. Results indicate the potential benefits of health promotion intervention. Opportunities for such intervention are identified and discussed within the context of caring for an efficient utilisation of the Offshore Industry`s human resources. (Author)

  8. High oxygen consumption rates in the deep layers of the North Aegean Sea (eastern Mediterranean



    Full Text Available Severe winter meteorological conditions promote dense water formation over the shelves of the North Aegean Sea. The newly formed dense water fills the deep basins of the North Aegean Sea, contributing to their ventilation and the downward transport of organic and inorganic material. The great bathymetric variability imposes limitations on the deep circulation and the communication between the various basins and makes the North Aegean Sea an appropriate area for the monitoring of oxygen consumption in the deep layers. Historical hydrographic data suggest that there was extensive production of dense water in the North Aegean Sea on two occasions during the last decade, the winters of 1987 and 1992-1993. Our data series from August 1986 to September 1989 and from March 1997 to February 1999, permitted us to follow, step by step, the oxygen consumption and the nutrient regeneration in the deep basins of the northern Aegean Sea during these periods of isolation. The organic matter reaching the bottom layer just after the deep water formation event is rich in labile and easily oxidizable material and its decomposition leads to a significant oxygen uptake during the first year of stagnation. The further decomposition of the remaining semi-labile and refractory material turns over on greater time scales, by consuming lesser amounts of oxygen. A more significant oxygen decrease is recorded in the eastern basin (Lemnos Basin of the North Aegean Trough, than in the central (Athos Basin and the western (North Sporades Basin ones and is attributed to the irregular contribution of the Black Sea Water (BSW to the water masses formed on the different shelves of the North Aegean Sea. Our results and the existing data on the Turkish straits showed that dissolved organic matter is the major constituent responsible for this high oxygen consumption. The slightly different particulate organic carbon fluxes to these depressions play a secondary role.

  9. Dissolved inorganic radiocarbon in the North Pacific Ocean and Sargasso Sea

    Druffel, Ellen R. M.; Bauer, James E; Griffin, Sheila; Beaupré , Steven R; Hwang, Jeomshik


    We present radiocarbon measurements of dissolved inorganic carbon (DIC) in depth profiles from reoccupations of our central North Pacific Ocean and Sargasso Sea (SS) sites. From 1985 to 1999, an increase in Δ14C values of 6–17‰ was measured between 1150 and 2400 m depth in the North Central Pacific. Natural changes in deep circulation are likely responsible for variability of Δ14C signatures in the deep ocean, though we cannot rule out the presence of bomb 14C at this depth range. Bomb 14C ha...

  10. Temperature profile and pressure data from CTD casts in the Baltic Sea, Greenland Sea, North Sea, and North Atlantic Ocean from 25 February 1990 to 15 February 2006 (NODC Accession 0002681)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and pressure data were collected using CTD casts from several vessels in the Baltic Sea, Greenland Sea, North Sea, and North Atlantic Ocean from...

  11. Fluctuation of dominant mesozooplankton species in the Black Sea, North Sea and the Baltic Sea: Is a general trend recognisable?

    NIERMANN, Ulrich; BİNGEL, Ferit; ERGÜN, Güner


    The distribution and fluctation of dominant pelagic species>300µ(Copepoda, Chaetognatha, Scyhozoa, Ctenophora and ichthyoplankton) of the southern Black Sea were compared with that of dominant species of the North Sea and the Baltic Sea in relation to oceanographic and environmental features. In all three seas, similar changes in the zooplankton composition took place at the end of the 1980's, and the beginning of the 1990's. - decreasing or increasing abundances of certain s...

  12. The Potential for Wave Energy in the North Sea

    Sørensen, H. C.; Chozas, Julia Fernandez


    The North Sea has not yet been regarded as prime area for wave energy development in Europe except in Denmark, Benelux and Germany. The reason is the relatively low intensity of waves (12-17kW/m) compared to the Atlantic with a wave climate of 24-48kW/m. Further on the design wave load is almost...... as in the Atlantic and the distance to shore relatively long compared to sites with good wave climate like Ireland, Portugal, Spain and the west coast of UK. The increasing activities within offshore wind in the North Sea and the attempt to build a super grid connecting the wind sites with the major consumers around...... the North Sea are expected to change the priority in favour of utilising wave energy from the North Sea. The paper describes the opportunities for power production in the North Sea considering the competition for space and the synergy with offshore wind. Two approaches are used: a traditional national...

  13. Sea Surface Temperature (14 KM North America)

    National Oceanic and Atmospheric Administration, Department of Commerce — Product shows local sea surface temperatures (degrees C). It is a composite gridded-image derived from 8-km resolution SST Observations. It is generated every 48...

  14. North Pacific High Seas Squid Jig Logbook

    National Oceanic and Atmospheric Administration, Department of Commerce — This is a federally mandated logbook program high seas squid jig fishing, and it is required to be mailed in to PIFSC after a fishing trip. Fishing occurs in the...

  15. The importance of North Sea oil to European energy supply

    There is no doubt about the importance of North Sea oil to the energy supply of the European Community. One might however be used to it and forget about the nature and the size of its impact on our economies. Firstly, this paper intends to estimate this impact - past, present and future. Secondly, a more qualitative approach will explore possible consequences of the implementation of the internal market for North Sea oil. Thirdly, the assistance given by the Community to innovative technologies which enabled North Sea oil to contribute, under better economic conditions and within a safer environment, to our supply is recalled. And finally, some remarks on energy policy form an EC perspective, are offered. (author)

  16. Seasonal variability in the Central Mediterranean Sea circulation

    R. Sorgente

    Full Text Available A high resolution eddy-resolving primitive equation numerical model, based on the Princeton Ocean Model (POM, is used to study the seasonal variability of the general circulation in the Central Mediterranean Sea. The model is run on a seasonal cycle, perpetual year simulation for five years, with nesting to the coarser resolution Ocean General Circulation Model (OGCM, covering the whole Mediterranean Sea. The model results are compared to the current knowledge on the hydrography and dynamics of the area, with a special focus on the annual cycle of the Modified Atlantic Water (MAW, on the circulation in the Sardinia Channel, the water exchange across the Strait of Sicily, and on the transition and fate of the Levantine Intermediate Water (LIW. The results show that the adopted coupling techniques between the two models give a proficient downscaling of the large-scale OGCM flow field into the regional scale model. The numerical solution is also used to highlight the seasonal characteristics of important dynamical features in the area, as well as to shed light on the scarcely known circulation regimes along the north African shelf and slope.

    Key words. Oceanography: general (numerical modelling; Oceanography: physical (currents; general circulation

  17. Observed mean sea level changes around the North Sea coastline from 1800 to present

    Wahl, T.; Haigh, I.D.; Woodworth, P. L.; Albrecht, F.; Dillingh, D.; Jensen, J; Nicholls, R J; Weisse, R.; Wöppelmann, G.


    This paper assesses historic changes in mean sea level around the coastline of the North Sea, one of the most densely populated coasts in the world. Typically, such analyses have been conducted at a national level, and detailed geographically wider analyses have not been undertaken for about 20 years. We analyse long records (up to 200 years) from 30 tide gauge sites, which are reasonably uniformly distributed along the coastline, and: (1) calculate relative sea level trends; (2) examine the ...

  18. Regionalization of climate model results for the North Sea

    Kauker, F.


    A dynamical downscaling is presented that allows an estimation of potential effects of climate change on the North Sea. Therefore, the ocean general circulation model OPYC is adapted for application on a shelf by adding a lateral boundary formulation and a tide model. In this set-up the model is forced, first, with data from the ECMWF reanalysis for model validation and the study of the natural variability, and, second, with data from climate change experiments to estimate the effects of climate change on the North Sea. (orig.)

  19. Emissions from oil platforms in the North Sea

    When oil and gas are extracted from below the sea bed, emissions generally occur drilling and extraction and when offshore installations are abandoned. The sources of such emissions are the drilling fluids which contain many chemicals, cuttings, extracted hydrocarbons, substances released as a result of accidents, and the improper disposal of substances used in drilling and production. Platforms are regarded as land-based installations. Regulations to limit emissions have been put into effect within the scope of the Paris Convention on the protection of the North Sea and the North-East Atlantic. (orig.)

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

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


    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.

  1. Modelling thermal stratification in the North Sea: Application of a 2-D potential energy model

    Nielsen, Morten Holtegaard; St. John, Michael


    dynamics we have developed and tested a potential energy model of thermal stratification based on the energy equation (for turbulence). The energy equation relates the temporal and spatial changes of turbulent kinetic energy (TKE), the production of TKE and the dissipation of TKE to the change of potential...... forced with wind, dew point temperature from Ekofisk oilfield in the central North Sea, and tidal current and atmospheric radiation. The model is used to simulate the seasonal cycle of stratification in the central North Sea in the years 1988, 1989 and 1990 and is compared to density profiles in these...... years available from the ICES hydrographic database. We find that the model is able to simulate variations in thermal stratification including the seasonal onset and breakdown of stratification, the thermocline depth, and the effects of discrete wind and cooling events. For the years 1988–1990 we find...

  2. Transparency of the North Sea and Baltic Sea - a Secchi Depth data mining study

    Thorkild Aarup


    This paper presents the results of a Secchi depth data mining study for the North Sea - Baltic Sea region. 40,829 measurements of Secchi depth were compiled from the area as a result of this study. 4.3% of the observations were found in the international data centers [ICES Oceanographic Data Center in Denmark and the World Ocean Data Center A (WDC-A) in the USA], while 95.7% of the data was provided by individuals and ocean research institutions from the surrounding North Sea and Baltic...

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

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


    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.

  4. Environmental aspects of the offshore industry in the North Sea

    In the North Sea area a common policy has been developed with regard to the prevention of marine pollution. This policy is based on a number of international conventions, global as well as regional, regulating various pollution sources, such as dumping of wastes, shipping, 'land-based sources' and discharges from 'man-made' structures such as platforms. These conventions were mainly brought into force in the early 1970s. Their implementation in the North Sea area received political impetus from regularly held ministerial conferences on 'the protection of the North Sea'; the first of these conferences was held in 1984 in Bremen (Germany). As a result, the input of polluting substances in the North Sea has decreased very considerably and some activities, like the dumping of industrial waste into the sea, the dumping of sewage sludge (at the latest by the end of 1998) and the incineration of waste at sea, have been phased out completely. In the same period that this environmental policy took shape, the development of the offshore oil and gas industry took place. Discharges from these activities are also regulated by one of the conventions (the Paris Convention) an by national legislation based on these conventions. As a result, the input of polluting substances, especially of oil, has also decreased considerably since about 1985, mainly as a consequence of the phasing out in some countries of the use of oil-based muds. Due to the ageing of production wells, special attention is needed in the future with regard to increasing oil pollution. It is clear that progress has been made with regard to the reduction of discharge of oil and chemicals, but some developments give cause for concern. Measures that need to be taken by the oil and gas industry to minimize or prevent pollution must be in balance with those measures taken by other 'users' of the sea. (author)

  5. Clearing of the sea bed in the North Sea 1993

    The report relates to an NPD (Norwegian Petroleum Directorate) project which aimed to clear away objects from the sea bed on the Norwegian continental shelf. The project was divided in two phases. Phase 1 included the recording of objects by the use of sonars, and phase 2 covered the clearing operation itself. The results from the project, which included a fishery-intensive and oil-related area of 1300 km2 on Egersundbanken, are presented. 3 figs., 4 tabs

  6. Radiological implications from the temporal development of radioactivity in marine food from the North Sea

    A subject of the revision of authorised limits in 1994 for the discharge of liquid radioactive waste by the reprocessing plant Sellafield (UK) was an increase of these limits for certain radionuclides (3H, 14C, 60Co, 99Tc and 129I). It is investigated now how the radioactivity in marine biota from the North Sea and subsequently the public radiation exposure of seafood consumers has developed in the years since 1994. This is based on a compartment model for dispersion in the North-East Atlantic. Discharges from the reprocessing plants Dounreay (UK) and La Hague (F) are included in the assessment. It is deduced that about 60% of 137Cs in the North Sea originate presently in the remobilisation of old Sellafield discharges from the Irish Sea sediment. A comparison with measured biota data shows that the model is conservative in most cases. The public radiation exposure (artificial radionuclides) from ingestion of fish, crustaceans and molluscs from the central North Sea as the sum over 12 considered radionuclides has decreased from 1992 to 1998 from 0.13 to 0.08 μSv y-1. (orig.)

  7. Competitive interactions between two fishing fleets in the North Sea

    Sys, Klaas; Poos, Jan Jaap; Meensel, van Jef; Polet, Hans; Buysse, Jeroen


    We examine whether the landing rates of Belgian beam trawlers in the Southern Bight of the North Sea were affected through competitive interactions with the Dutch beam trawler fleet and whether the development of a pulse trawler fleet has altered competitive interactions between both fleets. Effe

  8. ETPM: major construction sites in the North sea

    The McDermott-ETPM joint venture has been particularly active in recent months in the North Sea, where it has obtained a number of first-class contracts, notably for developing export capabilities for Norwegian gas. Since the beginning of 1995, co-operation between the two groups has been extended to cover new areas of activity operated jointly; the Far East, the Mediterranean and African countries not covered by the previous agreement. As concerns the North Sea, Statoil, on behalf of several Norwegian companies, has awarded to McDermott-ETPM West Inc. a contract for the installation of three large diameter gas trunklines in the North Sea: the Zeepipe IIB, NorFra - bringing Sleipner gas to Dunkirk, France - and Haltenlik gaslines. Mobil North Sea Ltd has awarded to McDermott-ETPM UK Ltd an EPIC contract for the offshore pipelines forming part of the fast-track development of the Galahad gas field. And Elf Petroland BV has awarded to Mc Dermott-ETPM of a contract for three fabrication and installation of the K5B platform in the Dutch sector. (authors). 3 tabs., 1 photo

  9. The North Sea oil and gas market in Norway

    Norway is reducing its production activities in the North Sea in response to a call by OPEC in 1998 to decrease output to reduce the global oversupply of oil and to level oil prices. In December 1999, Norway announced that its decrease of 200,000 barrels per day would extend at least through the first quarter of 2000. An estimated 10.4 billion barrels of proven oil reserves can be found in the North Sea area of Norway. By 2003, about 35 new oil fields are expected to be developed, increasing the country's oil reserves by 6.4 billion barrels. The natural gas reserves in the North Sea region are estimated at 47.7 trillion cubic feet. The main types of equipment used in the North Sea oil and gas industry are seismic survey equipment, subsea vehicles and drilling rigs. This presents opportunities for Canadian service companies that are active in providing offshore seismic and drilling exploration services. Canadian companies have expertise in deep water exploration equipment, including bottom cable seismic exploration equipment and floating semi-exploration drilling equipment. In addition, Canadian companies can meet the demand for computer technology and seismic sensing arrays. It is recommended that foreign investment companies apply to the Ministry of Petroleum and Energy's offshore licensing boards. refs

  10. Stratigraphic guide to the Rogaland Group, Norwegian North Sea

    Brunstad, H.; Gradstein, F.; Lie, J.E.; Hammer, O.; Munsterman, D.K.; Ogg, G.; Hollerbach, M.


    This guide provides a major revision and update of the lithostratigraphy of the Rogaland Group for the Norwegian North Sea. An abundance of recent well and seismic data sheds new light on lithology, biostratigraphy, provenance, geographic distribution and terminology of all Rogaland rock units, used

  11. Why is the North Sea West of Us?:Principles behind naming of the Seas

    Gammeltoft, Peder


    This article focuses on the motivations behind sea-naming, by means of examples from Europe but also elsewhere. Why do certain sea names become dominant while others retract into local forms or simply die out? The article takes us back in time to the early days of map-making and, indeed, earlier. Occurrences of sea names such as the North Sea are examined and analysed to see how they spread from an original one-language form to exist in multiple languages, and analyses them from a linguistic,...

  12. What is the pollution status of North Sea sediments?

    A March 1990 international sea-going workshop in Bremerhaven, Germany provided the opportunity to conduct detailed sediment toxicity testing in concert with studies of fish histopathology, bioaccumulation, benthic community structure, and sediment chemical contamination in the North Sea. Two gradients of sediment chemical contamination were tested, one from an abandoned oil platform and the other from the mouth of the Elbe River northward to the Dogger Bank. Using a preponderance of evidence approach, it was determined that sediments nearest the Elbe are moderately polluted (pollution is defined as contamination, toxicity, and community alteration) and that sediments offshore and at the Dogger Bank are unpolluted. Sediments nearest the oil platform showed evidence for a low level of pollution, but there was no evidence of pollution 125 m from the platform. The results suggest the testable hypothesis that North Sea sediments away from point sources of pollution such as coastal areas and drilling platforms are presently not polluted. 46 refs., 2 figs., 6 tabs

  13. Variability of North Sea pH and CO2 in response to North Atlantic Oscillation forcing

    Salt, Lesley A.; Thomas, Helmuth; Prowe, Friederike;


    concentrates the net community production in the north through shallower stratification. These effects can be obscured by changing properties of the constituent North Sea water masses, which are also influenced by NAO. Our results highlight the importance of examining interannual trends in the North Sea CO2...

  14. Cleaning up the sea bed in the North Sea. 1994

    The yearly raid was executed in an efficient way and without excess technical equipment interruptions. The vessel ''Lance'' owned by the Norwegian Sea Mapping Authorities which was used for the sonar mapping of the sea bed, was equipped with a Klein 531T side seeking sonar, a Simrad echo sounder of the type EM100 (multiray) and differential GPS navigation system. The executive committee has earlier expressed desire for a strengthening of the co-operation with the Norwegian Sea Mapping Authorities. The use of the vessel was in accordance with this wish. Stolt Comex Seaway A/S used the vessel M/S ''Seaway Commander'' and the underwater vessel ''Solo'' for the cleaning up project. The systems worked satisfactory during the entire operation. The cleaning operation was in 1994 carried out in 2 sections. The Petroleum Directorate agreed to letting the M/S ''Seaway Commander'' complete the project for Norsk Hydro at the Troll field in order to avoid delays in the Troll Oil project. In both periods there were good weather conditions. There was no extensive discontinuations due to the weather. During the two periods of 13,5 days 259 out of 370 positions were investigated visually through the systems. This is in average about 20 inspected positions a day. The reason for the high average is that the sailing distances are short between the positions and the findings corresponded to stated positions and sonar interpretations. Also this year there was installed a side seeking sonar in the underwater vessel which resulted in reduced investigation time at each aim. It was possible with this type of sonar to identify the goal quicker and to seek during transit between goals at moderate distances. Few articles with certainty contributed by the petroleum activities were retrieved

  15. Why is the North Sea West of Us?

    Gammeltoft, Peder


    This article focuses on the motivations behind sea-naming, by means of examples from Europe but also elsewhere. Why do certain sea names become dominant while others retract into local forms or simply die out? The article takes us back in time to the early days of map-making and, indeed, earlier....... Occurrences of sea names such as the North Sea are examined and analysed to see how they spread from an original one-language form to exist in multiple languages, and analyses them from a linguistic, geographic and nautical perspective. It is found that Seas or bodies of water in stretches of sea are named...... according to six main principles. Many sea-names are formally secondary names whose specific element is the name of: a) a nearby settlement name; b) a nearby island or c) a nearby country or region. In addition, a sea-name may be a formally primary name named from: d) a directional perspective, e) its...

  16. North Pacific sea ice cover, a predictor for the Western North Pacific typhoon frequency?


    The relationship between the sea ice cover in the North Pacific and the typhoon frequency has been studied in this paper. It follows that the index for the sea ice cover in the North Pacific (ISA) both in December-January-February (DJF) and in March-April-May (MAM) is negatively correlated with annual typhoon number over the western North Pacific (TNWNP) during 1965―2004, with correlation coeffi-cients of -0.42 and -0.49 respectively (above 99% significant level). Large sea ice cover in the North Pacific tends to decrease TNWNP. Positive ISA (MAM) is associated with the tropical circulation and SST anomalies in the North Pacific, which may lead to unfavorable dynamic and thermal conditions for typhoon genesis over WNP from June to October (JJASO). The variability of the atmospheric circula-tion over the North Pacific, associated with the ISA anomaly in MAM is connected to the tropical at-mospheric circulation variability in MAM via the teleconnection wave train. Besides, as the tropical circulation has strong seasonal persistency from the MAM to JJASO, thus, the ISA in MAM-related variability of the tropical atmospheric circulation as well as the SST can affect the typhoon activity over the western North Pacific.

  17. Storing CO2 under the North Sea Basin - A key solution for combating climate change

    This report represents the first deliverable of the North Sea Basin Task Force, which Norway and the UK established in November 2005 to work together on issues surrounding the transport and storage of CO2 beneath the North Sea. The North Sea represents the best geological opportunity for storing our CO2 emissions away from the atmosphere for both the UK and Norway

  18. Investigation and evaluation of airborne pollution in the framework of PARCOM (North Sea) and HELCOM (Baltic Sea) - subproject: Measurements of trace metals

    On the basis of measurements of the deposition and concentrations of atmospheric trace metals the annual input of some selected elements (Pb, Zn, Cd, Ni, V) into the North Sea and the Baltic Sea was estimated. For the Baltic Sea, deposition measurements with a buoy system in the Kiel Bight and data from the EGAP(HELCOM)-monitoring network were used. Data from the measurement stations were extrapolated to related sub-basins according to the deposition fields obtained from model calculations (EMEP). For the North Sea, a mean atmospheric trace metal distribution was determined from numerous measurements at a coastal site and over the central North Sea and the annual input was calculated by multiplication with corresponding deposition velocities and scavenging ratios. A comparison of the deposition data based on measurements with those from model calculations show good agreement in the case of Pb in the Baltic Sea as well as in the North Sea. However, for Zn and Cd large discrepancies are observed. Additionally, deposition processes were studied. Scavenging ratios were determined and dry deposition velocities were estimated by the use of a new method for high time resolution measurements of atmospheric trace metal concentrations (impactor/TXRF). (orig.). 9 figs., 14 tabs

  19. Effect of North Sea waters containing radioactive industrial wastes on the radioactivity of the Baltic Sea

    Results of field studies of the Baltic Sea radioactive contamination, carried out in 1984, are presented. The investigations are aimed at the evaluation of the effect of the North Sea waters, contaminated with industrial radioactive wastes of Western European countries on the environmental radioactivity in the Baltic Sea refion 134Cs was used as an indicator of radioactive waste presence in sea water. The whole water area of the Baltic Sea is shown to be affected by industrial radioactive contamination of various degrees. It is established that the part of industrial 137Cs in the total radionuclide content in benthic waters of the Arkonskaya hollow constitutes ∼ 50% and it decreases down to 16-18% in benthic waters of the western part of the Gulf of Finland. Empirical dependences permitting to predict the content of industrial 137Cs in the Baltic Sea water with the variation in the volume of annular radionuclide disposal by Sellafield radiochemical plant, are obtained

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

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


    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. Review of the physical oceanography of the North Sea

    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.

  2. Cenozoic sequence stratigraphy in the eastern North Sea

    Michelsen, O.; Thomsen, E.; Danielsen, M.; Heilmann-Clausen, C.; Jordt, H.; Laursen, G.V.


    The Cenozoic evolution of the epicontinental North Sea Basin is described on the basis of sequence stratigraphy, comprising analyses of seismic sections, petrophysical logs, and biostratigraphic studies of foraminifera, dinoflagellates, and calcareous nannofossils. Stratigraphic, palaeogeographic, and palaeoecological information from the Danish onshore area is integrated in the study. The deposits are subdivided into 21 sequences, which groups into seven informal major units. The sequence boundaries are identified by differences in seismic facies and by seismic onlap, toplap, and truncation features. The maximum flooding surface is placed at an internal downlap surface which correlates with high values on the gamma ray log. The source of sediments and the direction of sediment transport changed several times during the Cenozoic. Transport was mainly from the north during the Late Paleocene and Early Eocene, from the west during the Middle and Late Eocene, and from the north and northwest during the Oligocene to quaternary. The depocenters of the seven major units are generally located marginally, probably adjoining the source areas. There is only minor evidence for changes in subsidence rates in the basin. A constant rate is assumed from the Paleocene to the mid Middle Miocene. For the remaining part of the Cenozoic and increased rate is indicated. A tentative relative sea-level curve for the North Sea Basin is proposed. The overall trends of the curve are broadly comparable with the global sea-level curve of Haq et al. Discrepancies may be caused by differences in the biostratigraphic calibrations. The most pronounced Oligocene sea-level fall is dated ot the latest Oligocene. (au) (83 refs.)

  3. Distribution and activity of petroleum hydrocarbon degrading bacteria in the North Sea and Baltic Sea

    Data were collected in 1988 and 1989 on the distribution and activity of petroleum hydrocarbon degrading bacteria in the North Sea and Baltic Sea. Crude oil degrading bacteria and the number of bacteria which in particular degrade naphthalene were quantified using a modified dilution method (MPN). Crude oil degrading bacteria were present in all of about 100 water samples, with as many as 103 ml-1 in some samples. Numbers of naphthalene degrading bacteria were at least tenfold lower. There is obviously a greater connection between this bacteria group and petroleum hydrocarbon (PHC) contamination than between the more nonspecific group of crude oil degrading bacteria and PHC contamination. Data from the North Sea show an extremely high abundance of hydrocarbon degrading bacteria, even in winter, while in the southern Baltic Sea low numbers of bacteria were found and slower crude oil degradation was observed. (orig.)

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

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


    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.

  5. Observed mean sea level changes around the North Sea coastline from 1800 to present

    Wahl, T.; Haigh, I. D.; Woodworth, P. L.; Albrecht, F.; Dillingh, D.; Jensen, J.; Nicholls, R. J.; Weisse, R.; Wöppelmann, G.


    This paper assesses historic changes in mean sea level around the coastline of the North Sea, one of the most densely populated coasts in the world. Typically, such analyses have been conducted at a national level, and detailed geographically wider analyses have not been undertaken for about 20 years. We analyse long records (up to 200 years) from 30 tide gauge sites, which are reasonably uniformly distributed along the coastline, and: (1) calculate relative sea level trends; (2) examine the inter-annual and decadal variations; (3) estimate regional geocentric (sometimes also referred to as 'absolute') sea level rise throughout the 20th century; and (4) assess the evidence for regional acceleration of sea-level rise. Relative sea level changes are broadly consistent with known vertical land movement patterns. The inter-annual and decadal variability is partly coherent across the region, but with some differences between the Inner North Sea and the English Channel. Data sets from various sources are used to provide estimates of the geocentric sea level changes. The long-term geocentric mean sea level trend for the 1900 to 2011 period is estimated to be 1.5 ± 0.1 mm/yr for the entire North Sea region. The trend is slightly higher for the Inner North Sea (i.e. 1.6 ± 0.1 mm/yr), and smaller but not significantly different on the 95% confidence level for the English Channel (i.e. 1.2 ± 0.1 mm/yr). The uncertainties in the estimates of vertical land movement rates are still large, and the results from a broad range of approaches for determining these rates are not consistent. Periods of sea level rise acceleration are detected at different times throughout the last 200 years and are to some extent related to air pressure variations. The recent rates of sea level rise (i.e. over the last two to three decades) are high compared to the long-term average, but are comparable to those which have been observed at other times in the late 19th and 20th century.

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

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


    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

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

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


    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

  8. Detection of low bottom water oxygen concentrations in the North Sea; implications for monitoring and assessment of ecosystem health

    N. Greenwood; Parker, E.R.; Fernand, L; D. B. Sivyer; Weston, K.; Painting, S.J.; Kröger, S; R. M. Forster; H. E. Lees; D. K. Mills; Laane, R.W.P.M.


    This paper presents new results from high temporal resolution observations over two years (2007 and 2008) from instrumented moorings deployed in the central North Sea, at the Oyster Grounds and on the northern slope of Dogger Bank (North Dogger). The water column was stratified in the summer at both sites, leading to limited exchange of the water in the bottom mixed layer. Data from these moorings revealed the variable nature of summer oxygen depletion at the Oyster Grounds. The combination o...

  9. Detection of low bottom water oxygen concentrations in the North Sea; implications for monitoring and assessment of ecosystem health

    N. Greenwood; Parker, E.R.; Fernand, L; D. B. Sivyer; Weston, K.; Painting, S.J.; Kröger, S; R. M. Forster; H. E. Lees; D. K. Mills; Laane, R.W.P.M.


    This paper presents new results from high temporal resolution observations over two years (2007 and 2008) from instrumented moorings deployed in the central North Sea, at the Oyster Grounds and on the northern slope of Dogger Bank (North Dogger). The water column was stratified in the summer at both sites, leading to limited exchange of the water in the bottom mixed layer. Data from these moorings revealed the variable nature of summer oxygen depletion at the Oyster Grounds....

  10. Hydroclimatic modulation of diatom/Phaeocystis blooms in nutrient-enriched Belgian coastal waters (North Sea)

    Breton, E.; Rousseau, V.; Parent, J.-Y.; Ozer, J.; C. Lancelot


    Statistical analysis of 14 yr (1988-2001) of intensive phytoplankton monitoring at Station 330 in the central Belgian Coastal Zone (BCZ, Southern Bight of the North Sea) indicates that the long-term diatom biomass trend and the spring dominance of Phaeocystis colonies over diatoms are determined by the combined effect of the North Atlantic Oscillation (NAO) and freshwater and continental nitrate carried by the Scheldt. The strong correlation between diatoms and the NAO index is largely explai...

  11. Late Neogene and active orogenic uplift in the Central Pontides associated with the North Anatolian Fault; implications for the northern margin of the Central Anatolian Plateau, Turkey

    Yildirim, C.; Schildgen, T.F.; Helmut Echtler; H. Melnick; Strecker, M. R.


    Surface uplift at the northern margin of the Central Anatolian Plateau (CAP) is integrally tied to the evolution of the Central Pontides (CP), between the North Anatolian Fault (NAF) and the Black Sea. Our regional morphometric and plate kinematic analyses reveal topographic anomalies, steep channel gradients, and local high relief areas as indicators of ongoing differential surface uplift, which is higher in the western CP compared to the eastern CP and fault-normal components of geodetic sl...

  12. Frequent underwater volcanism in the central Aegean Sea

    Huebscher, C.; Ruhnau, M.; Dehghani, G. A.


    The extinction of the Minoan culture in the mid second millennium BCE is a well known consequence of the Plinian eruption of Thera volcano (Santorini Island). Santorini is a member of the South Aegean arc forming a chain from the Gulf of Saronikos (Susaki, Egina, Poros, Methana) at West, to an area close to the Anatolian coast at East (Kos, Nisyros and minor islands), through the central part (Milos and Santorini island groups). Underwater volcanic activity was manifested historically only once. During 1649-1650 CE the Kolumbo underwater volcano evolved about 8 km northeast of Santorini. As a consequence of this eruption volcanic ash covered the entire Aegean area and a hazardous tsunami was triggered. Here we show by means of reflection seismic and magnetic data that underwater volcanism occurred more frequently in the central Aegean Sea than previously assumed. Seismic data show that Kolumbo constitutes of five vertically stacked cones of pyroclastic sediment plus at least four smaller cones on the flank of the volcano. The formation of Kolumbo started synchronous with Santorini Island. The entire volume of the Kolumbo pyroclastic cones is estimated to more than 15 cubic-kilometers. Several small-scale cones have been detected in the Anyhdros Basin some km north-east of Kolumbo, being previously interpreted as mud volcanoes by other authors. However, the similarity of seismic and magnetic signatures of these cones and Kolumbo strongly suggest that these cones were also created by underwater volcanism. Volcanic cones, Kolumbo and Santorini are situated along a NE-SW striking graben system that evolved during five extensional tectonic pulses in the Pliocene.

  13. Security of natural gas supply from the North Sea

    This article deals with the measures taken to ensure uninterrupted oil- and gas supply from the Norwegian petroleum fields in the North Sea to the customers. Although there are about 700 interruptions of the gas deliveries on the shelf each year, all obligations are met. This demonstrates the flexibility of the delivery system. In Norway, the consumption of oil is only 7% of the oil produced and virtually no gas is consumed. Consequently, Norwegian economy depends heavily on the export, and so the supply security is very important. The production system involves a complex interplay between wells, platforms, landing pipelines and terminals. In a critical situation, the delivery obligations for gas are the first priority. The Norwegian shelf in the North Sea is partitioned into four regions: Tampen, Ekofisk, Oseberg and Troll. Independently of who is the owner or operator, the regions assist each other in delivering the gas that is to be exported at any given time

  14. FT guide to North Sea operators. 4. ed.

    This fourth edition of the FT Guide to North Sea Operators is published against a continuing background of optimism in North Sea exploration and development activity. Current forecasts suggest exploration activity on the UK Continental Shelf in 1991 will match, if not indeed surpass, 1990's record level of 224 exploration and appraisal well spuds. In the Norwegian sector, some analysts predict investment of over NKr 200bn in the offshore oil and gas industry in the next five years. As before, the guide contains an alphabetical listing of all the operators on the Northwest Europe Continental Shelf. Within each operator section, countries are detailed in the order UK, Norway, Netherlands, Denmark, Ireland and Germany and within the country sections fields are listed alphabetically. Block numbers are detailed in numerical order within each consecutive licence round. Development capex figures are given in money-of-the-day terms. (author)

  15. Marginal field development in mature areas of the North Sea

    In the North Sea a comprehensive infrastructure of production, installations and pipelines have been installed in the last 20 years. As the existing oil and gas fields start to decline, it is cost effective to use the spare capacity on these existing production installations for marginal fields. To ensure economy in the marginal field development the facilities on the outlying fields must be reduced to a minimum. The facilities needed are very dependant on the product being processed and the distance to the existing production installation. However, experience has shown that the modifications necessary on the existing installations can be extensive, difficult to estimate and normally has had significant cost escalation. This paper will outline the North Sea infrastructure, indicate the types of minimum facilities and installations used on the satellite fields, and briefly discuss the problems with modifications on existing installations

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

    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

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

    Kinne, O.


    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

  18. Cost overruns and cost estimation in the North Sea

    Emhjellen, Magne; Emhjellen, Kjetil; Osmundsen, Petter


    Recently, a Norwegian government report on the cost overruns of projects in the North Sea was presented (NOU 1999:11). It concluded that there was a 25% increase in development costs from project sanction (POD, Plan for Operation and Development) to last CCE (Capital Cost Estimate) for the 11 oil field projects investigated. Many reasons like unclear project assumptions in early phase, optimistic interpolation of previous project assumptions, too optimistic estimates, and underestimation of u...

  19. Phytoplankton of the North Sea and its dynamics: a review

    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...

  20. North Sea market update: Changes in both concept and content

    The current paradox facing the North Sea offshore industry is that while it is experiencing a current market boom, within two years contractors may be scrambling around in a much reduced market. West Europe is running at a massive $15.1 billion. A veritable feast giving contractors, especially in Norway, a full workload and the headache of a severe skilled workforce shortage. Themes discussed cover Norwegian needs, Danish developments, UK utilisation, Dutch demand, and new breed. 4 figs

  1. North Sea palaeogeographical reconstructions for the last 1 Ma

    Cohen, K.M.; Gibbard, P. L.; Weerts, H.J.T.


    The landscape evolution of the southern North Sea basin is complex and has left a geographically varying record of marine, lacustrine, fluvial and glacial sedimentation and erosion. Quaternary climatic history, which importantly included glaciation, combined with tectonics gave rise to cyclic and non-cyclic changes of sedimentation and erosion patterns. Large-scale landscape reorganisations left strong imprints in the preserved record, and are important for the detail that palaeogeographical ...

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

    Westerhoff, Wim; Donders, Timme; Luthi, Stefan


    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.

  3. First data of Uranium-236 in the North Sea

    In this paper we present the first 236U-measurements from North Sea water samples. The measurements are performed within an ongoing project that intends to map the distribution of 236U in the Atlantic Ocean and thus to explore the potential of 236U as a new oceanic tracer. We describe the latest modifications of the low energy ETH AMS system TANDY that allow determining the concentrations of both 238U and 236U and the 236U/238U ratio during only one AMS measurement. Further, we present our chemical preparation procedure and, finally, the first 236U data from the North Sea is discussed in detail. A simple conceptual model is used to simulate the temporal evolution of the 236U-concentration in the North Sea. The simulated water mass residence time is in good agreement with independent oceanographic data. Based on these initial results we conclude that anthropogenic 236U has a large potential as a new transient and extremely conservative tracer in Oceanography.

  4. Independent companies in the North Sea - exploration and operations opportunities

    The North Sea was the launching pad for many independent oil companies, particularly through exploration success in the UK and the Netherlands. Norway has an excellent history of oil exploration but, for the independents, the onerous tax regime, long lead times, and terms of trade are simply not conducive to the higher rate of return demanded by shareholders of independent E and P companies in exchange for shouldering the heavy burden of risk. The UK in particular has pursued imaginative licensing, tax and legislative policies which have allowed the independents an opportunity to participate and grow. The attraction of the UK is clearly reflected by the constant arrival of new entrants, even at this stage of maturity. This was demonstrated in the recent round of license awards. Such has been the success of the independents in the UK that, beginning with virtually nothing, they now hold a net 28% of the UK North Sea acreage, and a net 25% of its oil reserves. Equally, the independents play an important role in ensuring the comprehensive exploration of the offshore areas. Because of size and significance, a prime objective of the independents will remain the early evaluation, through drilling, and development of offshore interests to generate a financial return. This paper addresses the question of how independent companies can expand in the North Sea when the size and quality of new range acreage available through new license awards is reducing. (author)

  5. North Central regional environmental characterization report: executive summary - final

    This Executive Summary of the final North Central Regional Environmental Characterization Report (RECR) is issued primarily for public information purposes and provides a general overview of the report. The complete RECR presents available regional environmental information pertinent to siting a repository for high-level nuclear waste in crystalline rock in Minnesota, Wisconsin, and the Upper Peninsula of Michigan. For each of the States within the North Central Region, information is provided on the environmental disqualifying factors and the environmental regional screening variables to be used in region-to-area screening

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

    Delphine Nicolas

    Full Text Available 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.

  7. Geology of outer Horns Rev, Danish North Sea

    Jensen, Joern B.; Gravesen, P.; Lomholt, S. (Geological Survey of Denmark and Greenland, Copenhagen (Denmark))


    In 2006, Dong Energy initiated the development of the Horns Rev II offshore wind farm in the North Sea. In order to evaluate and map the characteristics of the surface features of the sea bed and to characterise the subsurface in the wind farm area, the Geological Survey of Denmark and Greenland (GEUS) conducted a geophysical survey of the area. The survey utilised a variety of instruments: sparker, side-scan sonar, marine caesium magnetometer and a multibeam echo-sounder. In addition, information on the subsurface sediments was obtained by cone penetration tests (CPT) and by drilling to 30-50 m below the sea bottom. Geological correlation of the CPT results with the other survey results was extremely complicated but was required in order to understand the architecture of the ice marginal glaciotectonic complex. Information on the geology is crucial for evaluation of the geotechnical problems of the region. (au)

  8. Rogue run-up events at the North Sea coast

    Didenkulova, Ira; Blossier, Brice; Daly, Christopher; Herbst, Gabriel; Senichev, Dmitry; Winter, Christian


    On the 1st of January, 1995, the Statoil-operated "Draupner" platform located in the North Sea recorded the so-called "New Year wave". Since then, rogue waves have been the topic of active scientific discussions and investigations. Waves of extreme height appearing randomly at the sea surface have been measured in both deep and shallow waters and have been involved in a number of ship accidents. Nowadays rogue waves are frequently recorded all over the world with several different instruments (range finders installed on offshore platforms, deployed buoys, radars including SAR, etc.). Rogue wave also occur at the coast, where they appear as either sudden flooding of coastal areas or high splashes over steep banks or sea walls. These waves are especially dangerous for beach users and lead regularly to human injuries and fatalities. Despite numerous reports of human accidents, coastal rogue waves have not yet been recorded experimentally. In this paper we discuss the recording of rogue wave events at German North Sea coasts by using high-resolution beach cameras. The recorded rogue waves are observed during different tide levels and different weather conditions. Possible mechanisms of their generation are discussed.

  9. Airborne gravity survey of Lincoln Sea and Wandel Sea, north Greenland

    Olesen, Arne Vestergaard; Forsberg, René; Keller, K.;


    In June 1998 National Survey and Cadastre Denmark (KMS) carried out an airborne gravity survey over the Polar Sea to the north of Greenland. A Twin Otter from Greenlandair, equipped with autopilot and additional fuel tanks, was employed for the survey. A modified marine LaCoste & Romberg gravimet...

  10. First report of the planktonic copepod Oithona davisae in the northern Wadden Sea (North Sea): Evidence for recent invasion?

    Cornils, Astrid; Wend-Heckmann, Britta


    In October 2010, specimens of Oithona were taken from the List Tidal Basin in the northern Wadden Sea (North Sea) for a biogeographic study on Oithona similis. These specimens could not be assigned to O. similis or any of the other Oithona species known from the North Sea genetically. These specimens were identified as Oithona davisae Ferrari and Orsi 1984, a Northwest Pacific species, known as an invasive species from the Black Sea and the northwestern Mediterranean Sea. Recent sampling provided evidence that O. davisae is still present in the northern Wadden Sea and may thus now be a permanent plankton species.

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

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


    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.

  12. Hydrogeological mapping of north-central Madagascar using limited data

    Davies, Jeffrey


    North-central Madagascar is well endowed with surface-water. Due to soil erosion and pollution, rivers can no longer provide year round clean water supplies. Shallow aquifers are being developed to provide sustainable rural and urban water supplies. A survey of water sources located 2760 boreholes, wells, ponds and springs in the area, but understanding of groundwater occurrence remains poor. The area comprises four hydrogeological zones: the dry Central High Plateau with erosi...

  13. The first ocurrence of the ctenophore Mnemiopsis leidyi in the North Sea

    M. Boersma; Malzahn, A. M.; Greve, W.; Javidpour, Jamileh


    After the discovery of large densities of Mnemiopsis leidyi in the Baltic Sea near Kiel by Javidpour et al. (First record of Mnemiopsis leidyi A. Agassiz 1865 in the Baltic Sea, 2006) in October 2006, we investigated the gelatinous zooplankton in the North Sea near Helgoland and recorded Mnemiopsis leidyi for the first time in the North Sea, albeit in much lower densities than those recorded in the Baltic Sea.

  14. Modeling the buoyancy-driven Black Sea Water outflow into the North Aegean Sea

    Nikolaos Kokkos


    Full Text Available A three-dimensional numerical model was applied to simulate the Black Sea Water (BSW outflux and spreading over the North Aegean Sea, and its impact on circulation and stratification–mixing dynamics. Model results were validated against satellite-derived sea surface temperature and in-situ temperature and salinity profiles. Further, the model results were post-processed in terms of the potential energy anomaly, ϕ, analyzing the factors contributing to its change. It occurs that BSW contributes significantly on the Thracian Sea water column stratification, but its signal reduces in the rest of the North Aegean Sea. The BSW buoyancy flux contributed to the change of ϕ in the Thracian Sea by 1.23 × 10−3 W m−3 in the winter and 7.9 × 10−4 W m−3 in the summer, significantly higher than the corresponding solar heat flux contribution (1.41 × 10−5 W m−3 and 7.4 × 10−5 W m−3, respectively. Quantification of the ϕ-advective term crossing the north-western BSW branch (to the north of Lemnos Island, depicted a strong non-linear relation to the relative vorticity of Samothraki Anticyclone. Similar analysis for the south-western branch illustrated a relationship between the ϕ-advective term sign and the relative vorticity in the Sporades system. The ϕ-mixing term increases its significance under strong winds (>15 m s−1, tending to destroy surface meso-scale eddies.

  15. Physical control of primary productivity on a seasonal scale in the central and eastern Arabian Sea

    S Prasanna kumar; M Madhupratap; M Dileep kumar; M Gauns; P M Muraleedharan; V V S S Sarma; S N De Souza


    Using in situ data collected during 1992-1997, under the Indian programme of Joint Global Ocean Flux Study (JGOFS), we show that the biological productivity of the Arabian Sea is tightly coupled to the physical forcing mediated through nutrient availability. The Arabian Sea becomes productive in summer not only along the coastal regions of Somalia, Arabia and southern parts of the west coast of India due to coastal upwelling but also in the open waters of the central region. The open waters in the north are fertilized by a combination of divergence driven by cyclonic wind stress curl to the north of the Findlater Jet and lateral advection of nutrient-rich upwelled waters from Arabia. Productivity in the southern part of the central Arabian Sea, on the other hand, is driven by advection from the Somalia upwelling. Surface cooling and convection resulting from reduced solar radiation and increased evaporation make the northern region productive in winter. During both spring and fall inter-monsoons, this sea remains warm and stratified with low production as surface waters are oligotrophic. Inter-annual variability in physical forcing during winter resulted in one-and-a-half times higher production in 1997 than in 1995.


    Patterson, Brian; Hanson, Steven D.; Robison, Lindon J.


    Leasing behavior differs across the North Central United States. Survey data is used to characterize leasing activity in the region. Data is collected on the amount of leased farmland, amount of cash and share leased land, and common output share levels. Factors influencing leasing and arrangements are also identified.

  17. World and experiences of AIDS orphans in north central Namibia

    Brug, van der M.


    How do young AIDS orphans deal with the loss of their parents and their changed circumstances? This thesis discusses the social environment, experiences and perceptions of fourteen orphans in north central Namibia. The author followed the children for five months from September 2003 until March 2004

  18. Spatiotemporal variations of fCO2 in the North Sea

    H. Thomas


    Full Text Available Data from two Voluntary Observing Ship (VOS (2005–2007 augmented with data subsets from ten cruises (1987–2005 were used to investigate the spatiotemporal variations of the CO2 fugacity in seawater (fCO2sw in the North Sea at seasonal and inter-annual time scales. The observed seasonal fCO2sw variations were related to variations in sea surface temperature (SST, biology plus mixing, and air-sea CO2 exchange. Over the study period, the seasonal amplitude in fCO2sw induced by SST changes was 0.4–0.75 times those resulting from variations in biology plus mixing. Along a meridional transect, fCO2sw normally decreased northwards (−12 μatm per degree latitude, but the gradient disappeared/reversed during spring as a consequence of an enhanced seasonal amplitude of fCO2sw in southern parts of the North Sea. Along a zonal transect, a weak gradient (−0.8 μatm per degree longitude was observed in the annual mean fCO2sw. Annually and averaged over the study area, surface waters of the North Sea were CO2 undersaturated and, thus, a sink of atmospheric CO2. However, during summer, surface waters in the region 55.5–54.5° N were CO2 supersaturated and, hence, a source for atmospheric CO2. Comparison of fCO2sw data acquired within two 1°×1° regions in the northern and southern North Sea during different years (1987, 2001, 2002, and 2005–2007 revealed large interannual variations, especially during spring and summer when year-to-year fCO2sw differences (≈160–200 μatm approached seasonal changes (≈200–250 μatm. The springtime variations resulted from changes in magnitude and timing of the phytoplankton bloom, whereas changes in SST, wind speed and total alkalinity may have contributed to the summertime interannual fCO2sw differences. The lowest interannual variation (10–50 μatm was observed during fall and early winter. Comparison with data reported in October 1967 suggests that the fCO2sw growth rate in the central North Sea was

  19. Palaeoenvironmental changes across the Danian–Selandian boundary in the North Sea Basin

    Clemmensen, Anne; Thomsen, Erik


    southern and eastern part of the North Sea Basin resulted in a huge influx of reworked Cretaceous chalk and an almost complete stop of carbonate production. Finally, later in the early Selandian, in connection to a general sea-level rise and a reduction in the gateway between the North Sea Basin and the...

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

    Androulidakis, Yannis; Krestenitis, Yannis; Kourafalou, Vassiliki


    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. Sea state projections for the North Sea: Impact of climate change on very high waves?

    Möller, Jens; Groll, Nikolaus; Heinrich, Hartmut


    The research program KLIWAS of the German Federal Ministry of Transport, Building and urban Development investigates the impacts of climate change on waterways and navigation and provides options for adaptations. One aspect of the research task is to analyse climate scenarios for the sea state, eg. Sea wave height (SWH), wave direction and wave periods for the North Sea. Of particular importance for the safety on waterways is the potential change of frequence and magnitude from severe waves. The scenarios together with the wave climate of the recent years will give an approximation of projected changes of the sea state in coastal and open sea areas. Here we show the results for projected changes of medium, high and very high waves in the North Sea for the period 2000-2100 in comparison to 1961-2000, based on the wave model WAM4.5.3 The wave model is driven with wind data from two different regional atmosphere-ocean-models (DMI-HIRHAM and MPI-REMO) in the scenario A1B. The wind data are delivered in a horizontal resolution of about 20 km and a time resolution of one hour, while the wave model provides data of the calculated sea state with a horizontal grid of 5 km and the time resolution of one hour. It is seen, that in the eastern North Sea and especially in the German Bight there is a trend to a increasing of the 99th percentile of SWH, while in the western part the 99th percentile of SWH decreases in the future. These changes are mainly caused by changing wind directions in the future, while the wind speed will be mostly unaltered. Supplementary, it was carried out an extrem value analysis with the same data. Although the very high waves (eg. waves with a return period of 1-, 5-, 10-, up to 100 years) displays a similar behavior as the median or 99th percentile, there are regions in the North Sea (eg. the German Bight) with stronger changes of the higher waves. For all wave heights a strong decadal variability is detected which superimposes the calculated trends.

  2. Not normally manned compression platforms for the North Sea

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

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


    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.

  4. Airborne Doppler measurements of the central California extended sea breeze

    Carroll, J. J.


    One data acquisition flight was executed in the late summer of 1984. The flight paths were designed to obtain measurements of the extended sea breeze penetration into the central valley of California over several hours. Data from this flight are being processed at Marshall Space Flight Center prior to release for analysis.

  5. Coccolithophores from the central Arabian Sea: Sediment trap results

    Mergulhao, L.P.; Mohan, R.; Murty, V.S.N.; Guptha, M.V.S.; Sinha, D.K.

    Sediment trap samples collected from a depth of 1018m in the Central Arabian Sea Trap (CAST) at 14 degrees 28.2 minutes N, 64 degrees 35.8 minutes E were analyzed for temporal variation of coccolithophore fluxes from October 1993 to August 1994. Out...

  6. Reservoir quality of deeply buried sandstones – a study of burial diagenesis from the North Sea


    List of papers and abstracts. Papers 1, 2, 3, 4 and 5 are removed from the thesis due to publisher restrictions. Paper 1: Maast, T. E., E. M. Jarsve, R. Flåt and J. Jahren, (submitted), The impact of quartz and illite cementation on deep reservoir quality in Upper Jurassic, syn-rift sandstones of the Central Graben, North Sea. Paper 2: Maast, T. E., J. Jahren, and K. Bjørlykke, 2011, Diagenetic controls on reservoir quality in Middle- to Upper Jurassic sandstones in the South Viking G...

  7. The North Sea Andrea storm and numerical simulations

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


    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.

  8. Wasp-waist interactions in the North Sea ecosystem.

    Per Fauchald

    Full Text Available 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.

  9. Neogene dinocyst zonation for the eastern North Sea Basin, Denmark

    Dybkjær, Karen; Piasecki, Stefan


    A dinocyst zonation for the Neogene succession in the eastern part of the North Sea Basin (Denmark) is presented. The zonation is based on an extensive database comprising data from more than fifty onshore and offshore boreholes and about twenty five outcrops. Most of the nineteen dinocyst zones...... method allowed the previous last occurrence of Cordosphaeridium cantharellus (one of the zonal index fossils) dated as between 17.95 My and 19.5 My in previous studies, to be assigned a new dating of 18.4 My. The timespan of the zones range from 2.6 My for the Amiculospharea umbraculum Zone to 0.4 My for...

  10. Environmental effects of a nitrogen emission control area on the North Sea

    Emissions in the North Sea of air pollutants from maritime transport has decreased. The question is whether the setting up of a nitrogen emission control area in the North Sea is a cost-effective next step to improve air quality. And what does it mean for the maritime sector? For answers to these questions an environmental and economic impact study is conducted on behalf of eight North Sea countries.

  11. The sea breeze circulation during the Land Sea Breeze Experiment (LASBEX) in central California.

    Fagan, Michael


    The sea breeze circulation was investigated using a combination of acoustic Doppler sodar, Doppler lidar and conventional observations in central California on the coast of Monterey Bay in September 1987. The study was called LASBEX (Land Sea Breeze EXperiment) and used the combined effort and resources of the Naval Postgraduate School (NPS), NOAA Wave Propagation Lab (WPL) and Naval Environmental Prediction Research Facility (NEPRF). A monostatic three-axis phased-array Doppler sodar was...

  12. Coccolithophores from the central Arabian Sea: Sediment trap results

    Lina P Mergulhao; Rahul Mohan; V S N Murty; M V S Guptha; D K Sinha


    Sediment trap samples collected from a depth of 1018 m in the Central Arabian Sea Trap (CAST) at 14° 28.2′N, 64° 35.8′E were analyzed for temporal variation of coccolithophore fluxes from October 1993 to August 1994.Out of the twenty species of coccolithophores encountered, \\tetit {Gephyrocapsa oceanica,Emiliania huxleyi,Umbilicosphaera sibogae} and Umbellosphaera irregularis were the most abundant.The total coccolithophore fluxes ranged from 28.5 × 106 m−2 d−1 to 50.3 × 106 m−2 d−1 showing seasonality with higher fluxes during the northeast (NE) monsoon and lower fluxes during the spring intermonsoon. The higher fluxes were attributed to the enhancement of primary production in the central Arabian Sea due to southward extent of nutrients from the northeast Arabian Sea by the prevailing surface currents. Similarly, the occurrences of relatively lower coc-colithophore fluxes during the spring intermonsoon and southwest (SW) monsoon were attributed to the low nutrients in the warm, shallow surface mixed layer and downwelling to the south of Findlater Jet respectively in the central Arabian Sea.Some of the coccolithophore species such as E.huxleyi, G.oceanica, Calcidiscus leptoporus and Umbellosphaera tenuis showed signs of dissolution.

  13. Modelling sea breeze climatologies and interactions on coasts in the southern North Sea: Implications for offshore wind energy

    Steele, Christopher; Dorling, Stephen; von Glasow, Roland; Bacon, Jim


    Current understanding of the behaviour of sea breezes in the offshore environment is limited but rapidly requires improvement due, not least, to the expansion of the offshore wind energy industry. Here we report on contrasting characteristics of three sea-breeze types on five coastlines around the southern North Sea from an 11 year model-simulated climatology. We present and test an identification method which distinguishes sea-breeze types which can, in principle, be adapted for other coastl...

  14. Quantifying the importance of sediment resuspension for the North Sea and Baltic Sea ecosystem

    Nissen, Cara; Schrum, Corinna; Daewel, Ute; Fennel, Katja; Castaño Primo, Rocío


    Including sedimentary processes such as resuspension in marine coupled bio-physical models is crucial to realistically simulate the dynamics of biologically important chemical variables (e.g oxygen and the macro-nutrients nitrate, phosphate and silicate). These comprise diffusive release of dissolved nutrients and resuspension of particulate organic material, which occurs when a critical bottom shear stress (τcrit) acting on the sediment particles is exceeded. In global and regional modelling approaches sediment-water exchange is often parametrized by sedimentation and constant release rates and dynamic resuspension resolving the tidal cycle is often neglected in coupled physical-biological ecosystem models. During resuspension, sediment particles get transported back into the water column. Thereby, both the turbidity of the water and nutrient availability by releasing dissolved nutrients from the pore-water are changed. Since both light and nutrients are limiting factors in primary production, it is near by hand to suspect resuspension to play an important role in the growth of phytoplankton. Here, we assess the role of resuspension and its dynamic consideration for the modelled productivity and CO2 air-sea exchange in the North Sea and Baltic Sea using the coupled 3D physical-biological model ECOSMO. ECOSMO is a coupled hydrodynamic-sea ice-NPZD-carbonate-system model and is implemented for the North Sea and Baltic Sea. Its ecosystem module includes interactions between three functional groups of phytoplankton, two of zooplankton, detritus, oxygen, three nutrient cycles (nitrogen, phosphorus, silicate) and sediment pools. In the North Sea, wind forcing and strong tides lead to a frequent exceedance of the critical bottom shear stress and therefore, resuspension events take place regularly, especially in the shallow coastal areas where the tidal range is largest. Here, the model results indicate a clear increase in estimated primary production when dynamical

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

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


    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.

  16. Seasonality of floc strength in the southern North Sea

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


    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.

  17. Analysis of North Sea Offshore Wind Power Variability

    Aymeric Buatois


    Full Text Available This paper evaluates, for a 2030 scenario, the impact on onshore power systems in terms of the variability of the power generated by 81 GW of offshore wind farms installed in the North Sea. Meso-scale reanalysis data are used as input for computing the hourly power production for offshore wind farms, and this total production is analyzed to identify the largest aggregated hourly power variations. Based on publicly available information, a simplified representation of the coastal power grid is built for the countries bordering the North Sea. Wind farms less than 60 km from shore are connected radially to the mainland, while the rest are connected to a hypothetical offshore HVDC (High-Voltage Direct Current power grid, designed such that wind curtailment does not exceed 1% of production. Loads and conventional power plants by technology and associated cost curves are computed for the various national power systems, based on 2030 projections. Using the MATLAB-based MATPOWER toolbox, the hourly optimal power flow for this regional hybrid AC/DC grid is computed for high, low and medium years from the meso-scale database. The largest net load variations are evaluated per market area and related to the extra load-following reserves that may be needed from conventional generators.

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

    Topcu, H D; Brockmann, U H


    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. PMID:26234616

  19. Ninian third party project: A unique North Sea challenge

    The Ninian Field, operated by Chevron on behalf of the Ninian Field Group, is a mature North Sea producer. Rationalization of the topside facilities and declining production rates had left spare equipment and capacity in the Platform production systems. This spare capacity coupled with Ninian's strategic location in the Northern North Sea made it an ideal candidate for tie-in of subsea fields. Staffa, Lyell and Strathspey, operated by Lasmo, Conoco and Texaco respectively, are three such third party subsea developments using Ninian topside facilities. The Ninian Third Party Project is unique since it is the first offshore development where three third party operated subsea fields are processed by another operator and developed within the same timescale. In addition, major topside modifications were performed while Ninian continued to operate. Through sharing the lessons learned by Chevron as operator and manager of the Third Party Project, others will benefit in improved efficiency, planning and organization for similar future endeavors. The impacts of managing a major project (over 3 million offshore construction manhours) with an existing operations infrastructure, interfaces with Third Party Entrants, safety, productivity and efficiency results are among the issues which will be addressed

  20. Formation of Barents Sea Branch Water in the north-eastern Barents Sea

    Vidar S. Lien


    Full Text Available The Barents Sea throughflow accounts for approximately half of the Atlantic Water advection to the Arctic Ocean, while the other half flows through Fram Strait. Within the Barents Sea, the Atlantic Water undergoes considerable modifications before entering the Arctic Ocean through the St. Anna Trough. While the inflow area in the south-western Barents Sea is regularly monitored, oceanographic data from the outflow area to the north-east are very scarce. Here, we use conductivity, temperature and depth data from August/September 2008 to describe in detail the water masses present in the downstream area of the Barents Sea, their spatial distribution and transformations. Both Cold Deep Water, formed locally through winter convection and ice-freezing processes, and Atlantic Water, modified mainly through atmospheric cooling, contribute directly to the Barents Sea Branch Water. As a consequence, it consists of a dense core characterized by a temperature and salinity maximum associated with the Atlantic Water, in addition to the colder, less saline and less dense core commonly referred to as the Barents Sea Branch Water core. The denser core likely constitutes a substantial part of the total flow, and it is more saline and considerably denser than the Fram Strait branch as observed within the St. Anna Trough. Despite the recent warming of the Barents Sea, the Barents Sea Branch Water is denser than observed in the 1990s, and the bottom water observed in the St. Anna Trough matches the potential density at 2000 m depth in the Arctic Ocean.

  1. Dynamic Mechanism of Interannual Sea Surface Height Variability in the North Pacific Subtropical Gyre

    ZHANG Yong-Chui; ZHANG Li-Feng; L(U) Qing-Ping


    In this study, the dynamic mechanisms of interannual sea surface height (SSH) variability are investigated based on the first-mode baroclinic Rossby wave model, with a focus on the effects of different levels of wind stress curl (WSC)、 Maximum covariance analysis (MCA) of WSC and SSH anomalies displays a mode with significant WSC anomalies located primarily in the mid-latitude eastern North Pacific and central tropical Pacific with corresponding SSH anomalies located to the west. This leading mode can be attributed to Ekman pumping induced by local wind stress and the westward-propagating Rossby wave driven by largescale wind stress. It is further found that in the middle latitudes, the SSH anomalies are largely determined by WSC variations associated with the North Pacific Gyre Oscillation (NPGO)、 rather than the Pacific Decadal Oscillation (PDO). The sensitivity of the predictive skill of the linear first-mode baroclinic model to different wind products is also examined.

  2. Growth pattern and growth dependent mortality of larval and pelagic juvenile North Sea cod Gadus morhua

    Nielsen, Rune; Munk, Peter


    . Otolith radius and larval standard length were highly correlated, and otolith growth was used as a measure of larval somatic growth. The larvae were divided into 3 groups dependent on their hatch-date, and for each hatch group, the same period of past growth was compared between fish sampled in April and...... May. A 2-way repeated-measurement ANOVA revealed a significant higher past growth of fish sampled in May in 2 of the 3 hatch-groups, implying a higher mortality of the slow growing larvae. Additionally, otolith size at age differed significantly between the April and May sampling of the oldest larvae......We investigated growth patterns and evidence of growth dependent survival for a population of Atlantic cod Gadus morhua using analysis of their otolith microstructure. Central concentrations of a population of cod larvae and juveniles in the north-eastern North Sea were sampled twice (in April and...

  3. The Interrelation between the North Atlantic Oscillation (NAO) and the mean sea level at the Baltic Sea-North Sea coastlines

    Bassal Mahmood, Ali


    Large changes in the wintertime atmospheric circulation had occurred since the mid of 1970s over the Atlantic Ocean basin of the Northern Hemisphere (NH). The variations over the North Atlantic were related to changes in the North Atlantic Oscillation (NAO), in which, the (NAO) has accompanied by a northeast shift between the continents 40 oN - 70 oN and tended to remain in one extreme positive phase over Europe and downstream over Eurasia. These changes have pronounced effects on the regional distributions of the mean sea level at Baltic Sea - North Sea coastlines. Detecting the impacts of the (NAO) on the mean sea levels, have done by correlation coefficient. The relative mean sea level trends have estimated before and after removing the average seasonal cycle with correction for all series residuals. In this respect, Pearson correlation and standard ordinary univariate linear regression models have applied on 86 data stations series of the mean sea level in boreal winter months (December, January, February) and season DJF (average of December, January, February months) time scales over the period (1960 - 2010). The changes in the North Atlantic Oscillation over the periods (1977-1994, 1981-1994) in boreal winter season DJF condition have detected in the mean sea level anomalies. Each of the mean sea level anomalies is linked to the behavior of the (NAO) anomaly by using the standard ordinary bivariate linear regression models. Where, the averages of the mean sea level anomalies are the residual of strong regional patterns of changes, and the anomalies average for each data series have recomputed linearly related to the variations in (NAO+) indices. The formal regression models have estimated strictly by using high accurately methods for satisfying all regression assumptions absolutely, (i.e., for univariate regression: - the observed values of the dependent variable are subject to errors which have zero mean such: normality (if violated, the nonparametric method

  4. The internal consistency of the North Sea carbonate system

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


    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.

  5. The outlook for investment in the Norwegian North Sea

    An outline of the investment potential for oil and gas production on the Norwegian continental shelf is given. The continental shelf includes the Haltenbanken area and the Barents Sea as well as the North Sea. A description of existing projects and present knowledge of future prospects is given. The total production of oil and gas in 1990 was 107 million toe, the ratio of oil to gas production being 4:1. The relationship between oil and gas will change dramatically in the future however as the gas share in fields under development is much greater than in currently producing fields. The greatest potential for gas is expected to be in the Barents Sea which, being located at a considerable distance from existing gas markets presents a great challenge for commercial development. The conclusion drawn from the outline is that the present level of investment will be maintained or increase slightly over the next four to five years. For the period up to the turn of the century there is increasing uncertainty over the investment level which will become more and more dependent upon further expansion of gas exports but a best estimate is for continued investment stability beyond the year 2000. The production level can be expected to increase and reach a peak during the late 1990s. The resource base is sufficient to maintain a high production level for several decades after the year 2000. (UK)

  6. A high-resolution hindcast of wind and waves for The North Sea, The Norwegian Sea and The Barents Sea

    Reistad, Magnar; Haakenstad, Hilde; Aarnes, Ole Johan; Furevik, Birgitte R; Bidlot, Jean-Raymond; 10.1029/2010JC006402


    A combined high-resolution atmospheric downscaling and wave hindcast based on the ERA-40 reanalysis covering the Norwegian Sea, the North Sea and the Barents Sea is presented. The period covered is from September 1957 to August 2002. The dynamic atmospheric downscaling is performed as a series of short prognostic runs initialized from a blend of ERA-40 and the previous prognostic run to preserve the fine-scale surface features from the high-resolution model while maintaining the large-scale synoptic field from ERA-40. The nested WAM wave model hindcast consists of a coarse 50 km model covering the North Atlantic forced with ERA-40 winds and a nested 10-11 km resolution model forced with downscaled winds. A comparison against in situ and satellite observations of wind and sea state reveals significant improvement in mean values and upper percentiles of wind vectors and the significant wave height over ERA-40. Improvement is also found in the mean wave period. ERA-40 is biased low in wind speed and significant ...

  7. The North Atlantic Oscillation: variability and interactions with the North Atlantic ocean and Artic sea ice

    Jung, T.


    The North Atlantic oscillation (NAO) represents the dominant mode of atmospheric variability in the North Atlantic region and describes the strengthening and weakening of the midlatitude westerlies. In this study, variability of the NAO during wintertime and its relationship to the North Atlantic ocean and Arctic sea ice is investigated. For this purpose, observational data are analyzed along with integrations of models for the Atlantic ocean, Arctic sea ice, and the coupled global climate system. From a statistical point of view, the observed NAO index shows unusually high variance on interdecadal time scales during the 20th century. Variability on other time scales is consistent with realizations of random processes (''white noise''). Recurrence of wintertime NAO anomalies from winter-to-winter with missing signals during the inbetween nonwinter seasons is primarily associated with interdecadal variability of the NAO. This recurrence indicates that low-frequency changes of the NAO during the 20th century were in part externally forced. (orig.)

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

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


    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.

  9. Zooplankton diversity and the predatory impact by larval and small juvenile fish at the Fisher Banks in the North Sea

    Nielsen, Torkel Gissel; Munk, Peter


    The biomass and diversity of the mesozooplankton and fish larvae community were investigated across a frontal zone in the central North Sea in the early summer, to investigate whether larval fish predation is a regulator of mesozooplankton production. Pronounced changes in the mesozooplankton...... community were observed across the front off the Jutlandic coast. The biomass and the diversity of copepods changed across the front as the population of Calanus finmarchicus became abundant in the deeper water. The crustaceans (Acartia spp. and Evadne spp.) and polychaete larvae dominated the...... and cod (Gadus morhua) was the dominant larval fish species on the deeper stations. The present investigation demonstrates two different trophic pathways related to hydrography in the central North Sea. First, in the shallow coastal water, the abundant small neritic copepods are predominately predated...

  10. Plio-Pleistocene changes in the vegetation of central North Africa

    Castaneda, I. S.; Phu, V.; Urann, B.


    The area of central North Africa (including the Sahara and the Sahel) is sensitive to migrations of the intertropical rainbelt and has experienced dramatic, and possibly abrupt, shifts between wet and arid conditions in the past. For example, during the humid period of the early Holocene, the region that is presently the Sahara desert was vegetated and contained permanent lakes, and was occupied by human populations (e.g. Kuper and Kröpelin, 2006). In this study, we investigate the hydrology of central North Africa during the Plio-Pleistocene (4-0.5 Ma), a period during which a number of key steps in hominin evolution occurred. ODP site 660 is located in the tropical NE Atlantic Ocean (offshore West Africa) and receives dust from central North Africa, which is transported offshore by the African Easterly Jet. Plant leaf waxes (n-alkanes) contained in this dust provide information on the type of vegetation present , which in turn, can be used to examine hydrological variability because in tropical Africa the large scale distribution of vegetation utilizing the C3 (mainly trees) vs. C4 (grasses and warm season sedges) photosynthetic pathways mainly depends on aridity (precipitation) (e.g. Schefuss et al., 2003). Here, we examine the carbon (δ13C) and deuterium (δD) isotopic composition of plant leaf waxes, proxies for vegetation type (C3 vs. C4 plants) and precipitation amount, respectively. We also examine sea surface temperature variability using the alkenone Uk'37 Index as several studies have demonstrated close ties between sea surface temperature variability and hydrological conditions in N Africa during the late Pleistocene and Holocene. Results of this study further support a close link between SST and hydrological conditions in the Sahel during the past 4 Ma while also highlighting regional differences in aridity between Plio-Pleistocene records of western, eastern and southern Africa.

  11. Phase equilibrium of North Sea oils with polar chemicals: Experiments and CPA modeling

    Frost, Michael Grynnerup; Kontogeorgis, Georgios M.; von Solms, Nicolas;


    This work consists of a combined experimental and modeling study for oil - MEG - water systems, of relevance to petroleum applications. We present new experimental liquid-liquid equilibrium data for the mutual solubility of two North Sea oils + MEG and North Sea oils + MEG + water systems in the...

  12. Spatial differences in growth of lesser sandeel in the North Sea

    Rindorf, Anna; Wright, Peter J.; Jensen, Henrik;


    Lesser sandeel, Ammodytes marinus, is a key prey to a variety of North Sea predators, including species such as single load seabirds which are highly sensitive to prey size and condition. Whilst differences in weight at age across the North Sea have been investigated previously, the scale and cause...

  13. On estimating the intensity of oil-pollution in the North-Sea

    Helmers, R.


    In a project, commissioned by the North Sea Directorate, Ministry of Transport and Public Works (RWS), the problem is to estimate the intensity of oil pollution in the Dutch part of the North Sea. A planar inhomogeneous Poisson point process with an intensity function, which is parametrized by a fin

  14. Carbon sources in the North Sea evaluated by means of radium and stable carbon isotope tracers

    Burt, W.J.; Thomas, H.; Hagens, M.; Pätsch, J.; Clargo, N.; Salt, L.A.; Winde, V.; Böttcher, M.E.


    A multitracer approach is applied to assess the impact of boundary fluxes (e.g., benthic input from sedimentsor 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 transect

  15. Micro contaminants in surface sediments and macrobenthic invertebrates of the North Sea

    Everaarts, J.M.; Fischer, C.V.


    Trace metal concentrations (copper, zinc, cadmium and lead) were measured in the silt fraction (grainsize < 63 µm) of surface sediment of the North Sea. The concentrations varied in different areas of the Dutch continental shelf of the North Sea. The trace metal concentrations were highly related wi

  16. Mapping the North Sea base-Quaternary: using 3D seismic to fill a gap in the geological record

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


    The identification and mapping of the base-Quaternary boundary in the central parts of the North Sea is problematic due to the change from an unconformable transition between Pliocene and Pleistocene deltaic deposits in the southern North Sea to a conformable one further north (Sejrup et al 1991; Gatliff et al 1994). The best estimates of the transition use seismic reflection data to identify a 'crenulated reflector' (Buckley 2012), or rely on correlating sparse biostratigraphy (Cameron et al 1987). 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) allows greater confidence in the correlation to a regional 3D seismic dataset and show that the base-Quaternary can 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 mapped horizon is presented here alongside the difference between this new interpretation and the previously interpreted base-Quaternary (Buckley 2012). The revised base-Quaternary surface reaches a depth of 1248 ms TWT or approximately 1120 m (assuming average velocity of 1800 m/s) showing an elongate basin shape that follows the underlying structure of the Central Graben. The difference between the revised base-Quaternary and the traditional base-Quaternary reaches a maximum of over 600 ms TWT or approximately 540 m in the south-west with over 300 ms TWT or approximately 270 m at the Josephine well (56° 36.11'N, 2° 27.09'E) in the centre of the basin. Mapping this new base-Quaternary allows for the interpretation of the paleo-envionrment during the earliest Quaternary. Seismic attribute analysis indicates a deep water basin with sediment deposition from multiple deltas and redistribution by deep

  17. Investigation of sea level trends and the effect of the north atlantic oscillation (NAO) on the black sea and the eastern mediterranean sea

    Ozgenc Aksoy, Aysegul


    The North Atlantic Oscillation (NAO) has significant effects on sea levels, weather, and climate. In this study, the sea level trends and the effects of the North Atlantic Oscillation Indices (NAOI) on annual mean sea level data were assessed for the Black Sea and the Eastern Mediterranean Sea. The trends of sea level and NAOI were determined using Mann-Kendall dimensionless z statistics. Generally, upward sea level trends were detected for the Black Sea and the Eastern Mediterranean Sea. In the Black Sea, significant and continuous upward trends were detected after the year 1950. Weaker trends were detected for the Eastern part of the Mediterranean Sea. Sea level trends were correlated with trends in NAO indices; negative correlations were detected for the Black Sea, whereas positive correlations were found for the Eastern Mediterranean Sea. Paired t tests were performed to determine the turning points for all sea level data sets. The value of t was positive for all data sets, which means that the mean value of the data set before the turning point was smaller than the mean value of the data set after the turning point.


    Lifanchuk A. V.


    Full Text Available In this article we present data on the effect of addition of mineral nutrition elements in the structure of the phytoplankton community in the north-eastern part of the Black Sea in the different seasons. Experimental studies have shown that the increase in biomass of microalgae occurs at the simultaneous addition of nitrogen and phosphorus in the accumulative cultures. In the spring can get biomass Emiliania huxleyi, P.pseudodelicatissima, Chaetoceros curvisetus and Skeletonema costatum, in the summer – E. huxleyi, C. curvisetus, P.pseudodelicatissima, S.costatum, Thalassionema nitzschioides, Leptocylindrus danicus, Dactyliosolen fragilissimus, Proboscia alata, Pseudosolenia calcar-avis, in the autumn - C. curvisetus, S.costatum, Th. nitzschioides, L. danicus, D. fragilissimus

  19. Rock physics model of glauconitic greensand from the North Sea

    Hossain, Zakir; Mukerji, Tapan; Dvorkin, Jack;


    The objective of this study was to establish a rock physics model of North Sea Paleogene greensand. The Hertz-Mindlin contact model is widely used to calculate elastic velocities of sandstone as well as to calculate the initial sand-pack modulus of the soft-sand, stiff-sand, and intermediate-stiff...... glauconite. Next, we use this Hertz-Mindlin contact model of two types of grains as the initial modulus for a soft-sand model and a stiff-sand model. By using these rock physics models, we examine the relationship between elastic modulus and porosity in laboratory and logging data and link rock....... Initially, greensand is a mixture of mainly quartz and glauconite; when weakly cemented, it has relatively low elastic modulus and can be modeled by a Hertz-Mindlin contact model of two types of grains. Silica-cemented greensand has a relatively high elastic modulus and can be modeled by an intermediate-stiff...

  20. Subsurface phytoplankton blooms fuel pelagic production in the North Sea

    Richardson, Kathrine; Visser, Andre; Pedersen, Flemming


    The seasonal phytoplankton biomass distribution pattern in stratified temperate marine waters is traditionally depicted as consisting of spring and autumn blooms. The energy source supporting pelagic summer production is believed to be the spring bloom. However, the spring bloom disappears...... relatively quickly from the water column and a large proportion of the material sedimenting to the bottom following the spring bloom is often comprised of intact phytoplankton cells. Thus, it is easy to argue that the spring bloom is fueling the energy demands of the benthos, but more difficult to argue...... convincingly that energy fixed during the spring bloom is fueling the pelagic production occurring during summer months. We argue here that periodic phytoplankton blooms are occurring during the summer in the North Sea at depths of >25 m and that the accumulated new production [sensu (Dugdale and Goering...

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

    Oconnor, W. P.


    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.

  2. Tritium concentration in the Baltic and North Sea surface waters in autumn 1985

    Tritium concentration in the surface waters of Baltic and North seas is investigated using liquid-scintillation technique after preliminary electrolysis concentrating. Prior to electrolysis water samples were subjected to double distillation. Single determination duration made up ∼150 min. The method cumulative error under 0.60 confidence probability makes up 30%. As a result of analyzing the water samples taken in the surface waters of the seas under investigation in the fall of 1985 the medium tritium concentration in the Baltic sea waters was 4.5 k Bq/m3 and in the North sea ones -3.6 kBq/m3. A more inhomogeneous tritium concentration distribution with gradual decrease to the South-West and North-West is detected in the Baltic sea as compared to the North sea

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

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


    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

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

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


    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

  5. The impact of North Atlantic sea surface temperature errors on the simulation of North Atlantic European region climate

    Keeley, Sarah; Sutton, Rowan; Shaffrey, Len


    Current state-of-the-art climate models fail to capture accurately the path of the Gulf Stream and North Atlantic Current. This leads to a warm bias near the North American coast, where the modelled Gulf Stream separates from the coast further north, and a cold anomaly to the east of the Grand Banks of Newfoundland, where the North Atlantic Current remains too zonal in this region. Using an atmosphere-only model forced with the sea surface temperature (SST) biases in the North Atlantic, we...

  6. Impact of North Atlantic Current changes on the Nordic Seas and the Arctic Ocean

    Kauker, Frank; Gerdes, Rüdiger; Karcher, Michael; Köberle, Cornelia


    The impact of North Atlantic Current (NAC) volume, heat, and salt transport variability onto the NordicSeas and the Arctic Ocean is investigated using numerical hindcast and sensitivity experiments. Theocean-sea ice model reproduces observed propagation pathways and speeds of SST anomalies.Part of the signal reaching the entrance to the Nordic Seas between Iceland and Scotland originatesin the lower latitude North Atlantic. Response experiments with different prescribed conditionsat 50N show ...

  7. Effects of the North Atlantic Oscillation on sea ice breeding habitats of harp seals ( Pagophilus groenlandicus) across the North Atlantic

    Friedlaender, Ari S.; Johnston, David W.; Halpin, Patrick N.


    Harp seals ( Pagophilus groenlandicus) are an abundant and commercially exploited species of phocid seal in the North Atlantic. Harp seals are entirely dependent on annual sea ice for breeding purposes and the distribution, abundance, and constitution of sea ice in this region are subject to tremendous interannual variability. As such, harp seal population dynamics are likely intimately tied to climate variability and global change. We used satellite-derived images of sea ice cover to determine trends in available habitat at the four major harp seal breeding areas in the North Atlantic, and assessed linkages amongst sea ice conditions and variability in the North Atlantic Oscillation (NAO) during 1978-2006. The White Sea breeding area had the highest annual ice concentrations, while the Gulf of St. Lawrence and Front regions were the most variable over time. We confirmed a consistent positive correlation between the NAO index and the amount of sea ice cover in Western North Atlantic breeding areas off Canada. Furthermore, we found an opposite and consistent negative correlation between the NAO and sea ice cover in the eastern-most breeding areas, leading to an out-of-phase signal between the Western and Eastern (particularly the White Sea) North Atlantic. These results indicate that sea ice dynamics in the breeding regions of harp seals are controlled, to some extent, by the phase of the NAO and its effects on weather across the North Atlantic. Previous studies indicate that poor ice conditions can have negative effects on harp seal survival and the consistent relationships between breeding habitat and NAO conditions that are described here have implications for both the biology and management of harp seal populations.

  8. The North Sea oil and gas industry and the environment

    The North Sea environment is described. Inputs into this environment from oil and gas installations are relatively modest compared with the pollution from effluent discharged or directly dumped into the sea by its highly populated and industrialized enclosing nations. Hydrocarbon discharges provide the greatest input from the oil and gas industry and make a substantial contribution to the total hydrocarbon input. The sources from offshore installations are analysed. Accidental spills, flaring, atmospheric emissions and other inputs are discussed. Biological and chemical monitoring over many year has shown that the most common environmental effect is a marked fall in the number of species of marine fauna and an increase in the number of individuals. These effects appear within 1000 metres of the installation. The spread of contaminants may be more widespread than the biological response indicates, though. The cost of environmental protection is briefly considered. A need to determined the wider impact of low levels of contamination detected at greater distances from platform activities and the development of effective environmental management plans are identified as two objectives for the future. (UK)

  9. Transport and hydraulically-induced recycling of phosphorous in the North Sea-Baltic Sea transition zone

    Kepp, Rikke; Struve, Anke; Christiansen, Christian;


    Bottom-mounted acoustic Doppler current profiler measurements indicate that the net transport of water (844 m3 s-1) in the Little Belt makes up only 6% of the total transport between the Baltic Sea and the North Sea. This is a smaller percentage than the 9% commonly found in the literature. Owing...

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

    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

  11. Airborne gravity survey of Lincoln Sea and Wandel Sea, north Greenland

    Olesen, Arne Vestergaard; Forsberg, René; Keller, K.; Gidskehaug, A.


    In June 1998 National Survey and Cadastre Denmark (KMS) carried out an airborne gravity survey over the Polar Sea to the north of Greenland. A Twin Otter from Greenlandair, equipped with autopilot and additional fuel tanks, was employed for the survey. A modified marine LaCoste & Romberg gravimeter...... and geodetic GPS receivers operating in differential mode made up the basic scientific instrumentation used to monitor the gravity field variations. A laser altimeter and a low cost inertial measurement unit consisting of three gyros and three accelerometers were included to sustain the postprocessing...

  12. Levels of norm in aging north sea oil installations

    The Marina II report identified that Oil and Gas Installations in the North Sea were discharging as much alpha emitting radionuclides a s nuclear installations and fuel processing plants on the UK mainland. However the figures were based on assumptions and extrapolation from the limited data available at the time. The actual levels of activity of dissolved radium in produced water will be reported and an estimate made of the activity discharged. It will be shown that the activities in produced water vary enormously and are impossible to predict. It is very difficult to extrapolate to cover all installations currently in production. Many of these installations are now over 20 years old and as the reservoirs age then the activities carried in the process fluids appear to be increasing with time. The formation of NORM/LSA occurs in many areas of the process. The radioisotopes present in the NORM/LSA also vary with the age of the reservoir and processes used. Vessels require regular cleaning during operation an d this will occur in situ. On some platforms this can take place every year and substantial volumes of waste are discharged into the sea. The various routes of discharges available will be described. The activity levels found and discharged to sea in the silt sand sludge during cleaning operations will also be discussed. The problems of disposal also affect the on shore facilities involved in the processing of oil and gas. NORM/LSA is also found downstream in the onshore terminals and the disposal routes are much more limited. The use of these more accurate figures, rather than those used in the Marina II estimates, do however confirm that the discharges of alpha emitters do approach those of the nuclear industry. Possible options for reducing these discharges will be identified. (authors)

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

    Kettle, A J


    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 ...

  14. Coherent decadal sea level variations across gyre boundaries in the North Atlantic

    Thompson, P. R.; Mitchum, G. T.


    Tide gauge sea level variability in the western Atlantic at periods greater than about 18 months is in phase and highly coherent from Texas to Nova Scotia. A simple mean over the gauges analyzed in this region explained more than 50% of the total variance in the gauges and has a primary time-scale of variation in the decadal band. Decadal sea level variability in the western Atlantic is most often attributed to open ocean wind forcing and long Rossby waves, which act to spin up or spin down the subtropical gyre. However, this explanation is not sufficient to explain why sea levels along the coastal edge of the Gulf Stream are in phase and highly correlated with sea levels in the Gulf of Mexico and subpolar gyre. Furthermore, there is evidence that decadal variations in North American sea levels are coherent and of opposite phase with respect to gauges along the European coast of the subtropical gyre, which is not expected from a mechanism requiring westward propagation. A linear regression of North Atlantic sea surface temperature onto the composite low-passed sea level signal from around the North Atlantic showed a basin-wide pattern of sea surface temperature similar to the North Atlantic Tripole (NAT) identified in various studies of decadal climate variability in the North Atlantic. The emergence of the NAT pattern from tide gauge sea levels suggested the low-frequency coherence of sea level is indicative of a basin-scale decadal climate mode and that the steric contribution to decadal sea level variability in the Gulf Stream region is as important as the dynamic contribution from open ocean wind forcing. We explored the relative roles of dynamic and steric sea level change in the coherent nature of decadal sea level signals around the North Atlantic basin, and we propose basin-scale mechanisms to link decadal sea level change between the gyres and zonally across the Atlantic.

  15. The North sea, one of the group's anchorage points

    The North Sea is one of the pillars of the Elf Aquitaine group's Exploration-Production strategy. The most recent start-up in the North Sea, last february, concerned the Froy field where Elf Petroleum Norge (AS) is an operator with a 24.573 % interest alongside Statoil, Total Norge AS (15.2346 %) and Norsk Hydro. The first gas sales occurred on June 15, as scheduled. The oil production marketed by Elf (net of royalties) remained stable at 13.9 Gm3. At january 1,1995, Elf Aquitaine's mining area covered a gross surface area of 435,894 km2. In countries where the group is already established, the policy is : - to withdraw from exploration licenses considered as being the least promising in terms of discovery or profitability; - to concentrate on sectors where the existing production means allow for an optimisation of later developments ; - to penetrate more extensive exploration areas with good targets. In the British zone, the additional reserves revealed in the Elgin and Franklin condensate fields have doubled the initial forecast, placing the former among the major fields. All the discoveries made in the British zone have allowed the group to renew productions until now. Elf's production in Piper, Saltire, Chanter is 100,000 b/d which is added to the production of the Claymore and Scapa fields (100,000 b/d). The Flotta terminal processes the crude coming from these fields to which is added the production from the neighbouring fields of Tartan (Texaco) and Ivanhoe-Rob Roy (Amerada Hess), i.e. a total of more than 300,000 b/d. Other than Elgin or the Viking Graben, the future of the Elf group in Great Britain will most certainly come from the West Shetlands and the Irish Sea. In the Norwegian zone, the group has interest in the Frigg, Heimldal, Ekofisk, Valhall, Lille-Frigg, Froy, Oseberg, Hod, Sleipner East an Sleipner West Brage, Troll, Snorre, Statfjord East and Tordis production fields. (authors). 3 tabs., 1 photo

  16. Late Miocene biogeography and paleoclimatology of the central North Atlantic

    Poore, R.Z.


    Quantitative analyses of planktonic foraminiferal assemblages from Deep Sea Drilling Project (DSDP) Holes 334 and 410 demonstrate that subpolar and subtropical faunal provinces existed in the North Atlantic during the late Miocene. Climatic oscillations are clearly recorded in Hole 410 by variations in abundance of the Neogloboquadrina subpolar assemblage. These climatic oscillations have a period of about 1 m.y. Higher frequency oscillations with a periodicity of one to several hundred thousand years are evident from about 6.5 to 7.5 m.y. and are probably present throughout the entire late Miocene. A revised age of 7.0 m.y. is proposed for the first occurrence of the calcareous nannofossil Amaurolithus primus (the Amaurolithus datum). ?? 1981.

  17. Comparison of stomach contents of haddock (Melanogrammus aeglefinus) from the 1981 and 1991 North Sea International Stomach Sampling Projects

    Adlerstein, S.A.; Temming, A.; Mergardt, N.


    This study analyses data from over 20 000 haddock stomachs collected during the 1981 and 1991 Stomach Sampling Projects of the North Sea. Sampling was within the framework of the Multispecies Virtual Population Analysis (MSVPA) for fisheries stock assessment. In 1981 stomachs were collected to calculate input feeding parameters from main predators. During 1991 the sampling exercise was repeated to test stability of the parameters in the region. We investigate stability of haddock stomach content weight between years accounting for ontogenic, spatial and temporal variations within the scope of the survey resolution. Analysis using generalized linear and additive models is performed for weight of the stomach content including and excluding empty stomachs and also for proportion of stomachs without food. Results indicate that haddock stomach contents varied significantly between years, quarters and North Sea roundfish areas. Content weights were overall higher in 1981 than in 1991. In 1981 levels were high from spring to fall and in 1991 mostly in spring. During both years levels were lowest in the central North Sea and in winter. Most of the deviance in modelling the stomach weight is explained by the length of the predator. Stomachs sampled in 1981 were most frequently empty in spring and those sampled in 1991 in winter. In both years, proportions decreased with fish length except in winter when levels increased. Proportion of empty stomachs was highest in the central region of the North Sea. Most of the proportion variation is explained by quarterly fluctuation. Variation of content weight can be related to prey composition found in the stomachs. High stomach contents are generally associated with high contribution of fish prey to the total stomach content, mainly sandeels. We propose that sandeels were more vulnerable to predation in 1981 than in 1991 due to colder temperatures. ?? 2002 International Council for the Exploration of the Sea. Published by Elsevier

  18. A Possible Feedback Mechanism Involving the Arctic Freshwater,the Arctic Sea Ice, and the North Atlantic Drift

    Odd Helge OTTER(A); Helge DRANGE


    Model studies point to enhanced warming and to increased freshwater fluxes to high northern latitudes in response to global warming. In order to address possible feedbacks in the ice-ocean system in response to such changes, the combined effect of increased freshwater input to the Arctic Ocean and Arctic warming--the latter manifested as a gradual melting of the Arctic sea ice--is examined using a 3-D isopycnic coordinate ocean general circulation model. A suite of three idealized experiments is carried out: one control integration, one integration with a doubling of the modern Arctic river runoff, and a third more extreme case, where the river runoff is five times the modern value. In the two freshwater cases, the sea ice thickness is reduced by 1.5-2 m in the central Arctic Ocean over a 50-year period. The modelled ocean response is qualitatively the same for both perturbation experiments: freshwater propagates into the Atlantic Ocean and the Nordic Seas, leading to an initial weakening of the North Atlantic Drift.Furthermore, changes in the geostrophic currents in the central Arctic and melting of the Arctic sea ice lead to an intensified Beaufort Gyre, which in turn increases the southward volume transport through the Canadian Archipelago. To compensate for this southward transport of mass, more warm and saline Atlantic water is carried northward with the North Atlantic Drift. It is found that the increased transport of salt into the northern North Atlantic and the Nordic Seas tends to counteract the impact of the increased freshwater originating from the Arctic, leading to a stabilization of the North Atlantic Drift.

  19. Subtropical Air-Sea Interaction and Development of Central Pacific El Ni(n)o

    XIE Ruihuang; HUANG Fei; REN Hongli


    The standard deviation of the central Pacific sea surface temperature anomaly (SSTA) during the period from October to February shows that the central Pacific SSTA variation is primarily due to the occurrence of the Central Pacific El Ni(n)o (CP-El Ni(n)o)and has a connection with the subtropical air-sea interaction in the northeastern Pacific.After removing the influence of the Eastern Pacific El Ni(n)o,an S-EOF analysis is conducted and the leading mode shows a clear seasonal SSTA evolving from the subtropical northeastern Pacific to the tropical central Pacific with a quasi-biennial period.The initial subtropical SSTA is generated by the wind speed decrease and surface heat flux increase due to a north Pacific anomalous cyclone.Such subtropical SSTA can further influence the establishment of the SSTA in the tropical central Pacific via the wind-evaporation-SST (WES) feedback.After established,the central equatorial Pacific SSTA can be strengthened by the zonal advective feedback and thermocline feedback,and develop into CP-El Ni(n)o.However,as the thermocline feedback increases the SSTA cooling after the mature phase,the heat flux loss and the reversed zonal advective feedback can cause the phase transition of CP-El Ni(n)o.Along with the wind stress variability,the recharge (discharge) process occurs in the central (eastern) equatorial Pacific and such a process causes the phase consistency between the thermocline depth and SST anomalies,which presents a contrast to the original recharge/discharge theory.

  20. A hydrographic time series station in the Wadden Sea (southern North Sea)

    Reuter, Rainer; Badewien, Thomas H.; Bartholomä, Alexander; Braun, Axel; Lübben, Andrea; Rullkötter, Jürgen


    In the tidal inlet between the East Frisian islands of Langeoog and Spiekeroog, southern North Sea, a time-series station was set up in autumn 2002 as part of the research programme BioGeoChemistry of Tidal Flats run by the University of Oldenburg. The purpose of the station is to provide continuous data on physical, biological and chemical parameters. In addition to instruments recording basic hydrographic and meteorological parameters, the time-series station is equipped with acoustic Doppler profilers for measuring surface waves and current profiles. Compact optical spectrometers are being used for spectral measurements of seawater transmission and for daylight reflectance. Additional sensors were installed for measuring oxygen, nutrients and methane in the seawater. The data shall help to quantify the flux of dissolved and suspended matter between the backbarrier tidal flat and the open sea and to characterise the material transformation in the tidal flat area by biogeochemical processes over the tidal cycle. Due to its novel design, operation of the station is also possible during winter and under extreme weather conditions (gales, storm surges, and sea ice) when data sampling with conventional platforms such as research vessels, buoys, or smaller poles could not be performed in the past. In this way, time series of data are obtained, which include events that are most relevant to the evolution of this coastal area. The performance of the station and its equipment are presented with data covering 6 years of operation. Time series of air and water temperature as well as seawater salinity demonstrate the multiyear dynamics of these parameters in the East Frisian Wadden Sea. Hydrographic data collected under specific meteorological conditions such as gales and storm surges exemplify the all-weather capabilities of the station and its value for studying hydrographic processes in the Wadden Sea.

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

    Karpytchev, Mikhail; Letetrel, Camille


    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).

  2. Reproduction Patterns of Scleractinian Corals in the Central Red Sea

    Bouwmeester, Jessica


    Early work on the reproductive seasonality of corals in the Red Sea suggested that corals exhibit temporal reproductive isolation, unlike on the Great Barrier Reef where many species spawn in synchrony. More recent work has however shown high synchrony in the maturity of gametes in Acropora species, suggesting multi-specific spawning is likely to occur in the Red Sea. In this thesis I investigate the patterns of coral reproduction in the central Red Sea. The spawning season in the central Red Sea lasts four months, from April to July and spawning occurs on nights around the full moon. During this period Acropora species show a peak of spawning in April, with some species spawning again in May. The level of synchrony, quantified with a spawning synchrony index, is comparable to other locations where multi-specific spawning has been reported. Observations over two consecutive years show that the synchrony of spawning was lower in spring 2012 than in spring 2011, and thus that spawning patterns are variable from one year to the other. Coral settlement patterns on artificial substrata confirmed a main spawning season in the spring but also supported reproductive data suggesting that some Porites spawn in October-November. Settlement was studied over 2.5 years on a reef, which had suffered recently from high mortality after a local bleaching event. Settlement appeared low but post-bleaching studies from other locations indicated similar abundances and showed that recruits generally did not increase until 5 years after the bleaching event. Abundance of juvenile corals however started to increase significantly three years after the bleaching. Successful recruitment, although low suggests that the coral assemblage on the affected reef will most likely recover as long as it is not affected by another disturbance.

  3. Lg Coda Variations in North-Central Iran

    Mojtaba Naghavi


    Full Text Available Ground motion records in north-central Iran have been used in order to obtain the Lg coda , using stack spectral ratio method. The lateral variations in 0 and its frequency dependence are estimated in the 0.3–7.0 Hz frequency range which led to =267(±32×0.71(±0.14. The observed variations in quality factor show low values of 0 in western part of the study region where bounded by relatively high values in southern and northern parts. Since the seismicity of the study area is quite shallow the obtained results can be attributed to the upper 30 km of the crust. The Damavand volcano and its surrounding region also exhibit variations in the value of 0 which result in low and intermediate values of 0 in western and eastern parts, respectively. Current seismicity in Damavand is mostly confined to its southwestern part, whereas our results proved to possess low values of 0. In general, most of factor variations can be attributed to the lateral heterogeneity as well as the severity of the crustal velocity gradient, and as expected the north-central Iran is well inferred as a tectonically active region.

  4. Studies on the distribution of transuranics in the Baltic Sea, the Danish Belts, the Kattegat and the North Sea

    The Danish Sounds and Belts connect the North Sea with the Baltic Sea. The salinity of the North Sea is approximately 34 per mille and of the Baltic approximately 9 per mille. In the inner Danish waters the bottom water consists mostly of ingoing, heavy North Sea water, while on the surface we find the low salinity Baltic water. The Danish waters make it possible within a limited area to study the influence on radionuclide levels of the varying salinities in the marine environment. The Thule samples referred to in the present report do not include those which were contaminated by unexploded nuclear weapon debris from the 1968 accident. The study of transuranics in Danish waters has been supported by the International Atomic Energy Agency (IAEA) since 1978

  5. Decadal oscillation of autumn precipitation in Central Vietnam modulated by the East Pacific–North Pacific (EP–NP) teleconnection

    Autumn precipitation over Central Vietnam is associated with an increase in the occurrence of tropical cyclones that lead to frequent flooding and pose a significant threat to lives and property. The present analyses reveal a pronounced decadal oscillation of autumn precipitation in Central Vietnam within the 8–11 year frequency band that is modulated by the East Pacific–North Pacific (EP–NP) teleconnection. The negative phase of the EP–NP pattern is associated with a positive sea surface temperature (SST) anomaly in the South China Sea (SCS) that induces low-level convergence, enhances convection, and increases precipitation over Central Vietnam and adjacent islands including Hainan (China) and the Philippines. This circulation feature around the SCS is embedded in a large-scale circulation associated with SST anomalies across the Pacific Ocean—i.e., cooling in the Eastern and Central tropical Pacific sandwiched by warming in the North and South Pacific as well as the Western Pacific Ocean. The positive phase of the EP–NP features opposite SST and circulation anomalies, with the result being reduced rainfall in Central Vietnam. This out-of-phase relationship and shared decadal spectral coherence between the EP–NP index and autumn precipitation in Central Vietnam might be useful for future climate predictions and flood management. (letter)

  6. Decadal oscillation of autumn precipitation in Central Vietnam modulated by the East Pacific-North Pacific (EP-NP) teleconnection

    Li, R.; Wang, S.-Y.; Gillies, R. R.; Buckley, B. M.; Truong, L. H.; Cho, C.


    Autumn precipitation over Central Vietnam is associated with an increase in the occurrence of tropical cyclones that lead to frequent flooding and pose a significant threat to lives and property. The present analyses reveal a pronounced decadal oscillation of autumn precipitation in Central Vietnam within the 8-11 year frequency band that is modulated by the East Pacific-North Pacific (EP-NP) teleconnection. The negative phase of the EP-NP pattern is associated with a positive sea surface temperature (SST) anomaly in the South China Sea (SCS) that induces low-level convergence, enhances convection, and increases precipitation over Central Vietnam and adjacent islands including Hainan (China) and the Philippines. This circulation feature around the SCS is embedded in a large-scale circulation associated with SST anomalies across the Pacific Ocean—i.e., cooling in the Eastern and Central tropical Pacific sandwiched by warming in the North and South Pacific as well as the Western Pacific Ocean. The positive phase of the EP-NP features opposite SST and circulation anomalies, with the result being reduced rainfall in Central Vietnam. This out-of-phase relationship and shared decadal spectral coherence between the EP-NP index and autumn precipitation in Central Vietnam might be useful for future climate predictions and flood management.

  7. Model investigations on the propagation of artificial radionuclides in the North Sea

    The radioactive discharges from the nuclear fuel reprocessing plants Sellafield Works and La Hague caused in the North Sea water an around 1 to 3 order of magnitude higher activity concentration of Cs then in the North Atlantic. The simulation method used for medium-term 3-dimensional spreading processes over time periods of at least several months was compared with the activity concentration distribution of Cs-137 in the North Sea water measured in the past. Accordingly, the model calculations reproduce correctly the large scale characteristics of the cesium spreading observed. An essential part of the investigation concerned itself with the radioactive contaminations of the North Sea water as the result of fictitious operational accidents at nuclear power stations near the coasts (Hartlepool, Sizewell) and adjacent to rivers (Rhine, Elbe). In addition, marine disasters in different regions of the North Sea, in which a threat of radioactivity comes into play, were simulated. (orig./DG)

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

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


    The Danish part of Norwegian-Danish Basin, which constitutes the eastern part of the North Sea Basin, has been the key area for sequence stratigraphic subdivision and analysis of the Cenozoic succession since the mid 1990's. Widespread 3D seismic data, in the central parts of the North Sea Basin, as well as more scattered 3D seismic data in the Danish part of the Norwegian-Danish Basin, have given a more detailed understanding of the sequences and indicate that climate is tenable for the origin of Cenozoic sequence boundaries. The previous sequence stratigraphic interpretations have been an integrated part of an ongoing debate concerning vertical movements of the Fennoscandian shield versus the impact of climate and erosion. A newly accessed coherent regional 2D and reprocessed 3D seismic data set, in the Norwegian part of the Norwegian-Danish Basin, constitute the database for a new sequence stratigraphic analysis of the entire area. The objective of the new study is to test previous subdivisions and introduce a coherent 3D sequence stratigraphic analysis and depositional model for the entire Norwegian-Danish Basin. This analysis is necessary to get out of the stalemate with the uplift discussion. The study shows that the original subdivision by Michelsen et al. (1995, 1998) stands. However, revision of few a sequence boundaries may have to be adjusted due to new biostratigraphic information published. Furthermore, high-angle clinoforms and geomorphological transport complexes observed in the Danish North Sea Basin can be traced into the Norwegian sector. This together with the recognition of several other high-angle clinoform complexes, and their associated seismic facies distribution maps and thickness-maps, enhances the level of detail and constrains the previous published paleogeographic reconstructions of the Cenozoic. The geometry of the Cenozoic infill, in the Norwegian part of the Norwegian-Danish Basin, is here interpreted to be controlled by relative sea

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

    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


    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

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

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


    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.