Palaeoenvironment in northern Norway between 22.2 and 14.5 cal. ka BP     

Tore O. Vorren  Karl‐Dag Vorren  Odd Aasheim  K. I. Torbjørn Dahlgren  Matthias Forwick  Kristian Hassel 《Boreas: An International Journal of Quaternary Research》2013,42(4):876-895

The stratigraphy of lake Endletvatn on northern Andøya, northern Norway, has been revisited to improve the understanding of the palaeoenvironment in the region during the Last Glacial Maximum (LGM). Four high‐quality cores were analysed with respect to various lithological parameters and macrofossil content, supplemented by 47 AMS radiocarbon dates. The sediments indicate a low‐energy environment with a mean sedimentation rate of 0.5 mm a^?1. We infer perennially frozen ground in the surroundings during the LGM. Climate proxies indicate a high arctic climate (i.e. July mean temperatures between 0 and 3°C) throughout most of the LGM. The warmest periods are marked by a rise in seed, moss and animal fossils, and often also by higher organic production in the lake. These periods took place from 21.4 to 20.1, from 18.8 to 18.1, around 17 and from 16.4 cal. ka BP onwards. The shifts between the different climatic regimes occurred rapidly – probably during one or two decades. The present data do not support recently published conclusions stating that Picea, Pinus and Betula pubescens grew on Andøya during parts of the LGM. The highest relative sea level after the final deglaciation on northern Andøya is bracketed between 36 and 38 m a.s.l. It occurred between 21.0 and 20.3 cal. ka BP, peaking around 20.7 cal. ka BP. The final deglaciation of the northern tip of Andøya occurred 22.2 cal. ka BP. Then the western margin of the Andfjorden ice stream receded to the Kjølhaugen Moraine and shortly thereafter to the Endleten Moraine. Our research confirms that northern Andøya is a key location for understanding the natural environment in northwestern Europe during the LGM.  相似文献   

Burial and scour of short cylinders under combined random waves and currents including effects of second order wave asymmetry     

Dag Myrhaug  Muk Chen Ong 《Coastal Engineering》2009

This paper provides an approach by which the burial and scour of short cylinders under combined second order random waves and currents can be derived. Here the formulas for burial and scour for regular waves plus currents presented by Catano-Lopera and Garcia [Catano-Lopera, Y.A. and Garcia, M.H. (2006). Burial of short cylinders induced by scour under combined waves and currents. ASCE J. Waterway, Port, Coastal and Ocean Eng. 132(6), 439–449., Catano-Lopera, Y.A. and Garcia, M.H. (2007). Geometry of scour hole around, and the influence of the angle of attack on the burial of finite cylinders under combined flows. Ocean Eng. 34(5, 6), 856–869.] are used together with Stokes second order wave theory by assuming the basic harmonic wave motion to be a stationary Gaussian narrow-band random process. An example of calculation is also presented.  相似文献   

Effects of wave age and air stability on whitecap coverage     

Dag Myrhaug  Lars Erik Holmedal 《Coastal Engineering》2008,55(12):959-966

The paper considers the effects of wave age and air stability on the whitecap coverage at sea. This is made by using the logarithmic mean wind velocity profile including a stability function as well as adopting a recent wave age dependent sea surface roughness formula. The results are valid for wind waves in local equilibrium with the steady wind. Examples of results demonstrate clear effects of wave age and air stability on the whitecap coverage. Comparisons are also made with field measurements by Sugihara et al. [Sugihara, Y., et al., 2007. Variation of whitecap coverage with wave-field conditions. J. Mar. Syst. 66, 47–60], representing unstable air stability conditions. Although the data basis is limited, the wave age independent Charnock sea roughness based predictions capture the main features of the observed whitecap coverage, suggesting a stronger dependence on air stability than on wave age in the data.  相似文献   

The rise and fall of factory trawlers: An eclectic approach     

Dag Standal 《Marine Policy》2008

Factory trawlers are the most controversial vessel group in Norwegian fisheries. At the time the fleet emerged, stern trawling in combination with on-board processing of cod fillets was regarded as a major innovation. However, the deep-sea fleet was intended to be a stable supplier of fish to the land-based industry. Factory trawlers were not a part of the political project. On the contrary, the vessels represented a serious departure from the traditional employment system for the fisheries’ dependent districts. Factory trawlers have, since the seventies, been regarded as the main enemy to the coastal vessels and the land-based industry. The vessels have been subject to a profound debate about several built-in contradictory goals for the fisheries policy, such as the ideal of employment for all and the need for a profitable sector without state subsidies. Despite a series of policy-driven initiatives to remove the factory trawlers, the fleet has been one of the most profitable vessel groups in the Norwegian fisheries. Nonetheless, the fleet is now marginalised in the number of vessels and transformed into an obedient supplier of round fish to the land-based industry. In this article, we outline the history of the Norwegian factory trawlers and how the fleet was subject to a series of critical changes reflecting the complexity of the vessels.  相似文献   

Identification and implications of fight hydrocarbon fluid inclusions from the Proterozoic Bidjovagge gold-copper deposit, Finnmark, Norway     

David C. Ettner  Sten Lindblom  Dag Karlsen 《Applied Geochemistry》1996,11(6):745-755

Carbonic fluid inclusions were observed in quartz-bearing veins at the Proterozoic Bidjovagge AuCu deposit within the Kautokeino greenstone belt in Norway, where mineralization occurred in oxidation zones of graphitic schists. A primary fluid inclusion zonation was observed with C0₂-rich fluid inclusions in the structural footwall of the deposit, and CH₄-rich inclusions within the ore zone in the oxidation zone. Microthermometry of the primary hydrocarbon inclusions revealed 2 groups; (1) a group which homogenized between −125°C and the critical temperature of CH₄ (−82.1°C), which indicated the presence of pure CH₄, and (2) a group which homogenized between the critical temperature of CH₄ and −42°C, which indicated the presence CH₄ and higher hydrocarbons (HHC). Raman microprobe analyses of the first group confirmed the presence of CH₄. The second inclusion group were fluorescent, and Raman spectra clearly displayed CH₄,C₂H₆, and rarer C₃H₈ peaks. A typical feature of the Raman spectra were elevated baselines at the hydrocarbon peaks. Carbon peaks were also usually detected in each inclusion by Raman analysis. Bulk gas chromatography analyses of samples containing the first group (CH₄) indicated the presence of CH₄ and low concentrations of C₂H₆ and C₃H₈. Gas chromatography analyses of samples containing the second group (CH₄ and higher hydrocarbons) confirmed the presence of CH₄, and higher hydrocarbons such as C₂H₆ and C₃H₈ and also butanes. Based on the spacial zonation of hydrocarbons and the estimated PT conditions of 300 to 375°C and 2 to 4 kbars, the authors suggest an abiotic origin for the hydrocarbons. It is suggested that the hydrothermal fluids oxidized the graphitic schist, precipitated Cu and Au and formed light gas hydrocarbons.  相似文献   

Random wave-induced onshore scour characteristics around submerged breakwaters using a stochastic method     

Dag Myrhaug  Muk Chen Ong 《Ocean Engineering》2010,37(13):1233-1238

This paper provides a stochastic method by which the two-dimensional onshore scour characteristics along the base of submerged breakwaters exposed to normally incident random waves on both sloping and horizontal sandy seabed can be derived. Here the formulas for the regular wave-induced scour characteristics provided by Young and Testik (2009) are used. These formulas are combined with describing the waves as a stationary Gaussian narrow-band random process to derive the random wave-induced onshore scour characteristics; the maximum scour depth, the scour length, and the distance of the maximum scour depth location from the onshore breakwater face. An example of calculation is also provided.  相似文献   

Input of organic carbon as determinant of nutrient fluxes,light climate and productivity in the Ob and Yenisey estuaries     

Dag O. Hessen  JoLynn Carroll  Berit Kjeldstad  Anton A. Korosov  Lasse H. Pettersson  Dmitry Pozdnyakov  Kai Sørensen 《Estuarine, Coastal and Shelf Science》2010

Spectral light attenuation profiles and concentrations of total and dissolved carbon (C), nutrients and chlorophyll a (Chla) were studied along transects running from the river mouth to the Kara Sea during late summer 2003 for the Yenisey and fall 2005 for the Ob estuaries. Earth Observation data were used to generate composite images of water color and Chla distribution over the estuaries and the Kara Sea to reveal the spatial impact of the river efflux in terms of optical properties.  相似文献   

Seabed shear stresses under random waves: predictions vs estimates from field measurements     

Dag Myrhaug  Olav H. Slaattelid  Kostas F. Lambrakos 《Ocean Engineering》1998,25(10):907-916

The paper discusses the seabed shear stresses under random waves, and compares model predictions with results from field measurements near the seabed in the Strait of Juan de Fuca, Washington State, and at EDDA, North Sea. The model predictions as well as the interpretation of data are based on three different representative measures of random wave velocities within 12 minute records: root-mean-square, significant and maximum values. From the two locations the best agreement is found for the Strait of Juan de Fuca data regardless of the random velocity measure used. This agreement is attributed to the absence of suspended sediment at this location.  相似文献   

A note on a theoretical model of oscillatory smooth turbulent boundary layers     

Dag Myrhaug 《Ocean Engineering》1984,11(3):315-320

An analytical theory which describes the motion in an oscillatory smooth turbulent boundary layer using a two-layer time invariant eddy viscosity model is presented. The eddy viscosity in the inner layer increases quadratically with the height above the wall. In the outer layer the eddy viscosity is taken as a constant.  相似文献   

Structure and resilience of overwintering habitats of Calanus finmarchicus in the Eastern Norwegian Sea     

Dag Slagstad  Kurt S. Tande 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2702

Very high concentrations of overwintering Calanus finmarchicus were found in the eastern Lofoten Basin of the Norwegian Sea close to the shelf break in January 2001–2002. A coupled 3D hydrodynamic and ecological model was used to study the formation of this deep overwintering aggregation and its stability. The ecological model includes nutrients, phytoplankton and microzooplankton in addition to a stage-structured model of C. finmarchicus. Using a Eulerian approach, the model was initiated with an overwintering stock evenly distributed in the oceanic regions of the Norwegian Sea, i.e. where depths>600 m. Spawning and development of the new generation take place in response to vertical mixing and phytoplankton development. Animals are assumed to begin their descent to overwintering depths of 700–1000 m as late stage Vs. Model results show that, in late summer, high concentrations of animals were found at overwintering depths near the shelf break north of the North Sea, off the northeastern Vøring Plateau and in the eastern Lofoten Basin along the slope of the Barents Sea shelf. They remained there for months due to deep eddies and southward, deep currents along the Norwegian shelf. The simulation experiments indicate that the combined effect of deep anticyclonic circulation and vertical migration behavior of the animals may explain the high concentrations of overwintering C. finmarchicus found in field surveys in the Eastern Lofoten Basin, close to the shelf break.  相似文献