scholarly journals Mind the gaps: a state-space model for analysing the dynamics of North Sea herring spawning components

2010 ◽  
Vol 67 (9) ◽  
pp. 1939-1947 ◽  
Author(s):  
Mark R. Payne
Keyword(s):  
State Space ◽  
North Sea ◽  
State Space Model ◽  
Missing Observations ◽  
Component Level ◽  
Space Model ◽  
The North ◽  
Abundance Indices ◽  
The North Sea ◽  
The Individual

Abstract Payne, M. R. 2010. Mind the gaps: a state-space model for analysing the dynamics of North Sea herring spawning components. – ICES Journal of Marine Science, 67: 1939–1947. The North Sea autumn-spawning herring (Clupea harengus) stock consists of a set of different spawning components. The dynamics of the entire stock have been well characterized, but although time-series of larval abundance indices are available for the individual components, study of the dynamics at the component level has historically been hampered by missing observations and high sampling noise. A simple state-space statistical model is developed that is robust to these problems, gives a good fit to the data, and proves capable of both handling and predicting missing observations well. Furthermore, the sum of the fitted abundance indices across all components proves an excellent proxy for the biomass of the total stock, even though the model utilizes information at the individual-component level. The Orkney–Shetland component appears to have recovered faster from historic depletion events than the other components, whereas the Downs component has been the slowest. These differences give rise to changes in stock composition, which are shown to vary widely within a relatively short time. The modelling framework provides a valuable tool for studying and monitoring the dynamics of the individual components of the North Sea herring stock.

scholarly journals Gaussian linear state-space model for wind fields in the North-East Atlantic

2014 ◽  
Vol 26 (1) ◽  
pp. 29-38 ◽  
Author(s):  
J. Bessac ◽  
P. Ailliot ◽  
V. Monbet
Keyword(s):  
State Space ◽  
State Space Model ◽  
Wind Fields ◽  
East Atlantic ◽  
Space Model ◽  
North East ◽  
The North ◽  
Linear State

Time-Variant Ultimate Strength Reliability of FPSOs Including Corrosion and Slamming Effects

2005 ◽  
Author(s):  
Ioannis Moatsos ◽  
Purnendu K. Das
Keyword(s):  
Reliability Analysis ◽  
Ultimate Strength ◽  
North Sea ◽  
Structural Reliability ◽  
Bending Moment ◽  
Green Water ◽  
Component Level ◽  
Reliability Indices ◽  
The North ◽  
The North Sea

This paper discusses the effects of corrosion and slamming on Floating Production Storage and Offloading (FPSO) structures in the North Sea by using a time variant structural reliability based approach. An FPSO structure currently in operation in the North Sea is analysed, an analytical approach is suggested and used to determine the Ultimate Strength of the FPSO structure and compared with other published methods. A non-linear corrosion method is then used to determine the effect of corrosion on the ultimate strength and subsequently in the reliability of the structure. Slamming loads on the midship section of the FPSO are calculated using closed form expressions. The effect of slamming and green water load on the overall vertical bending moment applied on the structure is combined with the vertical wave bending and still water loads using the Ferry Borges- Castanheta method and the SRSS rule, to provide the distribution and variation of a loading component for structural reliability analysis to be performed. Time variant reliability analysis using Monte Carlo Simulation is then used to determine reliability indices and probabilities of failure for the structural system analysed on a component level.

scholarly journals Molluscan Assemblages from the Marine Middle Miocene of South Jutland and their Environments. Vol. I.

1958 ◽  
Vol 79 ◽  
pp. 1-355
Author(s):  
Theodor Sorgenfrei
Keyword(s):  
North Sea ◽  
Middle Miocene ◽  
Short Review ◽  
Shell Morphology ◽  
Environmental Relationships ◽  
The North ◽  
Northwest Germany ◽  
Genetic Features ◽  
The North Sea ◽  
The Individual

This is a study of the fossil record of marine Miocene beds in South Jutland, Denmark. The beds have been defined as the Arnum formation and referred to the middle Miocene Hemmoor stage as known in Northwest Germany. The object of the work is to increase knowledge of the Danish Miocene and to contribute data on the development of the North Sea Basin during Miocene time.The introduction deals with the history of Tertiary stratigraphy in Europe and some related problems. Discrepancies and uncertainties regarding the correlation and dating of beds in the separate basins have been particularly emphasized. It is often possible to trace disagreements to the acceptance of unsound fossil evidence. Therefore it is concluded that the lithologic and fossil records of the individual basins should be known in much greater detail before adequate inferences as to the contemporaneity of particular beds can be made. It is also suggested that guide fossils should only be designated when statistically justified.The chapters on the South Jutland Miocene contain an outline of the geo-graphic distribution of the formations, a lithologic description of the water well sections from which the fossil material was derived, and definitions of the Arnum formation (marine) and the underlying Ribe formation (non-marine). The following formations are now recognized in the Miocene sequence of South Jutland:Gram formation: late Miocene Arnum formation and Ribe formation: middle Miocene Klintinghoved formation: early Miocene.The chapters on paleontology consist of a description of the molluscan fauna of the Arnum formation, a discussion of the environmental relationships of recent mollusca, and a section on biostratigraphy and paleobiology.The description of species follows a rigid pattern. The intention being to include as many pertinent facts as possible while using a minimum of technical terms. The variation of shell properties is illustrated by diagrams in a few species, and in some families genetic features have been particularly discussed. The chapter is terminated by a short review and some conclusions regarding the significance of shell morphology.The chapter on environmental relationships of recent mollusca includes discussion of the effects of inanimate environments on shell morphology and the distribution of mollusca. It is maintained that the reaction of recent mollusca to variations in their environment should be known in greater detail in order to provide a sound basis for biostratigraphic conclusions depending on the evidence of fossil mollusca.A discussion of the commonly adopted correlation procedures initiates the chapters dealing with biostratigraphy and paleobiology. It is shown that the "percentage" method by which faunas are correlated on the basis of percentages of species in common should be regarded with much criticism. New correlation formulae, in which are included the total numbers of species in the faunas involved are suggested. It is shown by these formulae and other evidence that the fauna of the Arnum formation in its entirety is apparently in better agreement with the Reinbek and Hemmoor faunas of Germany than with any other fauna of the North Sea Basin.The paleobiological analysis of the fauna of the Arnum formation is based on: the biology of living species; the actual frequencies of the mollusca in the different drilled sections; and the environmental relationships of recent mollusca. It is inferred that a decrease in salinity took place during deposition of the formation. The faunules of the different fossiliferous levels are shown to be derivatives of one community: the Aporrhais alata - Nassa sp.sp. community which inhabited relatively shallow waters of the middle Miocene North Sea Basin.In conclusion some comments are made on the correlation of the well sections as supported by paleobiology. The Nassa cimbrica and N. Fuchsi zones are defined, and the different elevations of correlated levels in the drilled sections are related to structural displacements.

scholarly journals ‘Organic nannofossils’: a new type of palynomorph from the Palaeogene of the North Sea

2000 ◽  
Vol 19 (2) ◽  
pp. 153-158 ◽  
Author(s):  
Peter A. Hochuli
Keyword(s):  
North Sea ◽  
Undescribed Species ◽  
Calcareous Nannoplankton ◽  
The North ◽  
Lower Oligocene ◽  
The North Sea ◽  
New Type ◽  
The Individual ◽  
Produce Acid ◽  
Organic Remains

Abstract. Organic microfossils of regular dodecahedral shape are found in the Palaeogene (Lower Oligocene) of the central and northern parts of the Norwegian North Sea. The shape and structure of these fossils are very similar to coccospheres of the calcareous nannoplankton genus Braarudosphaera. The individual pentagonal plates show the same morphological features as replicas of the inner surface of pentaliths forming calcareous coccospheres. It is the first evidence that a representative of calcareous nannoplankton (Haptophyta, Coccolithophorales) is found to produce acid-resistant organic microfossils. The organic remains might have been produced by an undescribed species of the genus Braarudosphaera or represent an unknown stage in the life cycle of species which normally produce calcareous plates.

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